Acts as transcriptional coactivator of estrogen and progesterone receptors (ESR1 and PGR) upon hormone activation. In presence of estrogen, binds to ESR1-responsive promoters. Required for YAP1 coactivation function on PGR activity. Synergizes with WBP2 in enhancing PGR activity (By similarity). Modulates expression of post-synaptic scaffolding proteins via regulation of ESR1, ESR2 and PGR (PubMed:26881968). Binds to the WW domain of YAP1, WWP1 and WWP2 (By similarity) (PubMed:7644498). Interacts with NEDD4 (PubMed:11042109). Interacts with ESR1 and UBE3A (By similarity). Translocates from cytoplasm to nucleus when phosphorylated. Expressed in the ear and the eye (PubMed:26881968). Isoform 1 is expressed in brain, inner ear and organ of Corti. Isoform 2 is only detected in brain (PubMed:26881968). The PPxY motif 1 mediates interaction with NEDD4 (PubMed:11042109). The PPxY motif 2 is required for the coactivation function (By similarity). Phosphorylated in repsonse to EGF as well as estrogen and progesterone hormones. Tyr-192 and Tyr-231 are phosphorylated by YES and SRC inducing nuclear translocation. Mutant animals have a progressive high-frequency hearing loss (PubMed:26881968). They show swelling of afferent terminals and abnormal expression of AMPA receptor subunit at post-synaptic densities (PubMed:26881968). Mice are fertile and show no other abnormalities (PubMed:26881968).