The function of TRIOBP (TRIO and F-actin binding protein, ENSG00000100106) is as follows. [Isoform 1]: Regulates actin cytoskeletal organization, cell spreading and cell contraction by directly binding and stabilizing filamentous F-actin and prevents its depolymerization (PubMed:18194665, PubMed:28438837). May also serve as a linker protein to recruit proteins required for F-actin formation and turnover (PubMed:18194665). Essential for correct mitotic progression (PubMed:22820163, PubMed:24692559). {ECO:0000269|PubMed:18194665, ECO:0000269|PubMed:22820163, ECO:0000269|PubMed:24692559, ECO:0000269|PubMed:28438837}. [Isoform 5]: Plays a pivotal role in the formation of stereocilia rootlets. . [Isoform 4]: Plays a pivotal role in the formation of stereocilia rootlets. .