UBC9 regulates cardiac sodium channel Nav1.5 ubiquitination, degradation and sodium current density. (April 2019)

• Record Type: Journal Article
• Authors: Tang, Bo; Hu, Yushuang; Wang, Zhijie; Cheng, Chen; Wang, Pengyun; Liang, Lina; Xiong, Hongbo; Luo, Chunyan; Xu, Chengqi; Chen, Qiuyun; Wang, Qing Kenneth
• Is Part Of: Journal of molecular and cellular cardiology. Volume 129(2019)
• Page Start: 79
• Page End: 91
• Publication Date: 2019-04
• Subjects: UBC9 -- SCN5A -- Nav1.5 sodium channel -- Ubiquitination -- Nedd4–2 -- Arrhythmia; Cardiology -- Periodicals; Heart Diseases -- Periodicals; Molecular Biology -- Periodicals; Cardiologie -- Périodiques; Cardiology; Electronic journals; Periodicals; 616.12
• DOI: 10.1016/j.yjmcc.2019.02.007
• Languages: English
• ISSNs: 0022-2828

Abstract

Abstract: Voltage-gated sodium channel Nav 1.5 is critical for generation and conduction of cardiac action potentials. Mutations and expression level changes of Nav 1.5 are associated with cardiac arrhythmias and sudden death. The ubiquitin (Ub) conjugation machinery utilizes three enzyme activities, E1, E2, and E3, to regulate protein degradation. Previous studies from us and others showed that Nedd4–2 acts as an E3 ubiquitin-protein ligase involved in ubiquitination and degradation of Nav 1.5, however, more key regulators remain to be identified. In this study, we show that UBC9, a SUMO-conjugating enzyme, regulates ubiquitination and degradation of Nav 1.5. Overexpression of UBC9 significantly decreased Nav 1.5 expression and reduced sodium current densities, whereas knockdown of UBC9 expression significantly enhanced Nav 1.5 expression and increased sodium current densities, in both HEK293 cells and primary neonatal cardiomyocytes. Overexpression of UBC9 increased ubiquitination of Nav 1.5, and proteasome inhibitor MG132 blocked the effect of UBC9 overexpression on Nav 1.5 degradation. Co-immunoprecipitation showed that UBC9 interacts with Nedd4–2. UBC9 with mutation C93S, which suppresses SUMO-conjugating activity of UBC9, was as active as wild type UBC9 in regulating Nav 1.5 levels, suggesting that UBC9 regulates Nav 1.5 expression levels in a SUMOylation-independent manner. Our findings thus identify a key structural element of the ubiquitin-conjugation machinery for Nav 1.5 and provide important insights into the regulatory mechanism for ubiquitination and turnover of Nav 1.5. Highlights: UBC9 overexpression decreases Nav 1.5 expression and sodium current densities. Knockdown of UBC9 expression enhances Nav 1.5 expression and sodium current densities. UBC9 promotes Nav 1.5 ubiquitination and degradation, but not SUMOylation. UBC9 interacts with NEDD4–2, an E3 ligase for ubiquitination and degradation of Nav 1.5. UBC9 is a key structural element of the ubiquitin-conjugation machinery for Nav 1.5. UBC9 may be a target for developing treatment or therapeutic interventions for sodium channelopathies.