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Journal of Biological Chemistry

Current research reports and chronological list of recent articles..




The international scientific Journal of Biological Chemistry (JBC) publishes papers based on original research that are judged to make a novel and important contribution to understanding the molecular and cellular basis of biological processes.

The publisher is the ASBM. The copyright and publishing rights of specialized products listed below are in this publishing house. This is also responsible for the content shown.

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Additional research articles see Current Chemistry Research Articles. Magazines with similar content (biological chemistry):

 - Biological Chemistry,



Journal of Biological Chemistry - Abstracts



Correction: Thyroid hormone receptor interacting protein 13 (TRIP13) AAA-ATPase is a novel mitotic checkpoint-silencing protein. [Additions and Corrections]

VOLUME 289 (2014) PAGES 23928–23937There was an error in the second paragraph under “Discussion.” “It was demonstrated using clever biochemistry methods that ATP hydrolysis at the β-γ high energy phosphodiester bond … ” should read, “It was demonstrated using clever biochemistry methods that ATP hydrolysis at the β-γ high energy phosphoanhydride bond … ”<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/nntiESUoJY8" height="1" width="1" alt=""/>
Datum: 21.06.2019


Expression of Concern: Identification of nitric oxide as an endogenous activator of the AMP-activated protein kinase in vascular endothelial cells. [Expressions of Concern]

VOLUME 283 (2008) PAGES 27452–27461The publisher of the Journal of Biological Chemistry is issuing an Expression of Concern to inform readers that credible concerns have been raised regarding some of the data and conclusions in the article listed above. The Journal of Biological Chemistry will provide additional information as it becomes available.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/1Jr9VABVHBM" height="1" width="1" alt=""/>
Datum: 21.06.2019


Expression of Concern: Thromboxane A2 receptor activates a Rho-associated kinase/LKB1/PTEN pathway to attenuate endothelium insulin signaling. [Expressions of Concern]

VOLUME 284 (2009) PAGES 17120–17128The publisher of the Journal of Biological Chemistry is issuing an Expression of Concern to inform readers that credible concerns have been raised regarding some of the data and conclusions in the article listed above. The Journal of Biological Chemistry will provide additional information as it becomes available.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/NTc5p0Br1YA" height="1" width="1" alt=""/>
Datum: 21.06.2019


Expression of Concern: Activation of AMP-activated protein kinase {alpha}1 alleviates endothelial cell apoptosis by increasing the expression of anti-apoptotic proteins Bcl-2 and Survivin. [Expressions of Concern]

VOLUME 285 (2010) PAGES 15346–15355The publisher of the Journal of Biological Chemistry is issuing an Expression of Concern to inform readers that credible concerns have been raised regarding some of the data and conclusions in the article listed above. The Journal of Biological Chemistry will provide additional information as it becomes available.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/hXIs0GoWHzQ" height="1" width="1" alt=""/>
Datum: 21.06.2019


Expression of Concern: Liver kinase B1 expression promotes phosphatase activity and abrogation of receptor tyrosine kinase phosphorylation in human cancer cells. [Expressions of Concern]

VOLUME 289 (2014) PAGES 1639–1648The publisher of the Journal of Biological Chemistry is issuing an Expression of Concern to inform readers that credible concerns have been raised regarding some of the data and conclusions in the article listed above. The Journal of Biological Chemistry will provide additional information as it becomes available.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/2kdvRqu2-p8" height="1" width="1" alt=""/>
Datum: 21.06.2019


Expression of Concern: Activation of the AMP-activated protein kinase by the anti-diabetic drug metformin in vivo: Role of mitochondrial reactive nitrogen species. [Expressions of Concern]

VOLUME 279 (2004) PAGES 43940–43951The publisher of the Journal of Biological Chemistry is issuing an Expression of Concern to inform readers that credible concerns have been raised regarding some of the data and conclusions in the article listed above. The Journal of Biological Chemistry will provide additional information as it becomes available.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/tNBK5vAvO5I" height="1" width="1" alt=""/>
Datum: 21.06.2019


Expression of Concern: Activation of 5'-AMP-activated kinase is mediated through c-Src and phosphoinositide 3-kinase activity during hypoxia-reoxygenation of bovine aortic endothelial cells: Role of peroxynitrite. [Expressions of Concern]

VOLUME 278 (2003) PAGES 34003–34010The publisher of the Journal of Biological Chemistry is issuing an Expression of Concern to inform readers that credible concerns have been raised regarding some of the data and conclusions in the article listed above. The Journal of Biological Chemistry will provide additional information as it becomes available.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/h-qRP7vcsio" height="1" width="1" alt=""/>
Datum: 21.06.2019


Expression of Concern: Protein kinase C{zeta}-dependent LKB1 serine 428 phosphorylation increases LKB1 nucleus export and apoptosis in endothelial cells. [Expressions of Concern]

VOLUME 283 (2008) PAGES 12446–12455The publisher of the Journal of Biological Chemistry is issuing an Expression of Concern to inform readers that credible concerns have been raised regarding some of the data and conclusions in the article listed above. The Journal of Biological Chemistry will provide additional information as it becomes available.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/XQe2j6p_r8w" height="1" width="1" alt=""/>
Datum: 21.06.2019


Expression of Concern: Nicotine-induced activation of AMP-activated protein kinase inhibits fatty acid synthase in 3T3L1 adipocytes: A role for oxidant stress. [Expressions of Concern]

VOLUME 282 (2007) PAGES 26793–26801The publisher of the Journal of Biological Chemistry is issuing an Expression of Concern to inform readers that credible concerns have been raised regarding some of the data and conclusions in the article listed above. The Journal of Biological Chemistry will provide additional information as it becomes available.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/iI81VdewLnU" height="1" width="1" alt=""/>
Datum: 21.06.2019


Low plasma adropin concentrations increase risks of weight gain and metabolic dysregulation in response to a high-sugar diet in male nonhuman primates [Molecular Bases of Disease]

Mouse studies linking adropin, a peptide hormone encoded by the energy homeostasis–associated (ENHO) gene, to biological clocks and to glucose and lipid metabolism suggest a potential therapeutic target for managing diseases of metabolism. However, adropin's roles in human metabolism are unclear. In silico expression profiling in a nonhuman primate diurnal transcriptome atlas (GSE98965) revealed a dynamic and diurnal pattern of ENHO expression. ENHO expression is abundant in brain, including ventromedial and lateral hypothalamic nuclei regulating appetite and autonomic function. Lower ENHO expression is present in liver, lung, kidney, ileum, and some endocrine glands. Hepatic ENHO expression associates with genes involved in glucose and lipid metabolism. Unsupervised hierarchical clustering identified 426 genes co-regulated with ENHO in liver, ileum, kidney medulla, and lung. Gene Ontology analysis of this cluster revealed enrichment for epigenetic silencing by histone H3K27 trimethylation and biological processes related to neural function. Dietary intervention experiments with 59 adult male rhesus macaques indicated low plasma adropin concentrations were positively correlated with fasting glucose, plasma leptin, and apolipoprotein C3 (APOC3) concentrations. During consumption of a high-sugar (fructose) diet, which induced 10% weight gain, animals with low adropin had larger increases of plasma leptin and more severe hyperglycemia. Declining adropin concentrations were correlated with increases of plasma APOC3 and triglycerides. In summary, peripheral ENHO expression associates with pathways related to epigenetic and neural functions, and carbohydrate and lipid metabolism, suggesting co-regulation in nonhuman primates. Low circulating adropin predicts increased weight gain and metabolic dysregulation during consumption of a high-sugar diet.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/C6nUY7HEEsU" height="1" width="1" alt=""/>
Datum: 21.06.2019


