GPR99

GPR99 is a human gene that encodes a G protein-coupled receptor (GPCR) named GPR99. It is a member of the class A rhodopsin-like GPCR family and is predicted to span the cell membrane seven times, a typical topology for this receptor class. The protein is believed to signal through heterotrimeric G proteins, though the specific signaling partners have not been definitively characterized.

GPR99 is considered an orphan receptor because no endogenous ligand has been conclusively identified and its precise physiological function remains unclear. Available expression data show GPR99 transcripts in multiple tissues, but patterns can vary between studies and quantitative protein-level information is limited.

Research on GPR99 is ongoing to determine whether it binds a ligand, which G proteins it engages, and what biological processes it may influence. As with other GPCRs, elucidating its signaling pathways and role in health or disease could have implications for understanding cellular communication and identifying potential therapeutic targets, pending clearer functional characterization.