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Protein folding in the ER

Suhui Yang, Andrea Shergalis, Dan Lu, Anahita Kyani, Ziwei Lu, Mats Ljungman, Nouri Neamati
Protein disulfide isomerase (PDI) is responsible for nascent protein folding in the endoplasmic reticulum (ER) and is critical for glioblastoma survival. To improve the potency of lead PDI inhibitor BAP2 ((E)-3-(3-(4-hydroxyphenyl)-3-oxoprop-1-en-1-yl)benzonitrile), we designed and synthesized 67 novel analogues. We determined that PDI inhibition relied on the A ring hydroxyl group of the chalcone scaffold and cLogP increase in the sulfonamide chain improved potency. Docking studies revealed that BAP2 and analogues bind to His256 in the b' domain of PDI, and mutation of His256 to Ala abolishes BAP2 analogue activity...
February 13, 2019: Journal of Medicinal Chemistry
Paola Genevini, Maria Nicol Colombo, Rossella Venditti, Stefania Marcuzzo, Sara Francesca Colombo, Pia Bernasconi, Maria Antonietta De Matteis, Nica Borgese, Francesca Navone
VAPB and VAPA are ubiquitously expressed ER membrane proteins that play key roles in lipid exchange at membrane contact sites. A mutant, aggregation-prone, form of VAPB (P56S) is linked to a dominantly inherited form of ALS, however, it has been unclear whether its pathogenicity is due to toxic gain of function, to negative dominance, or simply to insufficient levels of the wild-type protein produced from a single allele (haploinsufficiency). To investigate whether reduced levels of functional VAPB, independently from the presence of the mutant form, affect the physiology of mammalian motoneuron-like cells, we generated NSC34 clones, from which VAPB was partially or nearly completely depleted...
February 11, 2019: Journal of Cell Science
Ather Muneer, Rana Mozammil Shamsher Khan
The Endoplasmic reticulum (ER), an indispensable sub-cellular component of the eukaryotic cell carries out essential functions, is critical to the survival of the organism. The chaperone proteins and the folding enzymes which are multi-domain ER effectors carry out 3-dimensional conformation of nascent polypeptides and check misfolded protein aggregation, easing the exit of functional proteins from the ER. Diverse conditions, for instance redox imbalance, alterations in ionic calcium levels, and inflammatory signaling can perturb the functioning of the ER, leading to a build-up of unfolded or misfolded proteins in the lumen...
January 2019: Chonnam Medical Journal
Chet Raj Ojha, Myosotys Rodriguez, Mohan Kumar Muthu Karuppan, Jessica Lapierre, Fatah Kashanchi, Nazira El-Hage
The connection between Zika virus (ZIKV) and neurodevelopmental defects is widely recognized, although the mechanisms underlying the infectivity and pathology in primary human glial cells are poorly understood. Here we show that three isolated strains of ZIKV, an African strain MR766 (Uganda) and two closely related Asian strains R103451 (Honduras) and PRVABC59 (Puerto Rico) productively infect primary human astrocytes, although Asian strains showed a higher infectivity rate and increased cell death when compared to the African strain...
2019: PloS One
Chandramouli Ghosh, Aditi Nandi, Sudipta Basu
The endoplasmic reticulum (ER) is one of the most important organelles controlling myriads of cellular functions including protein folding/misfolding/unfolding, calcium ion homeostasis and lipid biosynthesis. Subsequently, due to its functional dysregulation in cancer cells, it has emerged as an interesting target for anti-cancer therapy. However, specific targeting of the ER in cancer cells remains a major challenge due to the lack of ER-selective chemical tools. Furthermore, for performing multiple cellular functions the ER is dependent on the nucleus through complicated cross-talk...
February 6, 2019: Nanoscale
Ryota Kondo, Kousuke Ishino, Ryuichi Wada, Hideyuki Takata, Wei-Xia Peng, Mitsuhiro Kudo, Shoko Kure, Yohei Kaneya, Nobuhiko Taniai, Hiroshi Yoshida, Zenya Naito
Protein disulfide‑isomerase A3 (PDIA3) is a chaperone protein that modulates folding of newly synthesized glycoproteins and responds to endoplasmic reticulum (ER) stress. Previous studies reported that increased expression of PDIA3 in hepatocellular carcinoma (HCC) is a marker for poor prognosis. However, the mechanism remains poorly understood. The aim of the present study, therefore, was to understand the role of PDIA3 in HCC development. First, immunohistochemical staining of tissues from 53 HCC cases revealed that HCC tissues with high PDIA3 expression exhibited a higher proliferation index and contained fewer apoptotic cells than those with low expression...
February 4, 2019: International Journal of Oncology
Amol V Shivange, Philip M Borden, Anand K Muthusamy, Aaron L Nichols, Kallol Bera, Huan Bao, Ishak Bishara, Janice Jeon, Matthew J Mulcahy, Bruce Cohen, Saidhbhe L O'Riordan, Charlene Kim, Dennis A Dougherty, Edwin R Chapman, Jonathan Marvin, Loren Looger, Henry A Lester
Nicotine dependence is thought to arise in part because nicotine permeates into the endoplasmic reticulum (ER), where it binds to nicotinic receptors (nAChRs) and begins an "inside-out" pathway that leads to up-regulation of nAChRs on the plasma membrane. However, the dynamics of nicotine entry into the ER are unquantified. Here, we develop a family of genetically encoded fluorescent biosensors for nicotine, termed iNicSnFRs. The iNicSnFRs are fusions between two proteins: a circularly permutated GFP and a periplasmic choline-/betaine-binding protein engineered to bind nicotine...
