Transcriptional down-regulation by insulin of the beta 3-adrenergic receptor expression in 3T3-F442A adipocytes: a mechanism for repressing the cAMP signaling pathway.
Modulation of the three beta-adrenergic receptor subtypes (beta-ARs) by insulin was investigated in mouse 3T3-F442A adipocytes. Saturation and competition experiments measuring binding of 125I-labeled (-)-cyanopindolol to adipocyte membranes demonstrated that cell exposure to insulin for 4 days caused a 3.5-fold decrease in the density of the major beta-AR component of the adipocyte, the beta 3-AR, while beta 1-AR sites remained unchanged and beta 2-ARs were undetectable. This correlated with a lower potency of the beta 3-AR-selective agonists CGP12177, ICI201651, and BRL37344 in stimulating adenylate cyclase. Northern blotting analysis indicated that insulin induced a rapid and sharp decrease in beta 3-AR mRNA levels. This effect was detectable at low insulin concentrations (EC50 = 3 nM) and was not observed in the presence of insulin-like growth factor I, suggesting an insulin receptor-mediated phenomenon. Reverse transcriptase-PCR analysis showed that, in contrast to its dramatic down-regulatory effect on beta 3-AR mRNA, insulin did not modify the levels of beta 1- and beta 2-AR transcripts. As assessed by nuclear run-on assays, insulin inhibited the beta 3-AR gene transcription rate by 90% within 30 min. mRNA turnover experiments showed that the half-life of beta 3-AR mRNA was short (90 min) and remained unaffected by insulin. These findings demonstrate the genetic control of a beta-AR subtype expression by insulin and reveal a mechanism for the regulation by this hormone of cAMP-dependent biological processes in adipocytes.
Fève
B
B
Institut National de la Santé et de la Recherche Médicale Unité 282, Hôpital Henri Mondor, Créteil, France.
Elhadri
K
K
Quignard-Boulangé
A
A
Pairault
J
J
D016475:3T3 Cells; D017667:Adipocytes; D000818:Animals; D001483:Base Sequence; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000502:physiology*; D017931:DNA Primers / Q000737:chemistry; D015536:Down-Regulation; D005786:Gene Expression Regulation / Q000187:drug effects; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D011943:Receptors, Adrenergic, beta / Q000235:genetics* / Q000378:metabolism; D015290:Second Messenger Systems; D015398:Signal Transduction; D013997:Time Factors; D014158:Transcription, Genetic
D017931:DNA Primers; D007328:Insulin; D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D000242:Cyclic AMP