Role of Ca(2+) in the regulation of nickel-inducible Cap43 gene expression.
We have recently cloned a gene, Cap43, that was significantly induced by exposure to nontoxic levels of both water-soluble and -insoluble Ni(2+) compounds. In this paper, we utilized the expression levels of this gene as a tool to identify second messengers involved in nickel-inducible transcription. We report here that the Ca(2+) ionophore A23187 substantially stimulated Cap43 gene expression. In addition, we found that BAPTA-AM, a specific chelator of free intracellular Ca(2+), consistently attenuated the induction of Cap43, indicating that elevation of intracellular Ca(2+) was essential for this response. TPEN, a chelator of heavy metals, such as Ni(2+) with a very low affinity for Ca(2+), did not attenuate Cap43 induced by Ni or calcium ionophore, suggesting that elevations of Ca(2+) but probably not elevations of other metal ions were involved in the induction of Cap43. A direct measurement of Ca(2+) levels using the fluorescent probe Fluo-3 AM showed elevations of free intracellular Ca(2+) in Ni-treated cells. A strong induction of Cap43 by okadaic acid suggested the involvement of a serine/threonine phosphorylation in a signaling pathway that was presumably activated by Ni and that led to enhanced Cap43 gene expression. However, calcium-dependent protein kinase(s) involved in the nickel-activated signaling pathway remains to be identified.
Salnikow
K
K
Kaplan Comprehensive Cancer Center, New York University Medical Center, New York, New York, 10016, USA. salnikow@env.med.nyu.edu
Kluz
T
T
Costa
M
M
D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D018797:Cell Cycle Proteins; D002460:Cell Line; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects*; D006710:Homocysteine / Q000494:pharmacology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D009532:Nickel / Q000494:pharmacology*; D010766:Phosphorylation; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics; D000099259:N-myc Downstream-Regulated Gene 1 Protein
D002118:Calcium; D002121:Calcium Channel Blockers; D018797:Cell Cycle Proteins; D006710:Homocysteine; D047908:Intracellular Signaling Peptides and Proteins; D009532:Nickel; D011506:Proteins; D000099259:N-myc Downstream-Regulated Gene 1 Protein