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Farinha CM, Gentzsch M. Revisiting CFTR Interactions: Old Partners and New Players. Int J Mol Sci 2021; 22:13196. [PMID: 34947992 PMCID: PMC8703571 DOI: 10.3390/ijms222413196] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 12/02/2021] [Accepted: 12/03/2021] [Indexed: 01/07/2023] Open
Abstract
Remarkable progress in CFTR research has led to the therapeutic development of modulators that rescue the basic defect in cystic fibrosis. There is continuous interest in studying CFTR molecular disease mechanisms as not all cystic fibrosis patients have a therapeutic option available. Addressing the basis of the problem by comprehensively understanding the critical molecular associations of CFTR interactions remains key. With the availability of CFTR modulators, there is interest in comprehending which interactions are critical to rescue CFTR and which are altered by modulators or CFTR mutations. Here, the current knowledge on interactions that govern CFTR folding, processing, and stability is summarized. Furthermore, we describe protein complexes and signal pathways that modulate the CFTR function. Primary epithelial cells display a spatial control of the CFTR interactions and have become a common system for preclinical and personalized medicine studies. Strikingly, the novel roles of CFTR in development and differentiation have been recently uncovered and it has been revealed that specific CFTR gene interactions also play an important role in transcriptional regulation. For a comprehensive understanding of the molecular environment of CFTR, it is important to consider CFTR mutation-dependent interactions as well as factors affecting the CFTR interactome on the cell type, tissue-specific, and transcriptional levels.
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Affiliation(s)
- Carlos M. Farinha
- BioISI—Biosystems and Integrative Sciences Institute, Faculty of Sciences, University of Lisboa, 1749-016 Lisboa, Portugal
| | - Martina Gentzsch
- Marsico Lung Institute and Cystic Fibrosis Research Center, School of Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
- Department of Pediatrics, Division of Pediatric Pulmonology, School of Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
- Department of Cell Biology and Physiology, School of Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
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2
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Meng X, Clews J, Ciuta AD, Martin ER, Ford RC. CFTR structure, stability, function and regulation. Biol Chem 2020; 400:1359-1370. [PMID: 30738013 DOI: 10.1515/hsz-2018-0470] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 01/30/2019] [Indexed: 12/15/2022]
Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) is a unique member of the ATP-binding cassette family of proteins because it has evolved into a channel. Mutations in CFTR cause cystic fibrosis, the most common genetic disease in people of European origin. The F508del mutation is found in about 90% of patients and here we present data that suggest its main effect is on CFTR stability rather than on the three-dimensional (3D) folded state. A survey of recent cryo-electron microscopy studies was carried out and this highlighted differences in terms of CFTR conformation despite similarities in experimental conditions. We further studied CFTR structure under various phosphorylation states and with the CFTR-interacting protein NHERF1. The coexistence of outward-facing and inward-facing conformations under a range of experimental conditions was suggested from these data. These results are discussed in terms of structural models for channel gating, and favour the model where the mostly disordered regulatory-region of the protein acts as a channel plug.
