Protein kinase C-mediated down-regulation of voltage-dependent sodium channels in adrenal chromaffin cells

• Published in: Journal of neurochemistry Vol. 66; no. 3; p. 1249
• Main Authors: Yanagita, T, Wada, A, Yamamoto, R, Kobayashi, H, Yuhi, T, Urabe, M, Niina, H
• Format: Journal Article
• Language: English
• Published: England 01.03.1996
• Subjects: Adrenal Glands - cytology; Adrenal Glands - metabolism; Animals; Cattle; Cells, Cultured; Chromaffin System - cytology; Chromaffin System - metabolism; Cyclic AMP-Dependent Protein Kinases - antagonists & inhibitors; Down-Regulation; Electrophysiology; Phorbol Esters - pharmacology; Protein Kinase C - antagonists & inhibitors; Protein Kinase C - physiology; Protein Synthesis Inhibitors - pharmacology; Saxitoxin - metabolism; Sodium Channels - drug effects; Sodium Channels - physiology; Tetradecanoylphorbol Acetate - pharmacology; Veratridine - pharmacology
• ISSN: 0022-3042
• DOI: 10.1046/j.1471-4159.1996.66031249.x

Treatment of cultured bovine adrenal chromaffin cells with 12-O-tetradecanoylphorbol 13-acetate (TPA), an activator of protein kinase C (PKC), decreased [3H]saxitoxin ([3H]STX) binding in a concentration (IC50 = 19 nM)- and time (t1/2 = 4.5 h)-dependent manner. TPA (100 nM for 15 h) lowered the Bmax of [3H]STX binding by 53% without altering the KD value. Phorbol 12,13-dibutyrate (PDBu) also reduced [3H]STX binding, whereas 4 alpha-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 22Na+ influx but did not alter the affinity of veratridine for Na channels as well as an allosteric potentiation of veratridine-induced 22Na+ 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.