Identification of a small-molecule compound that inhibits homodimerization of oncogenic NAC1 protein and sensitizes cancer cells to anticancer agents [Cell Biology]

Nucleus accumbens–associated protein-1 (NAC1) is a transcriptional repressor encoded by the NACC1 gene, which is amplified and overexpressed in various human cancers and plays critical roles in tumor development, progression, and drug resistance. NAC1 has therefore been explored as a potential therapeutic target for managing malignant tumors. However, effective approaches for effective targeting of this nuclear protein remain elusive. In this study, we identified a core unit consisting of Met7 and Leu90 in NAC1's N-terminal domain (amino acids 1–130), which is critical for its homodimerization and stability. Furthermore, using a combination of computational analysis of the NAC1 dimerization interface and high-throughput screening (HTS) for small molecules that inhibit NAC1 homodimerization, we identified a compound (NIC3) that selectively binds to the conserved Leu-90 of NAC1 and prevents its homodimerization, leading to proteasomal NAC1 degradation. Moreover, we demonstrate that NIC3-mediated down-regulation of NAC1 protein sensitizes drug-resistant tumor cells to conventional chemotherapy and enhances the antimetastatic effect of the antiangiogenic agent bevacizumab both in vitro and in vivo. These results suggest that small-molecule inhibitors of NAC1 homodimerization may effectively sensitize cancer cells to some anticancer agents and that NAC1 homodimerization could be further explored as a potential therapeutic target in the development of antineoplastic agents.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/DY9LXpotBaM" height="1" width="1" alt=""/>
Datum: 21.06.2019


The N terminus of the small heat shock protein HSPB7 drives its polyQ aggregation-suppressing activity [Cell Biology]

Heat shock protein family B (small) member 7 (HSPB7) is a unique, relatively unexplored member within the family of human small heat shock proteins (HSPBs). Unlike most HSPB family members, HSPB7 does not oligomerize and so far has not been shown to associate with any other member of the HSPB family. Intriguingly, it was found to be the most potent member within the HSPB family to prevent aggregation of proteins with expanded polyglutamine (polyQ) stretches. How HSPB7 suppresses polyQ aggregation has remained elusive so far. Here, using several experimental strategies, including in vitro aggregation assay, immunoblotting and fluorescence approaches, we show that the polyQ aggregation-inhibiting activity of HSPB7 is fully dependent on its flexible N-terminal domain (NTD). We observed that the NTD of HSPB7 is both required for association with and inhibition of polyQ aggregation. Remarkably, replacing the NTD of HSPB1, which itself cannot suppress polyQ aggregation, with the NTD of HSPB7 resulted in a hybrid protein that gained anti-polyQ aggregation activity. The hybrid NTDHSPB7–HSPB1 protein displayed a reduction in oligomer size and, unlike WT HSPB1, associated with polyQ. However, experiments with phospho-mimicking HSPB1 mutants revealed that de-oligomerization of HSPB1 alone does not suffice to gain polyQ aggregation–inhibiting activity. Together, our results reveal that the NTD of HSPB7 is both necessary and sufficient to bind to and suppress the aggregation of polyQ-containing proteins.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/Wcu3iiGbx34" height="1" width="1" alt=""/>
Datum: 21.06.2019


Stk40 deletion elevates c-JUN protein level and impairs mesoderm differentiation [Protein Synthesis and Degradation]

Mesoderm development is a finely tuned process initiated by the differentiation of pluripotent epiblast cells. Serine/threonine kinase 40 (STK40) controls the development of several mesoderm-derived cell types, its overexpression induces differentiation of mouse embryonic stem cells (mESCs) toward the extraembryonic endoderm, and Stk40 knockout (KO) results in multiple organ failure and is lethal at the perinatal stage in mice. However, molecular mechanisms underlying the physiological functions of STK40 in mesoderm differentiation remain elusive. Here, we report that Stk40 ablation impairs mesoderm differentiation both in vitro and in vivo. Mechanistically, STK40 interacts with both the E3 ubiquitin ligase mammalian constitutive photomorphogenesis protein 1 (COP1) and the transcriptional regulator proto-oncogene c-Jun (c-JUN), promoting c-JUN protein degradation. Consequently, Stk40 knockout leads to c-JUN protein accumulation, which, in turn, apparently suppresses WNT signaling activity and impairs the mesoderm differentiation process. Overall, this study reveals that STK40, together with COP1, represents a previously unknown regulatory axis that modulates the c-JUN protein level within an appropriate range during mesoderm differentiation from mESCs. Our findings provide critical insights into the molecular mechanisms regulating the c-JUN protein level and may have potential implications for managing cellular disorders arising from c-JUN dysfunction.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/vHIObBdrOcQ" height="1" width="1" alt=""/>
Datum: 21.06.2019


A clinical dose of angiotensin-converting enzyme (ACE) inhibitor and heterozygous ACE deletion exacerbate Alzheimer's disease pathology in mice [Neurobiology]

Inhibition of angiotensin-converting enzyme (ACE) is a strategy used worldwide for managing hypertension. In addition to converting angiotensin I to angiotensin II, ACE also converts neurotoxic β-amyloid protein 42 (Aβ42) to Aβ40. Because of its neurotoxicity, Aβ42 is believed to play a causative role in the development of Alzheimer's disease (AD), whereas Aβ40 has neuroprotective effects against Aβ42 aggregation and also against metal-induced oxidative damage. Whether ACE inhibition enhances Aβ42 aggregation or impairs human cognitive ability are very important issues for preventing AD onset and for optimal hypertension management. In an 8-year longitudinal study, we found here that the mean intelligence quotient of male, but not female, hypertensive patients taking ACE inhibitors declined more rapidly than that of others taking no ACE inhibitors. Moreover, the sera of all AD patients exhibited a decrease in Aβ42-to-Aβ40–converting activity compared with sera from age-matched healthy individuals. Using human amyloid precursor protein transgenic mice, we found that a clinical dose of an ACE inhibitor was sufficient to increase brain amyloid deposition. We also generated human amyloid precursor protein/ACE+/− mice and found that a decrease in ACE levels promoted Aβ42 deposition and increased the number of apoptotic neurons. These results suggest that inhibition of ACE activity is a risk factor for impaired human cognition and for triggering AD onset.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/q6AjdlCBvdE" height="1" width="1" alt=""/>
Datum: 21.06.2019


