Antiapoptotic effect of c-Jun N-terminal Kinase-1 through Mcl-1 stabilization in TNF-induced hepatocyte apoptosis.
OBJECTIVE
c-Jun N-terminal Kinase (JNK) is a key regulator in tumor necrosis factor (TNF)-mediated liver injury. However, distinct roles for JNK1 and JNK2 in hepatocyte apoptosis are still unresolved. Although myeloid cell leukemia-1 (Mcl-1) has been reported as a substrate of JNK, the role of Mcl-1 and its functional regulation by JNK in TNF-induced hepatocyte apoptosis and liver injury remain to be elucidated.


METHODS
TNF-induced hepatocyte apoptosis was investigated in wild-type, jnk1-/- and jnk2-/- mice in vitro and in the galactosamine/TNF (GalN/TNF) liver injury model. For further analysis, we used adenoviruses expressing wild-type Mcl-1 or its substitution mutant, and the Cre/loxP system (mcl-1f/f) to delete mcl-1.


RESULTS
jnk2-/- Hepatocytes showed increased Mcl-1 expression and were more resistant to TNF-induced apoptosis compared with wild-type or jnk1-/- hepatocytes. Increased Mcl-1 expression in jnk2-/- hepatocytes correlated with their JNK activity, which is mediated by residual JNK1 and higher than in wild-type or jnk1-/- hepatocytes. JNK activation led to phosphorylation of Mcl-1 in hepatocytes, and this increased the half-life of the Mcl-1 protein. Overexpression of Mcl-1 confirmed its antiapoptotic effect in TNF-induced hepatocyte apoptosis in vitro and in vivo. Deletion of mcl-1 in jnk2-/- hepatocytes increased TNF-induced hepatocyte apoptosis both in vitro and in GalN/TNF-induced liver injury model.


CONCLUSIONS
jnk2-/- Hepatocytes are resistant to TNF-induced apoptosis. Activated JNK1 contributes to this antiapoptotic phenotype of jnk2-/- hepatocytes through phosphorylation-mediated stabilization of Mcl-1.
Kodama
Yuzo
Y
Department of Medicine, University of California, San Diego, La Jolla, California 92093, USA.
Taura
Kojiro
K
Miura
Kouichi
K
Schnabl
Bernd
B
Osawa
Yosuke
Y
Brenner
David A
DA
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002478:Cells, Cultured; D004195:Disease Models, Animal; D005260:Female; D017353:Gene Deletion; D022781:Hepatocytes / Q000378:metabolism* / Q000473:pathology*; D008107:Liver Diseases / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D048055:Mitogen-Activated Protein Kinase 8 / Q000235:genetics / Q000378:metabolism*; D048056:Mitogen-Activated Protein Kinase 9 / Q000235:genetics / Q000378:metabolism; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
C579094:Mcl1 protein, mouse; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D014409:Tumor Necrosis Factor-alpha; D048056:Mitogen-Activated Protein Kinase 9; D048055:Mitogen-Activated Protein Kinase 8