Disorders of Cobalamin and Folate Transport and Metabolism

2012 ◽  
pp. 385-402 ◽  
Author(s):  
David Watkins ◽  
David S. Rosenblatt ◽  
Brian Fowler
Keyword(s):  
Folate Transport

Treatable neurodegenerative disorder: Cerebral folate transport deficiency––two children from Southern India

2021 ◽  
Vol 0 (0) ◽  
pp. 0
Author(s):  
VykuntarajuK Gowda ◽  
Balamurugan Natarajan ◽  
VarunvenkatM Srinivasan ◽  
SanjayK Shivappa
Keyword(s):  
Neurodegenerative Disorder ◽  
Southern India ◽  
Folate Transport

A rat model of maternal intermittent fasting during pregnancy impairs fetal growth but does not alter maternofetal folate transport

Placenta ◽  
2017 ◽  
Vol 57 ◽  
pp. 286 ◽  
Author(s):  
Rezwana Hussain ◽  
May Tassabehji ◽  
Nick Ashton ◽  
Jocelyn Glazier
Keyword(s):  
Fetal Growth ◽  
Rat Model ◽  
Intermittent Fasting ◽  
Folate Transport

Comparison of intestinal folate carrier clone expressed in IEC-6 cells and in Xenopusoocytes

1998 ◽  
Vol 274 (1) ◽  
pp. C289-C294 ◽  
Author(s):  
Chandira K. Kumar ◽  
Toai T. Nguyen ◽  
Francis B. Gonzales ◽  
Hamid M. Said
Keyword(s):  
Folic Acid ◽  
Epithelial Cells ◽  
Cdna Clone ◽  
Xenopus Oocytes ◽  
Intestinal Epithelial Cells ◽  
Maximal Velocity ◽  
Mrna Levels ◽  
Acidic Ph ◽  
Intestinal Epithelial ◽  
Folate Transport

We recently identified a cDNA clone from mouse small intestine, which appears to be involved in folate transport when expressed in Xenopus oocytes. The open reading frame of this clone is identical to that of the reduced folate carrier (RFC) (K. H. Dixon, B. C. Lanpher, J. Chiu, K. Kelley, and K. H. Cowan. J. Biol. Chem. 269: 17–20, 1994). The characteristics of this cDNA clone [previously referred to as intestinal folate carrier 1 (IFC-1)] expressed in Xenopus oocytes, however, were found to be different from the characteristics of folate transport in native small intestinal epithelial cells. To further study these differences, we determined the characteristics of RFC when expressed in an intestinal epithelial cell line, IEC-6, and compared the findings to its characteristics when expressed in Xenopus oocytes. RFC was stably transfected into IEC-6 cells by electroporation; its cRNA was microinjected into Xenopus oocytes. Northern blot analysis of poly(A)+RNA from IEC-6 cells stably transfected with RFC cDNA (IEC-6/RFC) showed a twofold increase in RFC mRNA levels over controls. Similarly, uptake of folic acid and 5-methyltetrahydrofolate (5-MTHF) by IEC-6/RFC was found to be fourfold higher than uptake in control sublines. This increase in folic acid and 5-MTHF uptake was inhibited by treating IEC-6/RFC cells with cholesterol-modified antisense DNA oligonucleotides. The increase in uptake was found to be mainly mediated through an increase in the maximal velocity ( V max) of the uptake process [the apparent Michaelis-Menten constant ( K m) also changed (range was 0.31 to 1.56 μM), but no specific trend was seen]. In both IEC-6/RFC and control sublines, the uptake of both folic acid and 5-MTHF displayed 1) pH dependency, with a higher uptake at acidic pH 5.5 compared with pH 7.5, and 2) inhibition to the same extent by both reduced and oxidized folate derivatives. These characteristics are very similar to those seen in native intestinal epithelial cells. In contrast, RFC expressed in Xenopus oocytes showed 1) higher uptake at neutral and alkaline pH 7.5 compared with acidic pH 5.5 and 2) higher sensitivity to reduced compared with oxidized folate derivatives. Results of these studies demonstrate that the characteristics of RFC vary depending on the cell system in which it is expressed. Furthermore, the results may suggest the involvement of cell- or tissue-specific posttranslational modification(s) and/or the existence of an auxiliary protein that may account for the differences in the characteristics of the intestinal RFC when expressed in Xenopus oocytes compared with when expressed in intestinal epithelial cells.

