PKCε-mediated c-Met endosomal processing directs fluctuant c-Met-JNK-paxillin signaling for tumor progression of HepG2

Cell Signal. 2015 Jul;27(7):1544-55. doi: 10.1016/j.cellsig.2015.02.031. Epub 2015 Mar 14.


Hepatocyte growth factor (HGF) induced c-Met signaling play critical roles in the progression of hepatocellular carcinoma (HCC). However, c-Met targeting approaches suffered resistance and side effect, thus identification of more suitable downstream targets is needed. Recently, we demonstrated HGF-induced fluctuant ERK/paxillin signaling within 24h. We further examined the underlying mechanisms for fluctuant c-Met/JNK/paxillin signal cascade within 12h. HGF-induced phosphorylation of c-Met, JNK, and paxillin (Ser178) shared a common fluctuation pattern characterized by an initial peak at 0.5h, a middle drop at 4h, and a later peak at 10h. Dynasore, the inhibitor of dynamin, suppressed HGF-induced c-Met internalization and phosphorylation of JNK and paxillin (Ser178) at 0.5h, indicating that endosome formation is required for initial signal enhancement. Further, depletion of PKCε not only enhanced HGF-induced phosphorylation of JNK and paxillin (Ser178) but also prevented c-Met degradation at 0.5h, suggesting that PKCε mediated c-Met degradation for signal declination. On the other hand, HGF induced colocalizations of both phosphorylated JNK and paxillin with the endosomal recycling protein GGA3 at 10h and depletion of GGA3 abolished membrane recycling of c-Met and phosphorylation of JNK/paxillin at the same time point. Interestingly, HGF induced GGA3 phosphorylation in a PKCε-dependent manner during 0.5-4h, which is associated with c-Met degradation in the same period. Finally, HGF-induced cell migration, invasion and intrahepatic metastasis of HepG2 were prevented by the inhibitors of endocytosis. Our results suggest that critical endosomal components are promising therapeutic targets for preventing HGF-induced progression of HCC.

Keywords: Hepatocellular carcinoma; Hepatocyte growth factor; JNK; Protein kinase C; Tumor metastasis; c-Met endocytosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Vesicular Transport / metabolism
  • Cell Movement / drug effects
  • Endosomes / metabolism*
  • Hep G2 Cells
  • Hepatocyte Growth Factor / pharmacology
  • Humans
  • Hydrazones / pharmacology
  • Indoles / pharmacology
  • JNK Mitogen-Activated Protein Kinases / metabolism*
  • Maleimides / pharmacology
  • Microscopy, Confocal
  • Paired Box Transcription Factors / metabolism
  • Paxillin / metabolism*
  • Phosphorylation / drug effects
  • Protein Kinase C-epsilon / antagonists & inhibitors
  • Protein Kinase C-epsilon / genetics
  • Protein Kinase C-epsilon / metabolism*
  • Proto-Oncogene Proteins c-met / metabolism*
  • RNA Interference
  • RNA, Small Interfering / metabolism
  • Signal Transduction / drug effects


  • Adaptor Proteins, Vesicular Transport
  • GGA adaptor proteins
  • Hydrazones
  • Indoles
  • Maleimides
  • N'-(3,4-dihydroxybenzylidene)-3-hydroxy-2-naphthahydrazide
  • Paired Box Transcription Factors
  • Paxillin
  • RNA, Small Interfering
  • Hepatocyte Growth Factor
  • Proto-Oncogene Proteins c-met
  • Protein Kinase C-epsilon
  • JNK Mitogen-Activated Protein Kinases
  • bisindolylmaleimide