title: Increased carbonylation of the lipid phosphatase PTEN contributes to Akt2 activation in a murine model of early alcohol-induced steatosis.
abstract: The production of reactive aldehydes such as 4-hydroxynonenal (4-HNE) is a key event in the pathogenesis of alcoholic liver disease (ALD), which ranges from simple steatosis to fibrosis. The lipid phosphatase PTEN plays a central role in the regulation of lipid metabolism in the liver. In this study, the effects of chronic ethanol feeding and carbonylation on the PTEN signaling pathway were examined in a 9-week mouse feeding model for ALD. Chronic ethanol consumption resulted in altered redox homeostasis as evidenced by decreased GSH, decreased Trx1, and increased GST activity. Both PTEN expression and PTEN phosphorylation were significantly increased in the livers of ethanol-fed mice. Carbonylation of PTEN increased significantly in the ethanol-fed mice compared to pair-fed control animals, corresponding to decreased PTEN 3-phosphatase activity. Concomitantly, increased expression of Akt2 along with increased Akt phosphorylation at residues Thr(308), Thr(450), and Ser(473) was observed resulting in increased Akt2 activity in the ethanol-fed animals. Akt2 activation corresponded to a decrease in cytosolic SREBP and ChREBP. Subsequent LC/MS/MS analysis of 4-HNE-modified recombinant human PTEN identified Michael addition adducts of 4-HNE on Cys(71), Cys(136), Lys(147), Lys(223), Cys(250), Lys(254), Lys(313), Lys(327), and Lys(344). Computational-based molecular modeling analysis of 4-HNE adducted to Cys(71) near the active site and Lys(327) in the C2 domain of PTEN suggested inhibition of enzyme catalysis via either stearic hindrance of the active-site pocket or prevention of C2 domain-dependent PTEN function. We hypothesize that 4-HNE-mediated PTEN inhibition contributes to the observed activation of Akt2, suggesting a possible novel mechanism of lipid accumulation in response to increased reactive aldehyde production during chronic ethanol administration in mice.
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado at Denver, Anschutz Medical Campus, Aurora, CO 80045, USA.
authors.forename: C T
authors.initials: CT
authors.lastname: Shearn
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado at Denver, Anschutz Medical Campus, Aurora, CO 80045, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: Smathers
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado at Denver, Anschutz Medical Campus, Aurora, CO 80045, USA.
authors.forename: D S
authors.initials: DS
authors.lastname: Backos
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado at Denver, Anschutz Medical Campus, Aurora, CO 80045, USA.
authors.forename: P
authors.initials: P
authors.lastname: Reigan
authors.affiliation: Department of Pathology, School of Medicine, University of Colorado at Denver, Anschutz Medical Campus, Aurora, CO 80045, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Orlicky
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado at Denver, Anschutz Medical Campus, Aurora, CO 80045, USA. Electronic address: Dennis.Petersen@ucdenver.edu.
authors.forename: Dennis R
authors.initials: DR
authors.lastname: Petersen
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid; D004195:Disease Models, Animal; D004789:Enzyme Activation; D005235:Fatty Liver, Alcoholic / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008958:Models, Molecular; D051059:PTEN Phosphohydrolase / Q000378:metabolism*; D050050:Protein Carbonylation / Q000187:drug effects*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D053719:Tandem Mass Spectrometry
chemical_list: C494922:Akt2 protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D051059:PTEN Phosphohydrolase; C487757:Pten protein, mouse
keywords: 4-HNE; 4-hydroxy-2-nonenal; ALD; ALT; Alcoholic liver disease; ChREBP; Free radicals; Lipid peroxidation; NASH; PI3K; PTEN; PTP; PtdIns(3,4,5)P(3); SREBP; Steatosis; Trx; TrxR; alanine aminotransferase; alcoholic liver disease; carbohydrate response element-binding protein; nonalcoholic steatohepatitis; phosphatase and tensin homolog deleted on chromosome 10; phosphatidylinositol 3,4,5-trisphosphate; phosphatidylinositol 3-kinase; protein tyrosine phosphatase; sterol-response element-binding protein; thioredoxin; thioredoxin reductase