Phorbol 12-myristate 13-acetate alters sr ca2+ atpase gene
expression in cultured neonatal rat heart cells.
Qi, Ming, Jos[acute]e W. M. Bassani, Donald M. Bers, and Allen M.
Samarel.
The Cardiovascular Institute and the Departments of Physiology and
Medicine, Loyola University Chicago, Stritch School of Medicine,
Maywood, Illinois 60153
APStracts 3:0107H, 1996.
Primary cultures of neonatal rat ventricular myocytes were used to
examine how the cardiac myocyte [Ca2+]i transient and sarcoplasmic
reticulum Ca2+ ATPase (SERCA2) gene expression change in response to
treatment with the protein kinase C (PKC) activator phorbol 12
-myristate-13-acetate (PMA). Exposure of neonatal myocytes to PMA (200
nM, 48-72 h) produced myocyte growth and a 70% prolongation of the
t1/2 for [Ca2+]i decline induced by potassium depolarization in the
absence of extracellular Na+ (in which the SR Ca2+ pump is the main
mechanism responsible for [Ca2+]i decline). The reduced rate of
[Ca2+]i transient decline corresponded to a 53% reduction in SERCA2
protein levels and a 43% reduction in SERCA2 mRNA levels as compared
to control myocytes. Exposure to PMA for as little as 30 min or for
as long as 48 h produced a similar degree of SERCA2 mRNA down
-regulation over time. PMA-induced down-regulation of SERCA2 mRNA
levels was blocked by either 10 nM staurosporine or 4 [mu]M
chelerythrine, whereas treatment with either agent alone increased
SERCA2 mRNA levels as compared to control cells. Actinomycin D mRNA
stability assays revealed that PMA treatment appeared to markedly
destabilize the relatively long-lived SERCA2 mRNA transcript. Taken
together, these results indicate that down-regulation of SERCA2 gene
by PMA in cultured neonatal myocytes occurs at least in part by
alterations in mRNA stability, and results in functional alterations
in [Ca2+]i decline that are similar to that observed in the
hypertrophied and failing adult myocardium.
Received 21 July 1995; accepted in final form 20 February 1996.
APS Manuscript Number H692-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 20 March 96