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This Article Full Text Full Text (PDF) All Versions of this Article: 292/6/C2226    most recent 00540.2006v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Hernández-Ochoa, E. O. Articles by García, D. E. Search for Related Content PubMed PubMed Citation Articles by Hernández-Ochoa, E. O. Articles by García, D. E.

RECEPTORS AND SIGNAL TRANSDUCTION

G protein activation inhibits gating charge movement in rat sympathetic neurons

Erick O. Hernández-Ochoa,^1,2 Rafael E. García-Ferreiro,^1, and David E. García¹

¹Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México, México D. F., México; and ²Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland

Submitted 20 October 2006 ; accepted in final form 12 February 2007

G protein-coupled receptors (GPCRs) control neuronal functions via ion channel modulation. For voltage-gated ion channels, gating charge movement precedes and underlies channel opening. Therefore, we sought to investigate the effects of G protein activation on gating charge movement. Nonlinear capacitive currents were recorded using the whole cell patch-clamp technique in cultured rat sympathetic neurons. Our results show that gating charge movement depends on voltage with average Boltzmann parameters: maximum charge per unit of linear capacitance (Q_max) = 6.1 ± 0.6 nC/µF, midpoint (V_h) = –29.2 ± 0.5 mV, and measure of steepness (k) = 8.4 ± 0.4 mV. Intracellular dialysis with GTPS produces a nonreversible 34% decrease in Q_max, a 10 mV shift in V_h, and a 63% increase in k with respect to the control. Norepinephrine induces a 7 mV shift in V_h and 40% increase in k. Overexpression of G protein ₁₄ subunits produces a 13% decrease in Q_max, a 9 mV shift in V_h, and a 28% increase in k. We correlate charge movement modulation with the modulated behavior of voltage-gated channels. Concurrently, G protein activation by transmitters and GTPS also inhibit both Na⁺ and N-type Ca²⁺ channels. These results reveal an inhibition of gating charge movement by G protein activation that parallels the inhibition of both Na⁺ and N-type Ca²⁺ currents. We propose that gating charge movement decrement may precede or accompany some forms of GPCR-mediated channel current inhibition or downregulation. This may be a common step in the GPCR-mediated inhibition of distinct populations of voltage-gated ion channels.

ion channel modulation; G protein-coupled receptors; charge movement