TY - JOUR
T1 - cAMP-dependent phosphorylation of the cardiac-type α1 subunit of the voltage-dependent Ca2+ channel in a murine pancreatic β-cell line
AU - Leiser, Margarita
AU - Fleischer, Norman
N1 - Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 1996
Y1 - 1996
N2 - Two voltage-dependent calcium channels (VDCCs) have been reported in pancreatic islets: the β-cell/endocrine-brain and cardiac subtypes. The cardiac-type α1 subunit was isolated from cultured βTC3 cells, a murine pancreatic β-cell line, by immunoprecipitation with a specific polyclonal antibody. We have examined the effects of 1-isobutyl-3-methylxanthine (IBMX) and forskolin, agonists that elevate cAMP in these cells, on the phosphorylation of this subunit in intact βTC3 cells using a sensitive back- phosphorylation technique. This technique allows quantitative detection of protein phosphorylation that is specifically stimulated by cAMP. The stimulation of intact βTC3 cells with forskolin or IBMX resulted in the phosphorylation of the cardiac-type α1 subunit as evidenced by a 40-60% decrease in the ability of the 257-kDa form to serve as a substrate in the in vitro back-phosphorylation reaction with [γ-32P]ATP and the catalytic subunit of cAMP-dependent protein kinase (PKA). The effects of forskolin were time- and concentration-dependent. The concentration-dependency of forskolin- induced phosphorylation of the cardiac-type α1 subunit and the potentiation of glucose-induced insulin secretion were highly correlated, a finding that is consistent with a role for such phosphorylation in mediating at least some of the effects of cAMP on secretion.
AB - Two voltage-dependent calcium channels (VDCCs) have been reported in pancreatic islets: the β-cell/endocrine-brain and cardiac subtypes. The cardiac-type α1 subunit was isolated from cultured βTC3 cells, a murine pancreatic β-cell line, by immunoprecipitation with a specific polyclonal antibody. We have examined the effects of 1-isobutyl-3-methylxanthine (IBMX) and forskolin, agonists that elevate cAMP in these cells, on the phosphorylation of this subunit in intact βTC3 cells using a sensitive back- phosphorylation technique. This technique allows quantitative detection of protein phosphorylation that is specifically stimulated by cAMP. The stimulation of intact βTC3 cells with forskolin or IBMX resulted in the phosphorylation of the cardiac-type α1 subunit as evidenced by a 40-60% decrease in the ability of the 257-kDa form to serve as a substrate in the in vitro back-phosphorylation reaction with [γ-32P]ATP and the catalytic subunit of cAMP-dependent protein kinase (PKA). The effects of forskolin were time- and concentration-dependent. The concentration-dependency of forskolin- induced phosphorylation of the cardiac-type α1 subunit and the potentiation of glucose-induced insulin secretion were highly correlated, a finding that is consistent with a role for such phosphorylation in mediating at least some of the effects of cAMP on secretion.
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U2 - 10.2337/diab.45.10.1412
DO - 10.2337/diab.45.10.1412
M3 - Article
C2 - 8826979
AN - SCOPUS:0029780355
VL - 45
SP - 1412
EP - 1418
JO - Diabetes
JF - Diabetes
SN - 0012-1797
IS - 10
ER -