The investigator plans to continue his studies into the roles of the polypeptide growth factors, platelet-derived growth factor (PDGF), acidic fibroblast growth factor (aFGF), and transforming growth factor-beta (TGF-beta) and their receptors in the regulation of growth of normal and transformed cells. The four specific aims are as follows: (1) To define the mechanism of intracellular loop autocrine transformation in cells transformed by v-sis and c-sis (PDGF-B). The signal transduction mediated by the intracellular, activated PDGF receptors will be studied by determination of the kinase activities of the intracellular activated PDGF receptors and by examination of the potential interaction of the intracellular activated PDGF receptors with phospholipase Cgamma, pp60 c-src, PI-3 kinase, or GTPase activating proteins. (2) To purify and characterize the cell surface binding protein(CSBP) for sis gene products from cultured fibroblasts and bovine liver membranes, to investigate the cell biology of CSBP, and to examine the effect of CSBP expression on the tumorigenicity of sis-transformed cells. CSBP will be purified from crude plasma membranes of cultured fibroblasts and bovine liver. The biosynthesis, processing and turnover of CSBP in cultured cells will be studied using specific anti-CSBP antibodies. (3)To characterize the Ser/Thr-specific protein kinase activity of bovine liver major aFGF- stimulated phosphoprotein (MAFP), a newly discovered ecto-protein kinase, and to examine the cell biology of MAFP. The MAFP-mediation of the mitogenic action of aFGF and its effect on cellular signalling will be examined in cells that do not express the aFGF receptor/protein tyrosine kinase. (4) To characterize the Ser/Thr-specific protein kinase activity of the type V TGF-beta receptor and to study the cell biology and molecular biology of this newly discovered receptor. The kinase activity of the type V TGF-beta receptor will be studied with respect to substrate specificity and identification of the autophosphorylation site and physiological substrates. The cloning from a bovine cDNA library and the sequencing and expression of the type V TGF-beta receptor will be carried out using standard cloning techniques.
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