Characterization of the folate-binding proteins associated with the plasma membrane of rat liver

Costa, Maria Da; Rothenberg, Sheldon P.

doi:10.1016/0005-2736(88)90100-9

Cited by 15 publications

(8 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The finding of FPB cDNA in pig liver is consistent with prior findings of FBP by gel filtration of isolated rat and human liver plasma membranes [9,10] and by immunoblot and activity measurements of isolated liver plasma membranes from the present micropigs [23].…”

Section: Discussionsupporting

confidence: 91%

“…The reported immunohistochemical locations of FBP to epithelial cells in placenta, choroid plexus and renal tubules support a homeostatic role of FBP in folate conservation by these tissues [34]. Supporting our findings of FBP transcripts in liver and kidney, others isolated FBP from rat, pig and human kidney tubules by affinity chromatography [4,5,35] and from rat and human liver plasma membranes by affinity labelling of proteins after gel filtration [9,10]. In contrast, the absence of FBP transcripts from pig jejunal mucosa ( Figures 4 and 5) does not support a prior report of FBP in isolated pig jejunal brush border membranes [11].…”

Section: Discussionsupporting

confidence: 85%

“…The nucleotide and amino acid similarities of FBPs from placenta and several different mammalian cells lines [1][2][3]7,8] suggest that they may play a role in folate homeostasis through regulation of transport across intestinal, liver and kidney membranes. In this context, previous investigators demonstrated FBPs by gel filtration of rat and human liver plasma membranes [9,10], affinity chromatography of rat [4] and pig [5] renal tubular membranes and by autoradiography of affinity-labelled pig jejunal mucosal proteins separated by gel electrophoresis [11]. So far, FBPs have not been described at the molecular level in these three tissues that regulate the intestinal absorption, hepatic storage and metabolism, and renal conservation of folates.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Folate binding protein: molecular characterization and transcript distribution in pig liver, kidney and jejunum

Hoozen

Ling

Halsted

1996

Biochemical Journal

View full text Add to dashboard Cite

Folate-binding protein (FBP) was identified and characterized in a pig liver cDNA library by screening with a 0.6 kb fragment from the cDNA of FBP from a human KB cell cancer line. The cDNA of pig liver FBP included 1230 bp containing 759 bp in the open reading frame with 80 % similarity to the human placenta FBP. The deduced 253 amino acid sequence showed 67-73 % similarity to previous sequences and contained 16 conserved cysteine residues, 11 tryptophan potential folate-

show abstract

Section: Discussionsupporting

confidence: 91%

Section: Discussionsupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Folate binding protein: molecular characterization and transcript distribution in pig liver, kidney and jejunum

Hoozen

Ling

Halsted

1996

Biochemical Journal

View full text Add to dashboard Cite

show abstract

“…First, the normal liver, a major storage site for folate, expresses a very low level of this GPI-FBP (i.e., only ϳ1% and ϳ10% of that measured in the kidney and brain, respectively), and second, expression of the protein did not increase in folate deficiency. In a previous study from our laboratory, a FBP was identified in a membrane preparation from the liver of folate-deficient rats but the nature of the protein was not established (14). However, the total folate-binding capacity of this preparation from the deficient rats was similar to the total folate bound to this protein in the control rats, indicating that folate deficiency served to ''unsaturate'' this FBP rather than upregulate its expression.…”

Section: Discussionmentioning

confidence: 84%

Folate deficiency reduces the GPI-anchored folate-binding protein in rat renal tubules

Costa

Rothenberg

Sadasivan

et al. 2000

American Journal of Physiology-Cell Physiology

Self Cite

View full text Add to dashboard Cite

A folate-binding protein (FBP) anchored to cell membranes by a glycosyl phosphatidylinositol (GPI) adduct is constitutively expressed in some transformed and cultured cell lines. Its expression is upregulated when these cells are grown in medium containing low folate, but whether this occurs in vivo with nutritional folate deficiency is unknown. To address this question, the GPI-FBP in the liver, kidney, and brain of rats on control and folate-deficient (FD) diets was measured. The GPI-FBP in the kidney of FD rats decreased significantly in contrast to the upregulation of this protein in cultured cells. Northern blot analysis and nuclear run-on assays indicated that transcription of the GPI-FBP gene in the kidney was not reduced by folate deficiency. This decrease of the GPI-FBP appears to result from its proteolysis, similar to the enzymatic degradation of the apoprotein that occurs in vitro. Because the GPI-FBP is on the brush borders of the proximal renal tubules and provides for the reabsorption of folate, this function diminishes when the protein decreases in folate deficiency.

