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Protein Kinase C‐Mediated Down‐Regulation of Voltage‐Dependent Sodium Channels in Adrenal Chromaffin Cells
Author(s) -
Yanagita Toshihiko,
Wada Akihiko,
Yamamoto Ryuichi,
Kobayashi Hideyuki,
Yuhi Tomoaki,
Urabe Masanobu,
Niina Hiromi
Publication year - 1996
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.1471-4159.1996.66031249.x
Subject(s) - veratridine , protein kinase c , cycloheximide , sodium channel , chromaffin cell , activator (genetics) , chemistry , allosteric regulation , protein kinase a , adrenal medulla , microbiology and biotechnology , endocrinology , medicine , phosphorylation , biochemistry , biology , sodium , receptor , protein biosynthesis , catecholamine , organic chemistry
Treatment of cultured bovine adrenal chromaffin cells with 12‐ O ‐tetradecanoylphorbol 13‐acetate (TPA), an activator of protein kinase C (PKC), decreased [ 3 H]saxitoxin ([ 3 H]STX) binding in a concentration (IC 50 = 19 n M )‐ and time ( t 1/2 = 4.5 h)‐dependent manner. TPA (100 n M for 15 h) lowered the B max of [ 3 H]STX binding by 53% without altering the K D value. Phorbol 12,13‐dibutyrate (PDBu) also reduced [ 3 H]STX binding, whereas 4α‐TPA, an inactive analogue, had no effect. The inhibitory effect of TPA was abolished when H‐7 (an inhibitor of PKC), but not H‐89 (an inhibitor of cyclic AMP‐dependent protein kinase), was included in the culture medium for 1 h before and during TPA treatment. Simultaneous treatment with TPA in combination with either actinomycin D or cycloheximide, an inhibitor of protein synthesis, nullified the effect of TPA. TPA treatment also attenuated veratridine‐induced 22 Na + influx but did not alter the affinity of veratridine for Na channels as well as an allosteric potentiation of veratridine‐induced 22 Na + influx by brevetoxin. These results suggest that an activation of PKC down‐regulates the density of Na channels without altering their pharmacological features; this down‐regulation is mediated via the de novo synthesis of an as yet unidentified protein(s), rather than an immediate effect of Na channel phosphorylation.