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Shu-Yu Wu, Ping Zou, Alexandra W Fuller, Sanjay Mishra, Zhen Wang, Kevin L Schey, Hassane S Mchaourab
The refractivity and transparency of the ocular lens is dependent on the stability and solubility of the crystallins in the fiber cells. A number of mutations of lens crystallins have been associated with dominant cataracts in humans and mice. Of particular interest were γB- and γD-crystallin mutants linked to dominant cataracts in mouse models. While thermodynamically destabilized and aggregation-prone, these mutants were found to have weak affinity to the resident chaperone α-crystallin in vitro To better understand the mechanism of the cataract phenotype, we transgenically expressed different γD-crystallin mutants in the zebrafish lens, and observed a range of lens defects that arise primarily from the aggregation of the mutant proteins...
October 21, 2016: Journal of Biological Chemistry
Laura de Diego-García, Mercedes Ramírez-Escudero, Álvaro Sebastián-Serrano, Juan Ignacio Diaz-Hernández, Jesús Pintor Just, José J Lucas, Miguel Díaz-Hernández
The Ubiquitin-Proteasome System (UPS) is essential for the regulation of the cellular proteostasis. Indeed, it has been postulated that an UPS dysregulation is the common mechanism that underlies several neurological disorders. Considering that extracellular nucleotides, through their selective P2Y2 receptor (P2Y2R), play a neuroprotective role in various neurological disorders that course with an UPS impairment, we wonder if this neuroprotective capacity resulted from their ability to modulate the UPS. Using a cellular model expressing two different UPS reporters, we found that the stimulation of P2Y2R by its selective agonist Up4U induced a significant reduction of UPS reporter levels...
October 18, 2016: Biochimica et Biophysica Acta
Sofia Lisanti, David S Garlick, Kelly G Bryant, Michele Tavecchio, Gordon B Mills, Yiling Lu, Andrew V Kossenkov, Louise C Showe, Lucia R Languino, Dario C Altieri
Protein homeostasis, or proteostasis is required for mitochondrial function, but its role in cancer is controversial. Here, we show that transgenic mice expressing the mitochondrial chaperone, TRAP1 in the prostate develop epithelial hyperplasia and cellular atypia. When examined on a Pten+/- background, a common alteration in human prostate cancer, TRAP1 transgenic mice showed accelerated incidence of invasive prostatic adenocarcinoma, characterized by increased cell proliferation and reduced apoptosis, in situ...
October 17, 2016: Journal of Biological Chemistry
Koning Shen, Barbara Calamini, Jonathan A Fauerbach, Boxue Ma, Sarah H Shahmoradian, Ivana L Serrano Lachapel, Wah Chiu, Donald C Lo, Judith Frydman
Many neurodegenerative diseases are linked to amyloid aggregation. In Huntington's disease (HD), neurotoxicity correlates with increased aggregation propensity of a polyglutamine (polyQ) expansion in exon 1 of mutant huntingtin protein (mHtt). Here we establish how the domains flanking the polyQ tract shape the mHtt conformational landscape in vitro and in neurons. In vitro, the flanking domains have opposing effects on the conformation and stabilities of oligomers and amyloid fibrils. The N-terminal N17 promotes amyloid fibril formation, while the C-terminal Proline Rich Domain destabilizes fibrils and enhances oligomer formation...
October 18, 2016: ELife
Elsa Perrody, Laurence Abrami, Michal Feldman, Beatrice Kunz, Sylvie Urbé, Gisou van der Goot
Many membrane proteins fold inefficiently and require the help of enzymes and chaperones. Here we reveal a novel folding assistance system that operates on membrane proteins from the cytosolic side of the endoplasmic reticulum (ER). We show that folding of the Wnt signaling coreceptor LRP6 is promoted by ubiquitination of a specific lysine, retaining it in the ER while avoiding degradation. Subsequent ER exit requires removal of ubiquitin from this lysine by the deubiquitinating enzyme USP19. This ubiquitination-deubiquitination is conceptually reminiscent of the glucosylation-deglucosylation occurring in the ER lumen during the calnexin/calreticulin folding cycle...
