title: Differential regulation of CFTRDeltaF508 degradation by ubiquitin ligases gp78 and Hrd1.
abstract: The most common mutation associated with cystic fibrosis is the deletion of phenylalanine 508 of cystic fibrosis transmembrane conductance regulator (CFTRDeltaF508). This mutation renders otherwise functional protein susceptible to ER-associated degradation (ERAD) and prevents CFTR from exiting the ER and trafficking to the plasma membrane. In this study, we demonstrate that RNAi-mediated silencing of gp78, an established ubiquitin ligase (E3) involved in ERAD, leads to accumulation of CFTRDeltaF508 protein in cells. gp78 facilitates the degradation of CFTRDeltaF508 by enhancing both its ubiquitination and interaction with p97/VCP. SVIP, which is the inhibitor of gp78, causes accumulation of CFTRDeltaF508. We showed that endogenous gp78 co-immunoprecipitates with Hrd1. Furthermore, the results indicate that silencing the expression of another ERAD E3, Hrd1, leads to stabilization of gp78 and decline in gp78 ubiquitination; thereby enhancing CFTRDeltaF508 degradation. The results support that gp78 is an E3 targeting CFTRDeltaF508 for degradation and Hrd1 inhibits CFTRDeltaF508 degradation by acting as an E3 for gp78.
authors.affiliation: Ege University, Faculty of Pharmacy, Izmir, 35100, Turkey. petek.ballar@ege.edu.tr
authors.forename: Petek
authors.initials: P
authors.lastname: Ballar
authors.forename: Ahmet Uygar
authors.initials: AU
authors.lastname: Ors
authors.forename: Hui
authors.initials: H
authors.lastname: Yang
authors.forename: Shengyun
authors.initials: S
authors.lastname: Fang
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism*; D020868:Gene Silencing; D006801:Humans; D051379:Mice; D050505:Mutant Proteins / Q000378:metabolism; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D054829:RING Finger Domains; D060285:Receptors, Autocrine Motility Factor; D018121:Receptors, Cytokine / Q000737:chemistry / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000378:metabolism*; D054875:Ubiquitination; D000074405:Valosin Containing Protein
chemical_list: D018797:Cell Cycle Proteins; D050505:Mutant Proteins; D018121:Receptors, Cytokine; C093349:cystic fibrosis transmembrane conductance regulator delta F508; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; C555000:AMFR protein, human; C555002:Amfr protein, mouse; D060285:Receptors, Autocrine Motility Factor; C482345:SYVN1 protein, human; D044767:Ubiquitin-Protein Ligases; D000251:Adenosine Triphosphatases; C000614178:VCP protein, human; D000074405:Valosin Containing Protein; C000614179:Vcp protein, mouse