February 4, 2019: Journal of General Physiology
Nicola Chiarelli, Giulia Carini, Nicoletta Zoppi, Marco Ritelli, Marina Colombi
Classical Ehlers-Danlos syndrome (cEDS) is a dominant inherited connective tissue disorder mainly caused by mutations in the COL5A1 and COL5A2 genes encoding type V collagen (COLLV), which is a fibrillar COLL widely distributed in a variety of connective tissues. cEDS patients suffer from skin hyperextensibility, abnormal wound healing/atrophic scars, and joint hypermobility. Most of the causative variants result in a non-functional COL5A1 allele and COLLV haploinsufficiency, whilst COL5A2 mutations affect its structural integrity...
2019: PloS One
Reiko Urade
For most of the proteins synthesized in the endoplasmic reticulum (ER), disulfide bond formation accompanies protein folding in a process called oxidative folding. Oxidative folding is catalyzed by a number of enzymes, including the family of protein disulfide isomerases (PDIs), as well as other proteins that supply oxidizing equivalents to PDI family proteins, like ER oxidoreductin 1 (Ero1). Oxidative protein folding in the ER is a basic vital function, and understanding its molecular mechanism is critical for the application of plants as protein production tools...
February 2, 2019: Bioscience, Biotechnology, and Biochemistry
Piotr Wasąg, Tomasz Grajkowski, Anna Suwińska, Marta Lenartowska, Robert Lenartowski
Calreticulin (CRT) is a multifunctional resident endoplasmic reticulum (ER) luminal protein implicated in regulating a variety of cellular processes, including Ca2+ storage/mobilization and protein folding. These multiple functions may be carried out by different CRT genes and protein isoforms. The plant CRT family consist of three genes: CRT1 and CRT2 classified in the common subclass (CRT1/2), and CRT3. These genes are highly conserved during evolution end encode three different protein products (CRT1, 2 and 3)...
January 31, 2019: Molecular Phylogenetics and Evolution
Ravichandran Vignesh, Gopala Krishna Aradhyam
Protein aggregation and inclusion body formation have been a key causal phenomenon behind a majority of neurodegenerative disorders. Various approaches aimed at preventing the formation/elimination of protein aggregates are being developed to control these diseases. Molecular chaperones are a class of protein that not only direct the functionally relevant fold of the protein but also perform quality control against stress, misfolding/aggregation. Genes that encode molecular chaperones are induced and expressed in response to extreme stress conditions to "salvage" the cell by the "unfolded protein response" (UPR) signaling pathway...
2019: Methods in Molecular Biology
Yahui Yan, Claudia Rato, Lukas Rohland, Steffen Preissler, David Ron
Despite its known role as a secreted neuroprotectant, much of the mesencephalic astrocyte-derived neurotrophic factor (MANF) is retained in the endoplasmic reticulum (ER) of producer cells. There, by unknown mechanisms, MANF plays a role in protein folding homeostasis in complex with the ER-localized Hsp70 chaperone BiP. Here we report that the SAF-A/B, Acinus, and PIAS (SAP) domain of MANF selectively associates with the nucleotide binding domain (NBD) of ADP-bound BiP. In crystal structures the SAP domain engages the cleft between NBD subdomains Ia and IIa, stabilizing the ADP-bound conformation and clashing with the interdomain linker that occupies this site in ATP-bound BiP...
February 1, 2019: Nature Communications
Jon K Cherry, Cheryl A Woolhead
The folding and targeting of hydrophobic transmembrane domains poses a major challenge to the cell. Several membrane proteins have been shown to gain some degree of secondary structure within the ribosome tunnel and to retain this conformation throughout maturation. However, there is little information on one of the largest classes of eukaryotic membrane proteins; the G protein-coupled receptors (GPCRs). In this study we show that the signal anchor domain of GPR35 remains in an extended conformation whilst exiting the ribosome tunnel, the polypeptide chain then forms interactions with components of the SRP targeting pathway, and the Sec61 translocon, resulting in a compacted conformation prior to integration into the ER membrane...
January 31, 2019: Journal of Bioenergetics and Biomembranes
Małgorzata Graul, Edyta Kisielnicka, Michał Rychłowski, Marieke C Verweij, Kurt Tobler, Mathias Ackermann, Emmanuel J H J Wiertz, Krystyna Bieńkowska-Szewczyk, Andrea D Lipińska
Bovine herpesvirus 1 (BoHV-1)-encoded UL49.5 (a homologue of herpesvirus glycoprotein N) can combine different functions, regulated by complex formation with viral glycoprotein M (gM). We aimed to identify the mechanisms governing the immunomodulatory activity of BoHV-1 UL49.5. In this study, we addressed the impact of gM/UL49.5-specific regions on heterodimer formation, folding and trafficking from the endoplasmic reticulum (ER) to the trans-Golgi network (TGN) - events previously found to be responsible for abrogation of the UL49...
