– The Nectin family has at least four members (Nectin-1‑4), all of which show alternate splicing, a transmembrane (TM) region (except for Nectin-1 gamma), and three extracellular Ig-domains. Nectins are highly homologous to the human receptor for poliovirus, and as such, have been alternatively-named poliovirus receptor-related proteins. They do not, however, appear to bind poliovirus. Nectin-3 (also named PRR3, CD113, and PVRL3) is an 83 kDa, type I TM glycoprotein. Its precursor is 549 amino acids (aa) in length. It contains an extended signal sequence of 57 aa, an extracellular domain (ECD) of 347 aa, a transmembrane segment of 21 aa (aa 405-425), and a cytoplasmic region of 124 amino acids.