Functional analysis of the DLC tumor suppressor family in 3D cell culture models

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Deleted in Liver Cancer 3 (DLC3) is a still poorly characterized Rho GTPase-activating protein (GAP) with potential tumor-suppressive function. Work from our lab has shown that DLC3 plays an important GAP-dependent role in maintaining cell-cell adhesions and in controlling RhoB-dependent endocytic membrane transport. The loss of DLC3 expression not only disrupts 3D epithelial morphogenesis, but also promotes the aberrant recycling of transmembrane proteins such as e.g. the epidermal growth factor receptor (EGFR) and the metalloproteinase MT1-MMP. We revealed that the differential recruitment of DLC3 to cell contacts and endosomal membranes is mediated by the PDZ adapter proteins Scribble and SNX27, respectively. Together with our biophysical partners, we have now identified within an intrinsically disordered region in DLC3 a polybasic region mediating the interaction with membranes and whose structural and membrane binding properties appear to be regulated by phosphorylation. This might constitute a central mechanism controlling target membrane recognition and spatiotemporal Rho signaling by DLC3. Interestingly, our database searches revealed the presence of several cancer-associated mutations within the DLC3-PBR. In this project, we will utilize a combination of advanced biophysical, molecular cell biological and imaging techniques to unravel the molecular mechanisms underlying DLC3 activity and interrogate whether mutations in DLC3 can lead to its functional inactivation and are associated with cellular transformation.