1
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Dong H, Yang J, He K, Zheng WB, Lai DH, Liu J, Ding HY, Wu RB, Brown KM, Hide G, Lun ZR, Zhu XQ, Long S. The Toxoplasma monocarboxylate transporters are involved in the metabolism within the apicoplast and are linked to parasite survival. eLife 2024; 12:RP88866. [PMID: 38502570 PMCID: PMC10950331 DOI: 10.7554/elife.88866] [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] [Indexed: 03/21/2024] Open
Abstract
The apicoplast is a four-membrane plastid found in the apicomplexans, which harbors biosynthesis and organelle housekeeping activities in the matrix. However, the mechanism driving the flux of metabolites, in and out, remains unknown. Here, we used TurboID and genome engineering to identify apicoplast transporters in Toxoplasma gondii. Among the many novel transporters, we show that one pair of apicomplexan monocarboxylate transporters (AMTs) appears to have evolved from a putative host cell that engulfed a red alga. Protein depletion showed that AMT1 and AMT2 are critical for parasite growth. Metabolite analyses supported the notion that AMT1 and AMT2 are associated with biosynthesis of isoprenoids and fatty acids. However, stronger phenotypic defects were observed for AMT2, including in the inability to establish T. gondii parasite virulence in mice. This study clarifies, significantly, the mystery of apicoplast transporter composition and reveals the importance of the pair of AMTs in maintaining the apicoplast activity in apicomplexans.
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Affiliation(s)
- Hui Dong
- National Key Laboratory of Veterinary Public Health Safety, and College of Veterinary Medicine, China Agricultural University, Beijing, China
- National Animal Protozoa Laboratory and School of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Jiong Yang
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Kai He
- National Key Laboratory of Veterinary Public Health Safety, and College of Veterinary Medicine, China Agricultural University, Beijing, China
- National Animal Protozoa Laboratory and School of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Wen-Bin Zheng
- College of Veterinary Medicine, Shanxi Agricultural University, Taigu, China
| | - De-Hua Lai
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Jing Liu
- National Key Laboratory of Veterinary Public Health Safety, and College of Veterinary Medicine, China Agricultural University, Beijing, China
- National Animal Protozoa Laboratory and School of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Hui-Yong Ding
- National Key Laboratory of Veterinary Public Health Safety, and College of Veterinary Medicine, China Agricultural University, Beijing, China
- National Animal Protozoa Laboratory and School of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Rui-Bin Wu
- National Key Laboratory of Veterinary Public Health Safety, and College of Veterinary Medicine, China Agricultural University, Beijing, China
- National Animal Protozoa Laboratory and School of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Kevin M Brown
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, United States
| | - Geoff Hide
- Biomedical Research and Innovation Centre and Environmental Research and Innovation Centre, School of Science, Engineering and Environment, University of Salford, Salford, United Kingdom
| | - Zhao-Rong Lun
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Xing-Quan Zhu
- College of Veterinary Medicine, Shanxi Agricultural University, Taigu, China
| | - Shaojun Long
- National Key Laboratory of Veterinary Public Health Safety, and College of Veterinary Medicine, China Agricultural University, Beijing, China
- National Animal Protozoa Laboratory and School of Veterinary Medicine, China Agricultural University, Beijing, China
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Tripathi R, Guglani A, Ghorpade R, Wang B. Biotin conjugates in targeted drug delivery: is it mediated by a biotin transporter, a yet to be identified receptor, or (an)other unknown mechanism(s)? J Enzyme Inhib Med Chem 2023; 38:2276663. [PMID: 37955285 PMCID: PMC10653662 DOI: 10.1080/14756366.2023.2276663] [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: 08/08/2023] [Accepted: 10/24/2023] [Indexed: 11/14/2023] Open
Abstract
Conjugation of drugs with biotin is a widely studied strategy for targeted drug delivery. The structure-activity relationship (SAR) studies through H3-biotin competition experiments conclude with the presence of a free carboxylic acid being essential for its uptake via the sodium-dependent multivitamin transporter (SMVT, the major biotin transporter). However, biotin conjugation with a payload requires modification of the carboxylic acid to an amide or ester group. Then, there is the question as to how/whether the uptake of biotin conjugates goes through the SMVT. If not, then what is the mechanism? Herein, we present known uptake mechanisms of biotin and its applications reported in the literature. We also critically analyse possible uptake mechanism(s) of biotin conjugates to address the disconnect between the results from SMVT-based SAR and "biotin-facilitated" targeted drug delivery. We believe understanding the uptake mechanism of biotin conjugates is critical for their future applications and further development.
