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Huang C, Hoque MT, Qu QR, Henderson J, Bendayan R. Antiretroviral drug dolutegravir induces inflammation at the mouse brain barriers. FASEB J 2024; 38:e23790. [PMID: 38982638 DOI: 10.1096/fj.202400558r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 06/05/2024] [Accepted: 06/24/2024] [Indexed: 07/11/2024]
Abstract
Integrase strand transfer inhibitors (INSTIs) based antiretroviral therapy (ART) is currently used as first-line regimen to treat HIV infection. Despite its high efficacy and barrier to resistance, ART-associated neuropsychiatric adverse effects remain a major concern. Recent studies have identified a potential interaction between the INSTI, dolutegravir (DTG), and folate transport pathways at the placental barrier. We hypothesized that such interactions could also occur at the two major blood-brain interfaces: blood-cerebrospinal fluid barrier (BCSFB) and blood-brain barrier (BBB). To address this question, we evaluated the effect of two INSTIs, DTG and bictegravir (BTG), on folate transporters and receptor expression at the mouse BCSFB and the BBB in vitro, ex vivo and in vivo. We demonstrated that DTG but not BTG significantly downregulated the mRNA and/or protein expression of folate transporters (RFC/SLC19A1, PCFT/SLC46A1) in human and mouse BBB models in vitro, and mouse brain capillaries ex vivo. Our in vivo study further revealed a significant downregulation in Slc19a1 and Slc46a1 mRNA expression at the BCSFB and the BBB following a 14-day DTG oral treatment in C57BL/6 mice. However, despite the observed downregulatory effect of DTG in folate transporters/receptor at both brain barriers, a 14-day oral treatment of DTG-based ART did not significantly alter the brain folate level in animals. Interestingly, DTG treatment robustly elevated the mRNA and/or protein expression of pro-inflammatory cytokines and chemokines (Cxcl1, Cxcl2, Cxcl3, Il6, Il23, Il12) in primary cultures of mouse brain microvascular endothelial cells (BBB). DTG oral treatment also significantly upregulated proinflammatory cytokines and chemokine (Il6, Il1β, Tnfα, Ccl2) at the BCSFB in mice. We additionally observed a downregulated mRNA expression of drug efflux transporters (Abcc1, Abcc4, and Abcb1a) and tight junction protein (Cldn3) at the CP isolated from mice treated with DTG. Despite the structural similarities, BTG only elicited minor effects on the markers of interest at both the BBB and BCSFB. In summary, our current data demonstrates that DTG but not BTG strongly induced inflammatory responses in a rodent BBB and BCSFB model. Together, these data provide valuable insights into the mechanism of DTG-induced brain toxicity, which may contribute to the pathogenesis of DTG-associated neuropsychiatric adverse effect.
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Affiliation(s)
- Chang Huang
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada
| | - Md Tozammel Hoque
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada
| | - Qing Rui Qu
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada
| | - Jeffrey Henderson
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada
| | - Reina Bendayan
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada
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2
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Yu Y, Martins LM. Mitochondrial One-Carbon Metabolism and Alzheimer's Disease. Int J Mol Sci 2024; 25:6302. [PMID: 38928008 PMCID: PMC11203557 DOI: 10.3390/ijms25126302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 05/13/2024] [Accepted: 05/15/2024] [Indexed: 06/28/2024] Open
Abstract
Mitochondrial one-carbon metabolism provides carbon units to several pathways, including nucleic acid synthesis, mitochondrial metabolism, amino acid metabolism, and methylation reactions. Late-onset Alzheimer's disease is the most common age-related neurodegenerative disease, characterised by impaired energy metabolism, and is potentially linked to mitochondrial bioenergetics. Here, we discuss the intersection between the molecular pathways linked to both mitochondrial one-carbon metabolism and Alzheimer's disease. We propose that enhancing one-carbon metabolism could promote the metabolic processes that help brain cells cope with Alzheimer's disease-related injuries. We also highlight potential therapeutic avenues to leverage one-carbon metabolism to delay Alzheimer's disease pathology.
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Affiliation(s)
- Yizhou Yu
- MRC Toxicology Unit, University of Cambridge, Gleeson Building, Tennis Court Road, Cambridge CB2 1QR, UK
| | - L. Miguel Martins
- MRC Toxicology Unit, University of Cambridge, Gleeson Building, Tennis Court Road, Cambridge CB2 1QR, UK
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3
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Hou X, Lu Z, Yu T, Zhang Y, Yao Q, Zhang C, Niu Y, Liang Q. Two maize homologs of mammalian proton-coupled folate transporter, ZmMFS_1-62 and ZmMFS_1-73, are essential to salt and drought tolerance. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2024; 210:108623. [PMID: 38626656 DOI: 10.1016/j.plaphy.2024.108623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 03/31/2024] [Accepted: 04/08/2024] [Indexed: 04/18/2024]
Abstract
Folates are essential to the maintenance of normal life activities in almost all organisms. Proton-coupled folate transporter (PCFT), belonging to the major facilitator superfamily, is one of the three major folate transporter types widely studied in mammals. However, information about plant PCFTs is limited. Here, a genome-wide identification of maize PCFTs was performed, and two PCFTs, ZmMFS_1-62 and ZmMFS_1-73, were functionally investigated. Both proteins contained the typical 12 transmembrane helixes with N- and C-termini located in the cytoplasm, and were localized in the plasma membrane. Molecular docking analysis indicated their binding activity with folates via hydrogen bonding. Interference with ZmMFS_1-62 and ZmMFS_1-73 in maize seedlings through virus-induced gene silencing disrupted folate homeostasis, mainly in the roots, and reduced tolerance to drought and salt stresses. Moreover, a molecular chaperone protein, ZmHSP20, was found to interact with ZmMFS_1-62 and ZmMFS_1-73, and interference with ZmHSP20 in maize seedlings also led to folate disruption and increased sensitivity to drought and salt stresses. Overall, this is the first report of functional identification of maize PCFTs, which play essential roles in salt and drought stress tolerance, thereby linking folate metabolism with abiotic stress responses in maize.
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Affiliation(s)
- Xiaowan Hou
- Biotechnology Research Institute, Chinese Academy of Agricultural Science, Beijing 100081, China; Key Laboratory of Hainan Province for Postharvest Physiology and Technology of Tropical Horticultural Products, South Subtropical Crops Research Institute, Chinese Academy of Tropical Agricultural Sciences, Zhanjiang, China; Key Laboratory of Forage and Endemic Crop Biotechnology, Ministry of Education, School of Life Sciences, Inner Mongolia University, Hohhot, China.
| | - Zhiwei Lu
- Key Laboratory of Hainan Province for Postharvest Physiology and Technology of Tropical Horticultural Products, South Subtropical Crops Research Institute, Chinese Academy of Tropical Agricultural Sciences, Zhanjiang, China.
| | - Taifei Yu
- Hunan Provincial Key Laboratory of the Research and Development of Novel Pharmaceutical Preparations, the "Double-First Class" Application Characteristic Discipline of Hunan Province (Pharmaceutical Science), Changsha Medical University, Changsha 410219, China.
| | - Yuanyuan Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Science, Beijing 100081, China; Key Laboratory of Hainan Province for Postharvest Physiology and Technology of Tropical Horticultural Products, South Subtropical Crops Research Institute, Chinese Academy of Tropical Agricultural Sciences, Zhanjiang, China.
| | - Quansheng Yao
- Key Laboratory of Hainan Province for Postharvest Physiology and Technology of Tropical Horticultural Products, South Subtropical Crops Research Institute, Chinese Academy of Tropical Agricultural Sciences, Zhanjiang, China.
| | - Chunyi Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Science, Beijing 100081, China; National Nanfan Research Institute, Chinese Academy of Agricultural Sciences, Sanya, 572000, China.
| | - Yiding Niu
- Key Laboratory of Forage and Endemic Crop Biotechnology, Ministry of Education, School of Life Sciences, Inner Mongolia University, Hohhot, China.
| | - Qiuju Liang
- Biotechnology Research Institute, Chinese Academy of Agricultural Science, Beijing 100081, China; National Nanfan Research Institute, Chinese Academy of Agricultural Sciences, Sanya, 572000, China.
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4
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Pan S, Hale AT, Lemieux ME, Raval DK, Garton TP, Sadler B, Mahaney KB, Strahle JM. Iron homeostasis and post-hemorrhagic hydrocephalus: a review. Front Neurol 2024; 14:1287559. [PMID: 38283681 PMCID: PMC10811254 DOI: 10.3389/fneur.2023.1287559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2023] [Accepted: 11/21/2023] [Indexed: 01/30/2024] Open
Abstract
Iron physiology is regulated by a complex interplay of extracellular transport systems, coordinated transcriptional responses, and iron efflux mechanisms. Dysregulation of iron metabolism can result in defects in myelination, neurotransmitter synthesis, and neuronal maturation. In neonates, germinal matrix-intraventricular hemorrhage (GMH-IVH) causes iron overload as a result of blood breakdown in the ventricles and brain parenchyma which can lead to post-hemorrhagic hydrocephalus (PHH). However, the precise mechanisms by which GMH-IVH results in PHH remain elusive. Understanding the molecular determinants of iron homeostasis in the developing brain may lead to improved therapies. This manuscript reviews the various roles iron has in brain development, characterizes our understanding of iron transport in the developing brain, and describes potential mechanisms by which iron overload may cause PHH and brain injury. We also review novel preclinical treatments for IVH that specifically target iron. Understanding iron handling within the brain and central nervous system may provide a basis for preventative, targeted treatments for iron-mediated pathogenesis of GMH-IVH and PHH.
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Affiliation(s)
- Shelei Pan
- Department of Neurosurgery, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
| | - Andrew T. Hale
- Department of Neurosurgery, University of Alabama at Birmingham School of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Mackenzie E. Lemieux
- Department of Neurosurgery, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
| | - Dhvanii K. Raval
- Department of Neurosurgery, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
| | - Thomas P. Garton
- Department of Neurology, Johns Hopkins University School of Medicine, Johns Hopkins University, Baltimore, MD, United States
| | - Brooke Sadler
- Department of Pediatrics, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
- Department of Hematology and Oncology, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
| | - Kelly B. Mahaney
- Department of Neurosurgery, Stanford University School of Medicine, Stanford University, Palo Alto, CA, United States
| | - Jennifer M. Strahle
- Department of Neurosurgery, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
- Department of Pediatrics, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
- Department of Orthopedic Surgery, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
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5
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Bharadwaj R, Lusi CF, Mashayekh S, Nagar A, Subbarao M, Kane GI, Wodzanowski KA, Brown AR, Okuda K, Monahan A, Paik D, Nandy A, Anonick MV, Goldman WE, Kanneganti TD, Orzalli MH, Grimes CL, Atukorale PU, Silverman N. Methotrexate suppresses psoriatic skin inflammation by inhibiting muropeptide transporter SLC46A2 activity. Immunity 2023; 56:998-1012.e8. [PMID: 37116499 PMCID: PMC10195032 DOI: 10.1016/j.immuni.2023.04.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 01/04/2023] [Accepted: 04/03/2023] [Indexed: 04/30/2023]
Abstract
Cytosolic innate immune sensing is critical for protecting barrier tissues. NOD1 and NOD2 are cytosolic sensors of small peptidoglycan fragments (muropeptides) derived from the bacterial cell wall. These muropeptides enter cells, especially epithelial cells, through unclear mechanisms. We previously implicated SLC46 transporters in muropeptide transport in Drosophila immunity. Here, we focused on Slc46a2, which was highly expressed in mammalian epidermal keratinocytes, and showed that it was critical for the delivery of diaminopimelic acid (DAP)-muropeptides and activation of NOD1 in keratinocytes, whereas the related transporter Slc46a3 was critical for delivering the NOD2 ligand MDP to keratinocytes. In a mouse model, Slc46a2 and Nod1 deficiency strongly suppressed psoriatic inflammation, whereas methotrexate, a commonly used psoriasis therapeutic, inhibited Slc46a2-dependent transport of DAP-muropeptides. Collectively, these studies define SLC46A2 as a transporter of NOD1-activating muropeptides, with critical roles in the skin barrier, and identify this transporter as an important target for anti-inflammatory intervention.
