A novel pathway for adrenergic stimulation of cAMP-response-element-binding protein (CREB) phosphorylation: mediation via alpha1-adrenoceptors and protein kinase C activation.
Because of the central role of adrenergic mechanisms in the expression of crucial genes during brown adipocyte differentiation, we examined the activation (phosphorylation) of CREB (cAMP-response-element-binding protein) in mouse brown adipocytes in primary culture. We found that noradrenaline ('norepinephrine') stimulated CREB phosphorylation rapidly (maximum effect in < or =5 min with slow decay) and efficiently (EC(50), 6 nM). The increase in CREB phosphorylation coincided with increased expression of an artificial cAMP-response-element-containing reporter construct. CREB phosphorylation was partly inhibitable, both by the beta-adrenergic antagonist propranolol and by the alpha(1)-adrenergic antagonist prazosin. Adenylate cyclase hyperactivation (by forskolin) could stimulate CREB phosphorylation to the same extent as noradrenaline. The alpha(1)-adrenergic agonist cirazoline also increased CREB phosphorylation. An increase in intracellular [Ca(2+)] had, however, no effect, but protein kinase C activation by PMA was a potent stimulator. The cirazoline-stimulated (alpha(1)-adrenergic) CREB phosphorylation was inhibited by a desensitizing pretreatment with PMA, demonstrating that the alpha(1)-stimulation was mediated via protein kinase C activation; neither Src nor extracellular-signal-regulated kinases 1 and 2 activation was involved in the signalling process. We conclude that CREB phosphorylation in brown adipocytes is mediated not only through the classical beta-adrenergic/cAMP pathway but also through a novel alpha(1)-adrenergic/protein kinase C/CREB pathway, which has not been described previously in any tissue.
Thonberg
Håkan
H
The Wenner-Gren Institute, The Arrhenius Laboratories F3, Stockholm University, SE-10691 Stockholm, Sweden.
Fredriksson
J Magnus
JM
Nedergaard
Jan
J
Cannon
Barbara
B
D017667:Adipocytes / Q000378:metabolism; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D002273:Carcinogens; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D004789:Enzyme Activation; D007093:Imidazoles / Q000494:pharmacology; D015151:Immunoblotting; D008156:Luciferases / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008297:Male; D051379:Mice; D008954:Models, Biological; D009638:Norepinephrine / Q000494:pharmacology; D010766:Phosphorylation; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism*; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism*; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection
D000316:Adrenergic alpha-Agonists; D002273:Carcinogens; D017362:Cyclic AMP Response Element-Binding Protein; D007093:Imidazoles; D018340:Receptors, Adrenergic, alpha-1; D000242:Cyclic AMP; D008156:Luciferases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; C014282:cirazoline; D009638:Norepinephrine