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Gerst, F. ; Kaiser, G. ; Panse, M.* ; Sartorius, T. ; Pujol, A.* ; Hennige, A.M.* ; Machicao, F. ; Lammers, R.* ; Bosch, F.* ; Häring, H.-U. ; Ullrich, S.

Protein kinase Cδ regulates nuclear export of FOXO1 through phosphorylation of the chaperone 14-3-3ζ.

Diabetologia 58, 2819-2831 (2015)
Forschungsdaten DOI PMC
Open Access Green möglich sobald Postprint bei der ZB eingereicht worden ist.
AIMS/HYPOTHESIS: Forkhead box protein O1 (FOXO1) is a transcription factor essential for beta cell fate. Protein kinase B-dependent phosphorylation of FOXO1 at S256 (P-FOXO1) enables its binding to 14-3-3 dimers and nuclear export. Dephosphorylated FOXO1 enters nuclei and activates pro-apoptotic genes. Since our previous observations suggest that protein kinase C delta (PKCδ) induces nuclear accumulation of FOXO1, the underlying mechanism was examined. METHODS: In human islets, genetically modified mice and INS-1E cells apoptosis was assessed by TUNEL staining. Subcellular translocation of proteins was examined by confocal microscopy and signalling pathways were analysed by western blotting and overlay assay. RESULTS: In PKCδ-overexpressing (PKCδ-tg) mouse islet cells and INS-1E cells FOXO1 accumulated in nuclei, surprisingly, as P-FOXO1. PKCδ-tg decelerated IGF-1-dependent stimulation of nuclear export, indicating that changes in export caused nuclear retention of P-FOXO1. Nuclear accumulation of P-FOXO1 was accompanied by increased phosphorylation of 14-3-3ζ at S58 and reduced dimerisation of 14-3-3ζ. Palmitic acid further augmented phosphorylation of 14-3-3ζ and triggered nuclear accumulation of FOXO1 in both INS-1E and human islet cells. Furthermore, the overexpression of a phosphomimicking mutant of 14-3-3ζ (S58D) enhanced nuclear FOXO1. In accordance with the nuclear accumulation of P-FOXO1, PKCδ overexpression alone did not increase apoptotic cell death. Additionally, insulin secretion and glucose homeostasis in PKCδ-overexpressing mice remained unaffected. CONCLUSIONS/INTERPRETATION: These results suggest that PKCδ-mediated phosphorylation of 14-3-3ζ contributes to the nuclear retention of FOXO1, even when FOXO1 is phosphorylated as under non-stress conditions. P-FOXO1 does not induce pro-apoptotic genes, but may rather exert beneficial effects on beta cells.  
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Publikationstyp Artikel: Journalartikel
Dokumenttyp Wissenschaftlicher Artikel
Schlagwörter 14-3-3 Zeta ; Apoptosis ; Foxo1 ; Insulin Secreting Beta Cells ; Jnk ; Palmitate ; Pkc Delta
Sprache englisch
Veröffentlichungsjahr 2015
HGF-Berichtsjahr 2015
ISSN (print) / ISBN 0012-186X
e-ISSN 1432-0428
Zeitschrift Diabetologia
Quellenangaben Band: 58, Heft: 12, Seiten: 2819-2831 Artikelnummer: , Supplement: ,
Verlag Springer
Verlagsort Berlin ; Heidelberg [u.a.]
Begutachtungsstatus Peer reviewed
POF Topic(s) 90000 - German Center for Diabetes Research
Forschungsfeld(er) Helmholtz Diabetes Center
PSP-Element(e) G-502400-002
G-502400-001
PubMed ID 26363783
Erfassungsdatum 2015-10-08