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Affiliation(s)
- Ravi Bharadwaj
- Program in Innate Immunity and Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Christina F Lusi
- Department of Biomedical Engineering, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | | | - Abhinit Nagar
- Program in Innate Immunity and Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Malireddi Subbarao
- Department of Immunology, St Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Griffin I Kane
- Department of Biomedical Engineering, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | | | - Ashley R Brown
- Chemistry and Biochemistry, University of Delaware, Newark, DE, USA
| | - Kendi Okuda
- Program in Innate Immunity and Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Amanda Monahan
- Program in Innate Immunity and Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Donggi Paik
- Program in Innate Immunity and Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Anubhab Nandy
- Program in Innate Immunity and Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | | | - William E Goldman
- Department of Microbiology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | | | - Megan H Orzalli
- Program in Innate Immunity and Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | | | - Prabhani U Atukorale
- Department of Biomedical Engineering, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Neal Silverman
- Program in Innate Immunity and Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA.
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6
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Gyimesi G, Hediger MA. Transporter-Mediated Drug Delivery. Molecules 2023; 28:molecules28031151. [PMID: 36770817 PMCID: PMC9919865 DOI: 10.3390/molecules28031151] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 01/12/2023] [Accepted: 01/18/2023] [Indexed: 01/27/2023] Open
Abstract
Transmembrane transport of small organic and inorganic molecules is one of the cornerstones of cellular metabolism. Among transmembrane transporters, solute carrier (SLC) proteins form the largest, albeit very diverse, superfamily with over 400 members. It was recognized early on that xenobiotics can directly interact with SLCs and that this interaction can fundamentally determine their efficacy, including bioavailability and intertissue distribution. Apart from the well-established prodrug strategy, the chemical ligation of transporter substrates to nanoparticles of various chemical compositions has recently been used as a means to enhance their targeting and absorption. In this review, we summarize efforts in drug design exploiting interactions with specific SLC transporters to optimize their therapeutic effects. Furthermore, we describe current and future challenges as well as new directions for the advanced development of therapeutics that target SLC transporters.
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7
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Sangha V, Hoque MT, Henderson JT, Bendayan R. Novel localization of folate transport systems in the murine central nervous system. Fluids Barriers CNS 2022; 19:92. [PMID: 36419095 PMCID: PMC9686069 DOI: 10.1186/s12987-022-00391-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 11/11/2022] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Folates are a family of B9 vitamins that serve as one-carbon donors critical to biosynthetic processes required for the development and function of the central nervous system (CNS) in mammals. Folate transport is mediated by three highly specific systems: (1) folate receptor alpha (FRα; FOLR1/Folr1), (2) the reduced folate-carrier (RFC; SLC19A1/Slc19a1) and (3) the proton-coupled folate transporter (PCFT; SLC46A1/Slc46a1). Folate transport into and out of the CNS occurs at the blood-cerebrospinal fluid barrier (BCSFB), mediated by FRα and PCFT. Impairment of folate transport at the BCSFB results in cerebral folate deficiency in infants characterized by severe neurological deficiencies and seizures. In contrast to the BCSFB, CNS folate transport at other brain barriers and brain parenchymal cells has not been extensively investigated. The aim of this study is to characterize folate transport systems in the murine CNS at several known barriers encompassing the BCSFB, arachnoid barrier (AB), blood-brain barrier (BBB) and parenchymal cells (astrocytes, microglia, neurons). METHODS Applying immunohistochemistry, localization of folate transport systems (RFC, PCFT, FRα) was examined at CNS barriers and parenchymal sites in wildtype (C57BL6/N) mice. Subcellular localization of the folate transport systems was further assessed in an in vitro model of the mouse AB. Gene and protein expression was analyzed in several in vitro models of brain barriers and parenchyma by qPCR and western blot analysis. RESULTS RFC, PCFT, and FRα expression was localized within the BCSFB and BBB consistent with previous reports. Only RFC and PCFT expression was detected at the AB. Varied levels of RFC and PCFT expression were detected in neuronal and glial cells. CONCLUSIONS Localization of RFC and PCFT within the AB, described here for the first time, suggest that AB may contribute to folate transport between the peripheral circulation and the CSF. RFC and PCFT expression observed in astrocytes and microglia is consistent with the role that one or both of these transporters may play in delivering folates into cells within brain parenchyma. These studies provide insights into mechanisms of folate transport in the CNS and may enhance our understanding of the critical role folates play in neurodevelopment and in the development of novel treatment strategies for disorders of brain folate deficiency due to impaired transporter function.
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Affiliation(s)
- Vishal Sangha
- grid.17063.330000 0001 2157 2938Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Canada
| | - Md. Tozammel Hoque
- grid.17063.330000 0001 2157 2938Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Canada
| | - Jeffrey T. Henderson
- grid.17063.330000 0001 2157 2938Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Canada
| | - Reina Bendayan
- grid.17063.330000 0001 2157 2938Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Canada
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Kumar M, Yoganathan S, Todari S, Suresh P, Chandran M, Danda S, Mathew LG, Koshy B, Thomas M. Hereditary Folate Malabsorption: A Rare Treatable Disorder with Hematological and Neurological Manifestations. Ann Indian Acad Neurol 2022; 25:1238-1241. [PMID: 36911455 PMCID: PMC9996535 DOI: 10.4103/aian.aian_1118_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Revised: 04/23/2022] [Accepted: 04/24/2022] [Indexed: 03/14/2023] Open
Affiliation(s)
- Madhan Kumar
- Department of Pediatrics, Christian Medical College, Vellore, Tamil Nadu, India
| | - Sangeetha Yoganathan
- Pediatric Neurology Unit, Department of Neurological Sciences, Christian Medical College, Vellore, Tamil Nadu, India
| | - Siddarth Todari
- Pediatric Hematology Oncology Unit, Department of Pediatrics, Christian Medical College, Vellore, Tamil Nadu, India
| | - Parvathy Suresh
- Department of Radiodiagnosis, Christian Medical College, Vellore, Tamil Nadu, India
| | - Mahalakshmi Chandran
- Pediatric Neurology Unit, Department of Neurological Sciences, Christian Medical College, Vellore, Tamil Nadu, India
| | - Sumita Danda
- Department of Medical Genetics, Christian Medical College, Vellore, Tamil Nadu, India
| | - Leni Grace Mathew
- Pediatric Hematology Oncology Unit, Department of Pediatrics, Christian Medical College, Vellore, Tamil Nadu, India
| | - Beena Koshy
- Developmental Pediatrics Unit, Department of Pediatrics, Christian Medical College, Vellore, Tamil Nadu, India
| | - Maya Thomas
- Pediatric Neurology Unit, Department of Neurological Sciences, Christian Medical College, Vellore, Tamil Nadu, India
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9
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Matherly LH, Schneider M, Gangjee A, Hou Z. Biology and therapeutic applications of the proton-coupled folate transporter. Expert Opin Drug Metab Toxicol 2022; 18:695-706. [PMID: 36239195 PMCID: PMC9637735 DOI: 10.1080/17425255.2022.2136071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 10/11/2022] [Indexed: 01/19/2023]
Abstract
INTRODUCTION The proton-coupled folate transporter (PCFT; SLC46A1) was discovered in 2006 as the principal mechanism by which folates are absorbed in the intestine and the causal basis for hereditary folate malabsorption (HFM). In 2011, it was found that PCFT is highly expressed in many tumors. This stimulated interest in using PCFT for cytotoxic drug targeting, taking advantage of the substantial levels of PCFT transport and acidic pH conditions commonly associated with tumors. AREAS COVERED We summarize the literature from 2006 to 2022 that explores the role of PCFT in the intestinal absorption of dietary folates and its role in HFM and as a transporter of folates and antifolates such as pemetrexed (Alimta) in relation to cancer. We provide the rationale for the discovery of a new generation of targeted pyrrolo[2,3-d]pyrimidine antifolates with selective PCFT transport and inhibitory activity toward de novo purine biosynthesis in solid tumors. We summarize the benefits of this approach to cancer therapy and exciting new developments in the structural biology of PCFT and its potential to foster refinement of active structures of PCFT-targeted anti-cancer drugs. EXPERT OPINION We summarize the promising future and potential challenges of implementing PCFT-targeted therapeutics for HFM and a variety of cancers.
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Affiliation(s)
- Larry H. Matherly
- Molecular Therapeutics Program, Barbara Ann Karmanos Cancer Institute, Detroit, Michigan 48201, United States
- Department of Oncology, Wayne State University School of Medicine, Detroit, Michigan 48201, United States
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, Michigan 48201, United States
| | - Mathew Schneider
- Department of Oncology, Wayne State University School of Medicine, Detroit, Michigan 48201, United States
| | - Aleem Gangjee
- Division of Medicinal Chemistry, Graduate School of Pharmaceutical Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282, United States
| | - Zhanjun Hou
- Molecular Therapeutics Program, Barbara Ann Karmanos Cancer Institute, Detroit, Michigan 48201, United States
- Department of Oncology, Wayne State University School of Medicine, Detroit, Michigan 48201, United States
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10
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Akiyama T, Kuki I, Kim K, Yamamoto N, Yamada Y, Igarashi K, Ishihara T, Hatano Y, Kobayashi K. Folic acid inhibits 5‐methyltetrahydrofolate transport across the blood–cerebrospinal fluid barrier: Clinical biochemical data from two cases. JIMD Rep 2022; 63:529-535. [PMID: 36341171 PMCID: PMC9626660 DOI: 10.1002/jmd2.12321] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 07/24/2022] [Accepted: 07/26/2022] [Indexed: 11/25/2022] Open
Abstract
Objective The use of folic acid (FA) has been discouraged in cerebral folate deficiency (CFD) because, theoretically, it could inhibit the transport of 5‐methyltetrahydrofolic acid (5MTHF) across the blood–cerebrospinal fluid (CSF) barrier. We present the clinical biochemical data of two cases with CFD to support this hypothesis. Methods We measured CSF and serum 5MTHF concentrations in a patient with Kearns‐Sayre syndrome (KSS) and a patient homozygous for MTHFR C677T polymorphism before and during folate supplementation therapy. To evaluate these 5MTHF concentrations, we also analyzed CSF and serum samples in pediatric patients without folate supplementation. Results Both patients had low CSF 5MTHF before treatment and high‐dose FA therapy did not normalize CSF 5MTHF. There was a dissociation between serum total folate and 5MTHF concentrations during FA therapy, which was considered to be due to the appearance of unmetabolized FA. The addition of folinic acid did not improve low CSF 5MTHF in the KSS patient and the cessation of FA resulted in the normalization of CSF 5MTHF. In the patient homozygous for MTHFR C677T, minimization of the FA dosage resulted in the normalization of CSF 5MTHF and an increased CSF‐to‐serum 5MTHF ratio. Conclusions Our data suggest that excess supplementation of FA impaired 5MTHF transport across the blood–CSF barrier. In the treatment of CFD, supplementation of folinic acid or 5MTHF (in cases of impaired 5MTHF synthesis) is preferred over the use of FA. The reference values of CSF 5MTHF concentration based on 600 pediatric cases were also provided.
