Constitutively active calcineurin mediates delayed neuronal death through Fas-ligand expression via activation of NFAT and FKHR transcriptional activities in mouse brain ischemia.
We recently demonstrated that a constitutively active form of calcineurin (CaN) is generated by calpain-mediated limited proteolysis following brain ischemia. The calpain-induced CaN activation mediated delayed neuronal death through translocation of nuclear factor of activated T-cells (NFAT) into nuclei after brain ischemia. We also previously demonstrated that activation of forkhead in rhabdomyosarcoma (FKHR), a forkhead transcription factor and substrate of protein kinase-B (Akt), mediated ischemia-induced neuronal death through Fas-ligand expression in gerbil hippocampus. FKHR activation occurred through decreased Akt activity and concomitant dephosphorylation mediated by undefined phosphatases. In this study, we show that phosphorylated Ser-256 of FKHR is dephosphorylated by constitutively active CaN and that in turn FKHR forms a complex with CaN that is translocated into nuclei after brain ischemia. After nuclear translocation of NFAT and FKHR, both NFAT and FKHR stimulated expression of Fas-ligand by binding to its promoter region. Consistent with activation of the Fas-ligand promoter by FKHR dephosphorylation, Fas-ligand expression increased 2 days after ischemia/reperfusion, and treatment with the CaN inhibitor FK506 inhibited that expression. These results suggest that FKHR is a downstream target of CaN and that constitutively active CaN mediates delayed neuronal death through Fas-ligand expression via up-regulation of both NFAT and FKHR transcriptional activity in brain ischemia.
Shioda
Norifumi
N
Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, JapanTohoku University 21st Century COE Program "CRESCENDO," Sendai, Japan.
Han
Feng
F
Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, JapanTohoku University 21st Century COE Program "CRESCENDO," Sendai, Japan.
Moriguchi
Shigeki
S
Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, JapanTohoku University 21st Century COE Program "CRESCENDO," Sendai, Japan.
Fukunaga
Kohji
K
Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, JapanTohoku University 21st Century COE Program "CRESCENDO," Sendai, Japan.
D000704:Analysis of Variance; D000818:Animals; D002545:Brain Ischemia / Q000188:drug therapy / Q000473:pathology*; D019703:Calcineurin / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects; D024202:Electrophoretic Mobility Shift Assay / Q000379:methods; D004789:Enzyme Activation / Q000187:drug effects; D053222:Fas Ligand Protein / Q000378:metabolism*; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D047468:Immunoprecipitation / Q000379:methods; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D050778:NFATC Transcription Factors / Q000378:metabolism*; D051058:Oncogene Protein v-akt / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D012694:Serine / Q000378:metabolism; D016559:Tacrolimus / Q000494:pharmacology
D053222:Fas Ligand Protein; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; C467200:Foxo1 protein, mouse; D007166:Immunosuppressive Agents; D050778:NFATC Transcription Factors; D012694:Serine; D051058:Oncogene Protein v-akt; D019703:Calcineurin; D016559:Tacrolimus