Down-regulation or long-term inhibition of protein kinase C (PKC) reduces noradrenaline release evoked via either PKC-dependent or PKC-independent pathways in human SH-SY5Y neuroblastoma cells.
Long-term (8-48 h) treatment of SH-SY5Y neuroblastoma cells with phorbol-12,13-dibutyrate (PDBu; 100 nM) promotes the down-regulation of protein kinase C (PKC) subtypes alpha and epsilon and reduces by up to 60% noradrenaline (NA) release evoked via both PKC-dependent (M3-muscarinic receptor activation) and PKC-independent (depolarization) pathways, over similar time courses. A similar effect on release is observed following long-term (16-48 h) incubation with the PKC inhibitor Ro 31-7549 (10 microM), even after removal of the inhibitor, indicating a mechanism which is not rapidly reversible. Evidence is presented which suggests that long-term treatment with PDBu does not (1) affect calcium entry, (2) modulate levels of proteins important in the secretory mechanism or (3) reduce the number of secretory vesicles. Thus, the decrease in NA release in SH-SYSY cells following down-regulation of PKC appears to be the result of a sustained reduction in PKC activity acting on a component of the secretory pathway not involved in the regulation of calcium entry or vesicle number.
Turner
N A
NA
Institute for Cardiovascular Research, University of Leeds, UK.
Walker
J H
JH
Ball
S G
SG
Vaughan
P F
PF
D002273:Carcinogens / Q000494:pharmacology; D015536:Down-Regulation; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D009447:Neuroblastoma; D009638:Norepinephrine / Q000493:pharmacokinetics*; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D002273:Carcinogens; D007211:Indoles; D008301:Maleimides; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C; D009638:Norepinephrine; C064755:Ro 31-7549