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Affiliation(s)
- Tomoyuki Akiyama
- Department of Child Neurology Okayama University Hospital Okayama Japan
- Department of Child Neurology, Okayama University Graduate School of Medicine Dentistry and Pharmaceutical Sciences Okayama Japan
| | - Ichiro Kuki
- Department of Pediatric Neurology Osaka City General Hospital Osaka Japan
| | - Kiyohiro Kim
- Department of Pediatric Neurology Osaka City General Hospital Osaka Japan
- Department of Pediatric Neurology Hyogo Prefectural Amagasaki General Medical Center Hyogo Japan
| | - Naohiro Yamamoto
- Department of Pediatric Neurology Osaka City General Hospital Osaka Japan
| | - Yumi Yamada
- Department of Neurology National Hospital Organization Nishiniigata Chuo Hospital Niigata Japan
- Department of Neurology, Brain Research Institute Niigata University Niigata Japan
| | - Kazuya Igarashi
- Department of Neurology National Hospital Organization Nishiniigata Chuo Hospital Niigata Japan
| | - Tomohiko Ishihara
- Department of Neurology, Brain Research Institute Niigata University Niigata Japan
| | - Yuya Hatano
- Department of Neurology, Brain Research Institute Niigata University Niigata Japan
| | - Katsuhiro Kobayashi
- Department of Child Neurology Okayama University Hospital Okayama Japan
- Department of Child Neurology, Okayama University Graduate School of Medicine Dentistry and Pharmaceutical Sciences Okayama Japan
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11
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Wang D, Wu H, Yang J, Li M, Ling C, Gao Z, Lu H, Shen H, Tang Y. Loss of SLC46A1 decreases tumor iron content in hepatocellular carcinoma. Hepatol Commun 2022; 6:2914-2924. [PMID: 35811443 PMCID: PMC9512484 DOI: 10.1002/hep4.2031] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 06/07/2022] [Accepted: 06/18/2022] [Indexed: 11/16/2022] Open
Abstract
It is interesting that high iron is an independent inducer or cofactor of hepatocellular carcinoma (HCC) while the amount of iron is decreased in the liver tumor tissues. Due to the previous findings that iron deficiency promoted HCC metastasis, it is of significance to identify the underlying mechanism of iron deficiency in HCC. The tumor iron content and expressions of iron‐metabolic molecules were observed in the primary liver cancers of rats and mice. The molecules that changed independently of iron were identified by comparing the expression profiles in the human HCC tissues and iron‐deprived HCC cells. The downstream effects of these molecules on regulating intracellular iron content were investigated in vitro and further validated in vivo. Both in primary liver cancers of rats and mice, we confirmed the decreased iron content in tumor tissues and the altered expressions of iron‐metabolic molecules, including transferrin receptor 1 (TfR1), six‐transmembrane epithelial antigen of prostate 3 (STEAP3), divalent metal transporter 1 (DMT1), SLC46A1, ferroportin, hepcidin, and ferritin. Among these, STEAP3, DMT1, and SLC46A1 were altered free of iron deficiency. However, only silence or overexpression of SLC46A1 controlled the intracellular iron content of HCC cells. The interventions of STEAP3 or DMT1 could not change the intracellular iron content. Lentivirus‐mediated regain of SLC46A1 expression restored the iron content in orthotopically implanted tumors, with correspondingly changes in the iron‐metabolic molecules as iron increasing. Conclusion: Taken together, these results suggest that the loss of SLC46A1 expression leads to iron deficiency in liver tumor tissues, which would be an effective target to manage iron homeostasis in HCC.
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Affiliation(s)
- Dongyao Wang
- School of Pharmacy, Second Military Medical University, Shanghai, China
| | - Huiwen Wu
- Department of Nutrition, Second Military Medical University, Shanghai, China.,Department of Nutrition, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Jianxin Yang
- Department of Nutrition, Second Military Medical University, Shanghai, China
| | - Min Li
- Department of Nutrition, Second Military Medical University, Shanghai, China
| | - Changquan Ling
- Department of Traditional Chinese Medicine, Changhai Hospital, Second Military Medical University, Shanghai, China
| | - Zelong Gao
- Department of Nutrition, Second Military Medical University, Shanghai, China
| | - Hongtao Lu
- Department of Nutrition, Second Military Medical University, Shanghai, China
| | - Hui Shen
- Department of Nutrition, Second Military Medical University, Shanghai, China
| | - Yuxiao Tang
- Department of Nutrition, Second Military Medical University, Shanghai, China
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12
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Sakurai Y, Toriumi N, Sarashina T, Ishioka T, Nagata M, Kobayashi H, Azuma H. An infantile case of hereditary folate malabsorption with sudden development of pulmonary hemorrhage: a case report. J Med Case Rep 2022; 16:268. [PMID: 35773682 PMCID: PMC9245286 DOI: 10.1186/s13256-022-03448-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 05/06/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Hereditary folate malabsorption-a rare disorder caused by impairment of the folate transporter-can develop into severe folate deficiency manifesting as megaloblastic anemia and occasionally thrombocytopenia. Reportedly, megaloblastic anemia can manifest with hemorrhagic episodes, possibly due to ineffective platelet production and platelet dysfunction. However, life-threatening hemorrhage events in hereditary folate malabsorption have not been well investigated. CASE PRESENTATION A 3-month-old Japanese boy was transferred to our hospital due to thrombocytopenia and severe megaloblastic anemia. During a thorough examination of hematopoietic abnormalities, the patient suddenly went into cardiac arrest due to pulmonary hemorrhage. Although intravenous folate supplementation was started soon after the identification of folate deficiency, the patient died of circulatory defect and multiple organ failure. The cause of pulmonary hemorrhage, such as respiratory infection, could not be confirmed. Genetic investigation revealed a mutation in the SLC46A1 gene to be the cause of the hereditary folate malabsorption. CONCLUSION We report an infantile case of hereditary folate malabsorption that progressed to lethal pulmonary hemorrhage before folate deficiency was identified. Clinicians should consider that megaloblastic anemia could lead to severe bleeding without warning, and that nutrient supplementation should be initiated as soon as possible.
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Affiliation(s)
- Yukari Sakurai
- Department of Pediatrics, Asahikawa Medical University, 2-1-1-1, Midorigaoka-Higashi, Asahikawa, Hokkaido, 078-8510, Japan.
| | - Naohisa Toriumi
- Department of Pediatrics, Asahikawa Medical University, 2-1-1-1, Midorigaoka-Higashi, Asahikawa, Hokkaido, 078-8510, Japan
| | - Takeo Sarashina
- Department of Pediatrics, Asahikawa Medical University, 2-1-1-1, Midorigaoka-Higashi, Asahikawa, Hokkaido, 078-8510, Japan
| | - Toru Ishioka
- Department of Pediatrics, Wakkanai City Hospital, 4-11-6, Chuou, Wakkanai, Hokkaido, 097-8555, Japan
| | - Marino Nagata
- Division of Immunopathology, Department of Pathology, Asahikawa Medical University, 2-1-1-1, Midorigaoka-Higashi, Asahikawa, Hokkaido, 078-8510, Japan
| | - Hiroya Kobayashi
- Division of Immunopathology, Department of Pathology, Asahikawa Medical University, 2-1-1-1, Midorigaoka-Higashi, Asahikawa, Hokkaido, 078-8510, Japan
| | - Hiroshi Azuma
- Department of Pediatrics, Asahikawa Medical University, 2-1-1-1, Midorigaoka-Higashi, Asahikawa, Hokkaido, 078-8510, Japan
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13
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Li HZ, Liu KG, Zeng NX, Wu XF, Lu WJ, Xu HF, Yan C, Wu LL. Luteolin Enhances Choroid Plexus 5-MTHF Brain Transport to Promote Hippocampal Neurogenesis in LOD Rats. Front Pharmacol 2022; 13:826568. [PMID: 35401160 PMCID: PMC8993213 DOI: 10.3389/fphar.2022.826568] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 02/22/2022] [Indexed: 12/19/2022] Open
Abstract
Folates, provided by food, are commonly used antidepressant synergists in late-onset depression (LOD). However, increased intake of folic acid in the elderly population might lead to the accumulation of unmetabolized folic acid in the systemic circulation, leading to enhanced deterioration of the central nervous system function. In addition, folates cannot access the brain directly because of the blood-brain barrier. Choroid plexus (CP) 5-methyltetrahydrofolate (5-MTHF) brain transport plays a critical role in regulating the cerebrospinal fluid (CSF) 5-MTHF content. Luteolin is a natural flavonoid that has antidepressant effects and is involved in the anti-folate resistance pathway. It remains unclear whether the antidepressant effects of luteolin are associated with the CP 5-MTHF brain transport. In this study, 20-21-month-old Wistar rats were exposed to the chronic unpredictable mild stress (CUMS) protocol for 6 consecutive weeks to explore the long-term effects of luteolin on behavior, 5-MTHF levels, hippocampal neurogenesis, and folate brain transport of the CP. In vitro primary hippocampal neural stem cells (NSCs) cultured in media containing 10% CSF from each group of rats and choroid plexus epithelial cells (CPECs) cultured in media containing 20 μM luteolin were treated with 100 μM corticosterone and 40 mg/ml D-galactose. We found that aged rats exposed to CUMS showed a significantly reduced sucrose preference, decreased locomotion activity in the open field test and accuracy of the Morris water maze test, increased immobility time in the forced swimming test, accelerated dysfunctional neurogenesis and neuronal loss in the dentate gyrus of LOD rats, as well as decreased CSF and hippocampus 5-MTHF levels, and zona occludens protein 1 (ZO-1), proton-coupled folate transporter (PCFT), and reduced folate carrier (RFC) protein levels. In vitro assays showed media containing 10% aged CSF or LOD+ Luteolin-CSF significantly increased the viability of CORT + D-gal-injured NSCs and alleviated dysfunctional neurogenesis and neuronal loss compared with the CORT + D-gal medium. However, media containing 10% LOD-CSF had no such effect. In the meantime, induction of CORT + D-gal significantly decreased the ZO-1, PCFT, RFC, and folate receptor alpha (FR-α) protein levels and transepithelial electrical resistance in rat CPECs. As expected, luteolin treatment was effective in improving these abnormal changes. These findings suggested that luteolin could ameliorate CUMS-induced LOD-like behaviors by enhancing the folate brain transport.
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Affiliation(s)
- Hui-Zhen Li
- Research Center for Basic Integrative Medicine, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Kai-Ge Liu
- Research Center for Basic Integrative Medicine, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Ning-Xi Zeng
- Research Center for Basic Integrative Medicine, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Xiao-Feng Wu
- Research Center for Basic Integrative Medicine, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Wen-Jun Lu
- Research Center for Basic Integrative Medicine, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Han-Fang Xu
- Research Center for Basic Integrative Medicine, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Can Yan
- Research Center for Basic Integrative Medicine, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Li-Li Wu
- Research Center for Basic Integrative Medicine, Guangzhou University of Chinese Medicine, Guangzhou, China
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14
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Hou Z, Gangjee A, Matherly LH. The evolving biology of the proton‐coupled folate transporter: New insights into regulation, structure, and mechanism. FASEB J 2022; 36:e22164. [PMID: 35061292 PMCID: PMC8978580 DOI: 10.1096/fj.202101704r] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 12/15/2021] [Accepted: 01/03/2022] [Indexed: 01/19/2023]
Abstract
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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Affiliation(s)
- Zhanjun Hou
- Molecular Therapeutics Program Barbara Ann Karmanos Cancer Institute Detroit Michigan USA
- Department of Oncology Wayne State University School of Medicine Detroit Michigan USA
| | - Aleem Gangjee
- Division of Medicinal Chemistry Graduate School of Pharmaceutical Sciences Duquesne University Pittsburgh Pennsylvania USA
| | - Larry H. Matherly
- Molecular Therapeutics Program Barbara Ann Karmanos Cancer Institute Detroit Michigan USA
- Department of Oncology Wayne State University School of Medicine Detroit Michigan USA
- Department of Pharmacology Wayne State University School of Medicine Detroit Michigan USA
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15
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Kobayashi R, Kishimoto K, Sano H, Hori D, Kobayashi K. Long follow-up of hereditary folate malabsorption using intravenous folinate. Pediatr Int 2022; 64:e14667. [PMID: 34529878 DOI: 10.1111/ped.14667] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 02/05/2021] [Accepted: 02/16/2021] [Indexed: 11/28/2022]
Affiliation(s)
- Ryoji Kobayashi
- Department of Hematology/Oncology for Children and Adolescents, Sapporo Hokuyu Hospital, Shiroishiku, Sapporo, Japan
| | - Kenji Kishimoto
- Department of Hematology/Oncology for Children and Adolescents, Sapporo Hokuyu Hospital, Shiroishiku, Sapporo, Japan
| | - Hirozumi Sano
- Department of Hematology/Oncology for Children and Adolescents, Sapporo Hokuyu Hospital, Shiroishiku, Sapporo, Japan
| | - Daiki Hori
- Department of Hematology/Oncology for Children and Adolescents, Sapporo Hokuyu Hospital, Shiroishiku, Sapporo, Japan
| | - Kunihiko Kobayashi
- Department of Hematology/Oncology for Children and Adolescents, Sapporo Hokuyu Hospital, Shiroishiku, Sapporo, Japan
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16
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Folate Transport and One-Carbon Metabolism in Targeted Therapies of Epithelial Ovarian Cancer. Cancers (Basel) 2021; 14:cancers14010191. [PMID: 35008360 PMCID: PMC8750473 DOI: 10.3390/cancers14010191] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Revised: 12/23/2021] [Accepted: 12/27/2021] [Indexed: 12/20/2022] Open
Abstract
New therapies are urgently needed for epithelial ovarian cancer (EOC), the most lethal gynecologic malignancy. To identify new approaches for targeting EOC, metabolic vulnerabilities must be discovered and strategies for the selective delivery of therapeutic agents must be established. Folate receptor (FR) α and the proton-coupled folate transporter (PCFT) are expressed in the majority of EOCs. FRβ is expressed on tumor-associated macrophages, a major infiltrating immune population in EOC. One-carbon (C1) metabolism is partitioned between the cytosol and mitochondria and is important for the synthesis of nucleotides, amino acids, glutathione, and other critical metabolites. Novel inhibitors are being developed with the potential for therapeutic targeting of tumors via FRs and the PCFT, as well as for inhibiting C1 metabolism. In this review, we summarize these exciting new developments in targeted therapies for both tumors and the tumor microenvironment in EOC.