Decreased expression of folate transport proteins in oral cancer

2019 ◽  
Vol 127 (5) ◽  
pp. 417-424
Author(s):  
Joanna Goral ◽  
Kayla Cuadros ◽  
Lenore Pitstick ◽  
Alice Meyer ◽  
Bruno Correia Jham ◽  
...  
Keyword(s):  
Oral Cancer ◽  
Transport Proteins ◽  
Folate Transport ◽  
Folate Transport Proteins

Disorders of Cobalamin and Folate Transport and Metabolism

2016 ◽  
pp. 385-399
Author(s):  
David Watkins ◽  
David S. Rosenblatt ◽  
Brian Fowler
Keyword(s):  
Folate Transport

Folate transport by human intestinal brush-border membrane vesicles

1987 ◽  
Vol 252 (2) ◽  
pp. G229-G236 ◽  
Author(s):  
H. M. Said ◽  
F. K. Ghishan ◽  
R. Redha
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicle ◽  
Membrane Vesicles ◽  
Disulfonic Acid ◽  
Folate Transport ◽  
Intestinal Brush Border Membrane ◽  
Transport Carrier ◽  
Incubation Buffer

Transport of folic acid (Pte-Glu) across the brush-border membrane of human intestine was studied using brush-border membrane vesicle (BBMV) technique. The transport of Pte-Glu was higher in BBMV prepared from the jejunum than those prepared from the ileum (0.70 +/- 0.05 and 0.14 +/- 0.02 pmol X mg protein-1 X 10 s-1, respectively). The transport of Pte-Glu appeared to be carrier mediated and was pH dependent and increased with decreasing incubation buffer pH; saturable (Kt = 1.69 microM, Vmax = 4.72 pmol X mg protein-1 X 10 s-1); inhibited in a competitive manner by the structural analogues 5-methyltetrahydrofolate, methotrexate, and 5-formyltetrahydrofolate (Ki = 2.2, 1.4 and 1.4 microM, respectively); not affected by inducing a relatively positive or negative intravesicular compartment; independent of Na+ gradient; and inhibited by 4,4'-diisothiocyanatostlibene-2,2'-disulfonic acid (DIDS), an anion exchange inhibitor. The increase in Pte-Glu transport on decreasing incubation buffer pH appeared to be in part mediated through a direct effect of acidic pH on the transport carrier and in part through the pH gradient imposed by activating Pte-Glu-:OH- exchange and/or Pte-Glu-:H+ co-transport mechanisms. The important role of an acidic extravesicular environment in Pte-Glu transport is consistent with a role for the intestinal surface acid microclimate in folate transport. These results demonstrate that Pte-Glu transport in human BBMV occurs by a carrier-mediated system that is similar to that described for rat and rabbit intestinal BBMV.

scholarly journals Acute Ethanol Exposure Inhibits Renal Folate Transport, but Repeated Exposure Upregulates Folate Transport Proteins in Rats and Human Cells

2007 ◽  
Vol 137 (5) ◽  
pp. 1260-1265 ◽  
Author(s):  
Rachelle L. Romanoff ◽  
Donna M. Ross ◽  
Kenneth E. McMartin
Keyword(s):  
Transport Proteins ◽  
Ethanol Exposure ◽  
Human Cells ◽  
Repeated Exposure ◽  
Folate Transport ◽  
Acute Ethanol ◽  
Folate Transport Proteins

Role of sodium ion in transport of folic acid in the small intestine

1986 ◽  
Vol 251 (2) ◽  
pp. G218-G222 ◽  
Author(s):  
J. Zimmerman ◽  
J. Selhub ◽  
I. H. Rosenberg
Keyword(s):  
Small Intestine ◽  
Folic Acid ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Test Solution ◽  
Brush Border Membrane Vesicles ◽  
Acid Uptake ◽  
Folate Transport ◽  
Luminal Membrane

The effect of sodium on folate transport across the intestinal luminal membrane was analyzed using two techniques: the "influx" chamber and isolated brush-border membrane vesicles. Preincubation of tissue in Na+-free medium did not have a consistent effect on folic acid influx provided that Na+ was present in the test solution. Replacement of Na+ in the test solution by choline+ resulted in a significant reduction of folic acid influx. However, when intestinal sheets that had been equilibrated in Na+-free solution were exposed to test solution containing either Na+, Li+, K+, Rb+, Cs+, Tris+, or guanidinium+ as main cations, folic acid influx was not significantly decreased. Concentration-dependence studies showed that replacement of Na+ by Rb+ did not affect the saturable mechanism of folate transport. Rather, a decrease in nonsaturable folic acid uptake accounted for the slightly reduced influx observed in the presence of Rb+. Experiments with brush-border membrane vesicles revealed that methotrexate uptake was significantly higher in the presence of external Na+ than in the presence of K+, but was not different from uptake in the presence of K+ plus valinomycin. These data suggest that the saturable component of folate transport is not Na+ dependent, and nonsaturable transport of folic acid across the luminal membrane occurs in part through a conductive pathway that involves a negatively charged species of folate and a cation whose membrane permeability affects the rate of folate transport. The importance of Na+ in this process in vivo derives from the fact that Na+ is the most permeant cation available at the absorptive site in the small intestine.

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