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Affiliation(s)
- Xin Meng
- School of Biological Sciences, Faculty of Biology Medicine and Health, Michael Smith Building, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Jack Clews
- School of Biological Sciences, Faculty of Biology Medicine and Health, Michael Smith Building, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Anca D Ciuta
- School of Biological Sciences, Faculty of Biology Medicine and Health, Michael Smith Building, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Eleanor R Martin
- School of Biological Sciences, Faculty of Biology Medicine and Health, Michael Smith Building, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Robert C Ford
- School of Biological Sciences, Faculty of Biology Medicine and Health, Michael Smith Building, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
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Liu Q, Sabirzhanova I, Bergbower EAS, Yanda M, Guggino WG, Cebotaru L. The CFTR Corrector, VX-809 (Lumacaftor), Rescues ABCA4 Trafficking Mutants: a Potential Treatment for Stargardt Disease. Cell Physiol Biochem 2019; 53:400-412. [PMID: 31403270 DOI: 10.33594/000000146] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2019] [Accepted: 08/08/2019] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND/AIMS Mutations in ABCA4 cause Stargardt macular degeneration, which invariably ends in legal blindness. We studied two common mutants, A1038V (in NBD1) and G1961E (in NBD2), with the purpose of exploring how they interact with the cell's quality control mechanism. The study was designed to determine how these mutants can be rescued. METHODS We expressed wt and mutant ABCA4 in HEK293 cells and studied the effect of the mutations on trafficking and processing and the ability of correctors to rescue them. We used a combination of western blotting, confocal microscopy and surface biotinylation coupled with pulldown of plasma membrane proteins. RESULTS G1961E is sensitive to inhibitors of the aggresome, tubacin and the lysosome, bafilomycin A. Both mutants cause a reduction in heat shock protein, Hsp27. Incubation of HEK293 cells expressing the mutants with VX-809, an FDA approved drug for the treatment of cystic fibrosis, increased the levels of A1038V and G1961E by 2- to 3-fold. Importantly, VX-809 increased the levels of both mutants at the plasma membrane suggesting that trafficking had been restored. Transfecting additional Hsp27 to the cells also increased the steady state levels of both mutants. However, in combination with VX-809 the addition of Hsp27 caused a dramatic increase in the protein expression particularly in the G1961 mutant which increased approximately 5-fold. CONCLUSION Our results provide a new mechanism for the rescue of ABCA4 trafficking mutants based on the restoration of Hsp27. Our results provide a pathway for the treatment of Stargardt disease.
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Affiliation(s)
- Qiangni Liu
- Division of Gastroenterology and Hepatology, Departments of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Inna Sabirzhanova
- Division of Gastroenterology and Hepatology, Departments of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Emily Anne Smith Bergbower
- Division of Gastroenterology and Hepatology, Departments of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Murali Yanda
- Division of Gastroenterology and Hepatology, Departments of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - William G Guggino
- Division of Gastroenterology and Hepatology, Departments of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Liudmila Cebotaru
- Division of Gastroenterology and Hepatology, Departments of Medicine, Johns Hopkins University, Baltimore, MD, USA,
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4
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Manos-Turvey A, Brodsky JL, Wipf P. The Effect of Structure and Mechanism of the Hsp70 Chaperone on the Ability to Identify Chemical Modulators and Therapeutics. TOPICS IN MEDICINAL CHEMISTRY 2015. [DOI: 10.1007/7355_2015_90] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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5
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Pranke IM, Sermet-Gaudelus I. Biosynthesis of cystic fibrosis transmembrane conductance regulator. Int J Biochem Cell Biol 2014; 52:26-38. [DOI: 10.1016/j.biocel.2014.03.020] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Revised: 03/19/2014] [Accepted: 03/20/2014] [Indexed: 01/19/2023]
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6
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Averna M, Pedrazzi M, Minicucci L, De Tullio R, Cresta F, Salamino F, Pontremoli S, Melloni E. Calpain inhibition promotes the rescue of F(508)del-CFTR in PBMC from cystic fibrosis patients. PLoS One 2013; 8:e66089. [PMID: 23785472 PMCID: PMC3681946 DOI: 10.1371/journal.pone.0066089] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 05/01/2013] [Indexed: 01/01/2023] Open
Abstract
A basal calpain activity promotes the limited proteolysis of wild type (WT) cystic fibrosis conductance regulator (CFTR), inducing the internalization of the split channel. This process contributes to the regulation in the level of the active CFTR at the plasma membranes. In peripheral blood mononuclear cells (PBMC) from 16 healthy donors, the inhibition of calpain activity induces a 3-fold increase in the amount of active WT CFTR at the plasma membranes. Instead, in PBMC from cystic fibrosis (CF) patients, calpain activity is expressed at aberrant levels causing the massive removal of F508del-CFTR from the cell surface. In these patients, the inhibition of such abnormal proteolysis rescues physiological amounts of active mutated CFTR in 90% of the patients (25 over 28). The recovery of functional F508del-CFTR at the physiological location, in cells treated with a synthetic calpain inhibitor, indicates that F508del-CFTR folding, maturation, and trafficking operate in CF-PBMC at significant rate. Thus, an increase in the basal calpain activity seems primarily involved in the CFTR defect observed in various CF cells. Furthermore, in CF-PBMC the recovery of the scaffolding protein Na+/H+ exchanger regulatory factor 1 (NHERF-1), occurring following inhibition of the aberrant calpain activity, can contribute to rescue CFTR-functional clusters.