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17
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Parker JL, Deme JC, Kuteyi G, Wu Z, Huo J, Goldman ID, Owens RJ, Biggin PC, Lea SM, Newstead S. Structural basis of antifolate recognition and transport by PCFT. Nature 2021; 595:130-134. [PMID: 34040256 PMCID: PMC9990147 DOI: 10.1038/s41586-021-03579-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Accepted: 04/23/2021] [Indexed: 12/20/2022]
Abstract
Folates (also known as vitamin B9) have a critical role in cellular metabolism as the starting point in the synthesis of nucleic acids, amino acids and the universal methylating agent S-adenylsmethionine1,2. Folate deficiency is associated with a number of developmental, immune and neurological disorders3-5. Mammals cannot synthesize folates de novo; several systems have therefore evolved to take up folates from the diet and distribute them within the body3,6. The proton-coupled folate transporter (PCFT) (also known as SLC46A1) mediates folate uptake across the intestinal brush border membrane and the choroid plexus4,7, and is an important route for the delivery of antifolate drugs in cancer chemotherapy8-10. How PCFT recognizes folates or antifolate agents is currently unclear. Here we present cryo-electron microscopy structures of PCFT in a substrate-free state and in complex with a new-generation antifolate drug (pemetrexed). Our results provide a structural basis for understanding antifolate recognition and provide insights into the pH-regulated mechanism of folate transport mediated by PCFT.
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Affiliation(s)
- Joanne L Parker
- Department of Biochemistry, University of Oxford, Oxford, UK.
| | - Justin C Deme
- Dunn School of Pathology, University of Oxford, Oxford, UK
- Central Oxford Structural Molecular Imaging Centre, University of Oxford, Oxford, UK
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, USA
| | - Gabriel Kuteyi
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Zhiyi Wu
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Jiandong Huo
- Structural Biology, The Rosalind Franklin Institute, Didcot, UK
- Division of Structural Biology, The Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
- Protein Production UK, The Research Complex at Harwell, Didcot, UK
| | - I David Goldman
- Departments of Molecular Pharmacology and Medicine, Albert Einstein College of Medicine, New York, NY, USA
| | - Raymond J Owens
- Structural Biology, The Rosalind Franklin Institute, Didcot, UK
- Division of Structural Biology, The Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
- Protein Production UK, The Research Complex at Harwell, Didcot, UK
| | - Philip C Biggin
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Susan M Lea
- Dunn School of Pathology, University of Oxford, Oxford, UK.
- Central Oxford Structural Molecular Imaging Centre, University of Oxford, Oxford, UK.
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, USA.
| | - Simon Newstead
- Department of Biochemistry, University of Oxford, Oxford, UK.
- The Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, UK.
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18
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Gowda VK, Battina M, Shivappa SK, Benakappa N. Treatable Cause of Pancytopenia, Recurrent Infections and Refractory Epilepsy: Secondary to Hereditary Folate Malabsorption (HFM) Due to Novel Pathogenic Variant. Indian J Pediatr 2021; 88:586-588. [PMID: 33146883 DOI: 10.1007/s12098-020-03548-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Accepted: 10/14/2020] [Indexed: 10/23/2022]
Abstract
Hereditary folate malabsorption (HFM) is a rare disorder of proton-coupled folate transporter deficiency. It is characterized by macrocytic anemia, recurrent infections, and epilepsy. A five-year-old girl presented with recurrent pneumonia, diarrhea, and mouth ulcers. On examination, pallor, microcephaly with spastic quadriparesis was noted. On investigations, leukopenia and thrombocytopenia with megaloblastic bone marrow picture and low folate levels was found. HFM was diagnosed at two years of age and the child was treated with folinic acid. Her diagnosis was confirmed by whole-exome sequencing which revealed a novel pathogenic homozygous frameshift insertion variation (c.620dupG) in the exon 2 of the SLC46A1 gene which was further confirmed by Sanger sequencing. The child improved significantly except for a partial improvement in neurological symptoms.
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Affiliation(s)
- Vykuntaraju K Gowda
- Department of Pediatric Neurology, Indira Gandhi Institute of Child Health, Bangalore, Karnataka, 560029, India.
| | - Manojna Battina
- Department of Pediatric Neurology, Indira Gandhi Institute of Child Health, Bangalore, Karnataka, 560029, India
| | - Sanjay K Shivappa
- Department of Pediatric Medicine, Indira Gandhi Institute of Child Health, Bangalore, Karnataka, India
| | - Naveen Benakappa
- Department of Pediatric Medicine, Indira Gandhi Institute of Child Health, Bangalore, Karnataka, India
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19
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Huddar A, Chiplunkar S, Nagappa M, Govindaraj P, Sinha S, Taly AB, Sankaran BP. Child Neurology: Hereditary Folate Malabsorption. Neurology 2021; 97:40-43. [PMID: 33893200 DOI: 10.1212/wnl.0000000000012083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Akshata Huddar
- From the Department of Neurology (A.H., S.S.) and Department of Clinical Neurosciences & Neuromuscular Lab (S.C., M.B.B.S., P.D.) and Department of Neurology & Neuromuscular Lab (M.N., A.B.T.), Neurobiology Research Centre, the National Institute of Mental Health and Neuro-Sciences (NIMHANS); Institute of Bioinformatics (P.G.), Manipal Academy of Higher Education, Bangalore, India; and The Children Hospital at Westmead Clinical School (B.P.S.), Sydney Medical School, The Faculty of Medicine and Health, The University of Sydney, Australia
| | - Shwetha Chiplunkar
- From the Department of Neurology (A.H., S.S.) and Department of Clinical Neurosciences & Neuromuscular Lab (S.C., M.B.B.S., P.D.) and Department of Neurology & Neuromuscular Lab (M.N., A.B.T.), Neurobiology Research Centre, the National Institute of Mental Health and Neuro-Sciences (NIMHANS); Institute of Bioinformatics (P.G.), Manipal Academy of Higher Education, Bangalore, India; and The Children Hospital at Westmead Clinical School (B.P.S.), Sydney Medical School, The Faculty of Medicine and Health, The University of Sydney, Australia
| | - Madhu Nagappa
- From the Department of Neurology (A.H., S.S.) and Department of Clinical Neurosciences & Neuromuscular Lab (S.C., M.B.B.S., P.D.) and Department of Neurology & Neuromuscular Lab (M.N., A.B.T.), Neurobiology Research Centre, the National Institute of Mental Health and Neuro-Sciences (NIMHANS); Institute of Bioinformatics (P.G.), Manipal Academy of Higher Education, Bangalore, India; and The Children Hospital at Westmead Clinical School (B.P.S.), Sydney Medical School, The Faculty of Medicine and Health, The University of Sydney, Australia
| | - Periyasamy Govindaraj
- From the Department of Neurology (A.H., S.S.) and Department of Clinical Neurosciences & Neuromuscular Lab (S.C., M.B.B.S., P.D.) and Department of Neurology & Neuromuscular Lab (M.N., A.B.T.), Neurobiology Research Centre, the National Institute of Mental Health and Neuro-Sciences (NIMHANS); Institute of Bioinformatics (P.G.), Manipal Academy of Higher Education, Bangalore, India; and The Children Hospital at Westmead Clinical School (B.P.S.), Sydney Medical School, The Faculty of Medicine and Health, The University of Sydney, Australia
| | - Sanjib Sinha
- From the Department of Neurology (A.H., S.S.) and Department of Clinical Neurosciences & Neuromuscular Lab (S.C., M.B.B.S., P.D.) and Department of Neurology & Neuromuscular Lab (M.N., A.B.T.), Neurobiology Research Centre, the National Institute of Mental Health and Neuro-Sciences (NIMHANS); Institute of Bioinformatics (P.G.), Manipal Academy of Higher Education, Bangalore, India; and The Children Hospital at Westmead Clinical School (B.P.S.), Sydney Medical School, The Faculty of Medicine and Health, The University of Sydney, Australia
| | - Arun B Taly
- From the Department of Neurology (A.H., S.S.) and Department of Clinical Neurosciences & Neuromuscular Lab (S.C., M.B.B.S., P.D.) and Department of Neurology & Neuromuscular Lab (M.N., A.B.T.), Neurobiology Research Centre, the National Institute of Mental Health and Neuro-Sciences (NIMHANS); Institute of Bioinformatics (P.G.), Manipal Academy of Higher Education, Bangalore, India; and The Children Hospital at Westmead Clinical School (B.P.S.), Sydney Medical School, The Faculty of Medicine and Health, The University of Sydney, Australia
| | - Bindu Parayil Sankaran
- From the Department of Neurology (A.H., S.S.) and Department of Clinical Neurosciences & Neuromuscular Lab (S.C., M.B.B.S., P.D.) and Department of Neurology & Neuromuscular Lab (M.N., A.B.T.), Neurobiology Research Centre, the National Institute of Mental Health and Neuro-Sciences (NIMHANS); Institute of Bioinformatics (P.G.), Manipal Academy of Higher Education, Bangalore, India; and The Children Hospital at Westmead Clinical School (B.P.S.), Sydney Medical School, The Faculty of Medicine and Health, The University of Sydney, Australia.
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20
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O'Connor C, Wallace-Povirk A, Ning C, Frühauf J, Tong N, Gangjee A, Matherly LH, Hou Z. Folate transporter dynamics and therapy with classic and tumor-targeted antifolates. Sci Rep 2021; 11:6389. [PMID: 33737637 PMCID: PMC7973545 DOI: 10.1038/s41598-021-85818-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 03/05/2021] [Indexed: 01/03/2023] Open
Abstract
There are three major folate uptake systems in human tissues and tumors, including the reduced folate carrier (RFC), folate receptors (FRs) and proton-coupled folate transporter (PCFT). We studied the functional interrelationships among these systems for the novel tumor-targeted antifolates AGF94 (transported by PCFT and FRs but not RFC) and AGF102 (selective for FRs) versus the classic antifolates pemetrexed, methotrexate and PT523 (variously transported by FRs, PCFT and RFC). We engineered HeLa cell models to express FRα or RFC under control of a tetracycline-inducible promoter with or without constitutive PCFT. We showed that cellular accumulations of extracellular folates were determined by the type and levels of the major folate transporters, with PCFT and RFC prevailing over FRα, depending on expression levels and pH. Based on patterns of cell proliferation in the presence of the inhibitors, we established transport redundancy for RFC and PCFT in pemetrexed uptake, and for PCFT and FRα in AGF94 uptake; uptake by PCFT predominated for pemetrexed and FRα for AGF94. For methotrexate and PT523, uptake by RFC predominated even in the presence of PCFT or FRα. For both classic (methotrexate, PT523) and FRα-targeted (AGF102) antifolates, anti-proliferative activities were antagonized by PCFT, likely due to its robust activity in mediating folate accumulation. Collectively, our findings describe a previously unrecognized interplay among the major folate transport systems that depends on transporter levels and extracellular pH, and that determines their contributions to the uptake and anti-tumor efficacies of targeted and untargeted antifolates.
