A deep intronic mutation of c.1166-285 T &gt; G in SLC46A1 is shared by four unrelated Japanese patients with hereditary folate malabsorption (HFM)

Tozawa, Yusuke; Abdrabou, Shimaa Said Mohamed Ali; Nogawa-Chida, Natsuko; Nishiuchi, Ritsuo; Ishida, Toshiaki; Suzuki, Yuichi; Sano, Hideki; Kobayashi, Ryōji; Kishimoto, Kenji; Ohara, Osamu; Imai, Kohsuke; Naruto, Takuya; Kobayashi, Kunihiko; Ariga, Tadashi; Yamada, Masafumi

doi:10.1016/j.clim.2019.108256

Cited by 10 publications

(18 citation statements)

References 22 publications

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“…Using the substituted cysteine accessibility method, the loss of function associated with substitutions at Asp109 locked the protein in an inward-open conformation as manifested by the loss of accessibility of residues, to a watersoluble sulfhydryl reagent, that are accessible in wild-type PCFT (PCFT-WT). The current study, focused on the role of Phe392 in PCFT function, complements a report of a F392V mutation in cohort of Japanese subjects with HFM (21). While a loss of function was observed in this report, the basis for the functional loss was not pursued nor was the role this residue plays in PCFT function clarified.…”

Section: Introductionmentioning

confidence: 63%

“…A recent report described a F392V PCFT mutation in a subject with HFM (21). Phe392, one of twelve fully conserved (human, monkey, horse, mouse, rat, dog, bovine, opossum, xenopus, zebrafish) phenylalanine residues, is located in the 11 th transmembrane segment near the cytoplasmic interface ( Figure 1, green fill).…”

Section: Characterization Of a Val Substitution At Phe392mentioning

confidence: 99%

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A proton-coupled folate transporter mutation causing hereditary folate malabsorption locks the protein in an inward-open conformation

Zhan

Najmi

Lin

et al. 2020

Journal of Biological Chemistry

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The proton-coupled folate transporter (PCFT, SLC46A1) is required for folate intestinal absorption and transport across the choroid plexus. Recent work has identified a F392V mutation causing hereditary folate malabsorption. However, the residue properties responsible for this loss of function remains unknown. Using site-directed mutagenesis, we observed complete loss-of-function with charged (Lys, Asp, Glu) and polar (Thr, Ser, Gln) Phe392 substitutions and minimal function with some neutral substitutions; however, F392M retained full function. Using the substituted-cysteine accessibility method (with MTSEA-biotin labeling), Phe392 mutations causing loss of function, while preserving membrane expression and trafficking, also resulted in loss of accessibility of the substituted cysteine in P314C-PCFT located within the aqueous translocation pathway. F392V function and accessibility of the P314C cysteine were restored by insertion of a G305L (suppressor) mutation. A S196L mutation localized in proximity to Gly305 by homology modeling was inactive. However, when inserted into the inactive F392V scaffold, function was restored (mutually compensatory mutations) as was accessibility of the P314C cysteine residue. Reduced function, documented with F392H PCFT was due to a 15-fold decrease in methotrexate influx Vmax, accompanied by a decreased influx Kt (4.5-fold) and Ki (3-fold). The data indicate that Phe392 is required for rapid oscillation of the carrier among its conformational states and suggest that this is achieved by dampening affinity of the protein for its folate substrates. F392V, and other inactivating Phe392 PCFT mutations, lock the protein in its inward-open conformation. Reach (length) and hydrophobicity of Phe392 appear to be features required for full activity.

