Stimulates guanine exchange activity of SOS1. May play a role in membrane ruffling and remodeling of the actin cytoskeleton (By similarity). In the cochlea, is required for stereocilia maintenance in adult hair cells (PubMed:23918390). Interacts with ABI1. Part of a complex that contains SOS1, ABI1 and EPS8L2. Associates with F-actin (By similarity). Localizes at the tips of the stereocilia of the inner and outer hair cells. Detected in fetal kidney, adrenal gland, salivary gland, stomach, gut, cartilage and skin. Detected in adult ovary, placenta, skin, adrenal gland, salivary gland, kidney, intestine and stomach. Expressed at the tips of cochlear hair cells stereocilia (PubMed:23918390). Mutant animal have a progressive and severe hearing loss at young adulthood (PubMed:23918390). The generation of receptor potentials in hair cells at lower sound pressure is impaired, which leads to a reduction in auditory nerve responses (PubMed:23918390). Belongs to the EPS8 family.