Jackson TR, Patterson SI, Thastrup O, Hanley MR. A novel tumour promoter, thapsigargin, transiently increases cytoplasmic free Ca2+ without generation of inositol phosphates in NG115-401L neuronal cells.
Biochem J 1988;
253:81-6. [PMID:
3138987 PMCID:
PMC1149260 DOI:
10.1042/bj2530081]
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Abstract
Thapsigargin, a sesquiterpene lactone with potent irritant and tumour-promoting activities, stimulates a rapid (within 15 s) transient increase in intracellular [Ca2+] in the NG115-401L neural cell line, as measured by the fluorescent indicator dye fura-2. This increase in cytoplasmic free [Ca2+] is concentration-dependent (ED50 around 20 nM) and occurs in the absence of extracellular Ca2+. Activation of NG115-401L cells by the inflammatory peptide bradykinin generates inositol phosphates, which parallel increases in intracellular [Ca2+]. However, the rise in cytoplasmic [Ca2+] stimulated by thapsigargin occurs in the absence of detectable production of inositol phosphates. Thapsigargin is unlike phorboid tumour promoters in that it has no action on two non-invasive indicators of phorbol stimulation of these cells, i.e. [3H]choline metabolite production and rise in intracellular pH. These data suggest that thapsigargin releases Ca2+ from an intracellular store by a novel mechanism, independent of the hydrolysis of phosphoinositides and concomitant activation of protein kinase C. Thus thapsigargin may provide a valuable tool for the analysis of intracellular signalling mechanisms.
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