Differentiating and proliferative effects of HGF in renal proximal tubular cells are mediated via different signalling pathways.
BACKGROUND
As a renotropic cytokine, hepatocyte growth factor (HGF) prevents acute renal failure and accelerates renal regeneration. HGF initiates its biological effects by interaction with specific transmembrane receptors, the c-Met proto-oncogene, possessing an intracellular tyrosine kinase domain. We tested the hypothesis of whether the complex biological effects of HGF in renal proximal tubular cells are mediated by different intracellular signalling cascades and/or different receptors.


METHODS
PT-1 cells, a proximal tubular cell line derived from rabbit kidney, were cultured under defined serum-free conditions to examine the biological effects of exogenously added HGF. By specific assays, we determined HGF binding and its effects on cell proliferation, migration, scattering and tubulogenic differentiation. To investigate whether HGF action could be inhibited by protein tyrosine kinase inhibitors (PTKIs), cells were incubated with HGF and different concentrations of herbimycin A, genestein, methyl-2,5-dihydroxycinnamate (MDC) and geldanamycin. All PTKIs are known inhibitors of pp60(c-src), a non-receptor tyrosine kinase involved in cell growth control.


RESULTS
HGF bound with high affinity to cell membrane receptors and displayed multiple biological effects. Compared with serum-free controls, HGF increased the number of microvilli 1.5-fold, enhanced cell proliferation and migration 1.8-fold, and stimulated the formation of tubular structures 2.3-fold. Consistent with the known tyrosine kinase activity of the c-Met receptor, the mitogenic and motogenic effects of HGF were inhibited by PTKIs in a dose-dependent manner with the following order of potency: geldanamycin > herbimycin A > genestein > MDC. In contrast, however, the HGF-induced tubulogenic cell differentiation was not inhibited specifically by PTKIs.


CONCLUSIONS
The finding that PTKIs inhibited the mitogenic response but not the tubulogenic differentiation induced by HGF indicates different intracellular signal transduction pathways. We suggest that pp60(c-src) plays a key role in mediating the mitogenic and motogenic action of HGF, whereas tubulogenic cell differentiation induced by HGF is transduced by a pp60(c-src)-independent signalling pathway.
Stracke
S
S
Department of Internal Medicine II, University of Ulm, Germany.
Ernst
F
F
Jehle
D R
DR
Grunewald
R W
RW
Haller
H
H
Keller
F
F
Jehle
P M
PM
D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D017228:Hepatocyte Growth Factor / Q000494:pharmacology* / Q000502:physiology; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000166:cytology* / Q000187:drug effects* / Q000502:physiology; D008854:Microscopy, Electron; D008871:Microvilli / Q000187:drug effects / Q000648:ultrastructure; D000090063:Proto-Oncogene Mas; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000502:physiology; D011817:Rabbits; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology
C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011994:Recombinant Proteins; D017228:Hepatocyte Growth Factor; D016392:Proto-Oncogene Proteins pp60(c-src)