Functional characterization of a subtilisin-like serine protease from Vibrio cholerae [Enzymology]

Vibrio cholerae, the causative agent of the human diarrheal disease cholera, exports numerous enzymes that facilitate its adaptation to both intestinal and aquatic niches. These secreted enzymes can mediate nutrient acquisition, biofilm assembly, and V. cholerae interactions with its host. We recently identified a V. cholerae-secreted serine protease, IvaP, that is active in V. cholerae-infected rabbits and human choleric stool. IvaP alters the activity of several host and pathogen enzymes in the gut and, along with other secreted V. cholerae proteases, decreases binding of intelectin, an intestinal carbohydrate-binding protein, to V. cholerae in vivo. IvaP bears homology to subtilisin-like enzymes, a large family of serine proteases primarily comprised of secreted endopeptidases. Following secretion, IvaP is cleaved at least three times to yield a truncated enzyme with serine hydrolase activity, yet little is known about the mechanism of extracellular maturation. Here, we show that IvaP maturation requires a series of sequential N- and C-terminal cleavage events congruent with the enzyme's mosaic protein domain structure. Using a catalytically inactive reporter protein, we determined that IvaP can be partially processed in trans, but intramolecular proteolysis is most likely required to generate the mature enzyme. Unlike many other subtilisin-like enzymes, the IvaP cleavage pattern is consistent with stepwise processing of the N-terminal propeptide, which could temporarily inhibit, and be cleaved by, the purified enzyme. Furthermore, IvaP was able to cleave purified intelectin, which inhibited intelectin binding to V. cholerae. These results suggest that IvaP plays a role in modulating intelectin–V. cholerae interactions.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/fQyLS0AUr04" height="1" width="1" alt=""/>
Datum: 21.06.2019


On &#x201C;Isomerization as the secret Achilles' heel of long-lived proteins&#x201D; [Letters to the Editor]

This summary (1) calls to our attention the importance of often-overlooked stochastic processes that occur as proteins age—especially long-lived proteins. The demonstration by Lyon et al. (2) of the failed chaperone function of α-crystallins and its relationship to cataract and potentially other protein precipitation diseases is elegant. They should, however, acknowledge that Groenen et al. (3) and Voorter et al. (4) published on this topic decades ago. Goenen showed how simple water-based hydrolysis after racemization can lead to the extensive cleavages that are observed in the aged lens.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/9RsbSd6mlbg" height="1" width="1" alt=""/>
Datum: 21.06.2019


Mechanism of cognate sequence discrimination by the ETS-family transcription factor ETS-1 [Gene Regulation]

Functional evidence increasingly implicates low-affinity DNA recognition by transcription factors as a general mechanism for the spatiotemporal control of developmental genes. Although the DNA sequence requirements for affinity are well-defined, the dynamic mechanisms that execute cognate recognition are much less resolved. To address this gap, here we examined ETS1, a paradigm developmental transcription factor, as a model for which cognate discrimination remains enigmatic. Using molecular dynamics simulations, we interrogated the DNA-binding domain of murine ETS1 alone and when bound to high-and low-affinity cognate sites or to nonspecific DNA. The results of our analyses revealed collective backbone and side-chain motions that distinguished cognate versus nonspecific as well as high- versus low-affinity cognate DNA binding. Combined with binding experiments with site-directed ETS1 mutants, the molecular dynamics data disclosed a triad of residues that respond specifically to low-affinity cognate DNA. We found that a DNA-contacting residue (Gln-336) specifically recognizes low-affinity DNA and triggers the loss of a distal salt bridge (Glu-343/Arg-378) via a large side-chain motion that compromises the hydrophobic packing of two core helices. As an intact Glu-343/Arg-378 bridge is the default state in unbound ETS1 and maintained in high-affinity and nonspecific complexes, the low-affinity complex represents a unique conformational adaptation to the suboptimization of developmental enhancers.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/M99C9UUlUdM" height="1" width="1" alt=""/>
Datum: 21.06.2019


Conformational resolution of nucleotide cycling and effector interactions for multiple small GTPases determined in parallel [Molecular Biophysics]

Small GTPases alternatively bind GDP/GTP guanine nucleotides to gate signaling pathways that direct most cellular processes. Numerous GTPases are implicated in oncogenesis, particularly the three RAS isoforms HRAS, KRAS, and NRAS and the RHO family GTPase RAC1. Signaling networks comprising small GTPases are highly connected, and there is some evidence of direct biochemical cross-talk between their functional G-domains. The activation potential of a given GTPase is contingent on a codependent interaction with the nucleotide and a Mg2+ ion, which bind to individual variants with distinct affinities coordinated by residues in the GTPase nucleotide-binding pocket. Here, we utilized a selective-labeling strategy coupled with real-time NMR spectroscopy to monitor nucleotide exchange, GTP hydrolysis, and effector interactions of multiple small GTPases in a single complex system. We provide insight into nucleotide preference and the role of Mg2+ in activating both WT and oncogenic mutant enzymes. Multiplexing revealed guanine nucleotide exchange factor (GEF), GTPase-activating protein (GAP), and effector-binding specificities in mixtures of GTPases and resolved that the three related RAS isoforms are biochemically equivalent. This work establishes that direct quantitation of the nucleotide-bound conformation is required to accurately determine an activation potential for any given GTPase, as small GTPases such as RAS-like proto-oncogene A (RALA) or the G12C mutant of KRAS display fast exchange kinetics but have a high affinity for GDP. Furthermore, we propose that the G-domains of small GTPases behave autonomously in solution and that nucleotide cycling proceeds independently of protein concentration but is highly impacted by Mg2+ abundance.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/uNY6IVyNg3s" height="1" width="1" alt=""/>
Datum: 21.06.2019


The Ser/Thr kinase p90RSK promotes kidney fibrosis by modulating fibroblast-epithelial crosstalk [Molecular Bases of Disease]

Healthy kidney structure and environment rely on epithelial integrity and interactions between epithelial cells and other kidney cells. The Ser/Thr kinase 90 kDa ribosomal protein S6 kinase 1 (p90RSK) belongs to a protein family that regulates many cellular processes, including cell motility and survival. p90RSK is predominantly expressed in the kidney, but its possible role in chronic kidney disease (CKD) remains largely unknown. Here, we found that p90RSK expression is dramatically activated in a classic mouse obstructive chronic kidney disease model, largely in the interstitial FSP-1–positive fibroblasts. We generated FSP-1–specific p90RSK transgenic mouse (RSK-Tg) and discovered that these mice, after obstructive injury, display significantly increased fibrosis and enhanced tubular epithelial damage compared with their wt littermates (RSK-wt), indicating a role of p90RSK in fibroblast–epithelial communication. We established an in vitro fibroblast–epithelial coculture system with primary kidney fibroblasts from RSK-Tg and RSK-wt mice and found that RSK-Tg fibroblasts consistently produce excessive H2O2 causing epithelial oxidative stress and inducing nuclear translocation of the signaling protein β-catenin. Epithelial accumulation of β-catenin, in turn, promoted epithelial apoptosis by activating the transcription factor forkhead box class O1 (FOXO1). Of note, blockade of reactive oxygen species (ROS) or β-catenin or FOXO1 activity abolished fibroblast p90RSK-mediated epithelial apoptosis. These results make it clear that p90RSK promotes kidney fibrosis by inducing fibroblast-mediated epithelial apoptosis through ROS-mediated activation of β-catenin/FOXO1 signaling pathway.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/vEjUvTLiZJo" height="1" width="1" alt=""/>
Datum: 21.06.2019


