title: The Cullin 4A/B-DDB1-Cereblon E3 Ubiquitin Ligase Complex Mediates the Degradation of CLC-1 Chloride Channels.
abstract: Voltage-gated CLC-1 chloride channels play a critical role in controlling the membrane excitability of skeletal muscles. Mutations in human CLC-1 channels have been linked to the hereditary muscle disorder myotonia congenita. We have previously demonstrated that disease-associated CLC-1 A531V mutant protein may fail to pass the endoplasmic reticulum quality control system and display enhanced protein degradation as well as defective membrane trafficking. Currently the molecular basis of protein degradation for CLC-1 channels is virtually unknown. Here we aim to identify the E3 ubiquitin ligase of CLC-1 channels. The protein abundance of CLC-1 was notably enhanced in the presence of MLN4924, a specific inhibitor of cullin-RING E3 ligases. Subsequent investigation with dominant-negative constructs against specific subtypes of cullin-RING E3 ligases suggested that CLC-1 seemed to serve as the substrate for cullin 4A (CUL4A) and 4B (CUL4B). Biochemical examinations further indicated that CUL4A/B, damage-specific DNA binding protein 1 (DDB1), and cereblon (CRBN) appeared to co-exist in the same protein complex with CLC-1. Moreover, suppression of CUL4A/B E3 ligase activity significantly enhanced the functional expression of the A531V mutant. Our data are consistent with the idea that the CUL4A/B-DDB1-CRBN complex catalyses the polyubiquitination and thus controls the degradation of CLC-1 channels.
authors.affiliation: Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Yi-An
authors.initials: YA
authors.lastname: Chen
authors.affiliation: Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Yi-Jheng
authors.initials: YJ
authors.lastname: Peng
authors.affiliation: Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Meng-Chun
authors.initials: MC
authors.lastname: Hu
authors.affiliation: Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Jing-Jia
authors.initials: JJ
authors.lastname: Huang
authors.affiliation: Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Yun-Chia
authors.initials: YC
authors.lastname: Chien
authors.affiliation: Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: June-Tai
authors.initials: JT
authors.lastname: Wu
authors.affiliation: Neuroscience Center, University of California, Davis, USA.
authors.forename: Tsung-Yu
authors.initials: TY
authors.lastname: Chen
authors.affiliation: 1] Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan [2] Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Chih-Yung
authors.initials: CY
authors.lastname: Tang
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D018118:Chloride Channels / Q000096:biosynthesis / Q000378:metabolism*; D044842:Cullin Proteins / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D009154:Mutation; D009224:Myotonia Congenita / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D010447:Peptide Hydrolases / Q000235:genetics* / Q000378:metabolism; D059748:Proteolysis; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C086321:CLC-1 channel; C502543:CRBN protein, human; C114234:CUL4A protein, human; C517832:CUL4B protein, human; D018118:Chloride Channels; D044842:Cullin Proteins; C091435:DDB1 protein, human; D004268:DNA-Binding Proteins; D046912:Multiprotein Complexes; D044767:Ubiquitin-Protein Ligases; D010447:Peptide Hydrolases