Referenced in: none

Automatically associated channels: Cav1.2 , Kir2.3 , Slo1

Title: Role of extracellular Ca2+ in gating of CaV1.2 channels.

Authors: Olga Babich, Dmytro Isaev, Roman Shirokov

Journal, date & volume: J. Physiol. (Lond.), 2005 Jun 15 , 565, 709-15

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/15845581

Abstract
We examined changes in ionic and gating currents in Ca(V)1.2 channels when extracellular Ca(2+) was reduced from 10 mm to 0.1 microm. Saturating gating currents decreased by two-thirds (K(D) approximately 40 microm) and ionic currents increased 5-fold (K(D) approximately 0.5 microm) due to increasing Na(+) conductance. A biphasic time dependence for the activation of ionic currents was observed at low [Ca(2+)], which appeared to reflect the rapid activation of channels that were not blocked by Ca(2+) and a slower reversal of Ca(2+) blockade of the remaining channels. Removal of Ca(2+) following inactivation of Ca(2+) currents showed that Na(+) currents were not affected by Ca(2+)-dependent inactivation. Ca(2+)-dependent inactivation also induced a negative shift of the reversal potential for ionic currents suggesting that inactivation alters channel selectivity. Our findings suggest that activation of Ca(2+) conductance and Ca(2+)-dependent inactivation depend on extracellular Ca(2+) and are linked to changes in selectivity.