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Regulation of c-fos and c-jun protooncogene expression by the Ca(2+)-ATPase inhibitor thapsigargin
A Schönthal1, J Sugarman, J H Brown
1Cancer Center, University of California at San Diego, La Jolla 92093.
Abstract:
Thapsigargin, a non-phorbol-ester-type tumor promoter, discharges intracellular Ca2+ stores by specific inhibition of the endoplasmic reticulum Ca(2+)-ATPase. We used this drug to analyze the involvement of Ca2+ and Ca(2+)-ATPases in the control of growth- and transformation-related genes. Here we show that treatment of mouse NIH 3T3 fibroblasts with thapsigargin induced rapid expression of the c-fos and c-jun protooncogenes. Inhibition or depletion of protein kinase C partially diminished the c-fos but not the c-jun response. Furthermore, thapsigargin could synergize with the tumor promoter phorbol 12-myristate 13-acetate to induce c-fos but not c-jun. However, thapsigargin had no effect on basal or phorbol ester-induced protein kinase C activity. Our results indicate that Ca2+ is a potent second messenger that controls expression of growth- and transformation-related genes. Since inhibition of the endoplasmic reticulum Ca(2+)-ATPase results in a strong induction of these genes, our data suggest that this Ca2+ pump may act as a negative regulator of cell growth.
Insights
Thapsigargin treatment rapidly increases expression of growth-related genes c-fos and c-jun in mouse cells. This suggests the endoplasmic reticulum Ca(2+)-ATPase may regulate cell growth by controlling intracellular calcium levels.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Thapsigargin inhibits the endoplasmic reticulum Ca(2+)-ATPase, releasing intracellular calcium stores.
- Calcium ions (Ca2+) act as crucial second messengers in cellular signaling pathways.
- Protooncogenes like c-fos and c-jun are key regulators of cell growth and transformation.
Purpose of the Study:
- To investigate the role of Ca2+ and Ca(2+)-ATPases in regulating genes associated with cell growth and transformation.
- To determine the effect of thapsigargin-induced calcium release on protooncogene expression.
Main Methods:
- Treatment of mouse NIH 3T3 fibroblasts with thapsigargin.
- Analysis of c-fos and c-jun protooncogene expression.
- Investigation of protein kinase C activity and its modulation by thapsigargin and phorbol esters.
Main Results:
- Thapsigargin treatment induced rapid expression of c-fos and c-jun protooncogenes.
- Inhibition of protein kinase C partially reduced the c-fos response but not c-jun.
- Thapsigargin synergized with phorbol 12-myristate 13-acetate to induce c-fos, but not c-jun.
- Thapsigargin did not affect basal or phorbol ester-induced protein kinase C activity.
Conclusions:
- Intracellular calcium (Ca2+) is a significant second messenger controlling the expression of growth- and transformation-related genes.
- The endoplasmic reticulum Ca(2+)-ATPase may function as a negative regulator of cell growth.
- Disruption of Ca2+ homeostasis through Ca(2+)-ATPase inhibition strongly induces genes linked to cell proliferation.