Subtype-selective regulation of beta adrenergic receptor-adenylyl cyclase coupling by phorbol esters in 3T3-L1 fibroblasts.
To study the epigenetic regulation of beta adrenergic receptor subtypes, we examined the effects of phorbol esters on beta adrenergic receptor coupling to adenylyl cyclase in 3T3-L1 fibroblasts, which express both beta-1 and beta-2 adrenergic receptor subtypes. Pretreatment of intact 3T3-L1 cells with the protein kinase C activator phorbol dibutyrate caused a dose- and time-dependent decrease in subsequent cyclic AMP (cAMP) accumulation mediated by the beta adrenergic agonist isoproterenol. This effect was selective for beta-adrenergic receptor-mediated responses because there was a potentiation of cAMP accumulation caused by other activators such as prostaglandin E1, forskolin or cholera toxin. The inactive phorbol, alpha-phorbol dibutyrate was ineffective at 1 microM in attenuating isoproterenol stimulation, and 25 nM of the protein kinase C inhibitor staurosporine blocked the effects of phorbol ester on beta adrenergic agonist responses. Stimulation of cAMP accumulation by isoproterenol occurred through a greater proportion of beta-2 adrenergic receptors in phorbol dibutyrate-treated cells than in control cells. This was demonstrated using the beta-1 adrenergic selective antagonist ICI 89.406 and the beta-2 adrenergic selective antagonist ICI 118.551 to inhibit competitively isoproterenol-stimulated cAMP accumulation. Beta-2 adrenergic receptor number and subtype in these cells are regulated by glucocorticoids and butyrate. Decreasing the proportion of beta-1 adrenergic receptors and concomitantly increasing beta-2 adrenergic receptors with either glucocorticoids or butyrate decreased the ability of phorbol ester pretreatment to attenuate cAMP accumulation by isoproterenol.(ABSTRACT TRUNCATED AT 250 WORDS)
Nakada
M T
MT
Department of Pharmacology, University of Pennsylvania, Philadelphia 19104.
Stadel
J M
JM
Crooke
S T
ST
D000262:Adenylyl Cyclases / Q000032:analysis*; D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D005938:Glucocorticoids / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D051379:Mice; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010703:Phorbol Esters / Q000494:pharmacology*; D010766:Phosphorylation; D011412:Propanolamines / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D019311:Staurosporine
D000470:Alkaloids; D005938:Glucocorticoids; D010703:Phorbol Esters; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; D015240:Phorbol 12,13-Dibutyrate; C026777:ICI 118551; C025716:ICI 89406; D000242:Cyclic AMP; D011493:Protein Kinase C; D000262:Adenylyl Cyclases; D019311:Staurosporine; D007545:Isoproterenol