A disintegrin-like and metalloproteinase domain with thrombospondin type 1 motif 9 (ADAMTS9) regulates fibronectin fibrillogenesis and turnover [Cell Biology]

The secreted metalloprotease ADAMTS9 has dual roles in extracellular matrix (ECM) turnover and biogenesis of the primary cilium during mouse embryogenesis. Its gene locus is associated with several human traits and disorders, but ADAMTS9 has few known interacting partners or confirmed substrates. Here, using a yeast two-hybrid screen for proteins interacting with its C-terminal Gon1 domain, we identified three putative ADAMTS9-binding regions in the ECM glycoprotein fibronectin. Using solid-phase binding assays and surface plasmon resonance experiments with purified proteins, we demonstrate that ADAMTS9 and fibronectin interact. ADAMTS9 constructs, including those lacking Gon1, co-localized with fibronectin fibrils formed by cultured fibroblasts lacking fibrillin-1, which co-localizes with fibronectin and binds several ADAMTSs. We observed no fibrillar ADAMTS9 staining after blockade of fibroblast fibronectin fibrillogenesis with a peptide based on the functional upstream domain of a Staphylococcus aureus adhesin. These findings indicate that ADAMTS9 binds fibronectin dimers and fibrils directly through multiple sites in both molecules. Proteolytically active ADAMTS9, but not a catalytically inactive variant, disrupted fibronectin fibril networks formed by fibroblasts in vitro, and ADAMTS9-deficient RPE1 cells assembled a robust fibronectin fibril network, unlike WT cells. Targeted LC-MS analysis of fibronectin digested by ADAMTS9-expressing cells identified a semitryptic peptide arising from cleavage at Gly2196–Leu2197. We noted that this scissile bond is in the linker between fibronectin modules III17 and I10, a region targeted also by other proteases. These findings, along with stronger fibronectin staining previously observed in Adamts9 mutant embryos, suggest that ADAMTS9 contributes to fibronectin turnover during ECM remodeling.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/vVy-pjo1su0" height="1" width="1" alt=""/>
Datum: 21.06.2019


DNA damage response activates respiration and thereby enlarges dNTP pools to promote cell survival in budding yeast [Gene Regulation]

The DNA damage response (DDR) is an evolutionarily conserved process essential for cell survival. Previously, we found that decreased histone expression induces mitochondrial respiration, raising the question whether the DDR also stimulates respiration. Here, using oxygen consumption and ATP assays, RT-qPCR and ChIP-qPCR methods, and dNTP analyses, we show that DDR activation in the budding yeast Saccharomyces cerevisiae, either by genetic manipulation or by growth in the presence of genotoxic chemicals, induces respiration. We observed that this induction is conferred by reduced transcription of histone genes and globally decreased DNA nucleosome occupancy. This globally altered chromatin structure increased the expression of genes encoding enzymes of tricarboxylic acid cycle, electron transport chain, oxidative phosphorylation, elevated oxygen consumption, and ATP synthesis. The elevated ATP levels resulting from DDR-stimulated respiration drove enlargement of dNTP pools; cells with a defect in respiration failed to increase dNTP synthesis and exhibited reduced fitness in the presence of DNA damage. Together, our results reveal an unexpected connection between respiration and the DDR and indicate that the benefit of increased dNTP synthesis in the face of DNA damage outweighs possible cellular damage due to increased oxygen metabolism.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/sgxqmBh3kfo" height="1" width="1" alt=""/>
Datum: 21.06.2019


Inhibition of enhancer of zeste homolog 2 (EZH2) overcomes enzalutamide resistance in castration-resistant prostate cancer [Cell Biology]

Enzalutamide, approved by the United States Food and Drug Administration in 2018 for the management of metastatic castration-resistant prostate cancer (CRPC), is an androgen receptor (AR) inhibitor. It blocks androgen binding to the AR, AR nuclear translocation, and AR-mediated DNA binding. Unfortunately, a considerable proportion of tumors eventually develop resistance during the treatment. The molecular mechanisms underlying enzalutamide resistance are not completely understood. Enhancer of zeste homolog 2 (EZH2), the catalytic subunit of polycomb repressor complex 2, has been proposed as a prognostic marker for prostate cancer (PCa). With the goal to test whether EZH2 also plays a critical role in acquisition of enzalutamide resistance in CRPC, here we examined whether EZH2 inhibition/depletion enhances the efficacy of enzalutamide in enzalutamide-resistant PCa cells. We show that combining the EZH2 inhibitor GSK126 with enzalutamide synergistically inhibits cell proliferation and colony formation and promotes apoptosis in enzalutamide-resistant PCa cells. EZH2 depletion also overcomes enzalutamide resistance in both cultured cells and xenograft tumors. Mechanistically, we found that EZH2 directly binds to the promoter of prostate-specific antigen and inhibits its expression in enzalutamide-resistant PCa cells. In agreement, bioinformatics analysis of clinical RNA sequencing data involving GSEA indicated a strong correlation between AR and EZH2 gene expression during PCa progression. Our study provides critical insights into the mechanisms underlying enzalutamide resistance, which may offer new approaches to enhance the efficacy of enzalutamide in CRPC.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/rRyIx0aRGV0" height="1" width="1" alt=""/>
Datum: 21.06.2019


Prolyl hydroxylase 3 stabilizes the p53 tumor suppressor by inhibiting the p53-MDM2 interaction in a hydroxylase-independent manner [Cell Biology]

Prolyl hydroxylase 3 (PHD3) has initially been reported to hydroxylase hypoxia-inducible factor α (HIFα) and mediate HIFα degradation. More recent studies have shown that, in addition to HIFα, PHD3 has also other substrates. Moreover, pHD3 is believed to act as a tumor suppressor, but the underlying mechanism remains to be elucidated. Here, we demonstrate that PHD3 stabilizes p53 in a hydroxylase-independent manner. We found that PHD3 overexpression increases and PHD3 knockdown decreases p53 levels. Mechanistically, PHD3 bound MDM2 proto-oncogene (MDM2) and prevented MDM2 from interacting with p53, thereby inhibiting MDM2-mediated p53 degradation. Interestingly, we found that PHD3 overexpression could enhance p53 in the presence of the prolyl hydroxylase inhibitor dimethyloxalylglycine, and the prolyl hydroxylase activity-deficient variant PHD3-H196A also inhibited the p53-MDM2 interaction and stabilized p53. Genetic ablation of PHD3 decreased p53 protein levels in mice intestinal epithelial cells, but a genetic knockin of PHD3-H196A did not affect p53 protein levels in vivo. These results suggest that the prolyl hydroxylase activity of PHD3 is dispensable for its ability to stabilize p53. We found that both PHD3 and PHD3-H196A suppress the expression of the stem cell-associated gene NANOG and inhibited the properties of colon cancer stem cells through p53. Our results reveal an additional critical mechanism underlying the regulation of p53 expression and highlight that PHD3 plays a role in the suppression of colon cancer cell stemness in a hydroxylase-independent manner.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/dRMOLkqR_aE" height="1" width="1" alt=""/>
Datum: 21.06.2019


