Perkins 97-23509 Protein tyrosine phosphorylation is a remarkably conserved mechanism which is implicated in the control of cell growth, differentiation and cell survival in organisms as distantly related as yeast and humans. Although many tyrosine kineses have been described, only recently have protein tyrosine phosphatases (PTPases) been implicated in receptor tyrosine kinase (RTK) mediated signal transduction pathways. The Drosophila gene corkscrew (csw) encodes a protein which is among the first PTPases whose gene mutations are facilitating a genetic analysis of function in vivo. Genetic, developmental and molecular studies have demonstrated that Csw functions positively in multiple RTK pathways, four of which are essential during embryonic development. These analyses suggest that Csw is a member of the conserved signaling cassette that operates downstream of all RTKs. Csw also has been functionally conserved through evolution since a structurally similar mammalian PTPase, SHP-2, can substitute for Csw during development; therefore, the observations made for Csw may be generally applied to its mammalian homolog. Preliminary work reveals that Csw physically interacts in viva with two novel proteins, D2 and 61. To understand the function of D2 and 61 in Csw, hence RTK, signaling a number of genetic and biochemical approaches have been designed. Specifically the experiments will: 1. determine the functions of D2 and 61 during Drosophila development and RTK signaling, 2. determine if their functions are dependent on the activation state of the RTK, 3. determine whether D2 and 61 are required to positively or negatively transduce an RTK signal, and if so 4. determine if D2 and 61 act upstream or downstream of Csw, and more precisely where in the signaling cassette they function. Understanding the genetic and molecular mechanisms of Csw action are critical first steps towards determining how a PTPase functions positively in RTK pathways that are essential for cell growth and differentiati on.
