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Structural and biophysical determinants of single CaV3.1 and CaV3.2 T-type calcium channel inhibition by N2O

2009; Elsevier BV; Volume: 46; Issue: 4 Linguagem: Inglês

10.1016/j.ceca.2009.09.002

1532-1991

Peter H. Bartels, Kerstin Behnke, Guido Michels, Ferdi Gröner, Toni Schneider, Margit Henry, Paula Q. Barrett, Ho‐Won Kang, Jung‐Ha Lee, Martin H. J. Wiesen, Jan Matthes, Stefan Herzig,

Nicotinic Acetylcholine Receptors Study

We investigated the biophysical mechanism of inhibition of recombinant T-type calcium channels Ca(V)3.1 and Ca(V)3.2 by nitrous oxide (N(2)O). To identify functionally important channel structures, chimeras with reciprocal exchange of the N-terminal domains I and II and C-terminal domains III and IV were examined. In whole-cell recordings N(2)O significantly inhibited Ca(V)3.2, and - less pronounced - Ca(V)3.1. A Ca(V)3.2-prevalent inhibition of peak currents was also detected in cell-attached multi-channel patches. In cell-attached patches containing < or = 3 channels N(2)O reduced average peak current of Ca(V)3.2 by decreasing open probability and open time duration. Effects on Ca(V)3.1 were smaller and mediated by a reduced fraction of sweeps containing channel activity. Without drug, single Ca(V)3.1 channels were significantly less active than Ca(V)3.2. Chimeras revealed that domains III and IV control basal gating properties. Domains I and II, in particular a histidine residue within Ca(V)3.2 (H191), are responsible for the subtype-prevalent N(2)O inhibition. Our study demonstrates the biophysical (open times, open probability) and structural (domains I and II) basis of action of N(2)O on Ca(V)3.2. Such a fingerprint of single channels can help identifying the molecular nature of native channels. This is exemplified by a characterization of single channels expressed in human hMTC cells as functional homologues of recombinant Ca(V)3.1.