Synergistic signaling by corticotropin-releasing hormone and leukemia inhibitory factor bridged by phosphorylated 3',5'-cyclic adenosine monophosphate response element binding protein at the Nur response element (NurRE)-signal transducers and activators of transcription (STAT) element of the proopiomelanocortin promoter.
Leukemia inhibitory factor (LIF) cooperates with CRH at the pituitary level to induce POMC gene transcription, resulting in activation of the pituitary-adrenal axis. However, the underlying molecular mechanisms remain elusive. Here, we show that the NurRE-signal transducers and activators of transcription (STAT) composite element of the POMC promoter was the predominant target of the LIF-CRH synergy. Whereas NurRE or STAT sites alone conferred synergy, the maximal response was found with the NurRE-STAT reporter, suggesting that direct DNA binding of both transcription factors is required for an optimal synergy. During LIF-CRH stimulation, Nur77 and activated STAT1-3 were bound to the composite element, and the binding of each factor was abolished by appropriate mutations. CREB was also detected in this complex in a stimulation-dependent and DNA binding-independent manner. Nur77 and STAT1-3 bound to the NurRE-STAT site were each sufficient for CREB recruitment. Recombinant CREB directly interacted with recombinant Nur77 or STAT1-3. Moreover, CREB-Nur77 interaction was increased by CREB phosphorylation at Ser-133 and the dominant-negative mutant CREB-M1 efficiently inhibited the synergistic LIF-CRH response. This synergism was also inhibited after transfection of CREB-small interfering RNA. We conclude that both CREB phosphorylation at Ser-133 and level of CREB expression are crucial in LIF-CRH synergism where CREB, without direct DNA binding, could improve the stability of Nur77 and STAT1-3 binding to POMC promoter and facilitate the recruitment of coactivators. This novel intrapituitary signaling mechanism may have more general implications in cross talks between cAMP-protein kinase A and Janus kinase-STAT pathways.
Institut Cochin, Département d'Endo-crinologie, 24 rue du Faubourg Saint Jacques, 75014 Paris, France.
Vanessa
V
Mynard
Olivier
O
Latchoumanin
Laurence
L
Guignat
Jocelyne
J
Devin-Leclerc
Xavier
X
Bertagna
Benjamin
B
Barré
Jerome
J
Fagart
Olivier
O
Coqueret
Maria Grazia
MG
Catelli
D000818:Animals; D002460:Cell Line; D003346:Corticotropin-Releasing Hormone / Q000235:genetics / Q000502:physiology*; D000242:Cyclic AMP / Q000378:metabolism / Q000502:physiology; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D015850:Interleukin-6 / Q000235:genetics / Q000502:physiology*; D053605:Leukemia Inhibitory Factor; D051379:Mice; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D010766:Phosphorylation; D010902:Pituitary Gland / Q000378:metabolism / Q000502:physiology; D011333:Pro-Opiomelanocortin / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011487:Protein Conformation; D034741:RNA, Small Interfering / Q000235:genetics; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D020218:Response Elements / Q000235:genetics*; D050794:STAT1 Transcription Factor; D050795:STAT2 Transcription Factor; D050796:STAT3 Transcription Factor; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D015534:Trans-Activators / Q000378:metabolism / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation / Q000235:genetics
D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D015850:Interleukin-6; D053605:Leukemia Inhibitory Factor; C507838:Lif protein, mouse; C539818:Nr4a1 protein, mouse; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D034741:RNA, Small Interfering; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D050794:STAT1 Transcription Factor; D050795:STAT2 Transcription Factor; D050796:STAT3 Transcription Factor; C494080:Stat1 protein, mouse; C494087:Stat3 protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; D011333:Pro-Opiomelanocortin; D003346:Corticotropin-Releasing Hormone; D000242:Cyclic AMP