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Unfolded Proteins

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https://www.readbyqxmd.com/read/28107951/investigating-the-structural-transitions-of-proteins-during-dissolution-by-mass-spectrometry
#1
Xiaoyun Gong, Xingchuang Xiong, Lin Qi, Xiang Fang
An appropriate solvent environment is essential for the implementation of biological functions of proteins. Interactions between protein residues and solvent molecules are of great importance for proteins to maintain their active structure and catalyze biochemical reactions. In this study, we investigated such interactions and studied the structural transitions of proteins during their dissolution process. Our previously developed technique, namely solvent assisted electric field induced desorption/ionization, was used for the dissolution and immediate ionization of proteins...
March 1, 2017: Talanta
https://www.readbyqxmd.com/read/28107409/targeted-deletion-of-a-plasmodium-site-2-protease-impairs-life-cycle-progression-in-the-mammalian-host
#2
Konstantinos Koussis, Evi Goulielmaki, Anna Chalari, Chrislaine Withers-Martinez, Inga Siden-Kiamos, Kai Matuschewski, Thanasis G Loukeris
Site-2 proteases (S2P) belong to the M50 family of metalloproteases, which typically perform essential roles by mediating activation of membrane-bound transcription factors through regulated intramembrane proteolysis (RIP). Protease-dependent liberation of dormant transcription factors triggers diverse cellular responses, such as sterol regulation, Notch signalling and the unfolded protein response. Plasmodium parasites rely on regulated proteolysis for controlling essential pathways throughout the life cycle...
2017: PloS One
https://www.readbyqxmd.com/read/28107009/nmr-and-computation-reveal-a-pressure-sensitive-folded-conformation-of-trp-cage
#3
Soichiro Kitazawa, Martin J Fossat, Scott A McCallum, Angel E Garcia, Catherine Ann Royer
Beyond defining the structure and stability of folded states of proteins, primary amino acid sequences determine all of the features of their conformational landscapes. Characterizing how sequence modulates the population of protein excited states or folding pathways requires atomic level detailed structural and energetic information. Such insight is essential for improving protein design strategies, as well as for interpreting protein evolution. Here, high pressure NMR and molecular dynamics simulations were combined to probe the conformational landscape of a small model protein, the tryptophan cage variant, Tc5b...
January 20, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28106827/neuroprotective-strategy-in-retinal-degeneration-suppressing-er-stress-induced-cell-death-via-inhibition-of-the-mtor-signal
#4
REVIEW
Bin Fan, Ying-Jian Sun, Shu-Yan Liu, Lin Che, Guang-Yu Li
The retina is a specialized sensory organ, which is essential for light detection and visual formation in the human eye. Inherited retinal degenerations are a heterogeneous group of eye diseases that can eventually cause permanent vision loss. UPR (unfolded protein response) and ER (endoplasmic reticulum) stress plays an important role in the pathological mechanism of retinal degenerative diseases. mTOR (the mammalian target of rapamycin) kinase, as a signaling hub, controls many cellular processes, covering protein synthesis, RNA translation, ER stress, and apoptosis...
January 19, 2017: International Journal of Molecular Sciences
https://www.readbyqxmd.com/read/28105371/unfolding-anti-tumor-immunity-er-stress-responses-sculpt-tolerogenic-myeloid-cells-in-cancer
#5
REVIEW
Juan R Cubillos-Ruiz, Eslam Mohamed, Paulo C Rodriguez
Established tumors build a stressful and hostile microenvironment that blocks the development of protective innate and adaptive immune responses. Different subsets of immunoregulatory myeloid populations, including dendritic cells, myeloid-derived suppressor cells (MDSCs) and macrophages, accumulate in the stressed tumor milieu and represent a major impediment to the success of various forms of cancer immunotherapy. Specific conditions and factors within tumor masses, including hypoxia, nutrient starvation, low pH, and increased levels of free radicals, provoke a state of "endoplasmic reticulum (ER) stress" in both malignant cells and infiltrating myeloid cells...
