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Department of Anesthesiology

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Protein kinase C downregulates I(Ks) by stimulating KCNQ1-KCNE1 potassium channel endocytosis.

TitleProtein kinase C downregulates I(Ks) by stimulating KCNQ1-KCNE1 potassium channel endocytosis.
Publication TypeJournal Article
Year of Publication2011
AuthorsKanda VA, Purtell K, Abbott GW
JournalHeart Rhythm
Volume8
Issue10
Pagination1641-7
Date Published2011 Oct
ISSN1556-3871
KeywordsAnimals, Cells, Cultured, Clathrin, Cricetinae, Cricetulus, Down-Regulation, Endocytosis, KCNQ1 Potassium Channel, Microscopy, Fluorescence, Patch-Clamp Techniques, Phosphorylation, Potassium Channels, Voltage-Gated, Protein Kinase C, Transfection
Abstract

BACKGROUND: The slow-activating cardiac repolarization K(+) current (I(Ks)), generated by the KCNQ1-KCNE1 potassium channel complex, is controlled via sympathetic and parasympathetic regulation in vivo. Inherited KCNQ1 and KCNE1 mutations predispose to ventricular fibrillation and sudden death, often triggered by exercise or emotional stress. Protein kinase C (PKC), which is activated by α1 adrenergic receptor stimulation, is known to downregulate I(Ks) via phosphorylation of KCNE1 serine 102, but the underlying mechanism has remained enigmatic. We previously showed that KCNE1 mediates dynamin-dependent endocytosis of KCNQ1-KCNE1 complexes.

OBJECTIVE: This study sought to determine the potential role of endocytosis in I(Ks) downregulation by PKC.

METHODS: We utilized patch clamping and fluorescence microscopy to study Chinese hamster ovary (CHO) cells coexpressing KCNQ1, KCNE1, and wild-type or dominant-negative mutant (K44A) dynamin 2, and neonatal mouse ventricular myocytes.

RESULTS: The PKC activator phorbol 12-myristate 13-acetate (PMA) decreased I(Ks) density by >60% (P < .05) when coexpressed with wild-type dynamin 2 in CHO cells, but had no effect when coexpressed with K44A-dynamin 2. Thus, functional dynamin was required for downregulation of I(Ks) by PKC activation. PMA increased KCNQ1-KCNE1 endocytosis in CHO cells expressing wild-type dynamin 2, but had no effect on KCNQ1-KCNE1 endocytosis in CHO cells expressing K44A-dynamin 2, determined using the Pearson correlation coefficient to quantify endosomal colocalization of KCNQ1 and KCNE1 with internalized fluorescent transferrin. KCNE1-S102A abolished the effect of PMA on I(Ks) currents and endocytosis. Importantly, PMA similarly stimulated endocytosis of endogenous KCNQ1 and KCNE1 in neonatal mouse myocytes.

CONCLUSION: PKC activation downregulates I(Ks) by stimulating KCNQ1-KCNE1 channel endocytosis.

DOI10.1016/j.hrthm.2011.04.034
Alternate JournalHeart Rhythm
PubMed ID21699843
PubMed Central IDPMC3183296
Grant ListHL079275 / HL / NHLBI NIH HHS / United States
HL101190 / HL / NHLBI NIH HHS / United States
R01 HL079275 / HL / NHLBI NIH HHS / United States
R01 HL079275-05S1 / HL / NHLBI NIH HHS / United States
R01 HL079275-06A1 / HL / NHLBI NIH HHS / United States
R01 HL101190-01 / HL / NHLBI NIH HHS / United States
R01 HL101190-03 / HL / NHLBI NIH HHS / United States