JNK1-dependent PUMA expression contributes to hepatocyte lipoapoptosis.
Free fatty acids (FFA) induce hepatocyte lipoapoptosis by a c-Jun N-terminal kinase (JNK)-dependent mechanism. However, the cellular processes by which JNK engages the core apoptotic machinery during lipotoxicity, especially activation of BH3-only proteins, remain incompletely understood. Thus, our aim was to determine whether JNK mediates induction of BH3-only proteins during hepatocyte lipoapoptosis. The saturated FFA palmitate, but not the monounsaturated FFA oleate, induces an increase in PUMA mRNA and protein levels. Palmitate induction of PUMA was JNK1-dependent in primary murine hepatocytes. Palmitate-mediated PUMA expression was inhibited by a dominant negative c-Jun, and direct binding of a phosphorylated c-Jun containing the activator protein 1 complex to the PUMA promoter was identified by electrophoretic mobility shift assay and a chromatin immunoprecipitation assay. Short hairpin RNA-targeted knockdown of PUMA attenuated Bax activation, caspase 3/7 activity, and cell death. Similarly, the genetic deficiency of Puma rendered murine hepatocytes resistant to lipoapoptosis. PUMA expression was also increased in liver biopsy specimens from patients with non-alcoholic steatohepatitis as compared with patients with simple steatosis or controls. Collectively, the data implicate JNK1-dependent PUMA expression as a mechanism contributing to hepatocyte lipoapoptosis.
Cazanave
Sophie C
SC
Miles and Shirley Fitterman Center for Digestive Diseases, Division of Gastroenterology and Hepatology, College of Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA.
Mott
Justin L
JL
Elmi
Nafisa A
NA
Bronk
Steven F
SF
Werneburg
Nathan W
NW
Akazawa
Yuko
Y
Kahraman
Alisan
A
Garrison
Sean P
SP
Zambetti
Gerard P
GP
Charlton
Michael R
MR
Gores
Gregory J
GJ
D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D005234:Fatty Liver / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D015870:Gene Expression / Q000187:drug effects; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D048055:Mitogen-Activated Protein Kinase 8 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010168:Palmitates / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D000873:Anthracenes; D051017:Apoptosis Regulatory Proteins; C438378:BBC3 protein, human; C488588:PUMA protein, mouse; D010168:Palmitates; D011518:Proto-Oncogene Proteins; D025521:Tumor Suppressor Proteins; D051028:bcl-2-Associated X Protein; C432165:pyrazolanthrone; D048055:Mitogen-Activated Protein Kinase 8