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Differential expression of human riboflavin transporters -1, -2, and -3 in polarized epithelia: a key role for hRFT-2 in intestinal riboflavin uptake. Biochim Biophys Acta 2011 Dec;1808(12):3016-21



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2-s2.0-80054773593   39 Citations


Transport of riboflavin (RF) across both the brush border membrane (BBM) and basolateral membrane (BLM) of the polarized enterocyte occurs via specific carrier-mediated mechanisms. Although, three human riboflavin transporters (hRFTs), i.e., hRFT-1, hRFT-2 and hRFT-3 are expressed in the intestine, little is known about the cell surface domain(s) at which these specific hRFTs are expressed. Here, we used live cell confocal imaging of intestinal epithelial Caco-2 and renal MDCK cells to show that the hRFT-1 is mainly expressed at the BLM, hRFT-2 is exclusively expressed at the apical membrane, while hRFT-3 is mostly localized inside intracellular vesicular structures (with some expression at the BLM). Further the level of hRFT-2 mRNA expression in Caco-2 cells and in native human intestine is significantly higher than that of hRFT-1 and -3; hRFT-2 was also more efficient in transporting 3H-RF than hRFT-1 and -3. These findings implied an important role for hRFT-2 in intestinal RF uptake, a conclusion that was further supported by findings of hRFT-2 gene-specific siRNA knockdown investigation. These results show that members of the hRFT family are differentially expressed in polarized epithelia, and that the apically expressed hRFT-2 plays a key role in intestinal RF accumulation.

Author List

Subramanian VS, Subramanya SB, Rapp L, Marchant JS, Ma TY, Said HM


Jonathan S. Marchant PhD Chair, Professor in the Cell Biology, Neurobiology and Anatomy department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Base Sequence
Carrier Proteins
Cell Line
DNA Primers
Intestinal Mucosa
RNA, Small Interfering
Real-Time Polymerase Chain Reaction
Reverse Transcriptase Polymerase Chain Reaction
jenkins-FCD Prod-482 91ad8a360b6da540234915ea01ff80e38bfdb40a