A distal super enhancer mediates estrogen-dependent mouse uterine-specific gene transcription of Igf1 (insulin-like growth factor 1) [Gene Regulation]

Insulin-like growth factor 1 (IGF1) is primarily synthesized in and secreted from the liver; however, estrogen (E2), through E2 receptor α (ERα), increases uterine Igf1 mRNA levels. Previous ChIP-seq analyses of the murine uterus have revealed a potential enhancer region distal from the Igf1 transcription start site (TSS) with multiple E2-dependent ERα-binding regions. Here, we show E2-dependent super enhancer-associated characteristics and suggest contact between the distal enhancer and the Igf1 TSS. We hypothesized that this distal super-enhancer region controls E2-responsive induction of uterine Igf1 transcripts. We deleted 430 bp, encompassing one of the ERα-binding sites, thereby disrupting interactions of the enhancer with gene-regulatory factors. As a result, E2-mediated induction of mouse uterine Igf1 mRNA is completely eliminated, whereas hepatic Igf1 expression remains unaffected. This highlights the central role of a distal enhancer in the assembly of the factors necessary for E2-dependent interaction with the Igf1 TSS and induction of uterus-specific Igf1 transcription. Of note, loss of the enhancer did not affect fertility or uterine growth responses. Deletion of uterine Igf1 in a PgrCre;Igf1f/f model decreased female fertility but did not impact the E2-induced uterine growth response. Moreover, E2-dependent activation of uterine IGF1 signaling was not impaired by disrupting the distal enhancer or by deleting the coding transcript. This indicated a role for systemic IGF1, suggested that other growth mediators drive uterine response to E2, and suggested that uterine-derived IGF1 is essential for reproductive success. Our findings elucidate the role of a super enhancer in Igf1 regulation and uterine growth.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/qNdj0FAt908" height="1" width="1" alt=""/>
Datum: 21.06.2019


The glycosyltransferase UGT76E1 significantly contributes to 12-O-glucopyranosyl-jasmonic acid formation in wounded Arabidopsis thaliana leaves [Enzymology]

Jasmonoyl-isoleucine (JA-Ile) is a phytohormone that orchestrates plant defenses in response to wounding, feeding insects, or necrotrophic pathogens. JA-Ile metabolism has been studied intensively, but its catabolism as a potentially important mechanism for the regulation of JA-Ile–mediated signaling is not well-understood. Especially the enzyme(s) responsible for specifically glycosylating 12-hydroxy-jasmonic acid (12-OH-JA) and thereby producing 12-O-glucopyranosyl-jasmonic acid (12-O-Glc-JA) is still elusive. Here, we used co-expression analyses of available Arabidopsis thaliana transcriptomic data, identifying four UDP-dependent glycosyltransferase (UGT) genes as wound-induced and 12-OH-JA–related, namely, UGT76E1, UGT76E2, UGT76E11, and UGT76E12. We heterologously expressed and purified the corresponding proteins to determine their individual substrate specificities and kinetic parameters. We then used an ex vivo metabolite-fingerprinting approach to investigate these proteins in conditions as close as possible to their natural environment, with an emphasis on greatly extending the range of potential substrates. As expected, we found that UGT76E1 and UGT76E2 are 12-OH-JA-UGTs, with UGT76E1 contributing a major in vivo UGT activity, as deduced from Arabidopsis mutants with abolished or increased UGT gene expression. In contrast, recombinant UGT76E11 acted on an unidentified compound and also glycosylated two other oxylipins, 11-hydroxy-7,9,13-hexadecatrienoic acid (11-HHT) and 13-hydroxy-9,11,15-octadecatrienoic acid (13-HOT), which were also accepted by recombinant UGT76E1, UGT76E2, and UGT76E12 enzymes. UGT76E12 glycosylated 12-OH-JA only to a low extent, but also accepted an artificial hydroxylated fatty acid and low amounts of kaempferol. In conclusion, our findings have elucidated the missing step in the wound-induced synthesis of 12-O-glucopyranosyl-jasmonic acid in A. thaliana.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/pTuNAw4gcjE" height="1" width="1" alt=""/>
Datum: 21.06.2019


Correction: Biological functions of miR-29b contribute to positive regulation of osteoblast differentiation. [Additions and Corrections]

VOLUME 284 (2009) PAGES 15676–15684The authors were recently made aware of an accidental duplication of two panels in Fig. 2C: day 4 and day 7 mock samples. Using the original Tiff images of each panel, a corrected Fig. 2C has been assembled. An Inquiry Committee at the University of Massachusetts Medical School determined that the error had no adverse effects on the conclusions reported in the publication, as multiple experimental approaches were presented that validated the findings. This correction does not affect the results or conclusions of this work. The authors apologize for this error.jbc;294/25/10018/F2F1F2Figure 2C<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/9XbiKPKQIK0" height="1" width="1" alt=""/>
Datum: 21.06.2019


Heat shock protein DNAJA1 stabilizes PIWI proteins to support regeneration and homeostasis of planarian Schmidtea mediterranea [Gene Regulation]

PIWI proteins are key regulators of germline and somatic stem cells throughout different evolutionary lineages. However, how PIWI proteins themselves are regulated remains largely unknown. To identify candidate proteins that interact with PIWI proteins and regulate their stability, here we established a yeast two-hybrid (Y2H) assay in the planarian species Schmidtea mediterranea. We show that DNAJA1, a heat shock protein 40 family member, interacts with the PIWI protein SMEDWI-2, as validated by the Y2H screen and co-immunoprecipitation assays. We found that DNAJA1 is enriched in planarian adult stem cells, the nervous system, and intestinal tissues. DNAJA1-knockdown abolished planarian regeneration and homeostasis, compromised stem cell maintenance and PIWI-interacting RNA (piRNA) biogenesis, and deregulated SMEDWI-1/2 target genes. Mechanistically, we observed that DNAJA1 is required for the stability of SMEDWI-1 and SMEDWI-2 proteins. Furthermore, we noted that human DNAJA1 binds to Piwi-like RNA-mediated gene silencing 1 (PIWIL1) and is required for PIWIL1 stability in human gastric cancer cells. In summary, our results reveal not only an evolutionarily conserved functional link between PIWI and DNAJA1 that is essential for PIWI protein stability and piRNA biogenesis, but also an important role of DNAJA1 in the control of proteins involved in stem cell regulation.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/xe8WLhxHZ4Y" height="1" width="1" alt=""/>
Datum: 21.06.2019


