Importance of tyrosine phosphorylation for Echinoids function. Peter P Saengthien, Erin J Andrews, Susan A Spencer. Saint Louis University, St. Louis, MO.

   Echinoid (Ed) is an Ig-domain cell adhesion protein implicated in Notch, EGFR, and Hippo-pathway signaling. The intracellular domain of Echinoid has been shown to be important to Eds function in these pathways, but how it acts is poorly understood. One of Ed's functions is to limit Epidermal Growth Factor Receptor (EGFR) activity in developing Drosophila eye. EGFR signaling has also been shown to promote tyrosine phosphorylation of Ed both in vitro and in vivo. Based on the Netphos phosphorylation prediction program, nine of Eds eighteen intracellular tyrosine residues are good candidates for phosphorylation. To test whether tyrosine phosphorylation is important for Ed function, we mutated these tyrosines to phenylalanines to create an unphosphorylatable form of Ed, EdYF. We have used this construct to examine the possible effects of tyrosine phosphorylation on Ed subcellular localization and activity in cultured S2 cells and in transgenic animals.