beta-Adrenoceptors and dexamethasone synergistically stimulate the expression of the angiotensinogen gene in opossum kidney cells.
We transiently co-transfected opossom kidney (OK) cells with the plasmid containing the cDNA for beta 1-adrenoceptor (pBC-beta 1 AR) or beta 2-adrenoceptor (pBC-beta 2 AR) and a fusion gene with the 5'-flanking region of the angiotensinogen (ANG) gene linked to a bacterial chloramphenicol acetyl transferase (CAT) coding sequence as a reporter, pOCAT (ANG N-1498/ +18). Co-transfection of plasmid pBC-beta 1 AR or pBC-beta 2 AR alone enhanced the expression of pOCAT (ANG N-1498/+18). The addition of isoproterenol further stimulated the expression of pOCAT (ANG N-1498/ +18) when co-transfected with pBC-beta 1AR, but not with pBC-beta 2AR. Moreover, the addition of a combination of dexamethasone and isoproterenol synergistically stimulated the expression of pOCAT (ANG N-1498/+18) when co-transfected with pBC-beta 1AR, but not when cotransfected with pBC-beta 2AR. The synergistic effect of dexamethasone and isoproterenol was inhibited by the presence of RU 486 (an antagonist of glucocorticoid) or Rp-cAMP (an inhibitor of cAMP-dependent protein kinase A I and II). To localize the putative cAMP-responsive element (CRE) and glucocorticoid responsive element (GRE) in the ANG gene, we constructed the fusion gene by inserting the DNA fragment, ANG N-806 to N-465 upstream of the thymidine kinase (TK) promoter fused to a CAT gene and introduced them with pBC-beta 1AR into OK cells. The addition of dexamethasone or isoproterenol alone stimulated the expression of pTKCAT (ANG N-806/-465). The addition of isoproterenol and dexamethasone synergistically stimulated the transcriptional activity of pTKCAT (N-806/-465). These studies demonstrate that the beta 1-adrenoceptor and dexamethasone act synergistically to stimulate the expression of the ANG gene in OK cells via the putative CRE and GREs in the 5'-flanking region of the rat ANG gene. These data should aid in the understanding of the molecular mechanism(s) of the stimulatory effect of catecholamines/glucocorticoid induced expression of the ANG gene in the kidney.
Ming
M
M
Maisonneuve-Rosemont Hospital Research Center, University of Montreal, Quebec, Canada.
Chan
W
W
Wang
T T
TT
Roberts
K D
KD
Bouvier
M
M
Lachance
S
S
Carrière
S
S
Chan
J S
JS
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000808:Angiotensinogen / Q000235:genetics*; D000818:Animals; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D005786:Gene Expression Regulation / Q000187:drug effects*; D007545:Isoproterenol / Q000494:pharmacology*; D007668:Kidney / Q000378:metabolism*; D015735:Mifepristone / Q000494:pharmacology; D009893:Opossums; D051381:Rats
D000318:Adrenergic beta-Agonists; D000808:Angiotensinogen; D015735:Mifepristone; D003907:Dexamethasone; D007545:Isoproterenol