Hereditary folate malabsorption: A positively charged amino acid at position 113 of the proton-coupled folate transporter (PCFT/SLC46A1) is required for folic acid binding

Lasry, Inbal; Berman, Bluma; Glaser, Fabian; Jansen, Gerrit; Assaraf, Yehuda G.

doi:10.1016/j.bbrc.2009.06.007

Cited by 29 publications

(30 citation statements)

References 13 publications

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“…The R113 residue, located in the first intracellular loop between the 2nd and 3rd TMDs was mutated in two subjects with HFM (10,34). Mutational analysis indicated that only preservation of the positive charge at this residue (R113H, R113K) could sustain slight residual function (10,34). The D156 residue, located in the 4th TMD, is critical for protein stability (21).…”

Section: C838 Functional Analysis Of Pcft Mutants In Hfmmentioning

confidence: 99%

Functional roles of the A335 and G338 residues of the proton-coupled folate transporter (PCFT-SLC46A1) mutated in hereditary folate malabsorption

Shin

Zhao

Fiser

et al. 2012

American Journal of Physiology-Cell Physiology

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Shin DS, Zhao R, Fiser A, Goldman ID. Functional roles of the A335 and G338 residues of the proton-coupled folate transporter (PCFT-SLC46A1) mutated in hereditary folate malabsorption. Am J Physiol Cell Physiol 303: C834 -C842, 2012. First published July 25, 2012; doi:10.1152/ajpcell.00171.2012.-The proton-coupled folate transporter (PCFT-SLC46A1) mediates intestinal folate absorption and folate transport across the choroid plexus, processes defective in hereditary folate malabsorption (HFM). This paper characterizes the functional defect, and the roles of two mutated PCFT residues, associated with HFM (G338R and A335D). The A335D-PCFT and other mutations at this residue result in an unstable protein; when expression of a mutant protein was preserved, function was always retained. The G338R and other charged mutants resulted in an unstable protein; substitutions with small neutral and polar amino acids preserved protein but with impaired function. Pemetrexed and methotrexate (MTX) influx kinetics mediated by the G338C mutant PCFT revealed marked (15-to 20-fold) decreases in K t and Vmax compared with wild-type PCFT. In contrast, there was only a small (ϳ2-fold) decrease in the MTX influx K i and an increase (ϳ3-fold) in the pemetrexed influx K i for the G338C-PCFT mutant. Neither a decrease in pH to 4.5, nor an increase to 7.4, restored function of the G338C mutant relative to wild-type PCFT excluding a role for this residue in proton binding or proton coupling. Homology modeling localized the A335 and G338 residues embedded in the 9th transmembrane, consistent with the inaccessibility of the A335C and G338C proteins to MTS reagents. Hence, the loss of intrinsic G338C-PCFT function was due solely to impaired oscillation of the carrier between its conformational states. The data illustrate how alterations in carrier cycling can impact influx K t without comparable alterations in substrate binding to the carrier.

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Section: C838 Functional Analysis Of Pcft Mutants In Hfmmentioning

confidence: 99%

Functional roles of the A335 and G338 residues of the proton-coupled folate transporter (PCFT-SLC46A1) mutated in hereditary folate malabsorption

Shin

Zhao

Fiser

et al. 2012

American Journal of Physiology-Cell Physiology

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“…1). In addition, residues mapping to a well conserved ␤-turn in a region between TMDs 2 and 3 (DXXGRR; positions 109 -114) were implicated as functionally important (6,8,13,32,33) (Fig. 1).…”

mentioning

confidence: 99%

“…1). From loss of transport for R113C hPCFT, a model was proposed in which TMDs 1, 3, 4, and 6 form a hydrophobic binding pocket into which Arg-113 protrudes (32). However, this has not been experimentally validated.…”

mentioning

confidence: 99%

Identification and Functional Impact of Homo-oligomers of the Human Proton-coupled Folate Transporter

Hou

Desmoulin

Etnyre

et al. 2012

Journal of Biological Chemistry

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Background:The human proton-coupled folate transporter (PCFT) may exist as homo-oligomers. Results: PCFT monomers form oligomers, and wild-type and inactive mutant PCFT monomers show dominant-positive activity when co-expressed. Conclusion: Wild-type PCFT may rescue the mutant phenotype via formation of hetero-oligomers. Significance: Better understanding of PCFT oligomerization may identify therapeutic applications for hereditary folate maladsorption and delivery of PCFT-targeted chemotherapy drugs for cancer.

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“…The R113 residue was shown to be mutated in 2 subjects with HFM, and its absence results in a profound loss of function irrespective of the substituted residue. 6,8,19 The current study encompasses an evaluation of the role of Asp residues in PCFT function. Only 2 of the 7 conserved Asp residues were found to be important.…”

Section: Introductionmentioning

confidence: 99%

Functional roles of aspartate residues of the proton-coupled folate transporter (PCFT-SLC46A1); a D156Y mutation causing hereditary folate malabsorption

Shin

Min

Russell

et al. 2010

Blood

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Hereditary folate malabsorption: A positively charged amino acid at position 113 of the proton-coupled folate transporter (PCFT/SLC46A1) is required for folic acid binding

Cited by 29 publications

References 13 publications

Functional roles of the A335 and G338 residues of the proton-coupled folate transporter (PCFT-SLC46A1) mutated in hereditary folate malabsorption

Functional roles of the A335 and G338 residues of the proton-coupled folate transporter (PCFT-SLC46A1) mutated in hereditary folate malabsorption

Identification and Functional Impact of Homo-oligomers of the Human Proton-coupled Folate Transporter

Functional roles of aspartate residues of the proton-coupled folate transporter (PCFT-SLC46A1); a D156Y mutation causing hereditary folate malabsorption

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