The role of Cytohesin dependent recycling in HGF stimulated migration and tissue repair

Incomplete repair of tissues after injury can lead to fibrosis and long-term impairment of organ function. Maladaptive repair after Acute Kidney Injury can lead to the development of Chronic Kidney Disease. Hepatocyte Growth Factor promotes repair and recovery after injury in a number of tissues, including kidney, liver, skin, lung and heart. One mechanism by which HGF promotes wound healing is by stimulating surviving epithelial cells to migrate into and repopulate the damaged regions. The Santy lab has shown that cytohesin family of ARF-activating proteins is required for HGF-stimulated migration in vitro and HGF-stimulated recovery of the kidney after acute injury. Migration requires the coordination of protrusion, adhesion and force generation at the leading edge of migrating cells. Specific cytohesin splice variants stimulate the movement of integrin adhesion receptors from recycling endosomes to the cell surface. Similarly, the Rac-activating protein Dock180 travels from recycling endosomes to the cell surface in a cytohesin-dependent manner in response to HGF signaling. The objective of this study is to determine the role and importance of cytohesin dependent trafficking in HGF stimulated migration and tissue repair. The driving hypothesis of the project is that HGF upregulates both the level and activity of pro-migratory cytohesin variants leading to enhanced cytohesin-dependent trafficking thereby stimulating migration during tissue repair. This will be tested with three specific aims: 1) Determine the role of cytohesin signaling in HGF stimulated tissue repair; 2) Determine the impact of HGF signaling on cytohesin expression and splicing; and 3) Determine the role of cytohesin stimulated endocytic recycling in HGF-stimulated migration. The importance of cytohesin signaling in HGF-stimulated repair pathways and on long-term repair of the kidney after acute kidney injury will be determined. The c-Met stimulated signaling pathways regulating changes in the production of cytohesin mRNAs in response to HGF will be determined. The impact of cytohesin activity on adhesion formation, polarized protrusive signaling and traction force generation at the leading edge of cells migrating in response to HGF will be determined. A molecular understanding of the pathways used by HGF to stimulate migration will provide a framework to develop treatments to stimulate healing after tissue damage and to understand conditions that impair recovery. A short-term treatment that promotes wound-healing could have profound impacts on the long-term health impacts of injury.