| First Author | Chiao JH | Year | 1997 |
| Journal | J Biol Chem | Volume | 272 |
| Issue | 17 | Pages | 11165-70 |
| PubMed ID | 9111015 | Mgi Jnum | J:39774 |
| Mgi Id | MGI:87123 | Doi | 10.1074/jbc.272.17.11165 |
| Citation | Chiao JH, et al. (1997) RFC-1 gene expression regulates folate absorption in mouse small intestine. J Biol Chem 272(17):11165-70 |
| abstractText | Mediated folate compound transport inward in isolated luminal epithelial cells from mouse small intestine was delineated as pH-dependent and non-pH-dependent components on the basis of their differential sensitivity to the stilbene inhibitor, 4, 4'-diisothiocyanatostilbene-2,2'-disulfonic acid. pH dependence was manifested as higher maximum capacity (Vmax) for influx of l, L-5-CH3-H4folate at acidic pH compared with neutral or alkaline pH with no effect on saturability (Km). The pH-dependent component was relatively insensitive to inhibition by 4, 4'-diisothiocyanatostilbene-2,2'-disulfonic acid and highly saturable (Km or Ki = 2 to 4 microM) in the case of folic acid, folate coenzymes, and 4-aminofolate analogues as permeants or inhibitors. The non-pH-dependent component was highly sensitive to 4, 4'-diisothiocyanatostilbene-2,2'-disulfonic acid and poorly and variably saturable (Km or Ki = 20 to >2000 microM) with respect to these folate compounds. Only the pH-dependent transport component was developmentally regulated, showing much higher maximum capacity for l,L-5-CH3-H4folate influx in mature absorptive rather than proliferative crypt cells. The increase in pH-dependent influx during maturation was associated with an increase in RFC-1 gene expression in the form of a 2.5-kilobase RNA transcript and 58-kDa brush-border membrane protein detected by folate-based affinity labeling and with anti-mouse RFC-1 peptide antibodies. The size of this protein was the same as that encoded by RFC-1 mRNA. The treatment of mature absorptive cells with either the affinity label or the anti-RFC-1 peptide antibodies inhibited influx of l, L-[3H]-5-CH3-H4folate in a concentration-dependent manner. These results strongly suggest that pH-dependent folate absorption in this tissue is regulated by RFC-1 gene expression. |
