May play a role in trophoblasts syncytialization, the spontaneous fusion of their plasma membranes, an essential process in placental development. May negatively regulate cell-cell fusion by interacting with SLC1A5, the probable receptor on the cell surface of the fusogenic syncytin-1/ERVW-1. . This is the function of ERVH48-1 (endogenous retrovirus group 48 member 1, envelope, Ensembl gene identifier ENSG00000233056).