Hepatocyte growth factor (FGF) and its high affinity tyrosine kinase receptor, c-met, are important mediators of mesenchymal/epithelial interactions and tubulogenesis during renal development, as well as maintenance and repair of tubular architecture in the adult kidney. A clear understanding of the mechanisms by which c-met activates these cellular events may aid in understanding developmental abnormalities of the renal tubules (such as cystic kidney diseases) as well as providing insight into events leading to tubular repair vs. scarring following renal injury. We have found that the chemotactic and tubulogenic actions of the c-met receptor require activation of the phosphatidylinositol 3-kinase (PI 3-K). Most recently we have exciting new data which demonstrates that the PI- 3,4,5-P3 lipid product of the PI 3-K is capable of directly initiating chemotaxis, for the first time demonstrating an in vivo role for this lipid as a member of a novel class of second messengers. To further characterize the subcellular events in c-met mediated epithelial morphogenesis, we will focus this research on two major areas. First wei will extensively examine the role of the PI 3-K in chemotaxis and tubulogenesis by: 1) determining the signalling events initiated by the novel second messenger PIP3 (Specific Aim 1a), and 3) elucidating the role of the p85 and p110 subunits of the PI 3-K in morphogenesis using a series of deletional mutants of the enzyme (Specific Aim 1b). Additional pathways required for normal epithelial chemotaxis and tubulogenesis will be identified by isolating a met-/-cell line followed by transfection of met receptor mutants which selectively associate with candidate signaling proteins identified in this proposal (Specific Aim 2a) as well as determination of the kinase specificity of c-met (Specific Aim 2b). The long term goals of this proposal are to identify which signaling pathways are critical for HGF/c-met-dependent cell changes, and to pursue means in which to intervene in these events so as to enhance recovery from renal tubular injury or promote normal renal tubular development.