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Affiliation(s)
- Ravi Tripathi
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, USA
| | - Anchala Guglani
- Department of Biology, Georgia State University, Atlanta, GA, USA
| | - Rujuta Ghorpade
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, USA
| | - Binghe Wang
- Department of Chemistry and Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, GA, USA
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3
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Neophytou C, Pitsouli C. Biotin controls intestinal stem cell mitosis and host-microbiome interactions. Cell Rep 2022; 38:110505. [PMID: 35263602 DOI: 10.1016/j.celrep.2022.110505] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 12/11/2021] [Accepted: 02/16/2022] [Indexed: 12/12/2022] Open
Abstract
Diet is a key regulator of metabolism and interacts with the intestinal microbiome. Here, we study the role of the Drosophila intestinal stem cell (ISC)-specific biotin transporter Smvt in midgut homeostasis, infection-induced regeneration, and tumorigenesis. We show that Smvt-transported biotin in ISCs is necessary for ISC mitosis. Smvt deficiency impairs intestinal maintenance, which can be rescued by the human Smvt, encoded by SLC5A6. ISC-specific, Smvt-silenced flies exhibit microbial dysbiosis, whereby the growth of Providencia sneebia, an opportunistic pathogen, is favored. Dysbiosis correlates with increased Nox expression, reactive oxygen species (ROS), and enterocyte apoptosis. Flies acquire biotin from their diet and microbiota. We show that, when dietary biotin is scarce, biotin-producing commensals, e.g., E. coli, can rescue reduced ISC mitosis. Smvt and commensals also control intestinal tumor growth. Our findings suggest that direct modification of the gut microbiome by biotin can serve as an approach for the treatment of dysbiosis-promoted diseases and tumorigenesis control.
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Affiliation(s)
- Constantina Neophytou
- Department of Biological Sciences, University of Cyprus, 1 University Avenue, Aglantzia 2109, Cyprus
| | - Chrysoula Pitsouli
- Department of Biological Sciences, University of Cyprus, 1 University Avenue, Aglantzia 2109, Cyprus.
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4
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Ramamoorthy K, Sabui S, Srinivasan P, Al-Juburi S, Pham Q, Chu BD, Simoes RD, Fleckenstein JM, Said HM. Effect of chronic alcohol exposure on gut vitamin B7 uptake: involvement of epigenetic mechanisms and effect of alcohol metabolites. Am J Physiol Gastrointest Liver Physiol 2021; 321:G123-G133. [PMID: 34077272 PMCID: PMC8410103 DOI: 10.1152/ajpgi.00144.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Vitamin B7 (biotin) is essential for normal health and its deficiency/suboptimal levels occur in a variety of conditions including chronic alcoholism. Mammals, including humans, obtain biotin from diet and gut-microbiota via absorption along the intestinal tract. The absorption process is carrier mediated and involves the sodium-dependent multivitamin transporter (SMVT; SLC5A6). We have previously shown that chronic alcohol exposure significantly inhibits intestinal/colonic biotin uptake via suppression of Slc5a6 transcription in animal and cell line models. However, little is known about the transcriptional/epigenetic factors that mediate this suppression. In addition, the effect of alcohol metabolites (generated via alcohol metabolism by gut microbiota and host tissues) on biotin uptake is still unknown. To address these questions, we first demonstrated that chronic alcohol exposure inhibits small intestinal and colonic biotin uptake and SMVT expression in human differentiated enteroid and colonoid monolayers. We then showed that chronic alcohol exposures of both, Caco-2 cells and mice, are associated with a significant suppression in expression of the nuclear factor KLF-4 (needed for Slc5a6 promoter activity), as well as with epigenetic alterations (histone modifications). We also found that chronic exposure of NCM460 human colonic epithelial cells as well as human differentiated colonoid monolayers, to alcohol metabolites (acetaldehyde, ethyl palmitate, ethyl oleate) significantly inhibited biotin uptake and SMVT expression. These findings shed light onto the molecular/epigenetic mechanisms that mediate the inhibitory effect of chronic alcohol exposure on intestinal biotin uptake. They further show that alcohol metabolites are also capable of inhibiting biotin uptake in the gut.NEW & NOTEWORTHY Using complementary models, including human differentiated enteroid and colonoid monolayers, this study shows the involvement of molecular and epigenetic mechanisms in mediating the inhibitory effect of chronic alcohol exposure on biotin uptake along the intestinal tract. The study also shows that alcohol metabolites (generated by gut microbiota and host tissues) cause inhibition in gut biotin uptake.
