Chronic activation of protein kinase C by phorbol ester reduces calcium channel expression in chick sympathetic neurons.
Chronic activation of protein kinase C (PKC) has been implicated in regulation of Ca2+ entry responsible for normal development of transmitter properties in cultured sympathetic neurons. The idea that PKC alters the expression of Ca2+ channels was tested using phorbol 12,13-dibutyrate (PDB) which activates PKC and also supports survival of chick sympathetic neurons in the absence of nerve growth factor (NGF). Whole cell voltage-clamp showed that neurons supported by PDB for 2 days had significantly lower Ca2+ current density (0.243 +/- 0.025 pA/microm2) than those supported by NGF (0.356 +/- 0.033 pA/microm2). [125I]omega-Conotoxin GVIA binding showed that PDB-supported neurons had significantly lower maximum binding (617 +/- 223 fmol/mg protein) compared with those supported by NGF (1099 +/- 192 fmol/mg protein). These results support the conclusion that chronic activation of PKC limits the expression of N-type Ca2+ channels. A reduction in Ca2+ channel number is consistent with, and could account for the mature type Ca2+ handling and transmitter release properties seen in sympathetic neuro-effector preparations, sympathetic neurons co-cultured with their targets, and neurons supported by PDB.
Przywara
D A
DA
Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Zhong
H
H
Kulkarni
J S
JS
Anderson
G F
GF
Wakade
A R
AR
D000818:Animals; D015220:Calcium Channels / Q000187:drug effects*; D002642:Chick Embryo; D005728:Ganglia, Sympathetic / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects; D010703:Phorbol Esters / Q000494:pharmacology*; D011493:Protein Kinase C / Q000187:drug effects* / Q000502:physiology; D013997:Time Factors
D015220:Calcium Channels; D010703:Phorbol Esters; D011493:Protein Kinase C