title: Nitric oxide augments voltage-gated P/Q-type Ca(2+) channels constituting a putative positive feedback loop.
abstract: P/Q-type Ca(2+) channels, which are postulated to play major roles in synaptic transmission, are regulated in a variety of ways. Ca(2+) currents through P/Q-type Ca(2+) channels (Ca(v)2.1/beta(1a)/alpha(2)delta) heterologously expressed in mammalian cells were recorded using the whole-cell patch clamp method. The oxidant H(2)O(2) increased the current amplitude and the effect was reversed by the reducing agent dithiothreitol (DTT). The stimulatory effect of H(2)O(2) on the Ca(2+) current was mimicked by the NO donors, SNAP, and diethylamine NONOate, and reversed by the reducing agent DTT. The presence of a soluble guanylate cyclase inhibitor did not abolish the ability of SNAP to increase the Ca(2+) current. Adenovirus-mediated overexpression of nitric oxide synthase in combination with application of the Ca(2+) ionophore A23187 also increased the Ca(2+) current amplitude and the effect was again reversed by DTT. The NOS inhibitor L-NAME abolished the stimulatory effect of A23187, and A23187 did not change the Ca(2+) currents in the cells treated with control adenovirus particles. The time course of the decline of the Ca(2+) current, but not of the Ba(2+) current, in response to repeated depolarization was markedly slowed by adenovirus-mediated overexpression of nitric oxide synthase. The results demonstrate that nitric oxide enhances the channel activity by promoting oxidation and suggest that Ca(2+), nitric oxide synthase, and nitric oxide could constitute a positive feedback loop for regulation of voltage-gated P/Q-type Ca(2+) channels.
authors.affiliation: Department of Physiology and Biophysics, The University of Iowa, Iowa City, IA, USA.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Chen
authors.forename: Heather
authors.initials: H
authors.lastname: Daggett
authors.forename: Michel
authors.initials: M
authors.lastname: De Waard
authors.forename: S H
authors.initials: SH
authors.lastname: Heinemann
authors.forename: Toshinori
authors.initials: T
authors.lastname: Hoshi
mesh_terms: D000256:Adenoviridae; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020864:Calcium Channels, N-Type / Q000378:metabolism*; D002478:Cells, Cultured / Q000187:drug effects* / Q000378:metabolism; D004229:Dithiothreitol / Q000378:metabolism; D004594:Electrophysiology; D025461:Feedback, Physiological / Q000502:physiology*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008322:Mammals; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D018408:Patch-Clamp Techniques; D014162:Transfection; D015854:Up-Regulation / Q000502:physiology*
chemical_list: D000001:Calcimycin; D002118:Calcium; D020864:Calcium Channels, N-Type; D004229:Dithiothreitol; D006861:Hydrogen Peroxide; D007476:Ionophores; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide; D020030:Nitric Oxide Donors; D019001:Nitric Oxide Synthase