Beta-adrenergic-cyclic AMP signalling pathway modulates cell function at the transcriptional level in 3T3-F442A adipocytes.
We studied the role of cAMP in the regulation of the expression of the adipsin gene and of some other adipose-specific genes including lipoprotein lipase (LPL), glycerophosphate dehydrogenase (G3PDH), and adipocyte P2 (aP2) in 3T3-F442A adipocytes. Northern blot analysis of isoproterenol (10(-6) M)-, forskolin (10(-5) M)- or 8-bromo-cAMP (10(-3) M)-treated adipocytes showed that the steady-state levels of adipsin mRNA were strongly reduced in a time-dependent and reversible manner. The concentration of isoproterenol giving a half-maximal effect in the down-regulation of the adipsin message was approximately 5 x 10(-8) M. Similarly, cell treatment by forskolin elicited a down-regulation of LPL and G3PDH mRNA levels but did not alter aP2 mRNA level. As determined by nuclear run-on assays, the rate of transcription of adipsin, LPL and G3PDH in isoproterenol-treated adipocytes was respectively 3, 3, and 2 times lower than in control adipocytes. These results indicate (1) that cAMP plays a dominant antilipogenic role in the fat cell through the transcriptional down-regulation of the expression of two major genes involved in triglyceride biosynthesis; (2) that cAMP does not reverse the adipocyte character; (3) hence, that cAMP suppresses adipsin expression at the transcriptional level, providing additional support for the role of adipsin protein in adipocyte metabolism.
Antras
J
J
Institut National de la Santé et de la Recherche Médicale, Hôpital Henri Mondor, Créteil, France.
Lasnier
F
F
Pairault
J
J
D016475:3T3 Cells; D000273:Adipose Tissue / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D015152:Blotting, Northern; D011416:Complement Factor D; D000242:Cyclic AMP / Q000378:metabolism*; D005786:Gene Expression Regulation; D005993:Glycerolphosphate Dehydrogenase / Q000235:genetics; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008071:Lipoprotein Lipase / Q000235:genetics; D051379:Mice; D012333:RNA, Messenger / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000235:genetics*; D015398:Signal Transduction; D014158:Transcription, Genetic
D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D000242:Cyclic AMP; D005993:Glycerolphosphate Dehydrogenase; D008071:Lipoprotein Lipase; D012697:Serine Endopeptidases; D011416:Complement Factor D; C493491:complement factor D, mouse; D007545:Isoproterenol