Overexpression of PEMT2 downregulates the PI3K/Akt signaling pathway in rat hepatoma cells.
Phosphatidylethanolamine N-methyltransferase 2 (PEMT2) is an isoform of PEMT that converts phosphatidylethanolamine to phosphatidylcholine in mammalian liver. Overexpression of PEMT2 led to inhibition of proliferation of hepatoma cells [J. Biol. Chem. 269 (1994) 24531]. The present study aims to unravel the molecular mechanism of the reduced proliferation, especially the signaling transducer proteins involved in this process. Thus, we chose PI3K/Akt pathway that is initiated by growth factors and leads to cell survival and proliferation. Rat hepatoma CBRH-7919 cells transfected with pemt2-cDNA showed that: (1) signaling proteins including c-Met, PDGF receptor, PI3K, Akt and Bcl-2 all had reduced expression as shown by Western blotting studies; (2) flow cytometric and DNA ladder assays showed that 22.9% of the pemt2-transfected cells were undergoing apoptosis; (3) the activity of Akt was decreased as shown by Western blotting using antibody directed against p-Akt (Thr308); (4) wortmannin and PD98059, inhibitors of PI3K and MEK, respectively, both inhibited Akt activity, indicating that PI3K and MAPK pathways were merging at Akt in CBRH-7919 cells. The above results suggest that overexpression of PEMT2 strongly downregulated the PI3K/Akt signaling pathway at multiple sites and induced apoptosis. This, at least partly, explains the molecular mechanism of impaired proliferation induced by pemt2 transfection.
Zou
Wei
W
Department of Physiology, Liaoning Teacher's University, Dalian, China.
Li
Zhao-Yu
ZY
Li
Ya-Li
YL
Ma
Ke-Li
KL
Tsui
Zhao-Chun
ZC
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D008114:Liver Neoplasms, Experimental / Q000201:enzymology* / Q000473:pathology; D008780:Methyltransferases / Q000235:genetics / Q000502:physiology*; D050918:Phosphatidylethanolamine N-Methyltransferase; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D015398:Signal Transduction; D014162:Transfection; D014407:Tumor Cells, Cultured; D000077191:Wortmannin
D000730:Androstadienes; D004791:Enzyme Inhibitors; D005419:Flavonoids; D008780:Methyltransferases; D050918:Phosphatidylethanolamine N-Methyltransferase; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D000077191:Wortmannin; C494920:Akt1 protein, rat; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one