The adaptor protein Cindr regulates JNK activity to maintain epithelial sheet integrity

• Reducing expression of the adaptor protein Cindr compromised epithelial integrity.
• Cells with reduced Cindr delaminated: some migrated short distances; most died.
• JNK activity mediated the behavior of cells lacking Cindr.
• Cindr complexed with dJNK to repress its signaling activity.
• The correct stoichiometry of Cindr-dJNK complexes maintains epithelial integrity.

Epithelia are essential barrier tissues that must be appropriately maintained for their correct function. To achieve this a plethora of protein interactions regulate epithelial cell number, structure and adhesion, and differentiation. Here we show that Cindr (the Drosophila Cin85 and Cd2ap ortholog) is required to maintain epithelial integrity. Reducing Cindr triggered cell delamination and movement. Most delaminating cells died. These behaviors were consistent with JNK activation previously associated with loss of epithelial integrity in response to ectopic oncogene activity. We confirmed a novel interaction between Cindr and Drosophila JNK (dJNK), which when perturbed caused inappropriate JNK signaling. Genetically reducing JNK signaling activity suppressed the effects of reducing Cindr. Furthermore, ectopic JNK signaling phenocopied loss of Cindr and was partially rescued by concomitant cindr over-expression. Thus, correct Cindr-dJNK stoichiometry is essential to maintain epithelial integrity and disturbing this balance may contribute to the pathogenesis of disease states, including cancer.