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Affiliation(s)
- Carrie O'Connor
- Departments of Oncology, Wayne State University School of Medicine, 421 E. Canfield, Detroit, MI, 48201, USA
| | - Adrianne Wallace-Povirk
- Departments of Oncology, Wayne State University School of Medicine, 421 E. Canfield, Detroit, MI, 48201, USA
| | - Changwen Ning
- Departments of Oncology, Wayne State University School of Medicine, 421 E. Canfield, Detroit, MI, 48201, USA
| | - Josephine Frühauf
- Departments of Oncology, Wayne State University School of Medicine, 421 E. Canfield, Detroit, MI, 48201, USA
| | - Nian Tong
- Division of Medicinal Chemistry, Duquesne University, Pittsburgh, PA, USA
| | - Aleem Gangjee
- Division of Medicinal Chemistry, Duquesne University, Pittsburgh, PA, USA
| | - Larry H Matherly
- Departments of Oncology, Wayne State University School of Medicine, 421 E. Canfield, Detroit, MI, 48201, USA.
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA.
- Molecular Therapeutics Program, Barbara Ann Karmanos Cancer Institute, Detroit, MI, USA.
| | - Zhanjun Hou
- Departments of Oncology, Wayne State University School of Medicine, 421 E. Canfield, Detroit, MI, 48201, USA.
- Molecular Therapeutics Program, Barbara Ann Karmanos Cancer Institute, Detroit, MI, USA.
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21
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Folylpoly-ɣ-glutamate synthetase association to the cytoskeleton: Implications to folate metabolon compartmentalization. J Proteomics 2021; 239:104169. [PMID: 33676037 DOI: 10.1016/j.jprot.2021.104169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 02/03/2021] [Accepted: 02/19/2021] [Indexed: 11/23/2022]
Abstract
Folates are essential for nucleotide biosynthesis, amino acid metabolism and cellular proliferation. Following carrier-mediated uptake, folates are polyglutamylated by folylpoly-ɣ-glutamate synthetase (FPGS), resulting in their intracellular retention. FPGS appears as a long isoform, directed to mitochondria via a leader sequence, and a short isoform reported as a soluble cytosolic protein (cFPGS). However, since folates are labile and folate metabolism is compartmentalized, we herein hypothesized that cFPGS is associated with the cytoskeleton, to couple folate uptake and polyglutamylation and channel folate polyglutamates to metabolon compartments. We show that cFPGS is a cytoskeleton-microtubule associated protein: Western blot analysis revealed that endogenous cFPGS is associated with the insoluble cellular fraction, i.e., cytoskeleton and membranes, but not with the cytosol. Mass spectrometry analysis identified the putative cFPGS interactome primarily consisting of microtubule subunits and cytoskeletal motor proteins. Consistently, immunofluorescence microscopy with cytosol-depleted cells demonstrated the association of cFPGS with the cytoskeleton and unconventional myosin-1c. Furthermore, since anti-microtubule, anti-actin cytoskeleton, and coatomer dissociation-inducing agents yielded perinuclear pausing of cFPGS, we propose an actin- and microtubule-dependent transport of cFPGS between the ER-Golgi and the plasma membrane. These novel findings support the coupling of folate transport with polyglutamylation and folate channeling to intracellular metabolon compartments. SIGNIFICANCE: FPGS, an essential enzyme catalyzing intracellular folate polyglutamylation and efficient retention, was described as a soluble cytosolic enzyme in the past 40 years. However, based on the lability of folates and the compartmentalization of folate metabolism and nucleotide biosynthesis, we herein hypothesized that cytoplasmic FPGS is associated with the cytoskeleton, to couple folate transport and polyglutamylation as well as channel folate polyglutamates to biosynthetic metabolon compartments. Indeed, using complementary techniques including Mass-spectrometry proteomics and fluorescence microscopy, we show that cytoplasmic FPGS is associated with the cytoskeleton and unconventional myosin-1c. This novel cytoskeletal localization of cytoplasmic FPGS supports the dynamic channeling of polyglutamylated folates to metabolon compartments to avoid oxidation and intracellular dilution of folates, while enhancing folate-dependent de novo biosynthesis of nucleotides and DNA/protein methylation.
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Pharmacoresistant Epilepsy in Childhood: Think of the Cerebral Folate Deficiency, a Treatable Disease. Brain Sci 2020; 10:brainsci10110762. [PMID: 33105619 PMCID: PMC7690394 DOI: 10.3390/brainsci10110762] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 10/16/2020] [Accepted: 10/19/2020] [Indexed: 12/11/2022] Open
Abstract
Cerebral folate deficiency (CFD) is a neurological disorder characterized by low levels of 5-methyltetrahydrofolate (5-MTHF) in the cerebrospinal fluid (CSF). The prevalence of this autosomal recessive disorder is estimated to be <1/1,000,000. Fifteen different pathogenic variants in the folate receptor 1 gene (FOLR1) encoding the receptor of folate α (FRα) have already been described. We present a new pathogenic variation in the FOLR1 in a childhood-stage patient. We aim to establish the core structure of the FRα protein mandatory for its activity. A three-year-old child was admitted at hospital for a first febrile convulsions episode. Recurrent seizures without fever also occurred a few months later, associated with motor and cognitive impairment. Various antiepileptic drugs failed to control seizures. Magnetic resonance imaging (MRI) showed central hypomyelination and biological analysis revealed markedly low levels of 5-MTHF in CSF. Next generation sequencing (NGS) confirmed a CFD with a FOLR1 homozygous variation (c.197 G > A, p.Cys66Tyr). This variation induces an altered folate receptor α protein and underlines the role of a disulfide bond: Cys66-Cys109, essential to transport 5-MTHF into the central nervous system. Fortunately, this severe form of CFD had remarkably responded to high doses of oral folinic acid combined with intravenous administrations.
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Zhan HQ, Najmi M, Lin K, Aluri S, Fiser A, Goldman ID, Zhao R. A proton-coupled folate transporter mutation causing hereditary folate malabsorption locks the protein in an inward-open conformation. J Biol Chem 2020; 295:15650-15661. [PMID: 32893190 DOI: 10.1074/jbc.ra120.014757] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 08/26/2020] [Indexed: 11/06/2022] Open
Abstract
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, and Glu) and polar (Thr, Ser, and Gln) Phe-392 substitutions and minimal function with some neutral substitutions; however, F392M retained full function. Using the substituted-cysteine accessibility method (with N-biotinyl aminoethyl methanethiosulfonate labeling), Phe-392 mutations causing loss of function, although 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 Gly-305 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 V max, accompanied by a decreased influx Kt (4.5-fold) and Ki (3-fold). The data indicate that Phe-392 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 Phe-392 PCFT mutations lock the protein in its inward-open conformation. Reach (length) and hydrophobicity of Phe-392 appear to be features required for full activity.
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Affiliation(s)
- He-Qin Zhan
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, USA; Department of Pathology, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Mitra Najmi
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Kai Lin
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, USA; Air Force Medical Center, People's Liberation Army, Beijing, China
| | - Srinivas Aluri
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Andras Fiser
- Department of Systems and Computational Biology, Albert Einstein College of Medicine, Bronx, New York, USA; Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, USA
| | - I David Goldman
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, USA; Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, USA.
| | - Rongbao Zhao
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, USA; Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, USA
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Li H, Wang D, Wu H, Shen H, Lv D, Zhang Y, Lu H, Yang J, Tang Y, Li M. SLC46A1 contributes to hepatic iron metabolism by importing heme in hepatocytes. Metabolism 2020; 110:154306. [PMID: 32621820 DOI: 10.1016/j.metabol.2020.154306] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 06/23/2020] [Accepted: 06/25/2020] [Indexed: 02/06/2023]
Abstract
BACKGROUND Iron is finely regulated due to its vital roles in organisms and the peroxidase reactivity if excess. Solute Carrier Family 46 Member 1 (SLC46A1), also named PCFT or HCP1, is the main importer of heme‑iron in the intestine, but has a high abundance in the liver. Since the liver has a central role in iron homeostasis, whether SLC46A1 regulates hepatic iron metabolism is of interest to be identified. METHODS The recombinant adeno-associated virus vectors were used to hepatic-specifically inhibit SLC46A1 expression to observe its effects on hepatic iron metabolism. Then the abilities of SLC46A1 in importing heme and folate, and consequent alterations of iron content in hepatocytes were determined. Furthermore, effects of iron on SLC46A1 expression were investigated both in vitro and in vivo. RESULTS The hepatocyte-specific inhibition of SLC46A1 decreases iron content in the liver and increases iron content in serum. Expressions of iron-related molecules, transferrin receptor 1, hepcidin and ferroportin, are correspondingly altered. Interestingly, free heme concentration in serum is increased, indicating a decreased import of heme by the liver. In hepatocytes, SLC46A1 is capable of importing hemin, increasing intracellular iron content. The import of hemin by SLC46A1 is unaffected by its other substrate, folate. Instead, hemin treatment decreases SLC46A1 expression, reducing the import of folate. In addition, SLC46A1 itself shows to be iron-responsive both in vivo and in vitro, making it available for regulating iron metabolism. CONCLUSION The results elucidate that SLC46A1 regulates iron metabolism in the liver through a folate-independent manner of importing heme. The iron-responsive characters of SLC46A1 give us a new clue to link heme or iron overload with folate deficiency diseases.
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Affiliation(s)
- Hongxia Li
- Department of Nutrition, Second Military Medical University, Shanghai, China
| | - Dongyao Wang
- School of Pharmacy, Second Military Medical University, Shanghai, China; Faculty of Pharmacy, Shanghai University, Shanghai, China
| | - Huiwen Wu
- Department of Nutrition, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Hui Shen
- Department of Nutrition, Second Military Medical University, Shanghai, China
| | - Diya Lv
- School of Pharmacy, Second Military Medical University, Shanghai, China
| | - Yinyin Zhang
- Department of Nutrition, Second Military Medical University, Shanghai, China
| | - Hongtao Lu
- Department of Nutrition, Second Military Medical University, Shanghai, China
| | - Jianxin Yang
- Department of Nutrition, Second Military Medical University, Shanghai, China
| | - Yuxiao Tang
- Department of Nutrition, Second Military Medical University, Shanghai, China.
| | - Min Li
- Department of Nutrition, Second Military Medical University, Shanghai, China; Institute of International Medical Science and Technology, Sanda University, Shanghai, China.
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Miyashita N, Kurosawa H, Yamashita Y, Miki Y, Ishida T. Pulmonary hypertension related to hereditary folate malabsorption in an infant. Pediatr Int 2020; 62:1119-1120. [PMID: 32893915 DOI: 10.1111/ped.14266] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 03/21/2020] [Accepted: 04/15/2020] [Indexed: 11/27/2022]
Affiliation(s)
- Norihisa Miyashita
- Division of Pediatric Critical Care Medicine, Hyogo Prefectural Kobe Children's Hospital, Kobe, Hyogo, Japan
| | - Hiroshi Kurosawa
- Division of Pediatric Critical Care Medicine, Hyogo Prefectural Kobe Children's Hospital, Kobe, Hyogo, Japan
| | - Yuriko Yamashita
- Division of Pediatric Critical Care Medicine, Hyogo Prefectural Kobe Children's Hospital, Kobe, Hyogo, Japan
| | - Yasunobu Miki
- Division of Cardiology, Hyogo Prefectural Kobe Children's Hospital, Kobe, Hyogo, Japan
| | - Toshiaki Ishida
- Division of Hematology and Oncology, Hyogo Prefectural Kobe Children's Hospital, Kobe, Hyogo, Japan
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26
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Alam C, Hoque MT, Sangha V, Bendayan R. Nuclear respiratory factor 1 (NRF-1) upregulates the expression and function of reduced folate carrier (RFC) at the blood-brain barrier. FASEB J 2020; 34:10516-10530. [PMID: 32543769 DOI: 10.1096/fj.202000239rr] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 05/25/2020] [Accepted: 05/26/2020] [Indexed: 01/10/2023]
Abstract
Folates are important for neurodevelopment and cognitive function. Folate transport across biological membranes is mediated by three major pathways: folate receptor alpha (FRα), proton-coupled folate transporter (PCFT), and reduced folate carrier (RFC). Brain folate transport primarily occurs at the choroid plexus through FRα and PCFT; inactivation of these transport systems results in suboptimal folate levels in the cerebrospinal fluid (CSF) causing childhood neurological disorders. Our group has reported that upregulation of RFC at the blood-brain barrier (BBB) through interactions with specific transcription factors, that is, vitamin D receptor (VDR) could increase brain folate delivery. This study investigates the role of nuclear respiratory factor 1 (NRF-1) in the regulation of RFC at the BBB. Activation of NRF-1/PGC-1α signaling through treatment with its specific ligand, pyrroloquinoline quinone (PQQ), significantly induced RFC expression and transport activity in hCMEC/D3 cells. In contrast, transfection with NRF-1 or PGC-1α targeting siRNA downregulated RFC functional expression in the same cell system. Applying chromatin immunoprecipitation (ChIP) assay, we further demonstrated that PQQ treatment increased NRF-1 binding to putative NRF-1 binding sites within the SLC19A1 promoter, which encodes for RFC. Additionally, in vivo treatment of wild type mice with PQQ-induced RFC expression in isolated mouse brain capillaries. Together, these findings demonstrate that NRF-1/PGC-1α activation by PQQ upregulates RFC functional expression at the BBB and could potentially enhance brain folate uptake.
