title: PKC mediates fluctuant ERK-paxillin signaling for hepatocyte growth factor-induced migration of hepatoma cell HepG2.
abstract: Hepatocyte growth factor (HGF) is critical for triggering metastasis of hepatocellular carcinoma cell (HCC). Extracellular signal-regulated kinase (ERK) mediates HGF-induced cell migration via focal adhesion signaling. Protein kinase C (PKC) is a negative regulator of ERK activation, however, both PKC and ERK were required for HGF-induced cell migration. To address this intriguing issue, the signal mechanisms for HGF-induced HepG2 cell migration were investigated in a long-term fashion. HGF-induced phosphorylations of ERK, Src (at Tyr 416) and paxillin (at Ser178 and Tyr31) were up and down for 3 times within 24h. HGF also induced fluctuant PKC activation and Rac degradation. Consistently, HGF induced intermittent actin polarization within 24h, which can be blocked by the inhibitors of PKC (Bisindolymaleimide) and ERK. Inhibitor studies revealed that ERK was required for HGF-induced paxillin phosphorylation at Ser178, whereas PKC and Rac-1 may suppress HGF-induced phosphorylation of ERK and paxillin (at Ser178) and upregulate phosphorylation of paxillin at Tyr31. Based on shRNA technique, PKCα and δ were responsible for suppressing HGF-induced phosphorylation of ERK and paxillin (at Ser178), whereas PKC ε and ζ were required for phosphorylation of paxillin at Tyr31. The HGF-induced fluctuant signaling is reminiscent of c-Met endocytosis. Using Concanavalin A, an inhibitor of endocytosis, we found that c-Met endocytosis was required for PKC to suppress ERK phosphorylation. Moreover, HGF-induced c-Met degradation was also fluctuant, which can be prevented by Bisindolymaleimide. In conclusion, PKC is critical for mediating HGF-induced fluctuant ERK-paxillin signaling during cell migration, probably via triggering endosomal degradation of c-Met.
authors.affiliation: Research Centre for Hepatology, Department of Internal Medicine, Buddhist Tzu Chi General Hospital and Tzu Chi University, Hualien, Taiwan.
authors.forename: Chi-Tan
authors.initials: CT
authors.lastname: Hu
authors.forename: Chuan-Chu
authors.initials: CC
authors.lastname: Cheng
authors.forename: Siou-Mei
authors.initials: SM
authors.lastname: Pan
authors.forename: Jia-Ru
authors.initials: JR
authors.lastname: Wu
authors.forename: Wen-Sheng
authors.initials: WS
authors.lastname: Wu
mesh_terms: D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000473:pathology; D002465:Cell Movement / Q000187:drug effects; D003208:Concanavalin A / Q000494:pharmacology; D004705:Endocytosis / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D056945:Hep G2 Cells; D017228:Hepatocyte Growth Factor / Q000494:pharmacology*; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology; D008301:Maleimides / Q000494:pharmacology; D051379:Mice; D016513:Mice, SCID; D008934:Mitogens / Q000494:pharmacology; D051419:Paxillin / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D019859:Proto-Oncogene Proteins c-met / Q000037:antagonists & inhibitors / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D014183:Transplantation, Heterologous; D020744:rac GTP-Binding Proteins / Q000378:metabolism
chemical_list: D007211:Indoles; D007527:Isoenzymes; D008301:Maleimides; D008934:Mitogens; D051419:Paxillin; D034741:RNA, Small Interfering; D003208:Concanavalin A; D017228:Hepatocyte Growth Factor; D019859:Proto-Oncogene Proteins c-met; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; D020744:rac GTP-Binding Proteins; C088060:bisindolylmaleimide