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Affiliation(s)
- Kalidas Ramamoorthy
- 1Department of Physiology/Biophysics, University of California, Irvine, California
| | - Subrata Sabui
- 1Department of Physiology/Biophysics, University of California, Irvine, California,5Veterans Affairs Medical Center, Long Beach, California
| | - Padmanabhan Srinivasan
- 1Department of Physiology/Biophysics, University of California, Irvine, California,5Veterans Affairs Medical Center, Long Beach, California
| | - Saleh Al-Juburi
- 1Department of Physiology/Biophysics, University of California, Irvine, California
| | - Quang Pham
- 1Department of Physiology/Biophysics, University of California, Irvine, California
| | - Brian D. Chu
- 1Department of Physiology/Biophysics, University of California, Irvine, California,5Veterans Affairs Medical Center, Long Beach, California
| | - Rita D. Simoes
- 3Department of Medicine, Division of Infectious Diseases, Washington University School of Medicine, St. Louis, Missouri
| | - James M. Fleckenstein
- 3Department of Medicine, Division of Infectious Diseases, Washington University School of Medicine, St. Louis, Missouri,4Veterans Affairs Medical Center, St. Louis Missouri
| | - Hamid M. Said
- 1Department of Physiology/Biophysics, University of California, Irvine, California,2Department of Medicine, University of California, Irvine, California,5Veterans Affairs Medical Center, Long Beach, California
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5
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Krishnan A, Kloehn J, Lunghi M, Soldati-Favre D. Vitamin and cofactor acquisition in apicomplexans: Synthesis versus salvage. J Biol Chem 2020; 295:701-714. [PMID: 31767680 PMCID: PMC6970920 DOI: 10.1074/jbc.aw119.008150] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The Apicomplexa phylum comprises diverse parasitic organisms that have evolved from a free-living ancestor. These obligate intracellular parasites exhibit versatile metabolic capabilities reflecting their capacity to survive and grow in different hosts and varying niches. Determined by nutrient availability, they either use their biosynthesis machineries or largely depend on their host for metabolite acquisition. Because vitamins cannot be synthesized by the mammalian host, the enzymes required for their synthesis in apicomplexan parasites represent a large repertoire of potential therapeutic targets. Here, we review recent advances in metabolic reconstruction and functional studies coupled to metabolomics that unravel the interplay between biosynthesis and salvage of vitamins and cofactors in apicomplexans. A particular emphasis is placed on Toxoplasma gondii, during both its acute and latent stages of infection.
