Multifunctional actin-bundling protein. Plays a major role in regulating the organization, dimension, dynamics and signaling capacities of the actin filament-rich microvilli in the mechanosensory and chemosensory cells (PubMed:29572253). Required for the assembly and stabilization of the stereociliary parallel actin bundles. Plays a crucial role in the formation and maintenance of inner ear hair cell stereocilia (By similarity). Involved in the elongation of actin in stereocilia (PubMed:29572253). In extrastriolar hair cells, required for targeting MYO3B to stereocilia tips, and for regulation of stereocilia diameter and staircase formation. Monomer. Binds F-actin in a Ca(2+)-resistant fashion. Interacts (via N-terminus) with BAIAP2 (via SH3-domain). Interacts with PFN2. Interacts with MYO3A (via C-terminus). Interacts with MYO3B (via C-terminus). The WH2-domain binds actin monomer and mediates actin bundle assembly. The disease is caused by variants affecting the gene represented in this entry. The disease may be caused by variants affecting the gene represented in this entry.