Role of Actin Microfilaments in the Regulation of Voltage-Gated Ion Channels in Salamander Retinal Neurons

Abstract

Abstract: : Purpose: Intracellular Ca regulates the structure and functions of actin cytoskeletal proteins. Moreover, the functional activity of some voltage-, and ligand-gated ion channels is regulated by actin microfilaments. In this study we investigated the effect of microfilament destruction on the functioning of voltage-gated K⁺ and Ca currents. Methods: Whole-cell patch clamp technique was used to record voltage-gated currents in ganglion cells from salamander retinal slice preparation. Intracellular Ca²⁺ measurements were performed on isolated neurons using Ca imaging. Results: Disruption of actin filament after intracellular treatment with microfilament depolymerizing agents cytochalasin B (CB), or latrunculin B (LB), markedly decreased the amplitude of delayed outward K⁺ current, at depolarizing step potentials ranging from +10 to +50 mV, from a holding potential of -70 mV, and increased the current amplitude at lower command steps from -30 to 0 mV. Both, CB and LB reduced the amplitude of high voltage activated Ca currents. Ca imaging revealed a decrease of high K⁺-induced Ca²⁺ signal after incubation of neurons with the membrane permeable, microfilament depolymerizing agent, latrunculin A. Conclusions: Actin microfilament are involved in the regulation of voltage-gated K⁺ and Ca currents, suggesting that ion channels in salamander retinal ganglion cells may be modified by a dynamic assembly and disassembly of the submembranous actin cytoskeleton.

Keywords: cytoskeleton • ion channels • retina