Nuclear Akt associates with PKC-phosphorylated Ebp1, preventing DNA fragmentation by inhibition of caspase-activated DNase.
Akt promotes cell survival through phosphorylation. The physiological functions of cytoplasmic Akt have been well defined, but little is known about the nuclear counterpart. Employing a cell-free apoptotic assay and NGF-treated PC12 nuclear extracts, we purified Ebp1 as a factor, which contributes to inhibition of DNA fragmentation by CAD. Depletion of Ebp1 from nuclear extracts or knockdown of Ebp1 in PC12 cells abolishes the protective effects of nerve growth factor, whereas overexpression of Ebp1 prevents apoptosis. Ebp1 (S360A), which cannot be phosphorylated by PKC, barely binds Akt or inhibits DNA fragmentation, whereas Ebp1 S360D, which mimics phosphorylation, strongly binds Akt and suppresses apoptosis. Further, phosphorylated nuclear but not cytoplasmic Akt interacts with Ebp1 and enhances its antiapoptotic action independent of Akt kinase activity. Moreover, knocking down of Akt diminishes the antiapoptotic effect of Ebp1 in the nucleus. Thus, nuclear Akt might contribute to suppressing apoptosis through interaction with Ebp1.
Ahn
Jee-Yin
JY
Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA.
Liu
Xia
X
Liu
Zhixue
Z
Pereira
Lorena
L
Cheng
Dongmei
D
Peng
Junmin
J
Wade
Paul A
PA
Hamburger
Anne W
AW
Ye
Keqiang
K
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism*; D053938:DNA Fragmentation; D003851:Deoxyribonucleases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004789:Enzyme Activation; D046912:Multiprotein Complexes; D020932:Nerve Growth Factor / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D016716:PC12 Cells; D000075223:Poly-ADP-Ribose Binding Proteins; D011493:Protein Kinase C / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D013347:Subcellular Fractions / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; C511885:PA2G4 protein, rat; D000075223:Poly-ADP-Ribose Binding Proteins; D020932:Nerve Growth Factor; D051057:Proto-Oncogene Proteins c-akt; D011493:Protein Kinase C; D003851:Deoxyribonucleases; C491882:Dffb protein, rat