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Acta Physiologica 2012; Volume 206, Supplement 693
Joint FEPS and Spanish Physiological Society Scientific Congress 2012
9/8/2012-9/11/2012
Santiago de Compostela, Spain
NOVEL REGULATION OF KV1.3 CHANNEL INACTIVATION BY INTRACELLULAR CA2+
Abstract number: O177
Martinez-Pinna1 J, McCloskey2 C, Fernandez-Martinez1 V, Wright2 J, Forsythe2 I, Kaczmarek3 L, Morales1 A, Mahaut-Smith2 M
1Fisiologa, Gentica y Microbiologa, Universidad de Alicante,
2Cell Physiology and Pharmacology, University of Leicester,
3Cellular and Molecular Physiology, Yale University
Objectives:
Kv1.3 is a ubiquitously expressed voltage-gated K+ channel with C-type inactivation. A recent study in platelets and megakaryocytes, has demonstrated that Kv1.3 is the exclusive voltage-gated K+ channel and the main determinant of the resting membrane potential (RMP; McCloskey et al, J Physiol 588.9 (2010)). We have now investigated the regulation of Kv1.3 during activation of GPCRs with the aim of understanding how this conductance may contribute to the membrane potential during Ca2+ signalling.
Materials:
Simultaneous electrophysiological recordings (whole-cell patch clamp or TEVC) and Ca2+ fluorimetry were performed in megakaryocytes from wild-type or Kv1.3-deficient mice, COS-7 cells (gift of S.Grissmer, Ulm, Germany) and Xenopus oocytes.
Results:
Purinergic P2Y1 GPCR stimulation (1 mM ADP) profoundly reduced voltage-dependent inactivation of Kv1.3 channels in mouse megakaryocytes. The current at the end of 3s step depolarisations was enhanced by up to 8-fold, with only a minor decrease in the peak current. The reduced Kv1.3 inactivation was mediated by an increase in [Ca2+]i since it was blocked by intracellular BAPTA and mimicked by application of ionomycin. The PKC blocker Ro-31-8220 had no effect. Experiments with Kv1.3-deficient megakaryocytes and K+ channel blockers showed that this was not due to activation of a Ca2+-gated K+ conductance. In current clamp recordings, Ca2+-dependent modulation of Kv1.3 inactivation stabilised the membrane potential close to RMP during activation of P2Y1-evoked non-selective cation channels. The Ca2+-dependence of Kv1.3 inactivation was not restricted to megakaryocytes, as similar modulation of inactivation was observed in murine Kv1.3 channels expressed in COS-7 cells or Xenopus oocytes.
Conclusions:
Ca2+-dependent reduction of Kv1.3 inactivation represents a novel modulatory mechanism whereby GPCR activation prolongs K+ currents and stabilises the membrane potential during Ca2+ signalling.
Funded by CSD2008-00005 (MEC, Spain) and the British Heart Foundation
To cite this abstract, please use the following information:
Acta Physiologica 2012; Volume 206, Supplement 693 :O177