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Affiliation(s)
- Monica Averna
- Department of Experimental Medicine (DIMES) - Biochemistry Section, and Center of Excellence for Biomedical Research (CEBR), University of Genoa, Genoa, Italy
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7
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Park HJ, Mylvaganum M, McPherson A, Fewell SW, Brodsky JL, Lingwood CA. A soluble sulfogalactosyl ceramide mimic promotes Delta F508 CFTR escape from endoplasmic reticulum associated degradation. ACTA ACUST UNITED AC 2009; 16:461-70. [PMID: 19389632 DOI: 10.1016/j.chembiol.2009.02.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2008] [Revised: 02/19/2009] [Accepted: 02/25/2009] [Indexed: 10/20/2022]
Abstract
AdaSGC binds Hsc70s to inhibit ATPase activity. Using single-turnover assays, adaSGC, a soluble SGC mimic, preferentially inhibited Hsp40-activated Hsc70 ATP hydrolysis (Ki approximately 10 microM) to reduce C-terminal Hsc70-peptide binding and, potentially, chaperone function. ERAD of misfolded Delta F508 CFTR requires Hsc70-Hsp40 chaperones. In transfected baby hamster kidney (BHK) cells, adaSGC increased Delta F508CFTR ERAD escape, and after low-temperature glycerol rescue, maturation, and iodide efflux. Inhibition of SGC biosynthesis reduced Delta F508CFTR but not wtCFTR expression, whereas depletion of other glycosphingolipids had no affect. WtCFTR transfected BHK cells showed increased SGC synthesis compared with Delta F508CFTR/mock-transfected cells. Partial rescue of Delta F508CFTR by low-temperature glycerol increased SGC synthesis. AdaSGC also increased cellular endogenous SGC levels. SGC in the lung, liver, and kidney was severely depleted in Delta F508CFTR compared with wtCFTR mice, suggesting a role for CFTR in SGC biosynthesis.
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Affiliation(s)
- Hyun-Joo Park
- Research Institute, Division of Molecular Structure and Function, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
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8
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Sun F, Mi Z, Condliffe SB, Bertrand CA, Gong X, Lu X, Zhang R, Latoche JD, Pilewski JM, Robbins PD, Frizzell RA. Chaperone displacement from mutant cystic fibrosis transmembrane conductance regulator restores its function in human airway epithelia. FASEB J 2008; 22:3255-63. [PMID: 18556464 DOI: 10.1096/fj.07-105338] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause cystic fibrosis (CF). The most common mutation, DeltaF508, omits the phenylalanine residue at position 508 in the first nucleotide binding domain (NBD1) of CFTR. The mutant protein is retained in the endoplasmic reticulum and degraded by the ubiquitin-proteasome system. We demonstrate that expression of NBD1 plus the regulatory domain (RD) of DeltaF508 CFTR (DeltaFRD) restores the biogenesis of mature DeltaF508 CFTR protein. In addition, DeltaFRD elicited a cAMP-stimulated anion conductance response in primary human bronchial epithelial (HBE) cells isolated from homozygous DeltaF508 CF patients. A protein transduction domain (PTD) could efficiently transduce (approximately 90%) airway epithelial cells. When fused to a PTD, direct addition of the DeltaFRD peptide conferred a dose-dependent, cAMP-stimulated anion efflux to DeltaF508 HBE cells. Hsp70 and Hsp90 associated equally with WT and DeltaF508 CFTR, whereas nearly twice as much of the Hsp90 cochaperone, Aha1, associated with DeltaF508 CFTR. Expression of DeltaFRD produced a dose-dependent removal of Aha1 from DeltaF508 CFTR that correlated with its functional rescue. These findings indicate that disruption of the excessive association of the cochaperone, Aha1, with DeltaF508 CFTR is associated with the correction of its maturation, trafficking and regulated anion channel activity in human airway epithelial cells. Thus, PTD-mediated DeltaFRD fragment delivery may provide a therapy for CF.