2017: Journal for Immunotherapy of Cancer
https://www.readbyqxmd.com/read/28104374/spectroscopic-characterisation-of-interaction-of-ferulic-acid-with-aldehyde-dehydrogenase-aldh
#6
Ayodele O Kolawole, Ruth J Agaba, Matthew O Oluwole
Interaction of pharmacological important phenolic, ferulic acid, with Aldehyde dehydrogenase (ALDH) at the simulative pH condition, was studied using spectroscopic approach. Ferulic acid caused a decrease in the fluorescence intensity formed from ALDH-ferulic acid complex resulting in mixed inhibition of ALDH activity (IC50=30.65μM). The intrinsic quenching was dynamic and induced altered conformation of ALDH and makes the protein less compact but might not unfold it. ALDH has two binding sites for ferulic acid at saturating concentrations having association constant of 1...
January 16, 2017: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/28103630/orientia-tsutsugamushi-ank9-is-a-multifunctional-effector-that-utilizes-a-novel-grip-like-golgi-localization-domain-for-golgi-to-endoplasmic-reticulum-trafficking-and-interacts-with-host-copb2
#7
Andrea R Beyer, Kyle G Rodino, Lauren VieBrock, Ryan S Green, Brittney K Tegels, Lee D Oliver, Richard T Marconi, Jason A Carlyon
Orientia tsutsugamushi causes scrub typhus, a potentially fatal infection that afflicts one million people annually. This obligate intracellular bacterium boasts one of the largest microbial arsenals of ankyrin repeat-containing protein (Ank) effectors, most of which target the endoplasmic reticulum (ER) by undefined mechanisms. Ank9 is the only one proven to function during infection. Here, we demonstrate that Ank9 bears a motif that mimics the GRIP domain of eukaryotic golgins and is necessary and sufficient for its Golgi localization...
January 19, 2017: Cellular Microbiology
https://www.readbyqxmd.com/read/28103054/interface-related-attributes-of-the-maillard-reaction-born-glycoproteins
#8
Mehri Karbasi, Ashkan Madadlou
Interfacial behavior of proteins which is a chief parameter to their emulsifying and foaming properties can be tailored through the Maillard reaction. The reaction can increase protein solubility at isoelectric point and ought to be controlled for example by high pressure processing to suppress melanoidins formation. Branched and long saccharides bring considerable steric hindrance which is associated with their site of conjugation to proteins. Conjugation with high molecular weight polysaccharides (such as 440 kDa dextran) may indeed increase the thickness of globular proteins interfacial film up to approximately 25 nm...
January 19, 2017: Critical Reviews in Food Science and Nutrition
https://www.readbyqxmd.com/read/28102930/modulation-of-the-thermodynamic-signatures-of-an-rna-thermometer-by-osmolytes-and-salts
#9
Mimi Gao, Loana Arns, Roland Winter
Folding of ribonucleic acids (RNAs) is driven by several factors, such as base pairing and stacking, chain entropy, and ion-mediated electrostatics, which have been studied in great detail. However, the power of background molecules in the cellular milieu is often neglected. Herein, we study the effect of common osmolytes on the folding equilibrium of a hairpin-structured RNA and, using pressure perturbation, provide novel thermodynamic and volumetric insights into the modulation mechanism. The presence of TMAO causes an increased thermal stability and a more positive volume change for the helix-to-coil transition, whereas urea destabilizes the hairpin and leads to an increased expansibility of the unfolded state...
January 19, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28102317/time-resolved-neutron-scattering-provides-new-insight-into-protein-substrate-processing-by-a-aaa-unfoldase
#10
Ziad Ibrahim, Anne Martel, Martine Moulin, Henry S Kim, Michael Härtlein, Bruno Franzetti, Frank Gabel
We present a combination of small-angle neutron scattering, deuterium labelling and contrast variation, temperature activation and fluorescence spectroscopy as a novel approach to obtain time-resolved, structural data individually from macromolecular complexes and their substrates during active biochemical reactions. The approach allowed us to monitor the mechanical unfolding of a green fluorescent protein model substrate by the archaeal AAA+ PAN unfoldase on the sub-minute time scale. Concomitant with the unfolding of its substrate, the PAN complex underwent an energy-dependent transition from a relaxed to a contracted conformation, followed by a slower expansion to its initial state at the end of the reaction...
