title: Hsp40 chaperones promote degradation of the HERG potassium channel.
abstract: Loss of function mutations in the hERG (human ether-a-go-go related gene or KCNH2) potassium channel underlie the proarrhythmic cardiac long QT syndrome type 2. Most often this is a consequence of defective trafficking of hERG mutants to the cell surface, with channel retention and degradation at the endoplasmic reticulum. Here, we identify the Hsp40 type 1 chaperones DJA1 (DNAJA1/Hdj2) and DJA2 (DNAJA2) as key modulators of hERG degradation. Overexpression of the DJAs reduces hERG trafficking efficiency, an effect eliminated by the proteasomal inhibitor lactacystin or with DJA mutants lacking their J domains essential for Hsc70/Hsp70 activation. Both DJA1 and DJA2 cause a decrease in the amount of hERG complexed with Hsc70, indicating a preferential degradation of the complex. Similar effects were observed with the E3 ubiquitin ligase CHIP. Both the DJAs and CHIP reduce hERG stability and act differentially on folding intermediates of hERG and the disease-related trafficking mutant G601S. We propose a novel role for the DJA proteins in regulating degradation and suggest that they act at a critical point in secretory pathway quality control.
authors: Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada.
authors: Valerie E
authors: VE
authors: Walker
authors: Michael J H
authors: MJ
authors: Wong
authors: Roxana
authors: R
authors: Atanasiu
authors: Christine
authors: C
authors: Hantouche
authors: Jason C
authors: JC
authors: Young
authors: Alvin
authors: A
authors: Shrier
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D018833:Chaperonins / Q000737:chemistry; D003720:Densitometry / Q000379:methods; D004721:Endoplasmic Reticulum / Q000378:metabolism; D051638:Ether-A-Go-Go Potassium Channels / Q000378:metabolism*; D050956:HSP40 Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008133:Long QT Syndrome; D018832:Molecular Chaperones / Q000737:chemistry; D009154:Mutation; D061988:Proteasome Inhibitors; D017510:Protein Folding
chemical_list: C107481:DNAJA1 protein, human; C494645:DNAJA2 protein, human; D051638:Ether-A-Go-Go Potassium Channels; D050956:HSP40 Heat-Shock Proteins; C496884:KCNH1 protein, human; D018832:Molecular Chaperones; D061988:Proteasome Inhibitors; C067713:lactacystin; D018833:Chaperonins; D000111:Acetylcysteine