Meta-Biol

• Pathways

The water-soluble vitamin riboflavin (RIB, vitamin B2) is essential for normal cellular functions. Three human riboflavin transporters mediate the transport of RIB into cells and play an important role in RIB homeostasis. The transporters are assigned to a new sub-family of the SLC superfamily; SLC52A1, SLC52A2 and SLC52A3 (aka RFVT1, RFVT2 and RFVT3 respectively). Solute carrier family 52, riboflavin transporter, member 1 (SLC52A1, RFVT1) is widely expressed with highest expression in the testis, placenta and small intestine (Yonezawa et al. 2008). Solute carrier family 52, riboflavin transporter, member 2 (SLC52A2, RFVT2) is highly expressed in brain, foetal brain and salivary gland (Yao et al. 2010). Solute carrier family 52, riboflavin transporter, member 3 (SLC52A3, RFVT3) transports riboflavin (RIB) from the lumen into small intestine epithelial cells (Yoshimatsu et al. 2014). Activity is inhibited by riboflavin analogues such as flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) (Yao et al. 2010). Defects in SLC52A3 cause Brown-Vialetto-Van Laere syndrome type 1 (BVVLS1; MIM:211530). BVVLS1 is a rare autosomal recessive neurologic disorder characterised by sensorineural hearing loss and a variety of cranial nerve palsies (Green et al. 2010). Defects in SLC52A3 also cause Fazio-Londe disease (FALOND; MIM:211500), a rare neurological disease characterised by progressive weakness of the muscles innervated by cranial nerves located at the lower brain stem (Bosch et al. 2011).