The thermophilic biomass-degrading bacterium Caldicellulosiruptor bescii utilizes two enzymes to oxidize glyceraldehyde 3-phosphate during glycolysis [Metabolism]

Caldicellulosiruptor bescii is an extremely thermophilic, cellulolytic bacterium with a growth optimum at 78 °C and is the most thermophilic cellulose degrader known. It is an attractive target for biotechnological applications, but metabolic engineering will require an in-depth understanding of its primary pathways. A previous analysis of its genome uncovered evidence that C. bescii may have a completely uncharacterized aspect to its redox metabolism, involving a tungsten-containing oxidoreductase of unknown function. Herein, we purified and characterized this new member of the aldehyde ferredoxin oxidoreductase family of tungstoenzymes. We show that it is a heterodimeric glyceraldehyde-3-phosphate (GAP) ferredoxin oxidoreductase (GOR) present not only in all known Caldicellulosiruptor species, but also in 44 mostly anaerobic bacterial genera. GOR is phylogenetically distinct from the monomeric GAP-oxidizing enzyme found previously in several Archaea. We found that its large subunit (GOR-L) contains a single tungstopterin site and one iron-sulfur [4Fe-4S] cluster, that the small subunit (GOR-S) contains four [4Fe-4S] clusters, and that GOR uses ferredoxin as an electron acceptor. Deletion of either subunit resulted in a distinct growth phenotype on both C5 and C6 sugars, with an increased lag phase, but higher cell densities. Using metabolomics and kinetic analyses, we show that GOR functions in parallel with the conventional GAP dehydrogenase, providing an alternative ferredoxin-dependent glycolytic pathway. These two pathways likely facilitate the recycling of reduced redox carriers (NADH and ferredoxin) in response to environmental H2 concentrations. This metabolic flexibility has important implications for the future engineering of this and related species.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/ivWK82SKNXk" height="1" width="1" alt=""/>
Datum: 21.06.2019


Effects of histone deacetylase inhibitor Scriptaid and parathyroid hormone on osteocyte functions and metabolism [Metabolism]

Bone is a highly metabolic organ that undergoes continuous remodeling to maintain its structural integrity. During development, bones, in particular osteoblasts, rely on glucose uptake. However, the role of glucose metabolism in osteocytes is unknown. Osteocytes are terminally differentiated osteoblasts orchestrating bone modeling and remodeling. In these cells, parathyroid hormone (PTH) suppresses Sost/sclerostin expression (a potent inhibitor of bone formation) by promoting nuclear translocation of class IIa histone deacetylase (HDAC) 4 and 5 and the repression of myocyte enhancer factor 2 (MEF2) type C. Recently, Scriptaid, an HDAC complex co-repressor inhibitor, has been shown to induce MEF2 activation and exercise-like adaptation in mice. In muscles, Scriptaid disrupts the HDAC4/5 co-repressor complex, increases MEF2C function, and promotes cell respiration. We hypothesized that Scriptaid, by affecting HDAC4/5 localization and MEF2C activation, might affect osteocyte functions. Treatment of the osteocytic Ocy454-12H cells with Scriptaid increased metabolic gene expression, cell respiration, and glucose uptake. Similar effects were also seen upon treatment with PTH, suggesting that both Scriptaid and PTH can promote osteocyte metabolism. Similar to PTH, Scriptaid potently suppressed Sost expression. Silencing of HDAC5 in Ocy454-12H cells abolished Sost suppression but not glucose transporter type 4 (Glut4) up-regulation induced by Scriptaid. These results demonstrate that Scriptaid increases osteocyte respiration and glucose uptake by mechanisms independent of HDAC complex inhibition. In osteocytes, Scriptaid, similar to PTH, increases binding of HDAC5 to Mef2c with suppression of Sost but only partially increases receptor activator of NF-κB ligand (Rankl) expression, suggesting a potential bone anabolic effect.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/Gdlug8tJBQo" height="1" width="1" alt=""/>
Datum: 21.06.2019


C-terminal {alpha}-synuclein truncations are linked to cysteine cathepsin activity in Parkinson's disease [Molecular Bases of Disease]

A pathological feature of Parkinson's disease (PD) is Lewy bodies (LBs) composed of α-synuclein (α-syn) amyloid fibrils. α-Syn is a 140 amino acids–long protein, but truncated α-syn is enriched in LBs. The proteolytic processes that generate these truncations are not well-understood. On the basis of our previous work, we propose that these truncations could originate from lysosomal activity attributable to cysteine cathepsins (Cts). Here, using a transgenic SNCAA53T mouse model, overexpressing the PD-associated α-syn variant A53T, we compared levels of α-syn species in purified brain lysosomes from nonsymptomatic mice with those in age-matched symptomatic mice. In the symptomatic mice, antibody epitope mapping revealed enrichment of C-terminal truncations, resulting from CtsB, CtsL, and asparagine endopeptidase. We did not observe changes in individual cathepsin activities, suggesting that the increased levels of C-terminal α-syn truncations are because of the burden of aggregated α-syn. Using LC-MS and purified α-syn, we identified C-terminal truncations corresponding to amino acids 1–122 and 1–90 from the SNCAA53T lysosomes. Feeding rat dopaminergic N27 cells with exogenous α-syn fibrils confirmed that these fragments originate from incomplete fibril degradation in lysosomes. We mimicked these events in situ by asparagine endopeptidase degradation of α-syn fibrils. Importantly, the resulting C-terminally truncated fibrils acted as superior seeds in stimulating α-syn aggregation compared with that of the full-length fibrils. These results unequivocally show that C-terminal α-syn truncations in LBs are linked to Cts activities, promote amyloid formation, and contribute to PD pathogenesis.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/XzCZ8t0Miy8" height="1" width="1" alt=""/>
Datum: 21.06.2019


Genome-wide CRISPR-based gene knockout screens reveal cellular factors and pathways essential for nasopharyngeal carcinoma [Cell Biology]

Early diagnosis of nasopharyngeal carcinoma (NPC) is difficult because of a lack of specific symptoms. Many patients have advanced disease at diagnosis, and these patients respond poorly to treatment. New treatments are therefore needed to improve the outcome of NPC. To better understand the molecular pathogenesis of NPC, here we used an NPC cell line in a genome-wide CRISPR-based knockout screen to identify the cellular factors and pathways essential for NPC (i.e. dependence factors). This screen identified the Moz, Ybf2/Sas3, Sas2, Tip60 histone acetyl transferase complex, NF-κB signaling, purine synthesis, and linear ubiquitination pathways; and MDM2 proto-oncogene as NPC dependence factors/pathways. Using gene knock out, complementary DNA rescue, and inhibitor assays, we found that perturbation of these pathways greatly reduces the growth of NPC cell lines but does not affect growth of SV40-immortalized normal nasopharyngeal epithelial cells. These results suggest that targeting these pathways/proteins may hold promise for achieving better treatment of patients with NPC.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/1VFZiEIrkTE" height="1" width="1" alt=""/>
Datum: 21.06.2019


