Plays a crucial role in regulating the dynamics and assembly of the actin cytoskeleton. Recruited to the cell cortex by interaction with ILK which allows it to cooperate with its effector DIAPH1 to locally stabilize microtubules and allow stable insertion of caveolae into the plasma membrane (By similarity). Binds to activated CDC42 but does not stimulate its GTPase activity. Associates with calmodulin. May promote neurite outgrowth (PubMed:15695813). May play a possible role in cell cycle regulation by contributing to cell cycle progression after DNA replication arrest (PubMed:20883816). {ECO:0000250|UniProtKB:Q9JKF1, ECO:0000269|PubMed:15695813, ECO:0000269|PubMed:20883816}. This is the function of IQGAP1 (IQ motif containing GTPase activating protein 1, Ensembl gene identifier ENSG00000140575).