Promotes cell-cell contacts by forming homophilic or heterophilic trans-dimers. Heterophilic interactions have been detected between NECTIN1 and NECTIN3 and between NECTIN1 and NECTIN4. Has some neurite outgrowth-promoting activity. ; (Microbial infection) Acts as a receptor for herpes simplex virus 1/HHV-1, herpes simplex virus 2/HHV-2, and pseudorabies virus/PRV.