Abstract
Echinoid (Ed), a component of adherens junctions (AJs), is classified in immunoglobulin superfamily of cell adhesion molecules (CAMs). As a transmembrane protein, Ed is divided into two main domains: the extracellular domain and the intracellular domain. Ed demonstrates the homophilic interaction between adjacent cells by the extracellular domain, composed of seven immunoglobulin (IG) domains and two fibronectin type III (FnIII) domains, and has a non-typical PDZ-binding motif in the intracellular domain interacting with actin filaments through Canoe or Bazooka. In previous reports, ed mutant clone strongly segregated from wild-type cells and formed smooth and round borders without Ed at the interface. The apical surface of clones decreased accompanying with actin cable which was formed at the clonal side of wild type cells. To see a process of ed mutant clone formation, a cleavage site activated by rho-4 has been designed on Ed trasmembrane domain. As Ed extracellular domain cleaved, we could see a process of ed mutant clone formation in short time by losing homophilic interaction. In addition, by combining ed-RNAi with overexpression experiments in this report, functional dissection of Ed can be performed. We found a certain part of Ed extracellular domain can be homophilic interaction and recruit WT-Ed at the interface. This could help to investigate Ed homophilic interaction. Finally, recent data showed that actin cable formation came from unevenly distribution of Ed intracellular domain in wild type cells surrounding ed mutant clone. A certain part of Ed intracellular domain influencing actin cable formation could be found by Ed intracellular truncations.