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Affiliation(s)
- Aarti Krishnan
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva CMU, 1 Rue Michel-Servet, 1211 Geneva 4 Switzerland
| | - Joachim Kloehn
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva CMU, 1 Rue Michel-Servet, 1211 Geneva 4 Switzerland
| | - Matteo Lunghi
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva CMU, 1 Rue Michel-Servet, 1211 Geneva 4 Switzerland
| | - Dominique Soldati-Favre
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva CMU, 1 Rue Michel-Servet, 1211 Geneva 4 Switzerland
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6
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Krishnan A, Kloehn J, Lunghi M, Soldati-Favre D. Vitamin and cofactor acquisition in apicomplexans: Synthesis versus salvage. J Biol Chem 2020. [DOI: 10.1016/s0021-9258(17)49928-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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7
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Remnant L, Booth DG, Vargiu G, Spanos C, Kerr ARW, Earnshaw WC. In vitro BioID: mapping the CENP-A microenvironment with high temporal and spatial resolution. Mol Biol Cell 2019; 30:1314-1325. [PMID: 30892990 PMCID: PMC6724601 DOI: 10.1091/mbc.e18-12-0799] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The centromere is located at the primary constriction of condensed chromosomes where it acts as a platform regulating chromosome segregation. The histone H3 variant CENP-A is the foundation for kinetochore formation. CENP-A directs the formation of a highly dynamic molecular neighborhood whose temporal characterization during mitosis remains a challenge due to limitations in available techniques. BioID is a method that exploits a “promiscuous” biotin ligase (BirA118R or BirA*) to identify proteins within close proximity to a fusion protein of interest. As originally described, cells expressing BirA* fusions were exposed to high biotin concentrations for 24 h during which the ligase transferred activated biotin (BioAmp) to other proteins within the immediate vicinity. The protein neighborhood could then be characterized by streptavidin-based purification and mass spectrometry. Here we describe a further development to this technique, allowing CENP-A interactors to be characterized within only a few minutes, in an in vitro reaction in lysed cells whose physiological progression is “frozen.” This approach, termed in vitro BioID (ivBioID), has the potential to study the molecular neighborhood of any structural protein whose interactions change either during the cell cycle or in response to other changes in cell physiology.
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Affiliation(s)
- Lucy Remnant
- Wellcome Trust Centre for Cell Biology, Institute of Cell Biology and
| | - Daniel G Booth
- Wellcome Trust Centre for Cell Biology, Institute of Cell Biology and.,Centre for Brain Discovery Sciences, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Giulia Vargiu
- Wellcome Trust Centre for Cell Biology, Institute of Cell Biology and
| | - Christos Spanos
- Wellcome Trust Centre for Cell Biology, Institute of Cell Biology and
| | - Alastair R W Kerr
- Wellcome Trust Centre for Cell Biology, Institute of Cell Biology and
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8
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Fets L, Driscoll PC, Grimm F, Jain A, Nunes PM, Gounis M, Doglioni G, Papageorgiou G, Ragan TJ, Campos S, Silva Dos Santos M, MacRae JI, O'Reilly N, Wright AJ, Benes CH, Courtney KD, House D, Anastasiou D. MCT2 mediates concentration-dependent inhibition of glutamine metabolism by MOG. Nat Chem Biol 2018; 14:1032-1042. [PMID: 30297875 PMCID: PMC6298574 DOI: 10.1038/s41589-018-0136-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 08/21/2018] [Indexed: 12/17/2022]
Abstract
α-Ketoglutarate (αKG) is a key node in many important metabolic pathways. The αKG analog N-oxalylglycine (NOG) and its cell-permeable prodrug dimethyloxalylglycine (DMOG) are extensively used to inhibit αKG-dependent dioxygenases. However, whether NOG interference with other αKG-dependent processes contributes to its mode of action remains poorly understood. Here we show that, in aqueous solutions, DMOG is rapidly hydrolyzed, yielding methyloxalylglycine (MOG). MOG elicits cytotoxicity in a manner that depends on its transport by monocarboxylate transporter 2 (MCT2) and is associated with decreased glutamine-derived tricarboxylic acid-cycle flux, suppressed mitochondrial respiration and decreased ATP production. MCT2-facilitated entry of MOG into cells leads to sufficiently high concentrations of NOG to inhibit multiple enzymes in glutamine metabolism, including glutamate dehydrogenase. These findings reveal that MCT2 dictates the mode of action of NOG by determining its intracellular concentration and have important implications for the use of (D)MOG in studying αKG-dependent signaling and metabolism.
