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Unfolded Proteins

Smita Gupta, Sunita Yadav, Venkatesan Suryanarayanan, Sanjeev K Singh, Jitendra K Saxena
Guanylate kinase is one of the key enzymes in nucleotide biosynthesis. The study highlights the structural and functional properties of Brugia malayi Guanylate kinase (BmGK) in the presence of chemical denaturants. An inactive, partially unfolded, dimeric intermediate was observed at 1-2M urea while GdnCl unfolding showed monomer molten globule like intermediate at 0.8-1.0M. The results also illustrate the protective role of substrates in maintaining the integrity of the enzyme. The thermo stability of protein was found to be significantly enhanced in the presence of the substrates...
October 14, 2016: International Journal of Biological Macromolecules
Tapasi Rana, Pravallika Kotla, Roderick Fullard, Marina Gorbatyuk
Expression of T17M rhodopsin (T17M) in rods activates the Unfolded Protein Response (UPR) and leads to the development of autosomal dominant retinitis pigmentosa (adRP). The rod death occurs in adRP retinas prior to cone photoreceptor death, so the mechanism by which cone photoreceptors die remains unclear. Therefore, the goal of the study was to verify whether UPR in rods induces TNFa-mediated signaling to the cones and to determine whether the TNFa deficit could prevent adRP cone cell death. Primary rod photoreceptors and cone-derived 661W cells transfected with siRNA against TNFa were treated with tunicamycin to mimic activation of UPR in T17M retinas expressing normal and reduced TNFa levels...
October 14, 2016: Biochimica et Biophysica Acta
Fiorenza Fumagalli, Julia Noack, Timothy J Bergmann, Eduardo Cebollero Presmanes, Giorgia Brambilla Pisoni, Elisa Fasana, Ilaria Fregno, Carmela Galli, Marisa Loi, Tatiana Soldà, Rocco D'Antuono, Andrea Raimondi, Martin Jung, Armin Melnyk, Stefan Schorr, Anne Schreiber, Luca Simonelli, Luca Varani, Caroline Wilson-Zbinden, Oliver Zerbe, Kay Hofmann, Matthias Peter, Manfredo Quadroni, Richard Zimmermann, Maurizio Molinari
The endoplasmic reticulum (ER) is a site of protein biogenesis in eukaryotic cells. Perturbing ER homeostasis activates stress programs collectively called the unfolded protein response (UPR). The UPR enhances production of ER-resident chaperones and enzymes to reduce the burden of misfolded proteins. On resolution of ER stress, ill-defined, selective autophagic programs remove excess ER components. Here we identify Sec62, a constituent of the translocon complex regulating protein import in the mammalian ER, as an ER-resident autophagy receptor...
October 17, 2016: Nature Cell Biology
Haiying Shen, Kiyoon Kim, Yoojung Oh, Kyung Sik Yoon, Hyung Hwan Baik, Sung Soo Kim, Joohun Ha, Insug Kang, Wonchae Choe
β-N-methylamino-L-alanine (BMAA) is a neurotoxin that is closely associated with the incidence of amyotrophic lateral sclerosis, Parkinson's disease and Alzheimer's disease. In cultured neuronal cells, BMAA notably induces the upregulation of endoplasmic reticulum (ER) chaperons and activates the unfolded protein response (UPR) receptor pathways of protein kinase RNA‑like endoplasmic reticulum kinase, inositol‑requiring kinase 1 and transcription factor 6. The ER stress‑specific protein CCAAT/‑enhancer‑binding protein homologous protein (CHOP) affords pro‑apoptotic responses that cause mitochondrial damage and caspase activation...
October 5, 2016: Molecular Medicine Reports
Noemí Arce-Varas, Giulia Abate, Chiara Prandelli, Carmen Martínez, Fernando Cuetos, Manuel Menéndez, Mariagrazia Marziano, David Cabrera-García, María Teresa Fernández-Sánchez, Antonello Novelli, Maurizio Memo, Daniela Uberti
Many studies suggest oxidative stress as an early feature of Alzheimer's Disease (AD). However, evidence of established oxidative stress in AD peripheral cells is still inconclusive, possibly due to both, differences in the type of samples and the heterogeneity of oxidative markers used in different studies. Here we measured the activity of Superoxide Dismutase, Catalase and Glutathione Peroxidase both in the extracellular and the intracellular blood compartments of AD, MCI and control subjects. The amount of an open isoform of p53 protein (unfolded p53), resulting from oxidative modifications was also determined...
October 10, 2016: Current Alzheimer Research
Zhe Meng, Cristina Ruberti, Zhizhong Gong, Federica Brandizzi
Completion of a plant's life cycle depends on successful prioritization of signaling favoring either growth or defense. Although hormones are pivotal regulators of growth-defense tradeoffs, the underlying signaling mechanisms remain obscure. The unfolded protein response (UPR) is essential for physiological growth as well as endoplasmic reticulum (ER)-stress management in unfavorable growth conditions. The plant UPR transducers are the kinase and ribonuclease IRE1 and the transcription factors bZIP28 and bZIP60...
