Supervillin is an F-actin-binding protein originally with two reported isoforms of 205/250 kDa. The longer isoform, named archvillin, is muscle-specific. Supervillin is a tightly bound peripheral membrane protein that is concentrated at sites of epithelial cell-cell adhesion. It contributes to cell-cell adhesion, motility regulation, and information transfer between cell compartments. The COOH-terminus of supervillin is homologous to villin/gelsolin but is not responsible for the tight binding to the actin cytoskeleton in vivo. The NH2-terminus contains functional nuclear localization sequences and F-actin and myosin II binding domains. It has been suggested that supervillin may mediate actin and myosin II filament organization at cholesterol-rich membrane domains. Supervillin has been identified as a transcriptional activator of the androgen receptor. Supervillin is found in many cells of several species, but is most abundant in muscle, bone marrow, thyroid gland, and salivary gland.