show abstract

“…Taken together, these observations suggest that some but not all components may be shared in the uptake of these two compounds. In addition, some Mtx-and folatebinding proteins present in cell membranes have been identified (1,5,6,12,15,16,19,20,22), although their role in the overall uptake process is unclear. A recent report, however, indicates that a mouse membrane 45-to 48-kilodalton protein may be involved (32).…”

mentioning

confidence: 99%

Complementation of a methotrexate uptake defect in Chinese hamster ovary cells by DNA-mediated gene transfer.

Underhill¹,

Flintoff²

1989

Mol. Cell. Biol.

View full text Add to dashboard Cite

A methotrexate-resistant Chinese hamster ovary cell line deficient in methotrexate uptake has been complemented to methotrexate sensitivity by transfection with DNA isolated from either wild-type Chinese hamster ovary or human G2 cells. Primary and secondary transfectants regained the ability to take up methotrexate in a manner similar to that of wild-type cells, and in the case of those transfected with human DNA, to contain human-specific DNA sequences. The complementation by DNA-mediated gene transfer of this methotrexate-resistant phenotype provides a basis for the cloning of a gene involved in methotrexate uptake.The folic acid analog methotrexate (Mtx) is a cytotoxic agent to dividing mammalian cells which exerts its effect by inhibiting the enzyme dihydrofolate reductase (2). To achieve this function, the drug must be transported across the cell membrane and released intracellularly. It is believed that this transport process is mediated by an energy-dependent carrier system requiring anion exchange (14). There is conflicting evidence from various studies as to whether the analog is transported by the same system that allows folic acid to enter the cell or whether a separate system for reduced folate is employed. Kinetic and competition analyses in L1210 mouse cells have shown that two systems exist under one set of conditions (26, 31), while only one system exists under alternative conditions (13). In addition, some mutants are defective in uptake of both Mtx and folic acid, while others are defective in uptake of only Mtx (9, 10; T. M. Underhill and W. F. Flintoff, Somat. Cell Mol. Genet., in press). Also, some Mtx-deficient mutants have increased requirements for reduced folates to maintain growth without a concomitant increase in the requirement for folic acid (18,25,27). Taken together, these observations suggest that some but not all components may be shared in the uptake of these two compounds. In addition, some Mtx-and folatebinding proteins present in cell membranes have been identified (1,5,6,12,15,16,19,20,22), although their role in the overall uptake process is unclear. A recent report, however, indicates that a mouse membrane 45-to 48-kilodalton protein may be involved (32).In a recent report, we have described an Mtx-resistant Chinese hamster ovary (CHO) cell line, designated Mtx RII OuaR 2-4, that was unable to transport Mtx but was able to take up folic acid in a manner similar to that of wild-type cells (Underhill and Flintoff, in press). Under conditions of folic acid-free medium, this cell line required 250 times the level of folinic acid required by wild-type cells to maintain optimum growth. This requirement for high levels of folinic acid in otherwise folic acid-free medium is a common property shown by several mutants defective in Mtx uptake (17,27). Pseudorevertants selected from this cell line for growth on low levels of folinic acid retained their resistance to Mtx. Because the Mtx-resistant phenotype was a genetically recessive trait (8), it should be possible to complement thi...

show abstract

Characterization of the folate-binding proteins associated with the plasma membrane of rat liver

Cited by 15 publications

References 24 publications

Folate binding protein: molecular characterization and transcript distribution in pig liver, kidney and jejunum

Folate binding protein: molecular characterization and transcript distribution in pig liver, kidney and jejunum

Folate deficiency reduces the GPI-anchored folate-binding protein in rat renal tubules

Complementation of a methotrexate uptake defect in Chinese hamster ovary cells by DNA-mediated gene transfer.

Contact Info

Product

Resources

About