October 16, 2016: Plant Journal: for Cell and Molecular Biology
Toru Hosoi, Yuka Suyama, Takaaki Kayano, Koichiro Ozawa
Leptin resistance is one of the mechanisms involved in the pathophysiology of obesity. The present study showed that glucose deprivation inhibited leptin-induced phosphorylation of signal transducer and activator of transcription 3 (STAT3) and signal transducer and activator of transcription 5 (STAT5) in neuronal cells. Flurbiprofen reversed glucose deprivation-mediated attenuation of STAT3, but not STAT5 activation, in leptin-treated cells. Glucose deprivation increased C/EBP-homologous protein and glucose regulated protein 78 induction, indicating the activation of unfolded protein responses (UPR)...
2016: Frontiers in Pharmacology
Romana Parveen, Tooba Naz Shamsi, Sadaf Fatima
This review helps to understand protein misfolding events, which results in protein aggregation, and hence to related neurodegenerative diseases. Many chaperones and folding factors are found inside the cell system for the proper folding of protein. If protein gets misfolded, it may accumulate in cells and can lead to several fatal diseases. In some cases, misfolded proteins aggregated in form of loop-sheet polymer and amyloid fibril when they escape the degradation process and leads to neurodegenerative disorders...
October 13, 2016: International Journal of Biological Macromolecules
Cody S Shirriff, John J Heikkila
Endoplasmic reticulum (ER) stress can result in the accumulation of unfolded/misfolded protein in the ER lumen, which can trigger the unfolded protein response (UPR) resulting in the activation of various genes including immunoglobulin-binding protein (BiP; also known as glucose-regulated protein 78 or HSPA5). BiP, an ER heat shock protein 70 (HSP70) family member, binds to unfolded protein, inhibits their aggregation and re-folds them in an ATP-dependent manner. While cadmium, an environmental contaminant, was shown to induce the accumulation of HSP70 in vertebrate cells, less information is available regarding the effect of this metal on BiP accumulation or function...
October 13, 2016: Comparative Biochemistry and Physiology. Toxicology & Pharmacology: CBP
Ranjeet Kumar, Candan Ariöz, Yaozong Li, Niklas Bosaeus, Sandra Rocha, Pernilla Wittung-Stafshede
After cellular uptake, Copper (Cu) ions are transferred from the chaperone Atox1 to the Wilson disease protein (ATP7B) for incorporation into Cu-dependent enzymes in the secretory pathway. Human ATP7B is a large multi-domain membrane-spanning protein which, in contrast to homologues in other organisms, has six similar cytoplasmic metal-binding domains (MBDs). The reason for multiple MBDs is proposed to be indirect modulation of enzymatic activity and it is thus intriguing that point mutations in MBDs can promote Wilson disease...
October 15, 2016: Biometals: An International Journal on the Role of Metal Ions in Biology, Biochemistry, and Medicine
Wolfgang Voos, Witold Jaworek, Anne Wilkening, Michael Bruderek
Mitochondria are essential constituents of a eukaryotic cell by supplying ATP and contributing to many mayor metabolic processes. As endosymbiotic organelles, they represent a cellular subcompartment exhibiting many autonomous functions, most importantly containing a complete endogenous machinery responsible for protein expression, folding and degradation. This article summarizes the biochemical processes and the enzymatic components that are responsible for maintaining mitochondrial protein homoeostasis. As mitochondria lack a large part of the required genetic information, most proteins are synthesized in the cytosol and imported into the organelle...
October 15, 2016: Essays in Biochemistry
Annika Strauch, Martin Haslbeck
All organisms rely on a conserved cellular machinery supporting and controlling the life cycle of proteins: the proteostasis network. Within this network, the main players that determine the fate of proteins are molecular chaperones, the ubiquitin-proteasome and the lysosome-autophagy systems. sHsps (small heat-shock proteins) represent one family of molecular chaperones found in all domains of life. They prevent irreversible aggregation of unfolded proteins and maintain proteostasis by stabilizing promiscuously a variety of non-native proteins in an ATP-independent manner...
October 15, 2016: Essays in Biochemistry
Takujiro Homma, Junichi Fujii
Heat stress induces intracellular protein denaturation and endoplasmic reticulum (ER) stress, which elicits unfolded protein response (UPR) in cells. UPR involves three ER-localized sensor proteins: the inositol-requiring protein 1α (IRE1α), the dsRNA-activated protein kinase-like ER kinase (PERK), and activating transcription factor-6 (ATF6). However, the precise mechanism by which cells deal with heat stress remains to be elucidated. We report herein that heat stress effectively activates all branches of the UPR...