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Affiliation(s)
- Camille Alam
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, ON, Canada
| | - Md Tozammel Hoque
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, ON, Canada
| | - Vishal Sangha
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, ON, Canada
| | - Reina Bendayan
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, ON, Canada
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Alam C, Kondo M, O'Connor DL, Bendayan R. Clinical Implications of Folate Transport in the Central Nervous System. Trends Pharmacol Sci 2020; 41:349-361. [PMID: 32200980 DOI: 10.1016/j.tips.2020.02.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Revised: 02/19/2020] [Accepted: 02/21/2020] [Indexed: 12/11/2022]
Abstract
Folates are essential for key biosynthetic processes in mammalian cells and play a crucial role in the maintenance of central nervous system homeostasis. Mammals lack the metabolic capacity for folate biosynthesis; hence, folate requirements are largely met through dietary sources. To date, three major folate transport pathways have been characterized: the folate receptors (FRs), reduced folate carrier (RFC), and proton-coupled folate transporter (PCFT). This article reviews current knowledge on the role of folate transport systems in mediating folate delivery to vital tissues, particularly the brain, and how these pathways are modulated by various regulatory mechanisms. We will also briefly highlight the clinical significance of cerebral folate transport in relation to neurodevelopmental disorders associated with folate deficiency.
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Affiliation(s)
- Camille Alam
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, Ontario M5S 3M2, Canada
| | - Misaki Kondo
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, Ontario M5S 3M2, Canada
| | - Deborah L O'Connor
- Translational Medicine Program, The Hospital for Sick Children, 686 Bay Street, Toronto, Ontario M5G 0A4, Canada; Department of Nutritional Sciences, University of Toronto, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada
| | - Reina Bendayan
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, Ontario M5S 3M2, Canada.
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Lubout CMA, Goorden SMI, van den Hurk K, Jaeger B, Jager NGL, van Koningsbruggen S, Chegary M, van Karnebeek CDM. Successful Treatment of Hereditary Folate Malabsorption With Intramuscular Folinic Acid. Pediatr Neurol 2020; 102:62-66. [PMID: 31371121 DOI: 10.1016/j.pediatrneurol.2019.06.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 06/08/2019] [Accepted: 06/12/2019] [Indexed: 01/28/2023]
Abstract
BACKGROUND Hereditary folate malabsorption is a multisystem disease owing to biallelic variants in the gene encoding the proton-coupled folate transporter. Hereditary folate malabsorption is treated with folinic acid, aimed to restore blood and cerebrospinal fluid folate levels. Little is known as to whether oral or intramuscular supplementation of folinic acid is most effective. METHODS Here we describe a one-year-old boy with hereditary folate malabsorption presenting with the typical features including failure to thrive, aphthous stomatitis, macrocytic anemia along with severe developmental impairment and epilepsy, as well as a magnetic resonance imaging of the brain showing bilateral occipital, cortical calcifications characteristic of hereditary folate malabsorption. We compared the effect of treatment with oral folinic acid versus intramuscular folinic acid supplementation by measuring plasma and cerebrospinal fluid folate levels. RESULTS Compared with oral administration, intramuscular treatment resulted in higher folate levels in blood and, most importantly, normalization of folate levels in cerebrospinal fluid. Clinically, nearly all systemic and neurological symptoms resolved. CONCLUSION Normal cerebrospinal fluid folate levels can be achieved in individuals with hereditary folate malabsorption with intramuscular (but not with oral) administration of folinic acid.
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Affiliation(s)
- Charlotte M A Lubout
- Department of Pediatric Metabolic Diseases, Emma Children's Hospital, Amsterdam Gastro-Enterology & Metabolism Research Institute, Amsterdam University Medical Centres, Amsterdam, The Netherlands
| | - Susanna M I Goorden
- Department of Clinical Chemistry, Laboratory of Genetic Metabolic Diseases, Amsterdam University Medical Centres, Amsterdam, The Netherlands
| | - Karin van den Hurk
- Department of Clinical Chemistry, OLVG Lab BV, Amsterdam, The Netherlands
| | - Bregje Jaeger
- Department of Pediatric Neurology, Emma Children's Hospital, Amsterdam University Medical Centres, Amsterdam, The Netherlands
| | - Nynke G L Jager
- Department of Clinical Pharmacology and Pharmacy, Amsterdam University Medical Centres, Amsterdam, The Netherlands
| | | | - Malika Chegary
- Department of Pediatrics, OLVG, Amsterdam, The Netherlands
| | - Clara D M van Karnebeek
- Department of Pediatric Metabolic Diseases, Emma Children's Hospital, Amsterdam Gastro-Enterology & Metabolism Research Institute, Amsterdam University Medical Centres, Amsterdam, The Netherlands; Department of Clinical Genetics, Amsterdam University Medical Centres, Amsterdam, The Netherlands.
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Brown TP, Ganapathy V. Lactate/GPR81 signaling and proton motive force in cancer: Role in angiogenesis, immune escape, nutrition, and Warburg phenomenon. Pharmacol Ther 2019; 206:107451. [PMID: 31836453 DOI: 10.1016/j.pharmthera.2019.107451] [Citation(s) in RCA: 171] [Impact Index Per Article: 34.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 11/22/2019] [Indexed: 12/15/2022]
Abstract
Reprogramming of biochemical pathways is a hallmark of cancer cells, and generation of lactic acid from glucose/glutamine represents one of the consequences of such metabolic alterations. Cancer cells export lactic acid out to prevent intracellular acidification, not only increasing lactate levels but also creating an acidic pH in extracellular milieu. Lactate and protons in tumor microenvironment are not innocuous bystander metabolites but have special roles in promoting tumor-cell proliferation and growth. Lactate functions as a signaling molecule by serving as an agonist for the G-protein-coupled receptor GPR81, involving both autocrine and paracrine mechanisms. In the autocrine pathway, cancer cell-generated lactate activates GPR81 on cancer cells; in the paracrine pathway, cancer cell-generated lactate activates GPR81 on immune cells, endothelial cells, and adipocytes present in tumor stroma. The end result of GPR81 activation is promotion of angiogenesis, immune evasion, and chemoresistance. The acidic pH creates an inwardly directed proton gradient across the cancer-cell plasma membrane, which provides driving force for proton-coupled transporters in cancer cells to enhance supply of selective nutrients. There are several molecular targets in the pathways involved in the generation of lactic acid by cancer cells and its role in tumor promotion for potential development of novel anticancer therapeutics.
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Affiliation(s)
- Timothy P Brown
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Vadivel Ganapathy
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
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Identification of the amino acid residue responsible for the myricetin sensitivity of human proton-coupled folate transporter. Sci Rep 2019; 9:18105. [PMID: 31792273 PMCID: PMC6889420 DOI: 10.1038/s41598-019-54367-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2019] [Accepted: 11/12/2019] [Indexed: 11/09/2022] Open
Abstract
Human proton-coupled folate transporter (hPCFT/SLC46A1) has recently been found to be inhibited by myricetin by a sustained mechanism, raising a concern that the inhibition might lead to malabsorption of folates in the intestine, where hPCFT works for their epithelial uptake. However, rat PCFT (rPCFT) has more recently been found not to be inhibited by myricetin. Prompted by this finding, we attempted to determine the amino acid residue involved in that by analyses comparing between hPCFT and rPCFT. In the initial analysis, chimeric constructs prepared from hPCFT and rPCFT were examined for myricetin sensitivity to determine the hPCFT segment involved in the sensitivity. Focusing on the thereby determined segment from 83rd to 186th amino acid residue, hPCFT mutants having a designated amino acid residue replaced with its counterpart in rPCFT were prepared for the subsequent analysis. Among them, only G158N-substituted hPCFT was found to be transformed to be insensitive to myricetin and, accordingly, oppositely N158G-substituted rPCFT was transformed to be sensitive to myricetin. These results indicate the critical role of Gly158 in the myricetin sensitivity of hPCFT. This finding would help advance the elucidation of the mechanism of the myricetin-induced inhibition of hPCFT and manage the potential risk arising from that.
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Tozawa Y, Abdrabou SSMA, Nogawa-Chida N, Nishiuchi R, Ishida T, Suzuki Y, Sano H, Kobayashi R, Kishimoto K, Ohara O, Imai K, Naruto T, Kobayashi K, Ariga T, Yamada M. A deep intronic mutation of c.1166-285 T > G in SLC46A1 is shared by four unrelated Japanese patients with hereditary folate malabsorption (HFM). Clin Immunol 2019; 208:108256. [DOI: 10.1016/j.clim.2019.108256] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 08/29/2019] [Accepted: 09/02/2019] [Indexed: 02/07/2023]
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Upregulation of reduced folate carrier by vitamin D enhances brain folate uptake in mice lacking folate receptor alpha. Proc Natl Acad Sci U S A 2019; 116:17531-17540. [PMID: 31405972 DOI: 10.1073/pnas.1907077116] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Folates are critical for central nervous system function. Folate transport is mediated by 3 major pathways, reduced folate carrier (RFC), proton-coupled folate transporter (PCFT), and folate receptor alpha (FRα/Folr1), known to be regulated by ligand-activated nuclear receptors. Cerebral folate delivery primarily occurs at the choroid plexus through FRα and PCFT; inactivation of these transport systems can result in very low folate levels in the cerebrospinal fluid causing childhood neurodegenerative disorders. These disorders have devastating effects in young children, and current therapeutic approaches are not sufficiently effective. Our group has previously reported in vitro that functional expression of RFC at the blood-brain barrier (BBB) and its upregulation by the vitamin D nuclear receptor (VDR) could provide an alternative route for brain folate uptake. In this study, we further demonstrated in vivo, using Folr1 knockout (KO) mice, that loss of FRα led to a substantial decrease of folate delivery to the brain and that pretreatment of Folr1 KO mice with the VDR activating ligand, calcitriol (1,25-dihydroxyvitamin D3), resulted in over a 6-fold increase in [13C5]-5-formyltetrahydrofolate ([13C5]-5-formylTHF) concentration in brain tissues, with levels comparable to wild-type animals. Brain-to-plasma concentration ratio of [13C5]-5-formylTHF was also significantly higher in calcitriol-treated Folr1 KO mice (15-fold), indicating a remarkable enhancement in brain folate delivery. These findings demonstrate that augmenting RFC functional expression at the BBB could effectively compensate for the loss of Folr1-mediated folate uptake at the choroid plexus, providing a therapeutic approach for neurometabolic disorders caused by defective brain folate transport.
