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IKs response to protein kinase A-dependent KCNQ1 phosphorylation requires direct interaction with microtubules

Céline S. Nicolas, Kyu-Ho Park, Aziza El Harchi, Jacques Camonis, Robert S. Kass, Denis Escande, Jean Mérot, Gildas Loussouarn, Françoise Le Bouffant, Isabelle Baró
DOI: http://dx.doi.org/10.1093/cvr/cvn085 427-435 First published online: 5 April 2008

Abstract

Aims KCNQ1 (alias KvLQT1 or Kv7.1) and KCNE1 (alias IsK or minK) co-assemble to form the voltage-activated K+ channel responsible for IKs—a major repolarizing current in the human heart—and their dysfunction promotes cardiac arrhythmias. The channel is a component of larger macromolecular complexes containing known and undefined regulatory proteins. Thus, identification of proteins that modulate its biosynthesis, localization, activity, and/or degradation is of great interest from both a physiological and pathological point of view.

Methods and results Using a yeast two-hybrid screening, we detected a direct interaction between β-tubulin and the KCNQ1 N-terminus. The interaction was confirmed by co-immunoprecipitation of β-tubulin and KCNQ1 in transfected COS-7 cells and in guinea pig cardiomyocytes. Using immunocytochemistry, we also found that they co-localized in cardiomyocytes. We tested the effects of microtubule-disrupting and -stabilizing agents (colchicine and taxol, respectively) on the KCNQ1–KCNE1 channel activity in COS-7 cells by means of the permeabilized-patch configuration of the patch-clamp technique. None of these agents altered IKs. In addition, colchicine did not modify the current response to osmotic challenge. On the other hand, the IKs response to protein kinase A (PKA)-mediated stimulation depended on microtubule polymerization in COS-7 cells and in cardiomyocytes. Strikingly, KCNQ1 channel and Yotiao phosphorylation by PKA—detected by phospho-specific antibodies—was maintained, as was the association of the two partners.

Conclusion We propose that the KCNQ1–KCNE1 channel directly interacts with microtubules and that this interaction plays a major role in coupling PKA-dependent phosphorylation of KCNQ1 with IKs activation.

KEYWORDS
  • K+ channel
  • Myocytes
  • PKA
  • Signal transduction
  • KCNQ1
  • β-tubulin
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