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Gastroenterology. 2009 Apr;136(4):1423-34. doi: 10.1053/j.gastro.2008.12.064. Epub 2009 Jan 6.

Antiapoptotic effect of c-Jun N-terminal Kinase-1 through Mcl-1 stabilization in TNF-induced hepatocyte apoptosis.

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  • 1Department of Medicine, University of California, San Diego, La Jolla, California 92093, USA.

Abstract

BACKGROUND & AIMS:

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.

PMID:
19249395
[PubMed - indexed for MEDLINE]
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