HGF is a multifunctional growth factor. It is produced as a single-chain inactive precursor protein. Mature active HGF is a heterodimer composed of an alpha- chain subunit (69 kDa) and a beta-chain subunit (34 kDa), which are linked by a disulfide bond. The alpha-chain subunit contains an N-terminal hairpin domain and four kringle domains; the beta-chain subunit is a serine-protease-like domain lacking catalytic activity due to mutations in essential residues. The intracellular portion of c-Met, which is responsible for signal transduction, is composed of a juxtamembrane domain, a tyrosine kinase domain, and a C-terminal regulatory tail.
In the tyrosine kinase domain, two tyrosine residues (Tyr 1234 and Tyr 1235) regulate the kinase activity of c-Met. HGF/c-Met signaling activates multiple signal transduction pathways including the Src/focal adhesion kinase (FAK) pathway, the p120/signal transducer and activator of transcription (STAT) 3 pathway, the phosphoinositide- 3 kinase (PI3K)/Akt pathway, and the Ras/MEK pathway.  Hepatocyte growth factor and its receptor (the product of the c-met protooncogene) are believed to be necessary for the normal growth and development of many tissues and organs. The expression of HGF and HGFR genes are unregulated in several types of human cancer; therefore, understanding the control mechanisms governing HGF and HGFR gene expression is of great clinical interest.

References

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