Differential expression of human riboflavin transporters-1,-2, and -3 in polarized epithelia: A key role for hRFT-2 in intestinal riboflavin uptake
Differential expression of human riboflavin transporters-1,-2, and -3 in polarized epithelia: A key role for hRFT-2 in intestinal riboflavin uptake
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DOI：
10.1016/j.bbamem.2011.08.004
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发表时间：
2011-12-01
影响因子：
3.4
通讯作者：
Said, Hamid M.
中科院分区：
文献类型：
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作者：
Subramanian, Veedamali S.;Subramanya, Sandeep B.;Said, Hamid M.
核黄素 (RF) 穿过极化肠上皮细胞的刷状缘膜 (BBM) 和基底外侧膜 (BLM) 的转运是通过特定的载体介导机制发生的。尽管三种人类核黄素转运蛋白 (hRFT)，即 hRFT-1、hRFT-2 和 hRFT-3 在肠道中表达，但人们对表达这些特定 hRFT 的细胞表面结构域知之甚少。在这里，我们使用肠上皮Caco-2和肾MDCK细胞的活细胞共聚焦成像显示hRFT-1主要在BLM表达，hRFT-2仅在顶膜表达，而hRFT-3主要位于细胞内囊泡结构内部（在BLM有一些表达）。此外，Caco-2细胞和天然人肠道中的hRFT-2 mRNA表达水平显着高于hRFT-1和-3； hRFT-2 在转运 H-3-RF 方面也比 hRFT-1 和 -3 更有效。这些发现暗示 hRFT-2 在肠道 RF 摄取中发挥重要作用，hRFT-2 基因特异性 siRNA 敲低研究结果进一步支持了这一结论。这些结果表明 hRFT 家族成员在极化上皮细胞中差异表达，并且顶部表达的 hRFT-2 在肠道 RF 积累中发挥关键作用。由 Elsevier B.V. 出版
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 H-3-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. Published by Elsevier B.V.