title: Regulation of large conductance Ca2+-activated K+ (BK) channel β1 subunit expression by muscle RING finger protein 1 in diabetic vessels.
abstract: The large conductance Ca(2+)-activated K(+) (BK) channel, expressed abundantly in vascular smooth muscle cells (SMCs), is a key determinant of vascular tone. BK channel activity is tightly regulated by its accessory β1 subunit (BK-β1). However, BK channel function is impaired in diabetic vessels by increased ubiquitin/proteasome-dependent BK-β1 protein degradation. Muscle RING finger protein 1 (MuRF1), a muscle-specific ubiquitin ligase, is implicated in many cardiac and skeletal muscle diseases. However, the role of MuRF1 in the regulation of vascular BK channel and coronary function has not been examined. In this study, we hypothesized that MuRF1 participated in BK-β1 proteolysis, leading to the down-regulation of BK channel activation and impaired coronary function in diabetes. Combining patch clamp and molecular biological approaches, we found that MuRF1 expression was enhanced, accompanied by reduced BK-β1 expression, in high glucose-cultured human coronary SMCs and in diabetic vessels. Knockdown of MuRF1 by siRNA in cultured human SMCs attenuated BK-β1 ubiquitination and increased BK-β1 expression, whereas adenoviral expression of MuRF1 in mouse coronary arteries reduced BK-β1 expression and diminished BK channel-mediated vasodilation. Physical interaction between the N terminus of BK-β1 and the coiled-coil domain of MuRF1 was demonstrated by pulldown assay. Moreover, MuRF1 expression was regulated by NF-κB. Most importantly, pharmacological inhibition of proteasome and NF-κB activities preserved BK-β1 expression and BK-channel-mediated coronary vasodilation in diabetic mice. Hence, our results provide the first evidence that the up-regulation of NF-κB-dependent MuRF1 expression is a novel mechanism that leads to BK channelopathy and vasculopathy in diabetes.
authors.affiliation: Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905; Department of Cardiology, Xijing Hospital, Fourth Military Medical University, Xian 710032, China.
authors.forename: Fu
authors.initials: F
authors.lastname: Yi
authors.affiliation: Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905.
authors.forename: Huan
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Chai
authors.affiliation: Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Internal Medicine, Mayo Clinic, Scottsdale, Arizona 85259.
authors.forename: Win-Kuang
authors.initials: WK
authors.lastname: Shen
authors.affiliation: Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, North Carolina 27599.
authors.forename: Monte S
authors.initials: MS
authors.lastname: Willis
authors.affiliation: Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905.
authors.forename: Hon-Chi
authors.initials: HC
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905. Electronic address: lu.tong@mayo.edu.
authors.forename: Tong
authors.initials: T
authors.lastname: Lu
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism; D003925:Diabetic Angiopathies / Q000378:metabolism*; D004594:Electrophysiology; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018715:Microscopy, Video; D009124:Muscle Proteins / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D017434:Protein Structure, Tertiary; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: C543091:Kcnmb1 protein, mouse; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D009124:Muscle Proteins; D016328:NF-kappa B; D000070584:Tripartite Motif Proteins; C499084:Trim63 protein, mouse; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex
keywords: Diabetes; Potassium Channels; Protein Degradation; Ubiquitin Ligase; Vascular Smooth Muscle Cells