Identification and comparative functional characterization of a new human riboflavin transporter hRFT3 expressed in the brain

Yoshiaki Yao, Atsushi Yonezawa, Hiroki Yoshimatsu, Satohiro Masuda, Toshiya Katsura, Ken Ichi Inui

Research output: Contribution to journalArticle

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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. Realtime 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.

Original languageEnglish
Pages (from-to)1220-1226
Number of pages7
JournalJournal of Nutrition
Volume140
Issue number7
DOIs
Publication statusPublished - Jul 1 2010

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Riboflavin
Brain
Messenger RNA
Small Intestine
Complementary DNA
Ribose
Substrate Specificity
Salivary Glands
Vitamins
Placenta
Testis
Prostate
Amino Acid Sequence
Protein Isoforms
Homeostasis
Ions

All Science Journal Classification (ASJC) codes

  • Medicine (miscellaneous)
  • Nutrition and Dietetics

Cite this

Identification and comparative functional characterization of a new human riboflavin transporter hRFT3 expressed in the brain. / Yao, Yoshiaki; Yonezawa, Atsushi; Yoshimatsu, Hiroki; Masuda, Satohiro; Katsura, Toshiya; Inui, Ken Ichi.

In: Journal of Nutrition, Vol. 140, No. 7, 01.07.2010, p. 1220-1226.

Research output: Contribution to journalArticle

Yao, Yoshiaki ; Yonezawa, Atsushi ; Yoshimatsu, Hiroki ; Masuda, Satohiro ; Katsura, Toshiya ; Inui, Ken Ichi. / Identification and comparative functional characterization of a new human riboflavin transporter hRFT3 expressed in the brain. In: Journal of Nutrition. 2010 ; Vol. 140, No. 7. pp. 1220-1226.
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