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Affiliation(s)
- Fei Sun
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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9
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The medium is the message: Glycosphingolipids and their soluble analogues. Biochim Biophys Acta Gen Subj 2008; 1780:347-52. [DOI: 10.1016/j.bbagen.2007.10.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2007] [Revised: 08/20/2007] [Accepted: 10/25/2007] [Indexed: 11/17/2022]
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McCracken AA, Brodsky JL. Recognition and delivery of ERAD substrates to the proteasome and alternative paths for cell survival. Curr Top Microbiol Immunol 2006; 300:17-40. [PMID: 16573235 DOI: 10.1007/3-540-28007-3_2] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Endoplasmic reticulum-associated protein degradation (ERAD) is a protein quality control mechanism that minimizes the detrimental effects of protein misfolding in the secretory pathway. Molecular chaperones and ER lumenal lectins are essential components of this process because they maintain the solubility of unfolded proteins and can target ERAD substrates to the cytoplasmic proteasome. Other factors are likely required to aid in the selection of ERAD substrates, and distinct proteinaceous machineries are required for substrate retrotranslocation/dislocation from the ER and proteasome targeting. When the capacity of the ERAD machinery is exceeded or compromised, multiple degradative routes can be enlisted to prevent the detrimental consequences of ERAD substrate accumulation, which include cell death and disease.
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Affiliation(s)
- A A McCracken
- Biology Department, University of Nevada, Reno, NV 89557, USA.
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11
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Coughlan CM, Brodsky JL. Use of yeast as a model system to investigate protein conformational diseases. Mol Biotechnol 2005; 30:171-80. [PMID: 15920289 DOI: 10.1385/mb:30:2:171] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Protein conformational diseases arise when a cellular protein adopts an aberrant shape that either directly or indirectly alters the physiology of its host cell. Notable conformational diseases include cystic fibrosis, Huntington's disease, the prion-related diseases, Alzheimer's disease, and antitrypsin deficiency. In principle, the severity and progression of conformational diseases can be altered by cellular factors that recognize and attempt to ameliorate the harmful effects of the disease-causing, misshapen protein. To better define the mechanistic underpinnings of cellular factors that mediate quality control, and to understand why a single misfolded protein can impact cell viability, specific proteins that cause each of the diseases listed above have been expressed in a model eukaryote, the yeast Saccharomyces cerevisiae. In this review, we describe what has been learned from these studies, and speculate on future uses of yeast expression systems.
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12
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Du K, Sharma M, Lukacs GL. The ΔF508 cystic fibrosis mutation impairs domain-domain interactions and arrests post-translational folding of CFTR. Nat Struct Mol Biol 2004; 12:17-25. [PMID: 15619635 DOI: 10.1038/nsmb882] [Citation(s) in RCA: 277] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2004] [Accepted: 11/19/2004] [Indexed: 02/03/2023]
Abstract
Misfolding accounts for the endoplasmic reticulum-associated degradation of mutant cystic fibrosis transmembrane conductance regulators (CFTRs), including deletion of Phe508 (DeltaF508) in the nucleotide-binding domain 1 (NBD1). To study the role of Phe508, the de novo folding and stability of NBD1, NBD2 and CFTR were compared in conjunction with mutagenesis of Phe508. DeltaF508 and amino acid replacements that prevented CFTR folding disrupted the NBD2 fold and its native interaction with NBD1. DeltaF508 caused limited alteration in NBD1 conformation. Whereas nonpolar and some aliphatic residues were permissive, charged residues and glycine compromised the post-translational folding and stability of NBD2 and CFTR. The results suggest that hydrophobic side chain interactions of Phe508 are required for vectorial folding of NBD2 and the domain-domain assembly of CFTR, representing a combined co- and post-translational folding mechanism that may be used by other multidomain membrane proteins.
