Inhibits the binding of prostaglandin F2-alpha (PGF2-alpha) to its specific FP receptor, by decreasing the receptor number rather than the affinity constant. Functional coupling with the prostaglandin F2-alpha receptor seems to occur (By similarity). In myoblasts, associates with tetraspanins CD9 and CD81 to prevent myotube fusion during muscle regeneration (By similarity). Interacts with CD9 and CD81 (PubMed:11278880). Part of a complex composed of CD9, CD81 and IGSF8 (By similarity). Also seems to interact with CD63, CD82 and CD151 (PubMed:11278880). Truncated C-terminus.