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Pope S, Artuch R, Heales S, Rahman S. Cerebral folate deficiency: Analytical tests and differential diagnosis. J Inherit Metab Dis 2019; 42:655-672. [PMID: 30916789 DOI: 10.1002/jimd.12092] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 03/19/2019] [Accepted: 03/25/2019] [Indexed: 11/07/2022]
Abstract
Cerebral folate deficiency is typically defined as a deficiency of the major folate species 5-methyltetrahydrofolate in the cerebrospinal fluid (CSF) in the presence of normal peripheral total folate levels. However, it should be noted that cerebral folate deficiency is also often used to describe conditions where CSF 5-MTHF is low, in the presence of low or undefined peripheral folate levels. Known defects of folate transport are deficiency of the proton coupled folate transporter, associated with systemic as well as cerebral folate deficiency, and deficiency of the folate receptor alpha, leading to an isolated cerebral folate deficiency associated with intractable seizures, developmental delay and/or regression, progressive ataxia and choreoathetoid movement disorders. Inborn errors of folate metabolism include deficiencies of the enzymes methylenetetrahydrofolate reductase, dihydrofolate reductase and 5,10-methenyltetrahydrofolate synthetase. Cerebral folate deficiency is potentially a treatable condition and so prompt recognition of these inborn errors and initiation of appropriate therapy is of paramount importance. Secondary cerebral folate deficiency may be observed in other inherited metabolic diseases, including disorders of the mitochondrial oxidative phosphorylation system, serine deficiency, and pyridoxine dependent epilepsy. Other secondary causes of cerebral folate deficiency include the effects of drugs, immune response activation, toxic insults and oxidative stress. This review describes the absorption, transport and metabolism of folate within the body; analytical methods to measure folate species in blood, plasma and CSF; inherited and acquired causes of cerebral folate deficiency; and possible treatment options in those patients found to have cerebral folate deficiency.
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Affiliation(s)
- Simon Pope
- Neurometabolic Unit, National Hospital for Neurology, London, UK
| | - Rafael Artuch
- Clinical Biochemistry Department, Institut de Recerca Sant Joan de Déu and CIBERER, ISCIII, Barcelona, Spain
| | - Simon Heales
- Neurometabolic Unit, National Hospital for Neurology, London, UK
- Department of Chemical Pathology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
- Mitochondrial Research Group, UCL Great Ormond Street Institute of Child Health, London, UK
| | - Shamima Rahman
- Mitochondrial Research Group, UCL Great Ormond Street Institute of Child Health, London, UK
- Department of Metabolic Medicine, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
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Regulation of differential proton-coupled folate transporter gene expression in human tumors: transactivation by KLF15 with NRF-1 and the role of Sp1. Biochem J 2019; 476:1247-1266. [PMID: 30914440 DOI: 10.1042/bcj20180394] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 03/07/2019] [Accepted: 03/26/2019] [Indexed: 12/18/2022]
Abstract
Tumors can be therapeutically targeted with novel antifolates (e.g. AGF94) that are selectively transported by the human proton-coupled folate transporter (hPCFT). Studies were performed to determine the transcription regulation of hPCFT in tumors and identify possible mechanisms that contribute to the highly disparate levels of hPCFT in HepG2 versus HT1080 tumor cells. Transfection of hPCFT-null HT1080 cells with hPCFT restored transport and sensitivity to AGF94 Progressive deletions of the hPCFT promoter construct (-2005 to +96) and reporter gene assays in HepG2 and HT1080 cells confirmed differences in hPCFT transactivation and localized a minimal promoter to between positions -50 and +96. The minimal promoter included KLF15, GC-Box and NRF-1 cis-binding elements whose functional importance was confirmed by promoter deletions and mutations of core consensus sequences and reporter gene assays. In HepG2 cells, NRF-1, KLF15 and Sp1 transcripts were increased over HT1080 cells by ∼5.1-, ∼44-, and ∼2.4-fold, respectively. In Drosophila SL2 cells, transfection with KLF15 and NRF-1 synergistically activated the hPCFT promoter; Sp1 was modestly activating or inhibitory. Chromatin immunoprecipitation and electrophoretic mobility shift assay (EMSA) and supershifts confirmed differential binding of KLF15, Sp1, and NRF-1 to the hPCFT promoter in HepG2 and HT1080 cells that paralleled hPCFT levels. Treatment of HT1080 nuclear extracts (NE) with protein kinase A increased Sp1 binding to its consensus sequence by EMSA, suggesting a role for Sp1 phosphorylation in regulating hPCFT transcription. A better understanding of determinants of hPCFT transcriptional control may identify new therapeutic strategies for cancer by modulating hPCFT levels in combination with hPCFT-targeted antifolates.
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Aluri S, Zhao R, Lin K, Shin DS, Fiser A, Goldman ID. Substitutions that lock and unlock the proton-coupled folate transporter (PCFT-SLC46A1) in an inward-open conformation. J Biol Chem 2019; 294:7245-7258. [PMID: 30858177 DOI: 10.1074/jbc.ra118.005533] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 03/06/2019] [Indexed: 11/06/2022] Open
Abstract
The proton-coupled folate transporter (PCFT) mediates intestinal absorption of folates and their transport from blood to cerebrospinal fluid across the choroid plexus. Substitutions at Asp-109 in the first intracellular loop between the first and second transmembrane domains (TMDs) abolish PCFT function, but protein expression and trafficking to the cell membrane are retained. Here, we used site-directed mutagenesis, the substituted-cysteine accessibility method, functional analyses, and homology modeling to determine whether the D109A substitution locks PCFT in one of its conformational states. Cys-substituted residues lining the PCFT aqueous translocation pathway and accessible in WT PCFT to the membrane-impermeable cysteine-biotinylation reagent, MTSEA-biotin, lost accessibility when introduced into the D109A scaffold. Substitutions at Gly-305 located exofacially within the eighth TMD, particularly with bulky residues, when introduced into the D109A scaffold largely restored function and MTSEA-biotin accessibility to Cys-substituted residues within the pathway. Likewise, Ser-196 substitution in the fifth TMD, predicted by homology modeling to be in proximity to Gly-305, also partially restored function found in solute transporters, is critical to oscillation of the carrier among its conformational states. Substitutions at Asp-109 and Gly-112 lock PCFT in an inward-open conformation, resulting in the loss of function. However, the integrity of the locked protein is preserved, indicated by the restoration of function after insertion of a second "unlocking" mutation. and accessibility. Similarly, the inactivating G112K substitution within the first intracellular loop was partially reactivated by introducing the G305L substitution. These data indicate that the first intracellular loop, with a sequence identical to "motif A" (GXXXDXXGR(R/K)).
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Affiliation(s)
| | | | - Kai Lin
- From the Departments of Pharmacology.,the Air Force Medical Center, PLA, Beijing 100142, China
| | | | - Andras Fiser
- Systems and Computational Biology, and.,Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461 and
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Kok DE, Steegenga WT, Smid EJ, Zoetendal EG, Ulrich CM, Kampman E. Bacterial folate biosynthesis and colorectal cancer risk: more than just a gut feeling. Crit Rev Food Sci Nutr 2018; 60:244-256. [DOI: 10.1080/10408398.2018.1522499] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Dieuwertje E. Kok
- Division of Human Nutrition and Health, Wageningen University & Research, Wageningen, The Netherlands
| | - Wilma T. Steegenga
- Division of Human Nutrition and Health, Wageningen University & Research, Wageningen, The Netherlands
| | - Eddy J. Smid
- Laboratory of Food Microbiology, Wageningen University & Research, Wageningen, The Netherlands
| | - Erwin G. Zoetendal
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, The Netherlands
| | - Cornelia M. Ulrich
- Department of Population Health Sciences and Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah, USA
| | - Ellen Kampman
- Division of Human Nutrition and Health, Wageningen University & Research, Wageningen, The Netherlands
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Evaluation of the effects of antiepileptic drugs on folic acid uptake by human placental choriocarcinoma cells. Toxicol In Vitro 2018; 48:104-110. [DOI: 10.1016/j.tiv.2017.12.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 10/22/2017] [Accepted: 12/05/2017] [Indexed: 01/19/2023]
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Zhao R, Najmi M, Aluri S, Spray DC, Goldman ID. Concentrative Transport of Antifolates Mediated by the Proton-Coupled Folate Transporter (SLC46A1); Augmentation by a HEPES Buffer. Mol Pharmacol 2018; 93:208-215. [PMID: 29326243 DOI: 10.1124/mol.117.110445] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 01/08/2018] [Indexed: 11/22/2022] Open
Abstract
The proton-coupled folate transporter (PCFT) is ubiquitously expressed in solid tumors to which it delivers antifolates, particularly pemetrexed, into cancer cells. Studies of PCFT-mediated transport, to date, have focused exclusively on the influx of folates and antifolates. This article addresses the impact of PCFT on concentrative transport, critical to the formation of the active polyglutamate congeners, and at pH levels relevant to the tumor microenvironment. An HeLa-derived cell line was employed, in which folate-specific transport was mediated exclusively by PCFT. At pH 7.0, there was a substantial chemical gradient for methotrexate that decreased as the extracellular pH was increased. A chemical gradient was still detected at pH 7.4 in the usual HEPES-based transport buffer in contrast to what was observed in a bicarbonate/CO2-buffered medium. This antifolate gradient correlated with an alkaline intracellular pH in the former (pH 7.85), but not the latter (pH 7.39), buffer and was abolished by the protonophore carbonyl cyanide-4-(trifluoromethoxy)phenylhydrazone. The gradient in HEPES buffer at pH 7.4 was the result of the activity of Na+/H+ exchanger(s); it was eliminated by inhibitors of Na+/H+ exchanger (s) or Na+/K+ ATPase. An antifolate chemical gradient was also detected in bicarbonate buffer at pH 6.9 versus 7.4, also suppressed by carbonyl cyanide-4-(trifluoromethoxy)phenylhydrazone. When the membrane potential is considered, PCFT generates substantial transmembrane electrochemical-potential gradients at extracellular pH levels relevant to the tumor microenvironment. The augmentation of intracellular pH, when cells are in a HEPES buffer, should be taken into consideration in studies that encompass all proton-coupled transporter families.
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Affiliation(s)
- Rongbao Zhao
- Departments of Molecular Pharmacology (R.Z., M.N., S.A., I.D.G.), Medicine (R.Z., I.D.G.), and Dominick P. Purpura Department of Neuroscience (D.C.S.), Albert Einstein College of Medicine, Bronx, New York
| | - Mitra Najmi
- Departments of Molecular Pharmacology (R.Z., M.N., S.A., I.D.G.), Medicine (R.Z., I.D.G.), and Dominick P. Purpura Department of Neuroscience (D.C.S.), Albert Einstein College of Medicine, Bronx, New York
| | - Srinivas Aluri
- Departments of Molecular Pharmacology (R.Z., M.N., S.A., I.D.G.), Medicine (R.Z., I.D.G.), and Dominick P. Purpura Department of Neuroscience (D.C.S.), Albert Einstein College of Medicine, Bronx, New York
| | - David C Spray
- Departments of Molecular Pharmacology (R.Z., M.N., S.A., I.D.G.), Medicine (R.Z., I.D.G.), and Dominick P. Purpura Department of Neuroscience (D.C.S.), Albert Einstein College of Medicine, Bronx, New York
| | - I David Goldman
- Departments of Molecular Pharmacology (R.Z., M.N., S.A., I.D.G.), Medicine (R.Z., I.D.G.), and Dominick P. Purpura Department of Neuroscience (D.C.S.), Albert Einstein College of Medicine, Bronx, New York
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Hereditary folate malabsorption due to a mutation in the external gate of the proton-coupled folate transporter SLC46A1. Blood Adv 2018; 2:61-68. [PMID: 29344585 DOI: 10.1182/bloodadvances.2017012690] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 11/28/2017] [Indexed: 01/08/2023] Open
Abstract
Hereditary folate malabsorption (HFM) is an autosomal recessive disorder characterized by impaired intestinal folate absorption and impaired folate transport across the choroid plexus due to loss of function of the proton-coupled folate transporter (PCFT-SLC46A1). We report a novel mutation, causing HFM, affecting a residue located in the 11th transmembrane helix within the external gate. The mutant N411K-PCFT was stable, trafficked to the cell membrane, and had sufficient residual activity to characterize the transport defect and the structural requirements at this site for gate function. The influx Vmax of the N411K mutant was markedly decreased, as was the affinity for most, but not all, folate/antifolate substrates. The greatest loss of activity was for 5-methyltetrahydrofolate. Substitutions with positive charged residues resulted in a loss of activity (arginine > lysine > histidine). Function was retained for the negative charged aspartate, but not the larger glutamate substitutions, whereas the bulky hydrophobic (leucine), or polar (glutamine) substitutions, were tolerated. Homology models of PCFT, in the inward and outward open conformations, based upon the mammalian Glut5 fructose transporter structures, localize Asn411 protruding into the aqueous pathway. This is most prominent when the carrier is in the inward open conformation when the external gate is closed. Mutations at this site likely result in highly specific steric and electrostatic interactions between the Asn411-substituted, and other, residues in the gate region that impede carrier function. The substrate specificity of the N411K mutant may be due to alterations of substrate flows through the external gate, downstream allosteric alterations in the folate-binding pocket, or both.
