Examining the Interaction between Cindr and the JNK Signaling Pathway in Drosophila Larval Epithelia

Adaptor proteins are accessory proteins in signal transduction pathways that provide an environment for protein complexes and interactions to form. These protein interactions may be crucial during biological events such as cell adhesion and organization of the actin cytoskeleton. Indeed, if adaptor proteins are mutated, this may lead to severe defects that compromise the integrity of epithelial tissues. An adaptor protein of critical importance in the regulation of cell adhesion and actin organization is Cindr, the sole Drosophila orthologue of the CD2AP/CIN85 family of mammalian proteins. Cindr links activity at adhesion sites on the apical surface of epithelial cells to the actin cytoskeleton. Moreover, the c-Jun-N-terminal kinase (JNK) signal transduction pathway functions in a variety of biological processes, including proliferation, apoptosis, and cell migration. Previous Johnson lab members have used co-immunoprecipitation assays to detect an interaction between Cindr and Basket (Bsk), the sole Drosophila JNK orthologue (Christina Feiler and Sam Van Rensburg, Johnson Lab). However, the nature of this interaction is unclear. In this study, we reduced Cindr via RNAi technology in order to characterize cell behavior modifications in larval wing epithelia. Subsequently, Bsk was reduced at the same time as Cindr to observe if modifications in the cindrRNAi phenotype occurred. We found that downregulation of Cindr severely compromised developing epithelia such that loss of adhesion, cell migration, and apoptosis occurred. Reducing Bsk and Cindr concurrently partially rescued some of these tissue defects. Taken together, the data presented in this study show for the first time that Cindr has an inhibitory effect on Bsk in Drosophila larval wing epithelia.