Referenced in: none

Automatically associated channels: Kir2.1

Title: Comparative analysis of inactivated-state block of N-type (Ca(v)2.2) calcium channels.

Authors: Timothy A Vortherms, Andrew M Swensen, Wende Niforatos, James T Limberis, Torben R Neelands, Richard S Janis, Rama Thimmapaya, Diana L Donnelly-Roberts, Marian T Namovic, Di Zhang, C Brent Putman, Ruth L Martin, Carol S Surowy, Michael F Jarvis, Victoria E Scott

Journal, date & volume: Inflamm. Res., 2011 Jul , 60, 683-93

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/21394563

Abstract
The aim of this study was to compare a diverse set of peptide and small-molecule calcium channel blockers for inactivated-state block of native and recombinant N-type calcium channels using fluorescence-based and automated patch-clamp electrophysiology assays.The pharmacology of calcium channel blockers was determined at N-type channels in IMR-32 cells and in HEK cells overexpressing the inward rectifying K(+) channel Kir2.1. N-type channels were opened by increasing extracellular KCl. In the Kir2.1/N-type cell line the membrane potential could be modulated by adjusting the extracellular KCl, allowing determination of resting and inactivated-state block of N-type calcium channels. The potency and degree of state-dependent inhibition of these blockers were also determined by automated patch-clamp electrophysiology.N-type-mediated calcium influx in IMR-32 cells was determined for a panel of blockers with IC(50) values of 0.001-7 μM and this positively correlated with inactivated-state block of recombinant channels measured using electrophysiology. The potency of several compounds was markedly weaker in the state-dependent fluorescence-based assay compared to the electrophysiology assay, although the degree of state-dependent blockade was comparable.The present data demonstrate that fluorescence-based assays are suitable for assessing the ability of blockers to selectively interact with the inactivated state of the N-type channel.