Referenced in: none

Automatically associated channels: Kv2.1

Title: Mitsugumin 53-mediated maintenance of K+ currents in cardiac myocytes.

Authors: Haruko Masumiya, Yasuhide Asaumi, Miyuki Nishi, Susumu Minamisawa, Satomi Adachi-Akahane, Morikatsu Yoshida, Kenji Kangawa, Kenta Ito, Yutaka Kagaya, Teruyuki Yanagisawa, Tetsuo Yamazaki, Jianjie Ma, Hiroshi Takeshima

Journal, date & volume: Channels (Austin), 2009 Jan-Feb , 3, 6-11

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/19202355

Abstract
Mitsugumin 53 (MG53) is a muscle-specific RBCC/TRIM family member predominantly localized on small vesicles underneath the plasma membrane. Upon cell-surface lesion MG53 recruits the vesicles to the repair site in an oxidation-dependent manner and MG53-knockout mice develop progressive myopathy associated with defective membrane repair. In this report, we focus on MG53-knockout cardiomyocytes showing abnormal action potential profile and a reduced K+ current density. In cDNA expression experiments using cultured cells, KV2.1-mediated currents were remarkably increased by MG53 without affecting the total and cell-surface levels of channel expression. In imaging analysis MG53 seemed to facilitate the mobility of KV2.1-containing endocytic vesicles with acidic pH. However, similar effects on the current density and vesicular mobility were not observed in the putative dominant-negative form of MG53. Our data suggest that MG53 is involved in a constitutive cycle of certain cell-surface proteins between the plasma membrane and endosome-like vesicles in striated muscle, and also imply that the vesicular dynamics are essential for the quality control of KV2.1 in cardiomyocytes.