Plays a role in the adhesion and fusion of the sperm-oocyte membrane through its interactions with IZUMO1 and IZUMO1R/JUNO (By similarity). When cross-linked to form dimers and trimers, it has a regulatory effect on ERK signaling pathway activity in response to EGF stimulation. Colocalizes with the EGF receptor in WDR54-specific vesicle where it sustains the internalization and controls the degradation of the EGF receptor after EGF stimulation (PubMed:30458214). {ECO:0000250|UniProtKB:D3ZX63, ECO:0000269|PubMed:30458214}. This is the function of WDR54 (WD repeat domain 54, ENSG00000005448).