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Multiple Calcium Pathways Induce the Expression of SNAP‐25 Protein in Chromaffin Cells
Author(s) -
GarcíaPalomero Esther,
Montiel Carmen,
Herrero Carlos J.,
García Antonio G.,
Alvarez Rocio M.,
Arnalich Francisco M.,
Renart Jaime,
Lara Hernan,
Cárdenas Ana M.
Publication year - 2000
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2000.0741049.x
Subject(s) - voltage dependent calcium channel , chromaffin cell , channel blocker , cytosol , chemistry , calcium , stimulation , biophysics , receptor , endocrinology , medicine , g protein , microbiology and biotechnology , biology , adrenal medulla , biochemistry , catecholamine , enzyme , organic chemistry
Incubation of bovine adrenal chromaffin cells in high K + (38 m M ) during 24‐48 h enhanced 2.5 to five times the expression of SNAP‐25 protein and mRNA, respectively. This increase was reduced 86% by furnidipine (an L‐type Ca 2+ channel blocker) but was unaffected by either ω‐conotoxin GVIA (an N‐type Ca 2+ channel blocker) or ω‐agatoxin IVA (a P/Q‐type Ca 2+ channel blocker). Combined blockade of N and P/Q channels with ω‐conotoxin MVIIC did, however, block by 76% the protein expression. The inhibitory effects of furnidipine were partially reversed when the external Ca 2+ concentration was raised from 1.6 to 5 m M . These findings, together with the fact that nicotinic receptor activation or Ca 2+ release from internal stores also enhanced SNAP‐25 protein expression, suggest that an increment of cytosolic Ca 2+ concentration ([Ca 2+ ] i ), rather than its source or Ca 2+ entry pathway, is the critical signal to induce the protein expression. The greater coupling between L‐type Ca 2+ channels and protein expression might be due to two facts: (a) L channels contributed 50% to the global [Ca 2+ ] i rise induced by 38 m M K + in indo‐1‐loaded chromaffin cells and (b) L channels undergo less inactivation than N or P/Q channels on sustained stimulation of these cells.