October 18, 2016: ELife
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
Martin Gamerdinger
The biogenesis of new polypeptides by ribosomes and their subsequent correct folding and localization to the appropriate cellular compartments are essential key processes to maintain protein homoeostasis. These complex mechanisms are governed by a repertoire of protein biogenesis factors that directly bind to the ribosome and chaperone nascent polypeptide chains as soon as they emerge from the ribosomal tunnel exit. This nascent chain 'welcoming committee' regulates multiple co-translational processes including protein modifications, folding, targeting and degradation...
October 15, 2016: Essays in Biochemistry
Cheryl Li, Olivia Casanueva
Abundant evidence shows that the genome is not as static as once thought and that gene expression can be reversibly modulated by the environment. In some cases, these changes can be transmitted to the next generation even if the environment has reverted. Such transgenerational epigenetic inheritance requires that information be stored in the germline in response to exogenous stressors. One of the most elusive questions in the field of epigenetic inheritance is the identity of such inherited factor(s). Answering this question would allow us to understand how the environment can shape human populations for multiple generations and may help to explain the rapid rise in obesity and neurodegenerative diseases in modern society...
October 15, 2016: Essays in Biochemistry
Matthew P Jackson, Eric W Hewitt
Proteostasis refers to the regulation of the cellular concentration, folding, interactions and localization of each of the proteins that comprise the proteome. One essential element of proteostasis is the disposal of misfolded proteins by the cellular pathways of protein degradation. Lysosomes are an important site for the degradation of misfolded proteins, which are trafficked to this organelle by the pathways of macroautophagy, chaperone-mediated autophagy and endocytosis. Conversely, amyloid diseases represent a failure in proteostasis, in which proteins misfold, forming amyloid deposits that are not degraded effectively by cells...
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
John S Bett
Cells have developed an evolutionary obligation to survey and maintain proteome fidelity and avoid the possible toxic consequences of protein misfolding and aggregation. Disturbances to protein homoeostasis (proteostasis) can result in severe cellular phenotypes and are closely linked with the accumulation of microscopically visible deposits of aggregated proteins. These include inclusion bodies found in AD (Alzheimer's disease), HD (Huntington's disease) and ALS (amyotrophic lateral sclerosis) patient neurons...
October 15, 2016: Essays in Biochemistry
Daniel O'Brien, Patricija van Oosten-Hawle
Cells have developed robust adaptation mechanisms to survive environmental conditions that challenge the integrity of their proteome and ensure cellular viability. These are stress signalling pathways that integrate extracellular signals with the ability to detect and efficiently respond to protein-folding perturbations within the cell. Within the context of an organism, the cell-autonomous effects of these signalling mechanisms are superimposed by cell-non-autonomous stress signalling pathways that allow co-ordination of stress responses across tissues...
October 15, 2016: Essays in Biochemistry
Annabel Y Minard, Martin K L Wong, Rima Chaudhuri, Shi-Xiong Tan, Sean J Humphrey, Benjamin L Parker, Jean Y Yang, D Ross Laybutt, Gregory J Cooney, Adelle C F Coster, Jacqueline Stoeckli, David E James
Hyperinsulinemia, which is associated with aging and metabolic disease, may lead to defective protein homeostasis (proteostasis) due to hyper-activation of insulin sensitive pathways such as protein synthesis. We investigated the effect of chronic hyperinsulinemia on proteostasis, by generating a time-resolved map of insulin-regulated protein turnover in adipocytes using metabolic pulse chase labelling and high-resolution mass spectrometry. Hyperinsulinemia increased the synthesis of nearly half of all detected proteins and did not affect protein degradation, despite suppressing autophagy...
October 13, 2016: Journal of Biological Chemistry
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
Chunya Ni, Marie-Sophie Narzt, Ionela-Mariana Nagelreiter, Cheng Feng Zhang, Lionel Larue, Heidemarie Rossiter, Johannes Grillari, Erwin Tschachler, Florian Gruber
Autophagy is a recycling program which allows cells to adapt to metabolic needs and to stress. Defects in autophagy can affect metabolism, aging, proteostasis and inflammation. Autophagy pathway genes, including autophagy related 7 (Atg7), have been associated with the regulation of skin pigmentation, and autophagy defects disturb the biogenesis and transport of melanosomes in melanocytes as well as transfer and processing of melanin into keratinocytes. We have previously shown that mice whose melanocytes or keratinocytes lack Atg7 (and thus autophagy) as a result of specific gene knockout still retained functioning melanosome synthesis and transfer, and displayed only moderate reduction of pigmentation...