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Matherly LH, Hou Z, Gangjee A. The promise and challenges of exploiting the proton-coupled folate transporter for selective therapeutic targeting of cancer. Cancer Chemother Pharmacol 2018; 81:1-15. [PMID: 29127457 PMCID: PMC5756103 DOI: 10.1007/s00280-017-3473-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Accepted: 10/20/2017] [Indexed: 12/17/2022]
Abstract
This review considers the "promise" of exploiting the proton-coupled folate transporter (PCFT) for selective therapeutic targeting of cancer. PCFT was discovered in 2006 and was identified as the principal folate transporter involved in the intestinal absorption of dietary folates. The recognition that PCFT was highly expressed in many tumors stimulated substantial interest in using PCFT for cytotoxic drug targeting, taking advantage of its high level transport activity under the acidic pH conditions that characterize many tumors. For pemetrexed, among the best PCFT substrates, transport by PCFT establishes its importance as a clinically important transporter in malignant pleural mesothelioma and non-small cell lung cancer. In recent years, the notion of PCFT-targeting has been extended to a new generation of tumor-targeted 6-substituted pyrrolo[2,3-d]pyrimidine compounds that are structurally and functionally distinct from pemetrexed, and that exhibit near exclusive transport by PCFT and potent inhibition of de novo purine nucleotide biosynthesis. Based on compelling preclinical evidence in a wide range of human tumor models, it is now time to advance the most optimized PCFT-targeted agents with the best balance of PCFT transport specificity and potent antitumor efficacy to the clinic to validate this novel paradigm of highly selective tumor targeting.
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Affiliation(s)
- Larry H Matherly
- Molecular Therapeutics Program, Barbara Ann Karmanos Cancer Institute, 421 East Canfield Street, Detroit, MI, 48201, USA.
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI, 48201, USA.
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, 48201, USA.
| | - Zhanjun Hou
- Molecular Therapeutics Program, Barbara Ann Karmanos Cancer Institute, 421 East Canfield Street, Detroit, MI, 48201, USA
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI, 48201, USA
| | - Aleem Gangjee
- Division of Medicinal Chemistry, Graduate School of Pharmaceutical Sciences, Duquesne University, 600 Forbes Avenue, Pittsburgh, PA, 15282, USA
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41
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Radiosynthesis and biodistribution of 99mTc-Sulfamethoxazole: a novel molecule for in-vivo infection imaging. Med Chem Res 2017. [DOI: 10.1007/s00044-017-2009-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Tan J, Li X, Guo Y, Xie L, Wang J, Ma J, Jiang L. Hereditary folate malabsorption with a novel mutation on SLC46A1: A case report. Medicine (Baltimore) 2017; 96:e8712. [PMID: 29390264 PMCID: PMC5815676 DOI: 10.1097/md.0000000000008712] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
RATIONALE Hereditary folate malabsorption (HFM) is characterized by folate deficiency with impaired intestinal folate absorption and impaired folate transport into the central nervous system. Its manifestations mainly include macrocytic anemia, recurrent infections, and neurological deficits. The neurological manifestations include progressive psychomotor retardation, behavioral disorders, and early-onset seizures. PATIENT CONCERNS From early infancy, a Chinese boy had experienced macrocytic anemia, leukopenia, thrombocytopenia, recurrent pneumonia, diarrhea, and mouth ulcers. He also presented with progressive neurological symptoms. DIAGNOSIS A novel mutation in the SLC46A1 gene was identified, and HFM was diagnosed at 18 months of age. INTERVENTIONS After the HFM diagnosis, the boy was treated with folinic acid. LESSONS Folinic acid supplementation is effective and may offer life-changing therapy for patients with HFM.
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Aluri S, Zhao R, Fiser A, Goldman ID. Substituted-cysteine accessibility and cross-linking identify an exofacial cleft in the 7th and 8th helices of the proton-coupled folate transporter (SLC46A1). Am J Physiol Cell Physiol 2017; 314:C289-C296. [PMID: 29167151 DOI: 10.1152/ajpcell.00215.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The proton-coupled folate transporter (PCFT-SLC46A1) is required for folate transport across the apical membrane of the small intestine and across the choroid plexus. This study focuses on the structure/function of the 7th transmembrane domain (TMD), and its relationship to the 8th TMD as assessed by the substituted cysteine accessibility method (SCAM) and dicysteine cross-linking. Nine exofacial residues (I278C; H281C-L288C) of 23 residues in the 7th TMD were accessible to 2-((biotinoyl)amino)ethyl methanethiosulfonate (MTSEA-biotin). Pemetrexed, a high-affinity substrate for PCFT, decreased or abolished biotinylation of seven of these residues consistent with their location in or near the folate binding pocket. Homology models of PCFT based on Glut5 fructose transporter structures in both inward- and outward- open conformations were constructed and predicted that two pairs of residues (T289-I304C and Q285-Q311C) from the 7th and 8th TMDs should be in sufficiently close proximity to form a disulfide bond when substituted with cysteines. The single Cys-substituted mutants were accessible to MTSEA-biotin and functional with and without pretreatment with dithiotreitol. However, the double mutants were either not accessible at all, or accessibility was markedly reduced and function markedly impaired. This occurred spontaneously without inclusion of an oxidizing agent. Dithiotreitol restored accessibility and function consistent with disulfide bond disruption. The data establish the proximity of exofacial regions of the 7th and 8th TMDs and their role in defining the aqueous translocation pathway and suggest that these helices may be a component of an exofacial cleft through which substrates enter the protein binding pocket in its outward-open conformation.
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Affiliation(s)
- Srinivas Aluri
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York.,Department of Medicine, Albert Einstein College of Medicine, Bronx, New York
| | - Rongbao Zhao
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York.,Department of Medicine, Albert Einstein College of Medicine, Bronx, New York
| | - Andras Fiser
- Department of Systems and Computational Biology, Albert Einstein College of Medicine, Bronx, New York.,Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York
| | - I David Goldman
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York.,Department of Medicine, Albert Einstein College of Medicine, Bronx, New York
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Alam C, Hoque MT, Finnell RH, Goldman ID, Bendayan R. Regulation of Reduced Folate Carrier (RFC) by Vitamin D Receptor at the Blood-Brain Barrier. Mol Pharm 2017; 14:3848-3858. [PMID: 28885847 DOI: 10.1021/acs.molpharmaceut.7b00572] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Folates are essential for brain development and function. Folate transport in mammalian tissues is mediated by three major folate transport systems, i.e., reduced folate carrier (RFC), proton-coupled folate transporter (PCFT), and folate receptor alpha (FRα), known to be regulated by ligand-activated nuclear receptors, such as vitamin D receptor (VDR). Folate uptake at the choroid plexus, which requires the actions of both FRα and PCFT, is critical to cerebral folate delivery. Inactivating FRα or PCFT mutations cause severe cerebral folate deficiency resulting in early childhood neurodegeneration. The objective of this study was to investigate the role of RFC in folate uptake at the level of the blood-brain barrier (BBB) and its potential regulation by VDR. We detected robust expression of RFC in different in vitro BBB model systems, particularly in immortalized cultures of human cerebral microvascular endothelial cells (hCMEC/D3) and isolated mouse brain capillaries. [3H]-methotrexate uptake by hCMEC/D3 cells at pH 7.4 was inhibited by PT523 and pemetrexed, antifolates with high affinity for RFC. We also showed that activation of VDR through calcitriol (1,25-dihydroxyvitamin D3) exposure up-regulates RFC mRNA and protein expression as well as function in hCMEC/D3 cells and isolated mouse brain capillaries. We further demonstrated that RFC expression could be down-regulated by VDR-targeting siRNA, further confirming the role of VDR in the direct regulation of this folate transporter. Together, these data suggest that augmenting RFC functional expression could constitute a novel strategy for enhancing brain folate delivery for the treatment of neurometabolic disorders caused by loss of FRα or PCFT function.
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Affiliation(s)
- Camille Alam
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto , Toronto, Ontario M5S 3M2, Canada
| | - Md Tozammel Hoque
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto , Toronto, Ontario M5S 3M2, Canada
| | - Richard H Finnell
- Departments of Molecular and Cellular Biology and Medicine, Baylor College of Medicine , Houston, Texas 77030, United States
| | - I David Goldman
- Department of Molecular Pharmacology, Albert Einstein College of Medicine , Bronx, New York 10461, United States
| | - Reina Bendayan
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto , Toronto, Ontario M5S 3M2, Canada
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Aluri S, Zhao R, Fiser A, Goldman ID. Residues in the eighth transmembrane domain of the proton-coupled folate transporter (SLC46A1) play an important role in defining the aqueous translocation pathway and in folate substrate binding. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:2193-2202. [PMID: 28802835 DOI: 10.1016/j.bbamem.2017.08.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 07/28/2017] [Accepted: 08/08/2017] [Indexed: 01/12/2023]
Abstract
The proton-coupled folate transporter (PCFT-SLC46A1) is required for intestinal folate absorption and folate transport across the choroid plexus. This report addresses the structure/function of the 8th transmembrane helix. Based upon biotinylation of cysteine-substituted residues by MTSEA-biotin, 14 contiguous exofacial residues to Leu316 were accessible to the extracellular compartment of the 23 residues in this helix (Leu303-Leu325). Pemetrexed blocked biotinylation of six Cys-substituted residues deep within the helix implicating an important role for this region in folate binding. Accessibility decreased at 4°C vs RT. The influx Kt, Ki and Vmax were markedly increased for the P314C mutant, similar to what was observed for Y315A and Y315P mutants. However, the Kt, alone, was increased for the P314Y mutant. To correlate these observations with PCFT structural changes during the transport cycle, homology models were built for PCFT based upon the recently reported structures of bovine and rodent GLUT5 fructose transporters in the inward-open and outward- open conformations, respectively. The models predict substantial structural alterations in the exofacial region of the eighth transmembrane helix as it cycles between its conformational states that can account for the extended and contiguous aqueous accessibility of this region of the helix. Further, a helix break in one of the two conformations can account for the critical roles Pro314 and Tyr315, located in this region, play in PCFT function. The data indicates that the 8th transmembrane helix of PCFT plays an important role in defining the aqueous channel and the folate binding pocket.
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Affiliation(s)
- Srinivas Aluri
- Department of Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, United States; Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461, United States
| | - Rongbao Zhao
- Department of Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, United States; Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461, United States
| | - Andras Fiser
- Department of Systems and Computational Biology, Albert Einstein College of Medicine, Bronx, NY 10461, United States; Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, United States
| | - I David Goldman
- Department of Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, United States; Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461, United States.
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Role of Intramuscular Levofolinate Administration in the Treatment of Hereditary Folate Malabsorption: Report of Three Cases. JIMD Rep 2017; 39:7-12. [PMID: 28685492 DOI: 10.1007/8904_2017_39] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 05/17/2017] [Accepted: 06/09/2017] [Indexed: 01/19/2023] Open
Abstract
Hereditary folate malabsorption is a rare autosomal recessive disorder caused by impaired active folate transport across membranes and into the central nervous system due to loss-of-function mutations in proton-coupled folate transporter (PCFT). Newborns with this condition have initially normal folate stores, but as they are unable to absorb dietary folate and use rapidly their stores because of their growth demands, symptoms appear in the early infancy. Significant neurological morbidity usually follows the initial non-specific clinical presentation and delayed initiation of treatment. High dose oral and parenteral folinic acid treatment have been previously reported in literature to improve the clinical outcome without achieving optimal cerebrospinal fluid (CSF) folate levels though. The active isomer of 5-formyltetrahydrofolate, also known as levofolinic acid, is available for administration. We report our experience in achieving normal (age dependent) CSF 5-Methyltetrahydrofolate (5-MTHF) levels following daily intramuscular administration of levofolinic acid in three patients with HFM. Follow-up assessment with repeated lumbar punctures has shown a stabilization of 5-MTHF levels within normal range. Clinical features and brain MRI findings had as well either improvement or stabilization. To the best of our knowledge, we provide as well for the first time data in regard to the im levofolinate treatment dosage.
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