A novel cross-talk between endothelin-1 and cyclic AMP signaling pathways in the regulation of GLUT1 transcription in 3T3-L1 adipocytes.
We showed previously that chronic exposure to both endothelin-1 (ET-1) and cAMP resulted in a synergistic increase in Glut1 transcription in 3T3-L1 adipocytes via a protein kinase C (PKC)-dependent mechanism. In the present study, we further examined the molecular mechanism involved. Employing transient transfections with Glut1 promoter/enhancer -luciferase reporter and several dominant negative or constitutively active PKC mutants, we identified PKCε as the responsible PKC. Investigation with deletion and mutation mutants of the promoter/enhancer reporter suggested that Sp1, CREB and AP-1 responsive elements on enhancer 2 were involved. Furthermore, chromatin immunoprecipitation and co-immunoprecipitation analysis were applied to characterize the interactions between these transcription factors and their bindings to enhancer 2 in vivo. The results indicate that there are both negative and positive interactions between ET-1 and cAMP signaling pathways. On the one hand, cAMP inhibits ET-1 induced NF-κB activation required for ET-1-stimulated Glut1 transcription; on the other hand, cAMP, via sustained CREB phosphorylation, may activate AP-1 and cooperate with ET-1-activated PKCε to enhance Sp1 expression and consequently to generate a stable enhancer 2-bound Sp1/pCREB/AP-1 complex, which can strongly facilitate Glut1 transcription more than the additive effect of ET-1 and cAMP alone.
Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei, Taiwan, ROC.
Ying-Shiun
YS
Kao
Jim C
JC
Fong
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D050882:CREB-Binding Protein / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D000242:Cyclic AMP / Q000494:pharmacology*; D019332:Endothelin-1 / Q000494:pharmacology*; D051272:Glucose Transporter Type 1 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D051744:Protein Kinase C-epsilon; D015398:Signal Transduction; D016329:Sp1 Transcription Factor / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic
D019332:Endothelin-1; D051272:Glucose Transporter Type 1; D016328:NF-kappa B; D016329:Sp1 Transcription Factor; D018808:Transcription Factor AP-1; D000242:Cyclic AMP; D050882:CREB-Binding Protein; D051744:Protein Kinase C-epsilon