The immunosuppressive drugs cyclosporin A and tacrolimus inhibit membrane depolarization-induced CREB transcriptional activity at the coactivator level.
Cyclosporin A and tacrolimus are clinically important immunosuppressive drugs directly targeting the transcription factor nuclear factor of activated T cells (NFAT). Through inhibition of calcineurin phosphatase activity they block the dephosphorylation and thus activation of NFAT. Cyclosporin A and tacrolimus also inhibit other calcineurin-dependent transcription factors including the ubiquitously expressed cAMP response element-binding protein (CREB). Membrane depolarization by phosphorylating CREB on Ser119 leads to the recruitment of its coactivator CREB-binding protein (CBP) that stimulates initiation of transcription. It was unknown at what step in CREB-mediated transcription cyclosporin A and tacrolimus interfere. In transient transfection experiments, using GAL4-CREB fusion proteins and a pancreatic islet beta-cell line, cyclosporin A inhibited depolarization-induced activation of CREB proteins which carried various deletions or mutations throughout their sequence providing no evidence for the existence of a distinct CREB domain conferring cyclosporin A sensitivity. In a mammalian two-hybrid assay, cyclosporin A did not inhibit Ser119-dependent interaction of CREB with its coactivator CBP. Using GAL4-CBP fusion proteins, cyclosporin A inhibited depolarization-induced CBP activity, with cyclosporin A-sensitive domains mapped to both the N- (aa 1-451) and C-terminal (aa 2040-2305) ends of CBP. The depolarization-induced transcriptional activity of the CBP C-terminus was enhanced by overexpression of calcineurin and was inhibited by cyclosporin A and tacrolimus in a concentration-dependent manner with IC50 values (10 and 1 nM, respectively) consistent with their known IC50 values for inhibition of calcineurin. These data suggest that, in contrast to NFAT, cyclosporin A and tacrolimus inhibit CREB transcriptional activity at the coactivator level.
Oetjen
Elke
E
Department of Molecular Pharmacology, University of Göttingen, D-37099 Göttingen, Germany.
Thoms
Kai-Martin
KM
Laufer
Yvonne
Y
Pape
Daniela
D
Blume
Roland
R
Li
Pingfeng
P
Knepel
Willhart
W
D000818:Animals; D050882:CREB-Binding Protein; D006224:Cricetinae; D017362:Cyclic AMP Response Element-Binding Protein / Q000096:biosynthesis* / Q000235:genetics; D016572:Cyclosporine / Q000494:pharmacology*; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000235:genetics; D016559:Tacrolimus / Q000494:pharmacology*; D015534:Trans-Activators / Q000096:biosynthesis* / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology
D017362:Cyclic AMP Response Element-Binding Protein; D007166:Immunosuppressive Agents; D009687:Nuclear Proteins; D015534:Trans-Activators; D016572:Cyclosporine; D050882:CREB-Binding Protein; D016559:Tacrolimus