SLC52A1

SLC52A1 (riboflavin transporter 1, RFVT1/hRFT1) is a multi-pass plasma membrane transporter of the SLC52 riboflavin-transporter family that mediates cellular uptake of the water-soluble vitamin B2 (riboflavin), the precursor of the redox cofactors FMN and FAD. Because humans cannot synthesize riboflavin, SLC52A1 contributes to its absorption and distribution; transport is Na+-, Cl-- and pH-independent facilitated diffusion (KM ~1.4 uM) and is inhibited by riboflavin analogs such as lumiflavin. It is widely expressed with highest expression in testis, placenta and small intestine, where in polarized enterocytes it localizes to the basolateral membrane and mediates riboflavin exit toward the bloodstream, and is important for maternal-fetal riboflavin transfer across the placenta. Loss-of-function of maternal SLC52A1 causes transient neonatal riboflavin deficiency presenting as multiple acyl-CoA dehydrogenase deficiency / glutaric aciduria type 2, which resolves with riboflavin supplementation. In primates SLC52A1 arose by duplication of SLC52A2 and was neofunctionalized to additionally transport urate; basolaterally in enterocytes it works with the luminal efflux transporter ABCG2 to secrete urate into the intestine. It was originally identified as a human receptor (huPAR-2) for porcine endogenous retrovirus PERV-A.