The c-met protooncogene encodes a transmembrane tyrosine kinase receptor for hepatocyte growth factor (HGF). It has been widely suggested that HGF and its receptor constitute a paracrine signaling system, in which mesenchymally derived cells produce ligand that binds to the receptor predominantly expressed on cells of epithelial origin. In this study, we have isolated and completely sequenced the entire coding region of c-met cDNA from the rat kidney. The nucleotide sequence of the rat c-met cDNA revealed that the HGF receptor is encoded within single open-reading frame as 190 kDa of a transmembrane glycoprotein consisting of 1,382 amino acids. Determination of c-met mRNA levels in various tissues revealed a widespread expression of c-met with the highest levels in kidney, lung, and liver. We found simultaneous induction of both HGF and its receptor gene expression by interleukin-6 (IL-6) in primary cultured rat glomerular mesangial cells. The expression of HGF and c-met was remarkably stimulated following incubation of rat mesangial cells with IL-6, in a time- and dose-dependent manner Our data suggest that autocrine action of HGF may be achieved in vivo through simultaneous induction of both HGF and its receptor expression in renal mesenchymal cells.
