Gnaling is activated only in cells coexpressing RXFP4 and the promiscuous G protein Ga16. Direct evidence for RXFP4-G protein coupling is currently lacking. In contrast to RXFP1, the information available on proteins interacting with RXFP3 and RXFP4 is largely confined to G proteins and b-arrestins. RXFP3 couples to GaoA, GaoB Gai2, and Gai3, although the pattern observed varies with cell type and