Identification and Comparative Functional Characterization of a New Human Riboflavin Transporter hRFT3 Expressed in the Brain
Open Access
- 1 July 2010
- journal article
- research article
- Published by Elsevier BV in Journal of Nutrition
- Vol. 140 (7), 1220-1226
- https://doi.org/10.3945/jn.110.122911
Abstract
We isolated cDNA coding a new human riboflavin transporter (hRFT)3, which exhibits 86.7 and 44.1% amino acid identity with hRFT1 and hRFT2, respectively. It was predicted to have 10 putative membrane-spanning domains. The functional characteristics of hRFT3 were examined and compared with those of its isoforms, hRFT1 and hRFT2. Real-time PCR revealed that hRFT3 mRNA was strongly expressed in the brain and salivary gland. hRFT1 mRNA was strongly expressed in the placenta and small intestine, whereas hRFT2 mRNA was most abundantly expressed in the testis and strongly in the small intestine and prostate. hRFT-mediated uptake of [3H]riboflavin was evaluated using human embryonic kidney 293 cells transiently transfected with the cDNA coding each hRFT. The apparent Michaelis-Menten constants of hRFT1, hRFT2, and hRFT3 for riboflavin were 1.38, 0.98, and 0.33 μmol/L, respectively. The hRFT-mediated [3H]riboflavin uptake was independent of extracellular Na+ and Cl−. Specific uptake of [3H]riboflavin by hRFT2, but not hRFT1 and hRFT3, decreased as extracellular pH was changed from 5.4 to 8.4. The substrate specificities of the hRFT family were similar. hRFT-mediated uptake of [3H]riboflavin was inhibited by some riboflavin analogs, but not D-ribose, organic ions, or other vitamins. The newly isolated hRFT3 may play an important role in brain riboflavin homeostasis. Its amino acid sequence and functional characteristics are similar to those of hRFT1, but not hRFT2.Keywords
This publication has 24 references indexed in Scilit:
- Identification and Functional Characterization of Rat Riboflavin Transporter 2The Journal of Biochemistry, 2009
- Identification and functional characterization of a novel human and rat riboflavin transporter, RFT1American Journal of Physiology-Cell Physiology, 2008
- The Riboflavin Transporter RibU in Lactococcus lactis : Molecular Characterization of Gene Expression and the Transport MechanismJournal of Bacteriology, 2006
- The Monocarboxylate Transporter Homolog Mch5p Catalyzes Riboflavin (Vitamin B2) Uptake in Saccharomyces cerevisiaeOnline Journal of Public Health Informatics, 2005
- Ascorbic-acid transporter Slc23a1 is essential for vitamin C transport into the brain and for perinatal survivalNature Medicine, 2002
- Transport Functions of Riboflavin Carriers in the Rat Small Intestine and Colon: Site Difference and Effects of Tricyclic-Type DrugsDrug Delivery, 2001
- Uptake of riboflavin by intestinal basolateral membrane vesicles: a specialized carrier-mediated processBiochimica et Biophysica Acta (BBA) - Biomembranes, 1993
- Cloning and functional expression in bacteria of a novel glucose transporter present in liver, intestine, kidney, and β-pancreatic islet cellsCell, 1988
- Riboflavin Accumulation by Rabbit Brain Slices In VitroJournal of Neurochemistry, 1980
- INCORPORATION OF PERIPHERALLY ADMINISTERED RIBOFLAVINE INTO FLAVINE NUCLEOTIDES IN THE BRAINJournal of Neurochemistry, 1967