Coordinate and differential regulation of proenkephalin A and PNMT mRNA expression in cultured bovine adrenal chromaffin cells: responses to cAMP elevation and phorbol esters.
The expression of proenkephalin A (ProEnk A) mRNA and phenylethanolamine N-methyltransferase (PNMT) mRNA in response to cAMP analogues, forskolin and phorbol esters was examined in cultures of bovine adrenal chromaffin cells. Exposure of chromaffin cells to 1 mM dibutyryl cAMP for 24 h increased significantly the levels of ProEnk A mRNA, with no significant effect on the levels of PNMT mRNA. Cells exposed to the tumor promoting phorbol esters (phorbol 12-myristate 13-acetate, phorbol 12,13-dibutyrate or 4-beta-phorbol 12,13-didecanoate) for 12 h differentially activated PNMT mRNA and ProEnk A mRNA expression. The levels of PNMT mRNA were dramatically elevated in response to low concentrations (10(-9) to 10(-8)M) of these phorbol esters, but these increases were diminished at higher concentrations (10(-7) to 10(-6) M) of the phorbol esters. These responses were synergistically potentiated by dexamethasone (1 microM), a synthetic glucocorticoid. None of these effects was seen with the biologically inactive phorbol ester, 4-alpha-phorbol 12,13-didecanoate. By contrast, the expression of ProEnk A mRNA was activated by the tumor promoting phorbol esters in a concentration-dependent manner. The results of this study demonstrate a differential stimulatory effect of second messenger mechanisms in the control of PNMT and ProEnK A mRNA expression and provide further evidence for an independent control for the enkephalin and adrenaline synthesis in these cells.
Wan
D C
DC
Department of Biochemistry, University of Melbourne, Parkville, Vic., Australia.
Marley
P D
PD
Livett
B G
BG
D000313:Adrenal Medulla / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000494:pharmacology*; D003907:Dexamethasone / Q000494:pharmacology; D004745:Enkephalins / Q000096:biosynthesis* / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D008969:Molecular Sequence Data; D010625:Phenylethanolamine N-Methyltransferase / Q000096:biosynthesis* / Q000235:genetics; D010703:Phorbol Esters / Q000494:pharmacology*; D011498:Protein Precursors / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D015290:Second Messenger Systems; D013268:Stimulation, Chemical
D004745:Enkephalins; D010703:Phorbol Esters; D011498:Protein Precursors; D012333:RNA, Messenger; C029992:proenkephalin; D003907:Dexamethasone; D000242:Cyclic AMP; D010625:Phenylethanolamine N-Methyltransferase