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Affiliation(s)
- Louise Fets
- Cancer Metabolism Laboratory, Francis Crick Institute, London, UK
| | - Paul C Driscoll
- Metabolomics Science Technology Platform, Francis Crick Institute, London, UK
| | - Fiona Grimm
- Cancer Metabolism Laboratory, Francis Crick Institute, London, UK
| | - Aakriti Jain
- Cancer Metabolism Laboratory, Francis Crick Institute, London, UK
| | - Patrícia M Nunes
- Cancer Metabolism Laboratory, Francis Crick Institute, London, UK
| | - Michalis Gounis
- Cancer Metabolism Laboratory, Francis Crick Institute, London, UK
| | - Ginevra Doglioni
- Cancer Metabolism Laboratory, Francis Crick Institute, London, UK
| | - George Papageorgiou
- Peptide Chemistry Science Technology Platform, Francis Crick Institute, London, UK
| | | | - Sebastien Campos
- Crick-GSK Biomedical LinkLabs, GSK Medicines Research Centre, Stevenage, UK
| | | | - James I MacRae
- Metabolomics Science Technology Platform, Francis Crick Institute, London, UK
| | - Nicola O'Reilly
- Peptide Chemistry Science Technology Platform, Francis Crick Institute, London, UK
| | - Alan J Wright
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Cambridge, UK
| | - Cyril H Benes
- Massachusetts General Hospital Cancer Center & Department of Medicine, Harvard Medical School, Boston, MA, USA
| | - Kevin D Courtney
- Department of Internal Medicine, Division of Hematology/Oncology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - David House
- Crick-GSK Biomedical LinkLabs, GSK Medicines Research Centre, Stevenage, UK
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9
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Uchida Y, Ito K, Ohtsuki S, Kubo Y, Suzuki T, Terasaki T. Major involvement of Na(+) -dependent multivitamin transporter (SLC5A6/SMVT) in uptake of biotin and pantothenic acid by human brain capillary endothelial cells. J Neurochem 2015; 134:97-112. [PMID: 25809983 DOI: 10.1111/jnc.13092] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2015] [Revised: 03/08/2015] [Accepted: 03/09/2015] [Indexed: 12/24/2022]
Abstract
The purpose of this study was to clarify the expression of Na(+) -dependent multivitamin transporter (SLC5A6/SMVT) and its contribution to the supply of biotin and pantothenic acid to the human brain via the blood-brain barrier. DNA microarray and immunohistochemical analyses confirmed that SLC5A6 is expressed in microvessels of human brain. The absolute expression levels of SLC5A6 protein in isolated human and monkey brain microvessels were 1.19 and 0.597 fmol/μg protein, respectively, as determined by a quantitative targeted absolute proteomics technique. Using an antibody-free method established by Kubo et al. (2015), we found that SLC5A6 was preferentially localized at the luminal membrane of brain capillary endothelium. Knock-down analysis using SLC5A6 siRNA showed that SLC5A6 accounts for 88.7% and 98.6% of total [(3) H]biotin and [(3) H]pantothenic acid uptakes, respectively, by human cerebral microvascular endothelial cell line hCMEC/D3. SLC5A6-mediated transport in hCMEC/D3 was markedly inhibited not only by biotin and pantothenic acid, but also by prostaglandin E2, lipoic acid, docosahexaenoic acid, indomethacin, ketoprofen, diclofenac, ibuprofen, phenylbutazone, and flurbiprofen. This study is the first to confirm expression of SLC5A6 in human brain microvessels and to provide evidence that SLC5A6 is a major contributor to luminal uptake of biotin and pantothenic acid at the human blood-brain barrier. In humans, it was unclear (not concluded) about what transport system at the blood-brain barrier (BBB) is responsible for the brain uptakes of two vitamins, biotin and pantothenic acid, which are necessary for brain proper function. This study clarified for the first time that the solute carrier 5A6/Na(+) -dependent multivitamin transporter SLC5A6/SMVT is responsible for the supplies of biotin and pantothenic acid into brain across the BBB in humans. DHA, docosahexaenoic acid; NSAID, non-steroidal anti-inflammatory drug; PGE2, prostaglandin E2.