January 19, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28102311/plin2-is-a-key-regulator-of-the-unfolded-protein-response-and-endoplasmic-reticulum-stress-resolution-in-pancreatic-%C3%AE-cells
#11
Elaine Chen, Tsung Huang Tsai, Lan Li, Pradip Saha, Lawrence Chan, Benny Hung-Junn Chang
Progressive pancreatic β cell failure underlies the transition of impaired glucose tolerance to overt diabetes; endoplasmic reticulum (ER) stress expedites β cell failure in this situation. ER stress can be elicited by lipotoxicity and an increased demand for insulin in diabetes. We previously reported that the lipid droplet protein perilipin 2 (PLIN2) modulates lipid homeostasis in the liver. Here, we show that PLIN2 modulates the unfolded protein response (UPR) and ER stress in pancreatic β cells. PLIN2 expression goes up when β cells are exposed to a lipid load or to chemical ER stress inducers...
January 19, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28102071/temperature-induced-misfolding-in-prion-protein-evidences-of-multiple-partially-disordered-states-stabilized-by-non-native-hydrogen-bonds
#12
Neharika G Chamachi, Suman Chakrabarty
The structural basis of misfolding pathways of a cellular Prion (PrP(C)) into the toxic scrapie form (PrP(SC)) and identification of possible intermediates (e.g. PrP(*)) still eludes us. In this work, we have used a cumulative ~65µs of Replica Exchange Molecular Dynamics simulation data to construct the conformational free energy landscapes and capture the structural and thermodynamic characteristics associated with various stages of the thermal denaturation process in human Prion protein. The temperature dependent free energy surfaces consist of multiple metastable states stabilized by non-native contacts and hydrogen bonds, thus rendering the protein prone towards misfolding...
January 19, 2017: Biochemistry
https://www.readbyqxmd.com/read/28100786/inositol-depletion-induced-by-acute-treatment-of-the-bipolar-disorder-drug-valproate-increases-levels-of-phytosphingosine
#13
Shyamalagauri Jadhav, Sarah Russo, L Ashley Cowart, Miriam L Greenberg
Bipolar disorder (BD) is a severe psychiatric illness affecting ~2% of the world population. Valproate (VPA) and lithium, though widely used for the treatment of BD, are not universally effective. These drugs have been shown to cause inositol depletion, but translating this observation to a specific therapeutic mechanism has been difficult, hampering the development of more effective therapies. We have shown previously in yeast that chronic VPA treatment induces the unfolded protein response due to increasing ceramide levels...
January 18, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28100635/phospholipase-lpl1-links-lipid-droplet-function-with-quality-control-protein-degradation
#14
Nina Weisshaar, Hendrik Welsch, Angel Guerra-Moreno, John Hanna
Protein misfolding is toxic to cells and is thought to underlie many human diseases, including many neurodegenerative diseases. Accordingly, cells have developed stress responses to deal with misfolded proteins. The transcription factor Rpn4 mediates one such response, and is best known for regulating the abundance of the proteasome, the complex multisubunit protease that destroys proteins. Here we identify Lpl1 as an unexpected target of the Rpn4 response. Lpl1 is a phospholipase and a component of the lipid droplet...
January 18, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/28099529/a-possible-role-of-the-full-length-nascent-protein-in-post-translational-ribosome-recycling
#15
Debasis Das, Dibyendu Samanta, Arpita Bhattacharya, Arunima Basu, Anindita Das, Jaydip Ghosh, Abhijit Chakrabarti, Chanchal Das Gupta
Each cycle of translation initiation in bacterial cell requires free 50S and 30S ribosomal subunits originating from the post-translational dissociation of 70S ribosome from the previous cycle. Literature shows stable dissociation of 70S from model post-termination complexes by the concerted action of Ribosome Recycling Factor (RRF) and Elongation Factor G (EF-G) that interact with the rRNA bridge B2a/B2b joining 50S to 30S. In such experimental models, the role of full-length nascent protein was never considered seriously...