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Affiliation(s)
- Kai Du
- Hospital for Sick Children Research Institute, Program in Cell and Lung Biology, University of Toronto, Ontario M5G 1X8, Canada
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13
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Wang X, Matteson J, An Y, Moyer B, Yoo JS, Bannykh S, Wilson IA, Riordan JR, Balch WE. COPII-dependent export of cystic fibrosis transmembrane conductance regulator from the ER uses a di-acidic exit code. ACTA ACUST UNITED AC 2004; 167:65-74. [PMID: 15479737 PMCID: PMC2172508 DOI: 10.1083/jcb.200401035] [Citation(s) in RCA: 165] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cystic fibrosis (CF) is a childhood hereditary disease in which the most common mutant form of the CF transmembrane conductance regulator (CFTR) ΔF508 fails to exit the endoplasmic reticulum (ER). Export of wild-type CFTR from the ER requires the coat complex II (COPII) machinery, as it is sensitive to Sar1 mutants that disrupt normal coat assembly and disassembly. In contrast, COPII is not used to deliver CFTR to ER-associated degradation. We find that exit of wild-type CFTR from the ER is blocked by mutation of a consensus di-acidic ER exit motif present in the first nucleotide binding domain. Mutation of the code disrupts interaction with the COPII coat selection complex Sec23/Sec24. We propose that the di-acidic exit code plays a key role in linking CFTR to the COPII coat machinery and is the primary defect responsible for CF in ΔF508-expressing patients.
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Affiliation(s)
- Xiaodong Wang
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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14
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Fewell SW, Smith CM, Lyon MA, Dumitrescu TP, Wipf P, Day BW, Brodsky JL. Small molecule modulators of endogenous and co-chaperone-stimulated Hsp70 ATPase activity. J Biol Chem 2004; 279:51131-40. [PMID: 15448148 DOI: 10.1074/jbc.m404857200] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The molecular chaperone and cytoprotective activities of the Hsp70 and Hsp40 chaperones represent therapeutic targets for human diseases such as cancer and those that arise from defects in protein folding; however, very few Hsp70 and no Hsp40 modulators have been described. Using an assay for ATP hydrolysis, we identified and screened small molecules with structural similarity to 15-deoxyspergualin and NSC 630668-R/1 for their effects on endogenous and Hsp40-stimulated Hsp70 ATPase activity. Several of these compounds modulated Hsp70 ATPase activity, consistent with the action of NSC 630668-R/1 observed previously (Fewell, S. W., Day, B. W., and Brodsky, J. L. (2001) J. Biol. Chem. 276, 910-914). In contrast, three compounds inhibited the ability of Hsp40 to stimulate Hsp70 ATPase activity but did not affect the endogenous activity of Hsp70. Two of these agents also compromised the Hsp70/Hsp40-mediated post-translational translocation of a secreted pre-protein in vitro. Together, these data indicate the potential for continued screening of small molecule Hsp70 effectors and that specific modulators of Hsp70-Hsp40 interaction can be obtained, potentially for future therapeutic use.
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Affiliation(s)
- Sheara W Fewell
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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15
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McCracken AA, Brodsky JL. Evolving questions and paradigm shifts in endoplasmic-reticulum-associated degradation (ERAD). Bioessays 2003; 25:868-77. [PMID: 12938176 DOI: 10.1002/bies.10320] [Citation(s) in RCA: 169] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
ER-associated degradation (ERAD) is a component of the protein quality control system, ensuring that aberrant polypeptides cannot transit through the secretory pathway. This is accomplished by a complex sequence of events in which unwanted proteins are selected in the ER and exported to the cytosol for degradation by the proteasome. Given that protein quality control can be essential for cell survival, it is not surprising that ERAD is linked to numerous disease states. Here we review the molecular mechanisms of ERAD, its role in metabolic regulation and biomedical implications, and the unanswered questions regarding this process.
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Abstract
Completion of the human genome project raises the possibility of genetically based treatments for a multitude of human diseases. As yet only a handful of patients have benefited clinically from this approach. Why gene transfer is such a complex issue is discussed in this article. Theoretically, the easiest diseases to treat are single gene recessive diseases, where, presumably, gene delivery to somatic cells is all that is required. Two prime candidates for gene therapy are severe combined immunodeficiency disease (SCID) and cystic fibrosis (CF). Attempts to treat both of these diseases by gene therapy commenced in the late 1980s. Some clinical benefit has been recorded with SCID, but none, as yet, has been recorded with CF.
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Affiliation(s)
- Alan W Cuthbert
- Dept of Medicine, University of Cambridge, Addenbrooke's Hospital, CB2 2QQ, Cambridge, UK.
