May play a role in intracellular immune modulation by activating NF-kappaB response and attenuating Toll-like-receptor response. (Microbial infection) Plays an essential function in adeno-associated virus (AAV) transduction, across multiple serotypes except AAV5. May play a critical role in mediating the endosomal virus escape or in the AAV virions trafficking from endosomes to the nucleus. Colocalizes with TLR3, -7, -4, and -9. High expression in spleen, lung, stomach, large and small intestine, and thymus. (Microbial infection) N- and C-terminal domains are essential for mediating AAV transduction. Deficient mice are viable and fertile and exhibit normal Mendelian segregation, however deficient mice exhibit increased LPS-induced mortality. TLR-mediated pro-inflammatory signaling are increased in embryonic fibroblasts and macrophages from Gpr108 deficient mice (PubMed:30332431). Depending on the AAV serotype used, 10-fold to 100-fold reduced expression for AAV is observed in Gpr108 knockout mice following retro-orbital administration (PubMed:31784416). Belongs to the LU7TM family.