The long term goal for this proposal is aimed at elucidating the functions of integrins and integrin-associated molecules in growth cone motility. The proposal is focused on alpha-3 integrin and an alpha-3 integrin-associated protein, CD151, a member of the transmembrane-4- superfamily. The first specific aim will study the association of CD151 with alpha-3 integrin and the signaling molecule phosphatidylinositol 4-kinase in human NT2N neurons using co-immunoprecipitation, immunoblotting, and lipid kinase assays. The second specific aim will use antibody blockade to characterize alpha-3 integrin and CD151 function in neurite initiation and outgrowth by NT2N neurons. The third specific aim will address the in vivo relevance of the work with NT2N neurons by examining the expression of alpha-3 integrin and CD151 in the developing murine nervous system using immunohistochemistry and in situ hybridization. The fourth specific aim will address the functional relevance of alpha-3 integrin s association with CD151. Chimeric molecules designed to perturb the alpha-3 integrin-CD151 association will be transfected into NT2 precursor cells. NT2N neurons derived from the transfectants will be tested in neurite outgrowth assays. The studies in this proposal will add to our knowledge of integrin expression and function in neurons. Understanding integrin function in neurite outgrowth may allow us to exploit some aspect of that function in the repair of damaged nerves or the treatment of neurological disorders. NT2N neurons are transplantable human neurons that may themselves be useful in the treatment of nervous system diseases.