Abstract
A preneoplastic variant of Syrian hamster embryo cells, sup(+), exhibits decreased endoplasmic reticulum calcium levels and subsequently undergoes apoptosis in low serum conditions (Preston, G. A., Barrett, J. C., Biermann, J. A., and Murphy, E. (1997) Cancer Res. 57, 537-542). This decrease in endoplasmic reticulum calcium appears to be due, at least in part, to reduced capacitative calcium entry at the plasma membrane. Thus we investigated whether inhibition of capacitative calcium entry per se could reduce endoplasmic reticulum calcium and induce apoptosis of cells. We find that treatment with either SKF96365 (30-100 microM) or cell-impermeant 1,2-bis(o-amino-5-bromophenoxy)ethane-N,N,N', N'-tetraacetic acid (5-10 mM) is able to induce apoptosis of cells in conditions where apoptosis does not normally occur. Because previous work has implicated vesicular trafficking as a mechanism of regulating capacitative calcium entry, we investigated whether disruption of vesicular trafficking could lead to decreased capacitative calcium entry and subsequent apoptosis of cells. Coincident with low serum-induced apoptosis, we observed an accumulation of vesicles within the cell, suggesting deregulated vesicle trafficking. Treatment of cells with bafilomycin (30-100 nM), an inhibitor of the endosomal proton ATPase, produced an accumulation of vesicles, decreased capacitative entry, and induced apoptosis. These data suggest that deregulation of vesicular transport results in reduced capacitative calcium entry which in turn results in apoptosis.
Highlights
Calcium within the cell exhibits a highly compartmentalized distribution [15]
In a previous study we investigated the role of calcium alterations during apoptosis in two immortalized cell lines derived from mutagenized Syrian hamster embryo cells [1]
Capacitative Calcium Entry and Apoptosis in Sup(ϩ) Cells— Sup(ϩ) cells, an immortalized cell line derived from mutagenesis of Syrian hamster embryo cells [40], undergo apoptosis in response to low serum conditions [41]
Summary
Vol 274, No 12, Issue of March 19, pp. 8261–8268, 1999 Printed in U.S.A. Reduced Capacitative Calcium Entry Correlates with Vesicle Accumulation and Apoptosis*. Treatment of cells with bafilomycin (30 –100 nM), an inhibitor of the endosomal proton ATPase, produced an accumulation of vesicles, decreased capacitative entry, and induced apoptosis. These data suggest that deregulation of vesicular transport results in reduced capacitative calcium entry which in turn results in apoptosis. We find that perturbing vesicle trafficking in normally growing sup(ϩ) cells by treatment with the macrolide antibiotic bafilomycin (Baf) results in vesicle accumulation concomitant with decreased CCE and apoptosis. We find that in the sup(Ϫ) population, which does not undergo apoptosis in reduced serum conditions, perturbation of either CCE (with SKF96365) or vesicle trafficking (with bafilomycin) led to apoptosis. These findings support a role for vesicle trafficking and CCE in apoptosis
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