Author:
Laftah Abas H.,Latunde-Dada Gladys O.,Fakih Sarah,Hider Robert C.,Simpson Robert J.,McKie Andrew T.
Abstract
Haem carrier protein 1 (HCP1) was originally identified and characterised as a mammalian haem transporter. However, recent evidence has shown that it is also a proton-coupled folate transporter (PCFT) and mutations in the gene cause hereditary folate deficiency in humans. We therefore investigated haem and folate transport characteristics of PCFT/HCP1 bothin vivoandin vitroin CD-1 mice and in the presence or absence of a blocking antibody for PCFT/HCP1, and also in cultured cells (which express PCFT/HCP1 endogenously) to elucidate the specificity and selectivity of PCFT/HCP1. Thein vivostudy showed that the addition of folic acid inhibited59Fe-labelled haem transport in hypoxic mice but had no effect in normal mice. Usingin vitromethods, the results showed increased [3H]folate uptake into everted duodenum from hypoxic mice but uptake was reduced by the addition of haem or PCFT/HCP1 antibodies to the medium. Caco-2 cells transiently transfected with small interfering RNA (siRNA) PCFT/HCP1 duplex oligos resulted in a 69 % reduction in PCFT/HCP1 mRNA when compared with the control siRNA. Both haem and folate uptake were significantly (P < 0·05) reduced in cells transfected with PCFT/HCP1 siRNA; however, the magnitude of reduction with folic acid uptake was greater (48 %) than that of haem (22·5 %). Overall the data support PCFT/HCP1 as a primary folate transporter with a lower affinity for haem. PCFT/HCP1 could therefore play a physiological role in Fe nutrition and the data highlight the potential for the interaction of folate and haem at the level of intestinal absorption.
Publisher
Cambridge University Press (CUP)
Subject
Nutrition and Dietetics,Medicine (miscellaneous)
Cited by
65 articles.
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