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.
Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, JapanTohoku University 21st Century COE Program "CRESCENDO," Sendai, Japan.
Norifumi
N
Shioda
Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, JapanTohoku University 21st Century COE Program "CRESCENDO," Sendai, Japan.
Feng
F
Han
Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, JapanTohoku University 21st Century COE Program "CRESCENDO," Sendai, Japan.
Shigeki
S
Moriguchi
Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, JapanTohoku University 21st Century COE Program "CRESCENDO," Sendai, Japan.
Kohji
K
Fukunaga
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