Upregulation of multiple signaling pathways by Dock5 deletion in epithelial cells.

Purpose: Rupture of lens cataract (RLC) is a hereditary mouse model that shows spontaneous rupture of the lens at the posterior pole at 45-100 days of age. The responsible gene for this phenotype was identified as Dock5, a guanine nucleotide exchange factor for small GTPase Rac1. This study was performed to elucidate the pathway initiating this phenotype. Methods: We examined the RNA expression by microarray in lens epithelial cells (LECs) from wild-type and RLC mice at the pre-rupture age of 21 days. We applied the list of altered genes to an Ingenuity Pathway Analysis (IPA) to predict the pathways that are altered upon dedicator of cytokinesis-5 (Dock5) protein loss. The activation status of the predicted pathways was examined by western blotting in the cultured epithelial cells treated with a Dock5 inhibitor. Results: The highest-scored network was "Antimicrobial Response, Inflammatory Response, Dermatological Diseases and Conditions." In that network, it is predicted that extracellular signal-regulated kinase (Erk) is activated in LECs from RLC mice. Our test confirmed that Erk was more phosphorylated in the LECs at the equator in both Dock5-knockout mice and RLC mice. In an in vitro experiment of the cultured epithelial cells, the inhibition of Dock5 activity significantly induced Erk activation. It was also confirmed that Akt (cellular homolog of murine thymoma virus akt8 oncogene, also called protein kinase B) and nuclear factor-kappa B (NFκB), predicted to be the key molecules in two other high-scoring networks by IPA, were activated upon Dock5 inhibition in the cultured epithelial cells. Conclusions: Dock5 participates in epithelial cell maintenance by regulating gene expression.