ARHGAP1 and neoplasm: CDK5 increases its tumor suppressor activity by phosphorylating it at four serine residues namely S120, S205, S422 and S509 in the N-terminal region next to the Rho-GAP domain, which allows its binding to focal adhesions (talin, tensin) and increases its Rho-GAP activity [96] (Fig. 6B).