DROSOPHILA ALPHA-CATENIN AND E-CADHERIN BIND TO DISTINCT REGIONS OF DROSOPHILA-ARMADILLO

Adherens junctions are multiprotein complexes mediating cell-cell adhe sion and communication, They are organized around a transmembrane cadh erin, which binds a set of cytoplasmic proteins required for adhesion and to link the complex to the actin cytoskeleton, Three components of Drosophila adherens junctions, analogous to those in vertebrates, hav e been identified: Armadillo (homolog of beta-catenin), Drosophila E-c adherin (DE-cadherin), and alpha-catenin. We carried out the first ana lysis of the interactions between these proteins using in vitro bindin g assays, the yeast two-hybrid system, and in vivo assays, We identifi ed a 76-amino acid region of Armadillo that is necessary and sufficien t for binding alpha-catenin and found that the N-terminal 258 amino ac ids of alpha-catenin interact with Armadillo, A large region of Armadi llo, spanning six central Armadillo repeats, is required for DE-cadher in binding, whereas only 41 amino acids of the DE-cadherin cytoplasmic tail are sufficient for Armadillo binding. Our data complement and ex tend results obtained in studies of vertebrate adherens junctions, pro viding a foundation for understanding how junctional proteins assemble and a basis for interpreting existing mutations and creating new ones .