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Section: Introductionmentioning

confidence: 63%

Section: Characterization Of a Val Substitution At Phe392mentioning

confidence: 99%

A proton-coupled folate transporter mutation causing hereditary folate malabsorption locks the protein in an inward-open conformation

Zhan

Najmi

Lin

et al. 2020

Journal of Biological Chemistry

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“…The human SLC46A1 gene is located on chromosome 17q11.2 and includes five exons (Figure 1). Inherited variants in the SLC46A1 gene cause loss of expression or function of its encoded protein, resulting in a severely low levels of systemic and cerebral folates termed hereditary folate malabsorption (HFM) 1,9,20,21 . HFM syndrome appears shortly after birth and is accompanied by anemia, gastrointestinal (GI) symptoms, immune deficiency, and neurologic manifestations 21 …”

Section: Discovery and Tissue Expression Of Pcftmentioning

confidence: 99%

The evolving biology of the proton‐coupled folate transporter: New insights into regulation, structure, and mechanism

2022

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The human proton‐coupled folate transporter (PCFT; SLC46A1) or hPCFT was identified in 2006 as the principal folate transporter involved in the intestinal absorption of dietary folates. A rare autosomal recessive hereditary folate malabsorption syndrome is attributable to human SLC46A1 variants. The recognition that hPCFT was highly expressed in many tumors stimulated substantial interest in its potential for cytotoxic drug targeting, taking advantage of its high‐level transport activity under acidic pH conditions that characterize many tumors and its modest expression in most normal tissues. To better understand the basis for variations in hPCFT levels between tissues including human tumors, studies have examined the transcriptional regulation of hPCFT including the roles of CpG hypermethylation and critical transcription factors and cis elements. Additional focus involved identifying key structural and functional determinants of hPCFT transport that, combined with homology models based on structural homologies to the bacterial transporters GlpT and LacY, have enabled new structural and mechanistic insights. Recently, cryo‐electron microscopy structures of chicken PCFT in a substrate‐free state and in complex with the antifolate pemetrexed were reported, providing further structural insights into determinants of (anti)folate recognition and the mechanism of pH‐regulated (anti)folate transport by PCFT. Like many major facilitator proteins, hPCFT exists as a homo‐oligomer, and evidence suggests that homo‐oligomerization of hPCFT monomeric proteins may be important for its intracellular trafficking and/or transport function. Better understanding of the structure, function and regulation of hPCFT should facilitate the rational development of new therapeutic strategies for conditions associated with folate deficiency, as well as cancer.

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“…His respiratory condition and PH gradually ameliorated; he was extubated on day 17 and discharged from the ICU. Compound heterozygous mutations, p.G389Afs*20 and p.S318R, were detected in SLC46A1 prompting a diagnosis of hereditary folate malabsorption (HFM) 1 …”

mentioning

confidence: 99%

“…Compound heterozygous mutations, p.G389Afs*20 and p.S318R, were detected in SLC46A1 prompting a diagnosis of hereditary folate malabsorption (HFM). 1 At the age of 14 months, he received daily intravenous FA and his motor and mental development was normal. The developmental quotient was 97 in the Japanese Enjoji developmental test.…”

mentioning

confidence: 99%

Pulmonary hypertension related to hereditary folate malabsorption in an infant

Miyashita

Kurosawa

Yamashita

et al. 2020

Pediatrics International

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A deep intronic mutation of c.1166-285 T > G in SLC46A1 is shared by four unrelated Japanese patients with hereditary folate malabsorption (HFM)

Cited by 10 publications

References 22 publications

A proton-coupled folate transporter mutation causing hereditary folate malabsorption locks the protein in an inward-open conformation

A proton-coupled folate transporter mutation causing hereditary folate malabsorption locks the protein in an inward-open conformation

The evolving biology of the proton‐coupled folate transporter: New insights into regulation, structure, and mechanism

Pulmonary hypertension related to hereditary folate malabsorption in an infant

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A deep intronic mutation of c.1166-285 T > G in SLC46A1 is shared by four unrelated Japanese patients with hereditary folate malabsorption (HFM)

Cited by 10 publications

References 22 publications

A proton-coupled folate transporter mutation causing hereditary folate malabsorption locks the protein in an inward-open conformation

A proton-coupled folate transporter mutation causing hereditary folate malabsorption locks the protein in an inward-open conformation

The evolving biology of the proton‐coupled folate transporter: New insights into regulation, structure, and mechanism

Pulmonary hypertension related to hereditary folate malabsorption in an infant

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A deep intronic mutation of c.1166-285 T > G in SLC46A1 is shared by four unrelated Japanese patients with hereditary folate malabsorption (HFM)