October 9, 2016: International Journal of Biochemistry & Cell Biology
Chloé Sauzay, Alexandra Petit, Anne-Marie Bourgeois, Jean-Claude Barbare, Bruno Chauffert, Antoine Galmiche, Aline Houessinon
Alpha-foetoprotein (AFP), one of the first protein tumour markers discovered, is widely used today in clinical practice. Its application for the screening and diagnosis of hepatocellular carcinoma (HCC), the most frequent form of primary liver tumour, is a matter of extensive debate. In addition to the studies focused on the role of the AFP in the diagnosis of HCC, in recent years AFP has been used to guide the therapeutic choice in HCC and monitor the treatment. Here, we summarize the latest studies that show the interest of AFP quantification in determining the suitability of liver transplantation or to follow-up on patients receiving the targeted treatment sorafenib...
October 11, 2016: Clinica Chimica Acta; International Journal of Clinical Chemistry
John J Chen, Joseph C Genereux, Eul Hyun Suh, Vincent F Vartabedian, Bibiana Rius, Song Qu, Maria T A Dendle, Jeffery W Kelly, R Luke Wiseman
Transthyretin (TTR) is a tetrameric serum protein associated with multiple systemic amyloid diseases. In these disorders, TTR aggregates in extracellular environments through a mechanism involving rate-limiting dissociation of the tetramer to monomers, which then misfold and aggregate into soluble oligomers and amyloid fibrils that induce toxicity in distal tissues. Using an assay established herein, we show that highly destabilized, aggregation-prone TTR variants are secreted as both native tetramers and non-native conformations that accumulate as high-molecular-weight oligomers...
October 20, 2016: Cell Chemical Biology
Elvira Sondo, Emanuela Pesce, Valeria Tomati, Monica Marini, Nicoletta Pedemonte
BACKGROUND: Deletion of phenylalanine 508 is the most frequent mutation causing cystic fibrosis. It causes multiple defects: 1) misfolding of the protein causing retention at the ER (processing defect); 2) reduced channel activity (gating defect); 3) reduced plasma membrane residency time due to increased internalization rate and defective recycling. METHODS: Druggability of F508del-CFTR was demonstrated by several studies. Correctors are molecules able to improve maturation and trafficking to the membrane of F508del-CFTR...
October 6, 2016: Current Pharmaceutical Design
Dong-Kyu Kim, Tae Ho Kim, Seung-Jae Lee
Aging is the most important risk factor for human neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Pathologically, these diseases are characterized by the deposition of specific protein aggregates in neurons and glia, representing the impairment of neuronal proteostasis. However, the mechanism by which aging affects the proteostasis system and promotes protein aggregation remains largely unknown. The short lifespan and ample genetic resources of Caenorhabditis elegans (C. elegans) have made this species a favorite model organism for aging research, and the development of proteinopathy models in this organism has helped us to understand how aging processes affect protein aggregation and neurodegeneration...
October 7, 2016: Experimental & Molecular Medicine
Erik R P Zuiderweg, Jason E Gestwicki
Hsc70 is the constitutively expressed mammalian heat shock 70 kDa (Hsp70) cytosolic chaperone. It plays a central role in cellular proteostasis and protein trafficking. Here, we present the backbone and methyl group assignments for the 386-residue nucleotide binding domain of the human protein. This domain controls the chaperone's allostery, binds multiple co-chaperones and is the target of several classes of known chemical Hsp70 inhibitors. The NMR assignments are based on common triple resonance experiments with triple labeled protein, and on several (15)N and (13)C-resolved 3D NOE experiments with methyl-reprotonated samples...
October 3, 2016: Biomolecular NMR Assignments
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