USP9X-mediated deubiquitination of B-cell CLL/lymphoma 9 potentiates Wnt signaling and promotes breast carcinogenesis [Signal Transduction]

Hyperactivation of the canonical Wnt-signaling pathway is a prominent feature of a number of human malignancies. Transcriptional activation of this signaling cascade depends on the formation of the β-catenin–B-cell CLL/lymphoma 9 (BCL9)–pygopus (PYGO) family plant homeodomain finger 1 complex, yet how the assembly of this complex is regulated remains to be investigated. Here, using MCF-7, HeLa, HEK293T, MDA–MB-231, and Sf9 cells, along with immunoblotting and immunofluorescence, nano-HPLC–MS/MS, deubiquitination, immunoprecipitation, and chromatin immunoprecipitation (ChIP) assays, we report that BCL9 physically associates with a protein deubiquitinase, ubiquitin-specific peptidase 9, X-linked (USP9X), and that USP9X removes Lys-63–linked polyubiquitin on Lys-212 of BCL9. Importantly, the USP9X-mediated BCL9 deubiquitination facilitated the formation of the β-catenin–BCL9–PYGO complex, thereby potentiating the transcriptional activation of Wnt/β-catenin target genes. We also show that USP9X-mediated BCL9 deubiquitination promotes the proliferation and invasion of breast cancer cells. Together, these results uncover USP9X as a deubiquitinase of BCL9, implicating USP9X in Wnt/β-catenin signaling and breast carcinogenesis.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/TSMFZPztj8Y" height="1" width="1" alt=""/>
Datum: 21.06.2019


Setting fire to fat [Lipids]

Adropin is a liver-secreted peptide that is crucial for metabolic health. However, the molecular functions and clinical significance of adropin have not been adequately explored. Butler et al. now investigate adropin expression profiles and links to cardiometabolic disease risk in two nonhuman primate models, increasing our translational and mechanistic understanding of this fascinating hormone.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/BiGj6eYmjdg" height="1" width="1" alt=""/>
Datum: 21.06.2019


Porcine deltacoronavirus enters cells via two pathways: A protease-mediated one at the cell surface and another facilitated by cathepsins in the endosome [Microbiology]

Porcine deltacoronavirus (PDCoV) is a pathogen belonging to the genus Deltacoronavirus that in 2014 caused outbreaks of piglet diarrhea in the United States. To identify suitable therapeutic targets, a more comprehensive understanding of the viral entry pathway is required, particularly of the role of proteases. Here, we identified the proteases that activate the viral spike (S) glycoprotein to initiate cell entry and also pinpointed the host-cellular pathways that PDCoV uses for entry. Our results revealed that cathepsin L (CTSL) and cathepsin B (CTSB) in lysosomes and extracellular trypsin in cell cultures independently activate the S protein for membrane fusion. Pretreating the cells with the lysosomal acidification inhibitor bafilomycin-A1 (Baf-A1) completely inhibited PDCoV entry, and siRNA-mediated ablation of CTSL or CTSB expression significantly reduced viral infection, indicating that PDCoV uses an endosomal pathway for entry. Of note, trypsin treatment of cell cultures also activated PDCoV entry, even when the endosomal pathway was inhibited. This observation indicated that trypsin-induced S protein cleavage and activation in cell cultures enables viral entry directly from the cell surface. Our results provide critical insights into the PDCoV infection mechanism, uncovering two distinct viral entry pathways: one through cathepsin L and cathepsin B in the endosome and another via a protease at the cell surface. Because PDCoV infection sites represent a proteases-rich environment, these findings suggest that endosome inhibitor treatment alone is insufficient to block PDCoV entry into intestinal epithelial cells in vivo. Therefore, approaches that inhibit viral entry from the cell membrane should also be considered.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/245Lyfmw95Y" height="1" width="1" alt=""/>
Datum: 21.06.2019


Conserved juxtamembrane domains in the yeast golgin Coy1 drive assembly of a megadalton-sized complex and mediate binding to tethering and SNARE proteins [Membrane Biology]

The architecture and organization of the Golgi complex depend on a family of coiled-coil proteins called golgins. Golgins are thought to form extended homodimers that are C-terminally anchored to Golgi membranes, whereas their N termini extend into the cytoplasm to initiate vesicle capture. Previously, we reported that the Saccharomyces cerevisiae golgin Coy1 contributes to intra-Golgi retrograde transport and binds to the conserved oligomeric Golgi (COG) complex and multiple retrograde Golgi Q-SNAREs (where SNARE is soluble NSF-attachment protein receptor). Here, using various engineered yeast strains, membrane protein extraction and fractionation methods, and in vitro binding assays, we mapped the Coy1 regions responsible for these activities. We also report that Coy1 assembles into a megadalton-size complex and that assembly of this complex depends on the most C-terminal coiled-coil and a conserved region between this coiled-coil and the transmembrane domain of Coy1. We found that this conserved region is necessary and sufficient for binding the SNARE protein Sed5 and the COG complex. Mutagenesis of conserved arginine residues within the C-terminal coiled-coil disrupted oligomerization, binding, and function of Coy1. Our findings indicate that the stable incorporation of Coy1 into a higher-order oligomer is required for its interactions and role in maintaining Golgi homeostasis. We propose that Coy1 assembles into a docking platform that directs COG-bound vesicles toward cognate SNAREs on the Golgi membrane.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/iHdiT2Ajsc0" height="1" width="1" alt=""/>
Datum: 21.06.2019


The yeast protein Mam33 functions in the assembly of the mitochondrial ribosome [Protein Synthesis and Degradation]

Mitochondrial ribosomes are functionally specialized for the synthesis of several essential inner membrane proteins of the respiratory chain. Although remarkable progress has been made toward understanding the structure of mitoribosomes, the pathways and factors that facilitate their biogenesis remain largely unknown. The long unstructured domains of unassembled ribosomal proteins are highly prone to misfolding and often require dedicated chaperones to prevent aggregation. To date, chaperones that ensure safe delivery to the assembling ribosome have not been identified in the mitochondrion. In this study, a respiratory synthetic lethality screen revealed a role for an evolutionarily conserved mitochondrial matrix protein called Mam33 in Saccharomyces cerevisiae mitoribosome biogenesis. We found that the absence of Mam33 results in misassembled, aggregated ribosomes and a respiratory lethal phenotype in combination with other ribosome-assembly mutants. Using sucrose gradient sedimentation, native affinity purifications, in vitro binding assays, and SILAC-based quantitative proteomics, we found that Mam33 does not associate with the mature mitoribosome, but directly binds a subset of unassembled large subunit proteins. Based on these data, we propose that Mam33 binds specific mitoribosomal proteins to ensure proper assembly.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/4VxTW-7rHV8" height="1" width="1" alt=""/>
Datum: 21.06.2019


