Plasma membrane calcium ATPase plays a role in reducing Ca2+-mediated cytotoxicity in PC12 cells

In many cell types, cell death induced by a variety of insults is accompani ed by an increase in intracellular calcium, The Ca2+ homeostatic mechanisms affected by such insults, however, have not been fully determined. Recent evidence indicates that kainic acid-induced seizures alter plasma membrane calcium ATPase mRNA expression within vulnerable hippocampal cell populatio ns before the onset of cell death. We examined the effects of altering plas ma membrane calcium ATPase expression on cell vulnerability in rat pheochro mocytoma 12 cells. Pheochromocytoma 12 cells ave vulnerable to Ca2+ overloa d induced by the Ca2+ ionophore A23187. Reverse transcriptase-PCR and Weste rn blot data indicated that plasma membrane calcium ATPase isoform 4b const itutes a major calcium pump isoform in the pheochromocytoma 12 cells. There fore, permanently transfected pheochromocytoma 12-derived cell lines were e stablished that either over-expressed plasma membrane calcium ATPase isofor m 4b, or suppressed the expression of the endogenous plasma membrane calciu m ATPase isoform 4, Over-expressing clones were less vulnerable to Ca2+-med iated cell death induced by A23187 whereas "antisense" clones were consider ably more susceptible. These data indicate that regulation of plasma membra ne calcium ATPase expression may be critical to cellular survival when cell s are exposed to pathological increases in intracellular calcium. (C) 2001 Wiley-Liss, Inc.