title: Differential effect of membrane depolarization on levels of tyrosine hydroxylase and dopamine beta-hydroxylase mRNAs in PC12 pheochromocytoma cells.
abstract: Membrane depolarization has been widely used to elucidate the response of the nervous system to prolonged neuronal activity or stress. We studied the effect of treating PC12 cells with membrane depolarizing stimuli, 50 mM KCl, or 150 microM veratridine, and the subsequent changes in the mRNA levels of the catecholamine biosynthetic enzymes, tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH). TH mRNA levels were found to increase 2- to 5-fold after continuous treatment for 1-12 h with 50 mM KCl. Depolarization with 150 microM veratridine had a similar effect on TH mRNA. In contrast, DBH mRNA levels were unchanged by either KCl or veratridine treatment. The role of calcium in the increase of TH mRNA levels elicited by depolarization was examined. The increase in TH mRNA was inhibited by the chelation of calcium with 3 mM EGTA. However, in contrast to their effect on phosphorylation of TH elicited by acute depolarization, the calcium channel blockers, nitrendipine and verapamil, and the calmodulin antagonists, W7 and trifluoperazine, did not prevent the increase in TH mRNA levels subsequent to several hours exposure to depolarizing stimuli. The calcium ionophore, A23187, alone was unable to induce TH mRNA levels. Thus, the increase in TH mRNA elicited by depolarization is mediated differently than the acute phosphorylation of the enzyme.
authors.affiliation: Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595.
authors.forename: E J
authors.initials: EJ
authors.lastname: Kilbourne
authors.forename: E L
authors.initials: EL
authors.lastname: Sabban
mesh_terms: D000310:Adrenal Gland Neoplasms / Q000201:enzymology / Q000473:pathology*; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002147:Calmodulin / Q000037:antagonists & inhibitors; D004299:Dopamine beta-Hydroxylase / Q000096:biosynthesis* / Q000235:genetics; D004790:Enzyme Induction / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D010673:Pheochromocytoma / Q000201:enzymology / Q000473:pathology*; D011189:Potassium Chloride / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D012334:RNA, Neoplasm / Q000096:biosynthesis; D051381:Rats; D015290:Second Messenger Systems / Q000187:drug effects; D014407:Tumor Cells, Cultured / Q000201:enzymology; D014446:Tyrosine 3-Monooxygenase / Q000096:biosynthesis* / Q000235:genetics; D014701:Veratridine / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D002147:Calmodulin; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D000001:Calcimycin; D011189:Potassium Chloride; D014701:Veratridine; D014446:Tyrosine 3-Monooxygenase; D004299:Dopamine beta-Hydroxylase; D002118:Calcium