title: Thapsigargin-induced gene expression in nonexcitable cells is dependent on calcium influx.
abstract: Agents such as thapsigargin and endothelin elevate intracellular calcium levels by a combination of calcium release from intracellular stores and calcium influx across the plasma membrane; however, the relative contribution of influx vs. release in modulating calcium-dependent gene expression is not as well understood in nonexcitable cells as in excitable cells. In this report we have been able to separate thapsigargin-induced elevation of intracellular calcium into release and influx components, using carboxyamido-triazole (CAI), a known inhibitor of calcium influx with antiproliferative activity against a number of human carcinomas, to selectively inhibit influx without affecting release. The results of these experiments indicate that the ability of thapsigargin to induce calcium-dependent gene expression in nonexcitable cells is dependent on the induction of calcium influx, presumably through store-operated calcium channels. CAI treatment specifically inhibited thapsigargin- or endothelin-stimulated expression from the c-fos promoter in Rat-1 cells and in epithelial cell lines derived from ovary and breast. Use of the VL30 model system confirmed the ability of CAI to inhibit calcium-dependent gene expression and further demonstrated that the ability of elevated calcium to synergize with other signaling pathways required close temporal coupling. In addition to inhibiting endothelin-induced calcium influx, CAI treatment also resulted in a partial inhibition of IP3 production and calcium release. CAI treatment also blocked the increase in ERK1 kinase activity observed in response to either endothelin or thapsigargin, suggesting a role for calcium influx in the activation of mitogen-activated protein kinase pathways.
authors.affiliation: Department of Cell and Developmental Biology, Oregon Health Sciences University, Portland 97201-3098, USA.
authors.forename: K D
authors.initials: KD
authors.lastname: Rodland
authors.forename: R P
authors.initials: RP
authors.lastname: Wersto
authors.forename: S
authors.initials: S
authors.lastname: Hobson
authors.forename: E C
authors.initials: EC
authors.lastname: Kohn
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D019332:Endothelin-1 / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects*; D017930:Genes, Reporter / Q000187:drug effects / Q000235:genetics; D016762:Genes, fos / Q000187:drug effects* / Q000235:genetics; D007093:Imidazoles / Q000494:pharmacology; D051381:Rats; D019284:Thapsigargin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D014230:Triazoles / Q000494:pharmacology*
chemical_list: D002121:Calcium Channel Blockers; D019332:Endothelin-1; D007093:Imidazoles; D014230:Triazoles; D019284:Thapsigargin; C062058:carboxyamido-triazole; D015500:Chloramphenicol O-Acetyltransferase; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium