Plasma membrane transporter mediating the uptake by cells of the water soluble vitamin B2/riboflavin that plays a key role in biochemical oxidation-reduction reactions of the carbohydrate, lipid, and amino acid metabolism (  ). Humans are unable to synthesize vitamin B2/riboflavin and must obtain it via intestinal absorption . May also act as a receptor for 4-hydroxybutyrate (Probable).
(Microbial infection) In case of infection by retroviruses, acts as a cell receptor to retroviral envelopes similar to the porcine endogenous retrovirus (PERV-A).
Subcellular locations: Cell membrane
Highly expressed in brain, fetal brain and salivary gland. Weakly expressed in other tissues.