Micronutrient Laboratory, Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile.
Am J Physiol Cell Physiol. 2012 Jun 15;302(12):C1780-5. doi: 10.1152/ajpcell.00080.2012. Epub 2012 Apr 11.
Heme-Fe is an important source of dietary iron in humans; however, the mechanism for heme-Fe uptake by enterocytes is poorly understood. Heme carrier protein 1 (HCP1) was originally identified as mediating heme-Fe transport although it later emerged that it was a folate transporter. We asked what happened to heme-Fe and folate uptake and the relative abundance of hcp1 and ho1 mRNA in Caco-2 cells after knockdown by transfection with HCP1-directed short hairpin (sh)RNA. Control Caco-2 cells were cultured in bicameral chambers with 0-80 μM heme-Fe for selected times. Intracellular Fe and heme concentration increased in Caco-2 cells reflecting higher external heme-Fe concentrations. Maximum Fe, heme, and heme oxygenase 1 (HO1) expression and activity were observed between 12 and 24 h of incubation. Quantitative RT-PCR for hcp1 revealed that its mRNA decreased at 20 μM heme-Fe while ho1 mRNA and activity increased. When shRNA knocked down hcp1 mRNA, heme-(55)Fe uptake and [(3)H]folate transport mirrored the mRNA decrease, ho1 mRNA increased, and flvcr mRNA was unchanged. These data argue that HCP1 is involved in low-affinity heme-Fe uptake not just in folate transport.
血红素铁是人类膳食铁的重要来源；然而，肠细胞摄取血红素铁的机制还不清楚。血红素载体蛋白 1（HCP1）最初被鉴定为介导血红素铁转运，尽管后来发现它是一种叶酸转运体。我们想知道在 Caco-2 细胞中转染 HCP1 靶向短发夹（sh）RNA 敲低后，血红素铁和叶酸摄取以及 hcp1 和 ho1 mRNA 的相对丰度会发生什么变化。对照 Caco-2 细胞在含有 0-80 μM 血红素铁的双室培养室中培养选定的时间。细胞内铁和血红素浓度的增加反映了外部血红素铁浓度的升高。在孵育 12-24 小时时观察到最大的 Fe、血红素和血红素加氧酶 1（HO1）表达和活性。定量 RT-PCR 检测 hcp1 发现，其 mRNA 在 20 μM 血红素铁时减少，而 ho1 mRNA 和活性增加。当 shRNA 敲低 hcp1 mRNA 时，血红素-(55)Fe 摄取和 [(3)H]叶酸转运与 mRNA 减少相吻合，ho1 mRNA 增加，而 flvcr mRNA 不变。这些数据表明 HCP1 参与低亲和力血红素铁摄取，而不仅仅是叶酸转运。