2017: PloS One
https://www.readbyqxmd.com/read/28097745/immature-core-protein-of-hepatitis-c-virus-induces-an-unfolded-protein-response-through-inhibition-of-erad-l-in-a-yeast-model-system
#16
Shota Takahashi, Naoko Sato, Junichi Kikuchi, Hideaki Kakinuma, Jun Okawa, Yukiko Masuyama, Singo Iwasa, Hayato Irokawa, Gi-Wook Hwang, Akira Naganuma, Michinori Kohara, Shusuke Kuge
The structural protein Core of hepatitis C virus (HCV), a cytosolic protein, induces endoplasmic reticulum (ER) stress and unfolded protein response (UPR) in hepatocytes, and is responsible for the pathogenesis of persistent HCV infection. Using yeast as a model system, we evaluated mechanisms underlying Core-induced interference of ER homeostasis and UPR, and found that UPR is induced by the immature Core (aa 1-191, Core191) but not by the mature Core (aa 1-177, Core177). Interestingly, Core191 inhibits both ERAD-L, a degradation system responsible for misfolded/unfolded proteins in the ER lumen, and ERAD-M, a degradation system responsible for proteins carrying a misfolded/unfolded region in the ER membrane...
January 18, 2017: Genes to Cells: Devoted to Molecular & Cellular Mechanisms
https://www.readbyqxmd.com/read/28097712/force-generation-by-titin-folding
#17
Zsolt Mártonfalvi, Pasquale Bianco, Katalin Naftz, György G Ferenczy, Miklós Kellermayer
Titin is a giant protein that provides elasticity to muscle. As the sarcomere is stretched, titin extends hierarchically according to the mechanics of its segments. Whether titin's globular domains unfold during this process and how such unfolded domains might contribute to muscle contractility are strongly debated. To explore the force-dependent folding mechanisms, here we manipulated skeletal-muscle titin molecules with high-resolution optical tweezers. In force-clamp mode, after quenching the force (<10 pN), extension fluctuated without resolvable discrete events...
January 18, 2017: Protein Science: a Publication of the Protein Society
https://www.readbyqxmd.com/read/28096372/helical-structure-stability-and-dynamics-in-human-apolipoprotein-e3-and-e4-by-hydrogen-exchange-and-mass-spectrometry
#18
Palaniappan S Chetty, Leland Mayne, Sissel Lund-Katz, S Walter Englander, Michael C Phillips
Apolipoprotein E (apoE) plays a critical role in cholesterol transport in both peripheral circulation and brain. Human apoE is a polymorphic 299-residue protein in which the less common E4 isoform differs from the major E3 isoform only by a C112R substitution. ApoE4 interacts with lipoprotein particles and with the amyloid-β peptide, and it is associated with increased incidence of cardiovascular and Alzheimer's disease. To understand the structural basis for the differences between apoE3 and E4 functionality, we used hydrogen-deuterium exchange coupled with a fragment separation method and mass spectrometric analysis to compare their secondary structures at near amino acid resolution...
January 17, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28093457/functional-analysis-of-the-mammalian-rna-ligase-for-ire1-in-the-unfolded-protein-response
#19
Juthakorn Poothong, Witoon Tirasophon, Randal J Kaufman
The unfolded protein response (UPR) is a conserved signaling pathway activated upon the accumulation of unfolded proteins within the endoplasmic reticulum (ER), termed ER stress. Upon ER stress, HAC1 / XBP1 undergoes exon/intron specific excision by IRE1 to remove an intron and liberate the 5' and 3' exons. In yeast, the 5' and 3' HAC1 exons are subsequently ligated by tRNA ligase (Rlg1p) whereas XBP1 ligation in mammalian cells is catalyzed by a recently identified ligase, RtcB. In this study, the RNA ligase activity of the human RtcB involved in the unconventional splicing of XBP1 / HAC1 mRNA was explored in an rlg1-100 mutant yeast strain...
January 16, 2017: Bioscience Reports
https://www.readbyqxmd.com/read/28093214/the-upr-reduces-glucose-metabolism-via-ire1-signaling
#20
Judith M van der Harg, Jessica C van Heest, Fabian N Bangel, Sanne Patiwael, Jan R T van Weering, Wiep Scheper
Neurons are highly dependent on glucose. A disturbance in glucose homeostasis therefore poses a severe risk that is counteracted by activation of stress responses to limit damage and restore the energy balance. A major stress response that is activated under conditions of glucose deprivation is the unfolded protein response (UPR) that is aimed to restore proteostasis in the endoplasmic reticulum. The key signaling of the UPR involves the transient activation of a transcriptional program and an overall reduction of protein synthesis...
January 13, 2017: Biochimica et Biophysica Acta
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