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International Journal of Endocrinology
Volume 2011 (2011), Article ID 746482, 13 pages
Research Article

The Involvement of Ser1898 of the Human L-Type Calcium Channel in Evoked Secretion

Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 919104, Israel

Received 3 July 2011; Accepted 17 August 2011

Academic Editor: Maria L. Dufau

Copyright © 2011 Niv Bachnoff et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A PKA consensus phosphorylation site S1928 at the α11.2 subunit of the rabbit cardiac L-type channel, CaV1.2, is involved in the regulation of CaV1.2 kinetics and affects catecholamine secretion. This mutation does not alter basal CaV1.2 current properties or regulation of CaV1.2 current by PKA and the beta-adrenergic receptor, but abolishes CaV1.2 phosphorylation by PKA. Here, we test the contribution of the corresponding PKA phosphorylation site of the human α11.2 subunit S1898, to the regulation of catecholamine secretion in bovine chromaffin cells. Chromaffin cells were infected with a Semliki-Forest viral vector containing either the human wt or a mutated S1898A α11.2 subunit. Both subunits harbor a T1036Y mutation conferring nifedipine insensitivity. Secretion evoked by depolarization in the presence of nifedipine was monitored by amperometry. Depolarization-triggered secretion in cells infected with either the wt α11.2 or α11.2/S1898A mutated subunit was elevated to a similar extent by forskolin. Forskolin, known to directly activate adenylyl-cyclase, increased the rate of secretion in a manner that is largely independent of the presence of S1898. Our results are consistent with the involvement of additional PKA regulatory site(s) at the C-tail of α11.2, the pore forming subunit of CaV1.2.