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Insulin‐Like Growth Factor‐I‐Enhanced Secretion Is Abolished in Protein Kinase C‐Deficient Chromaffin Cells
Author(s) -
Penberthy W. Todd,
Dahmer Mary K.
Publication year - 1994
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.1471-4159.1994.62051707.x
Subject(s) - secretion , chromaffin cell , endocrinology , microbiology and biotechnology , protein kinase a , medicine , growth factor , insulin like growth factor , kinase , biology , chemistry , adrenal medulla , biochemistry , catecholamine , receptor
Previous studies have demonstrated that bovine chromaffin cells cultured in medium with 10 n M insulin‐like growth factor‐I (IGF‐I) secrete about twofold more catecholamine when exposed to secretory stimuli than do cells cultured without IGF‐I. The purpose of this study was to determine whether protein kinase C (PKC) is involved in the effect of IGF‐I on secretion from these cells. PKC was down‐regulated in the cells by 16–18 h of treatment with β‐phorbol didecanoate (β‐PDD; 100 n M ). Such treatment had no effect on high‐K + ‐stimulated secretion from cells cultured without IGF‐I; however, secretion from cells cultured with IGF‐I was reduced to a level comparable to that in cells cultured without the peptide. The inactive isomer, α‐PDD (100 n M ), had no effect on secretion from untreated or IGF‐I‐treated chromaffin cells. The effect of β‐PDD was time and concentration dependent, with 100 n M β‐PDD producing a maximal effect in 8–10 h. In situ PKC activity measured in permeabilized cells treated with PMA (300 n M ) was decreased by∼40% by 10 h and was reduced to almost basal levels by 18 h. Immunoblotting experiments demonstrated that both α‐and ε‐PKC were lost from the cells with time courses similar to that seen in the in situ PKC assay. Overnight treatment with the PKC inhibitor H7 (100 μ M ) prevented the enhanced secretion normally seen in IGF‐l‐treated cells, whereas HA1004 had no effect. High‐K + ‐stimulated 45 Ca 2+ uptake in IGF‐I‐treated cells was attenuated by long‐term treatment with β‐PDD (200 n M ) or H7 (100 μ M ). Together these observations suggest that PKC is required for IGF‐I‐enhanced secretion from chromaffin cells.