title: Role of Hsp90 in biogenesis of the beta-cell ATP-sensitive potassium channel complex.
abstract: The pancreatic beta-cell ATP-sensitive potassium (K(ATP)) channel is a multimeric protein complex composed of four inwardly rectifying potassium channel (Kir6.2) and four sulfonylurea receptor 1 (SUR1) subunits. K(ATP) channels play a key role in glucose-stimulated insulin secretion by linking glucose metabolism to membrane excitability. Many SUR1 and Kir6.2 mutations reduce channel function by disrupting channel biogenesis and processing, resulting in insulin secretion disease. To better understand the mechanisms governing K(ATP) channel biogenesis, a proteomics approach was used to identify chaperone proteins associated with K(ATP) channels. We report that chaperone proteins heat-shock protein (Hsp)90, heat-shock cognate protein (Hsc)70, and Hsp40 are associated with beta-cell K(ATP) channels. Pharmacologic inhibition of Hsp90 function by geldanamycin reduces, whereas overexpression of Hsp90 increases surface expression of wild-type K(ATP) channels. Coimmunoprecipitation data indicate that channel association with the Hsp90 complex is mediated through SUR1. Accordingly, manipulation of Hsp90 protein expression or function has significant effects on the biogenesis efficiency of SUR1, but not Kir6.2, expressed alone. Interestingly, overexpression of Hsp90 selectively improved surface expression of mutant channels harboring a subset of disease-causing SUR1 processing mutations. Our study demonstrates that Hsp90 regulates biogenesis efficiency of heteromeric K(ATP) channels via SUR1, thereby affecting functional expression of the channel in beta-cell membrane.
authors.affiliation: Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, OR 97239, USA.
authors.forename: Fei-Fei
authors.initials: FF
authors.lastname: Yan
authors.forename: Emily B
authors.initials: EB
authors.lastname: Pratt
authors.forename: Pei-Chun
authors.initials: PC
authors.lastname: Chen
authors.forename: Fang
authors.initials: F
authors.lastname: Wang
authors.forename: William R
authors.initials: WR
authors.lastname: Skach
authors.forename: Larry L
authors.initials: LL
authors.lastname: David
authors.forename: Show-Ling
authors.initials: SL
authors.lastname: Shyng
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000818:Animals; D016227:Benzoquinones / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D006224:Cricetinae; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D054086:KATP Channels / Q000096:biosynthesis*; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D050505:Mutant Proteins / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D021122:Protein Subunits / Q000378:metabolism; D051381:Rats; D011955:Receptors, Drug / Q000378:metabolism; D064233:Sulfonylurea Receptors; D014162:Transfection
chemical_list: D018528:ATP-Binding Cassette Transporters; C577509:Abcc8 protein, rat; D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; D054086:KATP Channels; D047029:Lactams, Macrocyclic; D050505:Mutant Proteins; D024661:Potassium Channels, Inwardly Rectifying; D021122:Protein Subunits; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors; C112765:tanespimycin