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17
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Chen EY, Clarke DM. The PEST sequence does not contribute to the stability of the cystic fibrosis transmembrane conductance regulator. BMC BIOCHEMISTRY 2002; 3:29. [PMID: 12361483 PMCID: PMC130031 DOI: 10.1186/1471-2091-3-29] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2002] [Accepted: 10/02/2002] [Indexed: 11/13/2022]
Abstract
BACKGROUND Endoplasmic reticulum retention of misfolded cystic fibrosis transmembrane conductance regulator (CFTR) mutants and their rapid degradation is the major cause of cystic fibrosis (CF). An important goal is to understand the mechanism of how the misfolded proteins are recognized, retained, and targeted for degradation. RESULTS Using a web-based algorithm, PESTFind, we found a PEST sequence in the regulatory (R) domain of CFTR. The PEST sequence is found in many short-lived eukaryotic proteins and plays a role in their degradation. To determine its role in the stability and degradation of misprocessed CFTR, we introduced a number of site-directed mutations into the PEST sequence in the cDNA of DeltaF508 CFTR, the most prevalent misprocessed mutation found in CF patients. Analysis of these mutants showed that the disruption of the PEST sequence plays a minor role in the degradation of the CFTR mutants. Multiple mutations to the PEST sequence within the R domain of CFTR inhibit maturation of CFTR and prevent the formation of a 100 kDa degradation product. The mutations, however, do not improve the stability of the mutant DeltaF508 CFTR. CONCLUSION These observations show that disruption of the structure of the R domain of CFTR can inhibit maturation of the protein and that the predicted PEST sequence plays no significant role in the degradation of CFTR.
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Affiliation(s)
- Eva Y Chen
- Canadian Institutes for Health Research Group in Membrane Biology, Departments of Medicine and Biochemistry, University of Toronto, Toronto, Ontario, M5S 1A8, Canada
| | - David M Clarke
- Canadian Institutes for Health Research Group in Membrane Biology, Departments of Medicine and Biochemistry, University of Toronto, Toronto, Ontario, M5S 1A8, Canada
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18
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Duszyk M, MacVinish L, Cuthbert AW. Phenanthrolines--a new class of CFTR chloride channel openers. Br J Pharmacol 2001; 134:853-64. [PMID: 11606326 PMCID: PMC1573018 DOI: 10.1038/sj.bjp.0704328] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. A number of phenanthrolines and benzoquinolines were examined for their ability to activate epithelial chloride secretion by measuring short circuit current (SCC) using the mouse colon epithelium. 1,10 phenanthroline stimulated electrogenic chloride secretion with an EC(50) of 612+/-10 microM and a Hill slope of 4.9+/-0.3. A similar pharmacology was demonstrated by both 1,7 and 4,7 phenanthrolines, 7,8 benzoquinoline and phenanthridine. 2. Evidence that the increase in SCC caused by 1,10 phenanthroline was due to chloride secretion is based upon (a) inhibition of the current by furosemide, (b) failure of cystic fibrosis (CF) colons to respond and (c) an associated net flux of (36)Cl(-). 3. 1,10 Phenanthroline affected neither the generation of cyclic AMP or the concentration of intracellular Ca(2+) in colonic epithelial cells. 4. 1,10 phenanthroline affected the chloride conductance of the apical membrane, as shown by an increase in chloride current in 'apical membrane only' preparations in the presence of an apical to basolateral chloride gradient. The increase in chloride current was inhibited by 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and was not present in CF colons. 5. Additionally, 1,10 phenanthroline activated basolateral K(+) channels, both Ca(2+)- and cyclic AMP-sensitive channels, as shown by inhibitor studies with charybdotoxin (ChTX) and XE991, and after the apical membrane was permeabilized with nystatin. 6. The phenanthrolines and benzoquinolines described here, with dual actions affecting CFTR and basolateral K(+) channels, may constitute useful lead compounds for adjunct therapy in CF.
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Affiliation(s)
- Marek Duszyk
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 2QQ
| | - Lesley MacVinish
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 2QQ
| | - Alan W Cuthbert
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 2QQ
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 2QQ. E-mail:
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Affiliation(s)
- B R Pitt
- Department of Environmental and Occupational Health, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania 15238, USA. brucep+@pitt.edu
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