Deubiquitylating enzyme USP2 counteracts Nedd4-2-mediated downregulation of KCNQ1 potassium channels.
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Krzystanek K, Rasmussen HB, Grunnet M, Staub O, Olesen SP, Abriel H, Jespersen T
Deubiquitylating enzyme USP2 counteracts Nedd4-2-mediated downregulation of KCNQ1 potassium channels.
Heart Rhythm. 2012 Mar;9(3):440-8. doi: 10.1016/j.hrthm.2011.10.026. Epub 2011 Oct 22.
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- 22024150 [ View in PubMed]
- Abstract
BACKGROUND: KCNQ1 (Kv7.1), together with its KCNE beta subunits, plays a pivotal role both in the repolarization of cardiac tissue and in water and salt transport across epithelial membranes. Nedd4/Nedd4-like (neuronal precursor cell-expressed developmentally downregulated 4) ubiquitin-protein ligases interact with the KCNQ1 potassium channel through a PY motif located in the C terminus of KCNQ1. This interaction induces ubiquitylation of KCNQ1, resulting in a reduced surface density of the channel. It was reported recently that the epithelial sodium channel is regulated by the reverse process-deubiquitylation-mediated by USP2 (ubiquitin-specific protease 2). OBJECTIVE: In this article, we investigated whether deubiquitylation may regulate KCNQ1 channel complexes. METHODS: In this study, we used electrophysiology, biochemistry, and confocal microscopy. RESULTS: Electrophysiological investigations of KCNQ1/KCNE1 proteins coexpressed with USP2-45 or USP2-69 isoforms and Nedd4-2 in Xenopus laevis oocytes and mammalian cells revealed that both USP2 isoforms counter the Nedd4-2-specific downregulation of I(Ks). Biochemical studies showed that the total and surface-expressed KCNQ1 protein was more abundant when coexpressed with USP2 and Nedd4-2 as compared with Nedd4-2 alone. Western blotting revealed partial protection against covalent attachment of ubiquitin moieties on KCNQ1 when USP2 was coexpressed with Nedd4-2. Coimmunoprecipitation assays suggested that USP2 can bind to KCNQ1 independently of the PY motif. Immunocytochemistry confirmed that USP2 restores the membrane localization of KCNQ1. CONCLUSION: These results demonstrate that USP2 can be a potent regulator of KCNQ1 surface density. USP2, which is well expressed in many tissues, may therefore be important in controlling the KCNQ1 channel dynamics in vivo.