October 12, 2016: Experimental Cell Research
Roi Isaac, Ido Goldstein, Noa Furth, Neta Zilber, Sarina Streim, Sigalit Boura-Halfon, Eytan Elhanany, Varda Rotter, Moshe Oren, Yehiel Zick
Earlier reported small interfering RNA (siRNA) high-throughput screens, identified seven-transmembrane superfamily member 3 (TM7SF3) as a novel inhibitor of pancreatic β-cell death. Here we show that TM7SF3 maintains protein homeostasis and promotes cell survival through attenuation of ER stress. Overexpression of TM7SF3 inhibits caspase 3/7 activation. In contrast, siRNA-mediated silencing of TM7SF3 accelerates ER stress and activation of the unfolded protein response (UPR). This involves inhibitory phosphorylation of eukaryotic translation initiation factor 2α activity and increased expression of activating transcription factor-3 (ATF3), ATF4 and C/EBP homologous protein, followed by induction of apoptosis...
October 14, 2016: Cell Death and Differentiation
Bani K Pathak, Surojit Mondal, Chandana Barat
The ability of the ribosome to assist in folding of proteins both in vitro and in vivo is well documented and is a non-translational function of the ribosome. The interaction of the unfolded protein with the peptidyltransferase centre (PTC) of the bacterial large ribosomal subunit is followed by release of the protein in the folding competent state and rapid dissociation of ribosomal subunits. Our studies demonstrate that the PTC specific antibiotics, chloramphenicol and blasticidin S inhibit unfolded protein mediated subunit dissociation...
October 14, 2016: Letters in Applied Microbiology
Amy M Lange, Ekaterina S Altynova, Giang N Nguyen, Denise E Sabatino
Factor VIII (FVIII) is a large glycoprotein that is challenging to express both in vitro and in vivo. Several studies suggest that high levels of FVIII expression can lead to cellular stress. After gene transfer, transgene expression is restricted to a subset of cells and the increased FVIII load per cell may impact activation of the unfolded protein response. We sought to determine whether increased FVIII expression in mice after adeno-associated viral liver gene transfer would affect the unfolded protein response and/or immune response to the transgene...
2016: Molecular Therapy. Methods & Clinical Development
Irene Zolotukhin, David M Markusic, Brett Palaschak, Brad E Hoffman, Meera A Srikanthan, Roland W Herzog
Hemophilia A and B are coagulation disorders resulting from the loss of functional coagulation factor VIII (FVIII) or factor IX proteins, respectively. Gene therapy for hemophilia with adeno-associated virus vectors has shown efficacy in hemophilia B patients. Although hemophilia A patients are more prevalent, the development of therapeutic adeno-associated virus vectors has been impeded by the size of the F8 cDNA and impaired secretion of FVIII protein. Further, it has been reported that over-expression of the FVIII protein induces endoplasmic reticulum stress and activates the unfolded protein response pathway both in vitro and in hepatocytes in vivo, presumably due to retention of misfolded FVIII protein within the endoplasmic reticulum...
2016: Molecular Therapy. Methods & Clinical Development
Meng Chen, Nathaniel Rothman, Yuanqing Ye, Jian Gu, Paul A Scheet, Maosheng Huang, David W Chang, Colin P Dinney, Debra T Silverman, Jonine D Figueroa, Stephen J Chanock, Xifeng Wu
Genome-wide association studies (GWAS) are designed to identify individual regions associated with cancer risk, but only explain a small fraction of the inherited variability. Alternative approach analyzing genetic variants within biological pathways has been proposed to discover networks of susceptibility genes with additional effects. The gene set enrichment analysis (GSEA) may complement and expand traditional GWAS analysis to identify novel genes and pathways associated with bladder cancer risk. We selected three GSEA methods: Gen-Gen, Aligator, and the SNP Ratio Test to evaluate cellular signaling pathways involved in bladder cancer susceptibility in a Texas GWAS population...
July 2016: Genes & Cancer
Fernando Bergasa-Caceres, Herschel A Rabitz
A simple analytical model is applied to study the effects of macromolecular crowding on the stability of partially folded states of the murine prion protein. It is found that relatively low levels of macromolecular crowding stabilize the partially folded states. The magnitude of the stabilization effect is similar for the partially folded to that of the fully folded state. Thus, the model suggests that it is on-pathway molten globule-like states, rather than partially folded states arising from unfolding of the native state, which play a key role in the pathogenic interconversion mechanism under crowded conditions...
October 13, 2016: Journal of Physical Chemistry. B
Prasad Kottayil Padmanabhan, Ouafa Zghidi-Abouzid, Mukesh Samant, Carole Dumas, Bruno Guedes Aguiar, Jerome Estaquier, Barbara Papadopoulou
DDX3 is a highly conserved member of ATP-dependent DEAD-box RNA helicases with multiple functions in RNA metabolism and cellular signaling. Here, we describe a novel function for DDX3 in regulating the mitochondrial stress response in the parasitic protozoan Leishmania. We show that genetic inactivation of DDX3 leads to the accumulation of mitochondrial reactive oxygen species (ROS) associated with a defect in hydrogen peroxide detoxification. Upon stress, ROS production is greatly enhanced, causing mitochondrial membrane potential loss, mitochondrial fragmentation, and cell death...
October 13, 2016: Cell Death & Disease
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