Impaired response to hepatocyte growth factor in FRTL-5 rat thyroid cells expressing a functional hepatocyte growth factor receptor

The FRTL-5 rat thyroid cell line is widely used for studies of thyrocyte fu nction and growth. The objective of the present study was to investigate th e effects of hepatocyte growth factor (HGF) on FRTL-5 cells. HGF has previo usly been known to be a potent regulator of thyrocyte growth and differenti ation. Met, the receptor for HGF was expressed in FRTL-5 cells, as well as in primary cultures of porcine thyrocytes included in the study as control. On HGF stimulation Met was tyrosine phosphorylated in both porcine and FRT L-5 cells, indicating an activation of the receptor. Addition of HGF induce d changes of cell shape, scattering and proliferation of the porcine thyroc ytes, but not in the FRTL-5 cells; yet, a functional coupling of Met to the p85 subunit of the phosphatidylinositol-3'-kinase (PI3'-K) in coprecipitat ion experiments, formation of focal adhesions detected in immunofluorescenc e staining with an antivinculin antibody, and induction of c-fos mRNA in No rthern blot analysis was observed in FRTL-5 cells, showing a transduction o f the HGF/Met signal. In summary, despite the expression of apparently func tional Met, the FRTL-5 cells are unable to properly respond to HGF.