Cytoskeletal remodeling by C3G to induce neurite-like extensions and inhibit motility in highly invasive breast carcinoma cells

Cytoskeletal remodeling is responsible for cell plasticity and facilitates differentiation, motility and adherence related functions. C3G (RAPGEF1), an exchange factor for Ras family of small GTPases, regulates cytoskeletal reorganization to induce filopodia in epithelial cells and neurite growth in neuroblastoma cells. Here we show that C3G overexpression induces neurite-like extensions (NLE) in MDA-MB-231 and BT549 breast carcinoma cells and not in a variety of other cancer cell lines examined. These processes were actin-rich with nodes, branches and microspikes. C3G associates with the cytoskeleton and its expression enabled stabilization of microtubules. NLE formation was dependent on Rap, Rac and Cdc42. C3G expression was associated with a decrease in cellular β-catenin levels specifically in MDA-MB-231 and BT549 cells. β-Catenin stabilization induced by GSK-3β inhibition, or coexpression of β-catenin, reduced C3G induced NLE formation. Time lapse analysis showed reduced motility of C3G expressing cells compared to GFP expressing cells. Our results suggest that C3G overexpression can induce phenotypic characteristics of neuronal cells in highly invasive breast cancer cells and inhibit their motility.

Research Highlights
► The ubiquitously expressed guanine nucleotide exchange factor C3G induced morphological differentiation of neurons specifically in highly invasive breast cancer cells.
► Microtubule stabilization and neurite-like extension formation represent previously undescribed functions of C3G.
► Morphological changes caused by C3G correlate with its ability to repress cellular β-catenin protein levels.
► C3G expression inhibits motility of aggressive breast cancer cells MDA-MB-231.