Pathogenic tau does not drive activation of the unfolded protein response [Molecular Bases of Disease]

The unfolded protein response (UPR) is commonly associated with a range of neurodegenerative diseases, and targeting UPR components has been suggested as a therapeutic strategy. The UPR surveys protein folding within the endoplasmic reticulum. However, many of the misfolded proteins that accumulate in neurodegeneration are localized so that they do not directly cause endoplasmic reticulum triggers that activate this pathway. Here, using a transgenic mouse model and primary cell cultures along with quantitative PCR, immunoblotting, and immunohistochemistry, we tested whether the UPR is induced in in vivo and in vitro murine models of tauopathy that are based on expression of mutant tauP301L. We found no evidence for the UPR in the rTg4510 mouse model, in which mutant tau is transgenically expressed under the control of tetracycline-controlled transactivator protein. This observation was supported by results from acute experiments in which neuronal cultures expressed mutant tau and accumulated misfolded cytoplasmic tau aggregates but exhibited no UPR activation. These results suggest that the UPR is not induced as a response to tau misfolding and aggregation despite clear evidence for progressive cellular dysfunction and degeneration. We propose that caution is needed when evaluating the implied significance of the UPR as a critical determinant across major neurodegenerative diseases.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/Y2Py9jqx9yg" height="1" width="1" alt=""/>
Datum: 21.06.2019


E46K-like {alpha}-synuclein mutants increase lipid interactions and disrupt membrane selectivity [Molecular Biophysics]

Parkinson's disease (PD) is one of the most common neurodegenerative disorders, and both genetic and histopathological evidence have implicated the ubiquitous presynaptic protein α-synuclein (αSyn) in its pathogenesis. Recent work has investigated how disrupting αSyn's interaction with membranes triggers trafficking defects, cellular stress, and apoptosis. Special interest has been devoted to a series of mutants exacerbating the effects of the E46K mutation (associated with autosomal dominant PD) through homologous Glu-to-Lys substitutions in αSyn's N-terminal region (i.e. E35K and E61K). Such E46K-like mutants have been shown to cause dopaminergic neuron loss and severe but L-DOPA–responsive motor defects in mouse overexpression models, presenting enormous translational potential for PD and other “synucleinopathies.” In this work, using a variety of biophysical techniques, we characterize the molecular pathology of E46K-like αSyn mutants by studying their structure and membrane-binding and remodeling abilities. We find that, although a slight increase in the mutants' avidity for synaptic vesicle–like membranes can be detected, most of their deleterious effects are connected to their complete disruption of αSyn's curvature selectivity. Indiscriminate binding can shift αSyn's subcellular localization away from its physiological interactants at the synaptic bouton toward trafficking vesicles and organelles, as observed in E46K-like cellular and murine models, as well as in human pathology. In conclusion, our findings suggest that a loss of curvature selectivity, rather than increased membrane affinity, could be the critical dyshomeostasis in synucleinopathies.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/3VrQBsKNYoQ" height="1" width="1" alt=""/>
Datum: 21.06.2019


Phosphorylation of Tyr-950 in the proteasome scaffolding protein RPN2 modulates its interaction with the ubiquitin receptor RPN13 [Protein Synthesis and Degradation]

Protein substrates are targeted to the 26S proteasome through several ubiquitin receptors. One of these receptors, RPN13, is recruited to the proteasome by binding of its N-terminal pleckstrin-like receptor of ubiquitin (PRU) domain to C-terminal residues of the scaffolding protein RPN2. The RPN13 PRU domain is followed by a flexible linker and a C-terminal deubiquitylase adaptor (DEUBAD) domain, which recruits and activates the deubiquitylase UCH37. Both RPN13 and UCH37 have been implicated in human cancers, and inhibitors of the RPN2–RPN13 interaction are being developed as potential therapeutic anticancer agents. Our current study builds on the recognition that a residue central to the RPN2–RPN13 interaction, RPN2 Tyr-950, is phosphorylated in Jurkat cells. We found that the Tyr-950 phosphorylation enhances binding to RPN13. The crystal structure of the RPN2–RPN13 pTyr-950–ubiquitin complex was determined at 1.76-Å resolution and reveals specific interactions with positively charged side chains in RPN13 that explain how phosphorylation increases binding affinity without inducing conformational change. Mutagenesis and quantitative binding assays were then used to validate the crystallographic interface. Our findings support a model in which RPN13 recruitment to the proteasome is enhanced by phosphorylation of RPN2 Tyr-950, have important implications for efforts to develop specific inhibitors of the RPN2–RPN13 interaction, and suggest the existence of a previously unknown stress-response pathway.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/KW7YsB7gWJw" height="1" width="1" alt=""/>
Datum: 21.06.2019


Smoothened-dependent and -independent pathways in mammalian noncanonical Hedgehog signaling [Signal Transduction]

Hedgehog proteins are pivotal morphogens acting through a canonical pathway involving first activation of ligand binding to Patched followed by alleviation of Smoothened receptor inhibition, leading to activation of Gli transcription factors. Noncanonical Hedgehog signaling remains poorly characterized but is thought to be mainly dependent on Smoothened. However, Smoothened inhibitors have yielded only partial success in combating Hedgehog signal transduction–dependent cancer, suggesting that noncanonical Smoothened-independent pathways also are clinically relevant. Moreover, several Smoothened-dependent effects (e.g. neurite projection) do not require transcriptional activation, further suggesting biological importance of noncanonical Smoothened-dependent pathways. We comprehensively characterized the cellular kinome in Hedgehog-challenged murine WT and Smoothened−/− fibroblasts as well as Smoothened agonist–stimulated cells. A peptide assay–based kinome analysis (in which cell lysates are used to phosphorylate specific kinase substrates), along with endocytosis, Lucifer Yellow–based, and immunoblotting assays, identified an elaborate signaling network of both Smoothened-dependent and -independent pathways that mediates actin reorganization through Src-like kinases, activates various proinflammatory signaling cascades, and concomitantly stimulates Wnt and Notch signaling while suppressing bone morphogenetic protein (BMP) signaling. The contribution of noncanonical Smoothened-independent signaling to the overall effects of Hedgehog on cellular physiology appears to be much larger than previously envisioned and may explain the transcriptionally independent effects of Hedgehog signaling on cytoskeleton. The observation that Patched-dependent, Smoothened-independent, noncanonical Hedgehog signaling increases Wnt/Notch signaling provides a possible explanation for the failure of Smoothened antagonists in combating Hedgehog-dependent but Smoothened inhibitor–resistant cancer. Our findings suggest that inhibiting Hedgehog–Patched interaction could result in more effective therapies as compared with conventional Smoothened-directed therapies.<img src="http://feeds.feedburner.com/~r/jbc/SUcv/~4/pN7TNmIzINc" height="1" width="1" alt=""/>
Datum: 21.06.2019


 


Category: Current Chemistry Research

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