Investigation of Rab GTPase Interaction with Focal Adhesion Proteins in Breast Cancer Cells

The acquisition of cancer cell invasive properties is a critical early event in primary cancer progression to metastasis. Increasing experimental and clinical evidence supports that metastasis formation is initiated by the acquisition of cancer cell motile properties driven by extensive remodelling of the cell cytoskeleton and dynamic recycling of focal adhesion proteins (FA); the later link the extracellular matrix to the cell cytoskeleton and intracellular signaling. Cancer cell invasion has been associated with elevated expression/activation of several proteins, including members of Rab GTPases. These proteins are key regulators of membrane trafficking of proteins and membrane receptor recycling, including that of integrins. Elevated expression of Rab GTPases has been linked to increased cell migration and invasion. Previously, biochemical and proteomic studies from my host laboratory, using paired non-invasive and invasive breast cancer cells have revealed a rapid turnover of FA proteins in invasive compared to non-invasive cancer cells, as well as differential expression of several Rab GTPase members, including Rab5, Rab11 and Rab7. Thus, I tested the hypothesis that Rab GTPases may regulate FA protein turnover, in part via interaction with focal adhesion kinase (FAK), a central protein of master focal adhesion signalling. Immunofluorescence and immunoprecipitation assays reveal that Rab11 and FAK interact and colocalize at FA sites. Development of cell lines where Rabs are depleted using siRNA revealed an impact of Rab on cell migration; Rab inhibition inhibited cell migration. I propose that Rab GTPases, and in particular Rab11 may contribute to the regulation of FAK function in FA turnover and cell migration.