CLONING OF A TGF-BETA TYPE-I RECEPTOR THAT FORMS A HETEROMERIC COMPLEX WITH THE TGF-BETA TYPE-II RECEPTOR

A cDNA clone encoding a 53 kd serine/threonine kinase receptor with an overall structure similar to that of the type II receptor for transforming growth factor beta (TGFbeta) was obtained. I-125-TGFbeta1 bound to porcine endothelial cells transfected with the cDNA and formed a cross-linked complex of 70 kd, characteristic of a TGFbeta type I receptor. Immunoprecipitation of the cross-linked complexes by antibodies against the cloned receptor revealed the 70 kd complex as well as a 94 kd TGFbeta type II receptor complex. The immunoprecipitated novel serine/threonine kinase receptor had biochemical properties of the TGFbeta type I receptor and was observed in different cell types. Transfection of the cloned cDNA into TGFbeta type I receptor-deficient cells restored TGFbeta-induced plasminogen activator inhibitor 1 production. These results suggest that signal transduction by TGFbeta involves the formation of a heteromeric complex of two different serine/threonine kinase receptors.