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 accompanied 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 populations before the onset of cell death. We examined the effects of altering plasma membrane calcium ATPase expression on cell vulnerability in rat pheochromocytoma 12 cells. Pheochromocytoma 12 cells ave vulnerable to Ca2+ overload induced by the Ca2+ ionophore A23187. Reverse transcriptase-PCR and Western blot data indicated that plasma membrane calcium ATPase isoform 4b constitutes a major calcium pump isoform in the pheochromocytoma 12 cells. Therefore, permanently transfected pheochromocytoma 12-derived cell lines were established that either over-expressed plasma membrane calcium ATPase isoform 4b, or suppressed the expression of the endogenous plasma membrane calcium ATPase isoform 4, Over-expressing clones were less vulnerable to Ca2+-mediated cell death induced by A23187 whereas antisense clones were considerably more susceptible. These data indicate that regulation of plasma membrane calcium ATPase expression may be critical to cellular survival when cells are exposed to pathological increases in intracellular calcium. (C) 2001 Wiley-Liss, Inc.