January 29, 2019: Journal of General Virology
Bongani Motaung, Gerhard Walzl, Andre G Loxton
Increased Mycobacterium tuberculosis (M.tb) burden inside the host leads to higher demand of response proteins. This in turn results in metabolic shift and cellular stress which is caused by accumulation and trafficking of these proteins within the ER. To resolve this, cells trigger UPR which is mainly mediated by BiP/GRP78 chaperone, which in turn upregulates its transcription. This chaperone protein facilitates proper protein folding within the ER, however, it can also be passively secreted to the extracellular environment or be expressed on cell surfaces attached to anchor proteins and transmembrane proteins...
January 23, 2019: International Journal of Infectious Diseases: IJID
Seyed Mojtaba Ghiasi, Tina Dahlby, Caroline Hede Andersen, Leena Haataja, Sólrun Petersen, Muhmmad Omar-Hmeadi, Mingyu Yang, Celina Pihl, Sophie Emilie Bresson, Muhammad Saad Khilji, Kristian Klindt, Oana Cheta, Marcelo J Perone, Björn Tyrberg, Clara Prats, Sebastian Barg, Anders Tengholm, Peter Arvan, Thomas Mandrup-Poulsen, Michal Tomasz Marzec
Although endoplasmic reticulum (ER) chaperone binding to mutant proinsulin has been reported, the role of protein chaperones in the handling of wild-type proinsulin is under-investigated. Here, we have explored the importance of glucose regulated protein 94 (GRP94), a prominent ER chaperone known to fold insulin-like growth factors, in proinsulin handling within β-cells. We found that GRP94 co-immunoprecipitated with proinsulin and that inhibition of GRP94 function and/or expression reduced glucose-dependent insulin secretion, shortened proinsulin half-life and lowered intracellular proinsulin and insulin levels...
January 22, 2019: Diabetes
Patrick G Needham, Christopher J Guerriero, Jeffrey L Brodsky
Misfolded proteins compromise cellular homeostasis. This is especially problematic in the endoplasmic reticulum (ER), which is a high-capacity protein-folding compartment and whose function requires stringent protein quality-control systems. Multiprotein complexes in the ER are able to identify, remove, ubiquitinate, and deliver misfolded proteins to the 26S proteasome for degradation in the cytosol, and these events are collectively termed ER-associated degradation, or ERAD. Several steps in the ERAD pathway are facilitated by molecular chaperone networks, and the importance of ERAD is highlighted by the fact that this pathway is linked to numerous protein conformational diseases...
January 22, 2019: Cold Spring Harbor Perspectives in Biology
G Elif Karagöz, Diego Acosta-Alvear, Peter Walter
Most of the secreted and plasma membrane proteins are synthesized on membrane-bound ribosomes on the endoplasmic reticulum (ER). They require engagement of ER-resident chaperones and foldases that assist in their folding and maturation. Since protein homeostasis in the ER is crucial for cellular function, the protein-folding status in the organelle's lumen is continually surveyed by a network of signaling pathways, collectively called the unfolded protein response (UPR). Protein-folding imbalances, or "ER stress," are detected by highly conserved sensors that adjust the ER's protein-folding capacity according to the physiological needs of the cell...
January 22, 2019: Cold Spring Harbor Perspectives in Biology
Unnati M Pandya, Chinaza Egbuta, Trefa M Abdullah Norman, Chih-Yuan Edward Chiang, Valerie R Wiersma, Rekha G Panchal, Edwin Bremer, Paul Eggleton, Leslie I Gold
The endoplasmic reticulum (ER) chaperone protein, calreticulin (CRT), is essential for proper glycoprotein folding and maintaining cellular calcium homeostasis. During ER stress, CRT is overexpressed as part of the unfolded protein response (UPR). In addition, CRT can be released as a damage-associated molecular pattern (DAMP) molecule that may interact with pathogen-associated molecular patterns (PAMPs) during the innate immune response. One such PAMP is lipopolysaccharide (LPS), a component of the gram-negative bacterial cell wall...
January 18, 2019: International Journal of Molecular Sciences
Tao Lin, Jae Eun Lee, Jung Won Kang, Hyeon Yeong Shin, Ju Bin Lee, Dong Il Jin
Mammalian oocytes and early embryos derived from in vitro production are highly susceptible to a variety of cellular stresses. During oocyte maturation and preimplantation embryo development, functional proteins must be folded properly in the endoplasmic reticulum (ER) to maintain oocyte and embryo development. However, some adverse factors negatively impact ER functions and protein synthesis, resulting in the activation of ER stress and unfolded protein response (UPR) signaling pathways. ER stress and UPR signaling have been identified in mammalian oocytes and embryos produced in vitro, suggesting that modulation of ER stress and UPR signaling play very important roles in oocyte maturation and the development of preimplantation embryos...
January 18, 2019: International Journal of Molecular Sciences
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