Abstract
Abstract Ecionoid（ED） is a cell-adhesion molecule(CAM) which is comprised of 7 immunoglobulin(Ig) domains, 2 fibronectin type III(FnIII) domains and a transmembrane domain, followed by intracellular 315 amino acids with no structural or functional motif except for the last 4 residues(EIIV) which is capable of binding PDZ domains. Ed has been reported to have multiple functions. Previous studies have shown that Ed negatively regulates EGFR signaling during development of Drosophila compound eye, whereas facilitates Notch signaling in mesothoratic bristle development. In addition, ED was reported to be an essential component cooperating with DE-cadherin, a adherens junctions（AJ） molecules, to mediate cell-cell adhesion. However, the detailed mechanisms of how Ed works remain unclear. To elucidate the mechanisms of ED’s diverse functions, it is essential to identify the molecules that directly interact with ED. We performed yeast two hybrid analysis and GST pulldown experiments in search of them. Three candidates were isolated: CG6167（by yeast two-hybrid screen）, Par6, and Stardust（by pulldown experiments）, each contains at least one PDZ domain. Par6 and stardust are two key determinants in regulating epithelial cell polarity. Genetic mosaic analysis in wing imaginal discs showed that Par6 is missing at the interface between ed clones and wildtype cells. Ectopic expression of Ed causes downregulation of Par6.However, removal of either Par6 or Stardust seems to affect neither expression level nor distribution of ED. The overall polarity and integrity of epithelial cells are not affected. The results suggest that (1) ED has a bias to bind PDZ-containing proteins (2) ED may binds Par6 and Stardust and localizes them to Ajs.