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Affiliation(s)
- Yasuo Uchida
- Graduate School of Pharmaceutical Sciences, Tohoku University, Miyagi, Japan
| | - Katsuaki Ito
- Graduate School of Pharmaceutical Sciences, Tohoku University, Miyagi, Japan
| | - Sumio Ohtsuki
- Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Yoshiyuki Kubo
- Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan
| | - Takashi Suzuki
- Department of Pathology and Histotechnology, Tohoku University Graduate School of Medicine, Miyagi, Japan
| | - Tetsuya Terasaki
- Graduate School of Pharmaceutical Sciences, Tohoku University, Miyagi, Japan
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10
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Diversity of membrane transport proteins for vitamins in bacteria and archaea. Biochim Biophys Acta Gen Subj 2015; 1850:565-76. [DOI: 10.1016/j.bbagen.2014.05.006] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 04/30/2014] [Accepted: 05/03/2014] [Indexed: 01/13/2023]
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11
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Ohkura Y, Akanuma SI, Tachikawa M, Hosoya KI. Blood-to-retina transport of biotin via Na+-dependent multivitamin transporter (SMVT) at the inner blood-retinal barrier. Exp Eye Res 2010; 91:387-92. [DOI: 10.1016/j.exer.2010.06.010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Revised: 05/27/2010] [Accepted: 06/12/2010] [Indexed: 11/27/2022]
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12
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Mall GK, Chew YC, Zempleni J. Biotin requirements are lower in human Jurkat lymphoid cells but homeostatic mechanisms are similar to those of HepG2 liver cells. J Nutr 2010; 140:1086-92. [PMID: 20357078 PMCID: PMC2869498 DOI: 10.3945/jn.110.121475] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Revised: 02/10/2010] [Accepted: 03/11/2010] [Indexed: 01/17/2023] Open
Abstract
The following proteins are candidates for maintaining biotin homeostasis in humans: the biotin transporters sodium-dependent multivitamin transporter (SMVT) and monocarboxylate transporter 1, the biotinyl-protein ligase holocarboxylase synthetase (HCS), and the lysine-epsilon-biotin hydrolase biotinidase. Liver cells are supplied through the portal vein with high levels of water-soluble vitamins compared with those of peripheral tissues. We hypothesized that the mechanisms of biotin homeostasis are qualitatively and quantitatively different in cells derived from human liver (HepG2 cells) and lymphoid tissues (Jurkat cells). Cells were cultured in biotin-defined media, representing deficient (D), normal (N), and supplemented (S) individuals. Biotinylation of carboxylases depended on biotin availability in both cell types, but HepG2 cells required 3 times more biotin than Jurkat cells to maintain normal levels of holocarboxylases. The expression of biotin transporters was less in both types in medium S compared with cells in media D and N; in contrast, the expression of HCS was higher in cells in medium S compared with the other cells. The abundance of 3-methylcrotonyl-CoA carboxylase mRNA was lower in cells in medium D than cells in media N and S. The enrichment of biotinylated histones was higher at the SMVT promoter 1 in HepG2 and Jurkat cells in medium S compared with the corresponding cells in media D and N, presumably repressing the SMVT gene. The mechanisms of biotin homeostasis are qualitatively similar but quantitatively different in HepG2 and Jurkat cells; HCS, histone biotinylation, and biotin transporters play a role in homeostasis in both.
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Affiliation(s)
| | | | - Janos Zempleni
- Department of Nutrition and Health Sciences, University of Nebraska, Lincoln, NE 68583
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13
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Development and characterization of a novel human in vitro blood-nerve barrier model using primary endoneurial endothelial cells. J Neuropathol Exp Neurol 2010; 69:82-97. [PMID: 20010300 DOI: 10.1097/nen.0b013e3181c84a9a] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
There are phenotypic and functional differences between vascular endothelium from different tissues and between microvascular and macrovascular endothelial cells (ECs) from the same tissue. Relatively little is known about the human blood-nerve barrier (BNB). We report the development of an in vitro BNB model using primary human endoneurial ECs freshly isolated and purified from decedent sciatic nerves via endoneurial stripping, connective tissue enzymatic digestion, and density centrifugation. Primary human endoneurial ECs are spindle shaped and contact inhibited. They rapidly differentiate to form capillary-like networks and microvessels, bind Ulex Europaeus Agglutinin 1 lectin, express von Willebrand factor, and endocytose acetylated low-density lipoprotein. They also express specific transport and cellular adhesion molecules and tight junction proteins, consistent with cells that form a highly restrictive endothelial barrier similar to the blood-brain barrier. When cultured on collagen-coated transwell inserts, the primary human endoneurial ECs develop an in vitro BNB with high transendothelial electrical resistances (160 Omega x cm(2); maximal 12 days after seeding) and low solute permeability coefficient to fluoresceinated high-molecular weight (70 kDa) dextran (2.75 x 10(-3) cm/minute). This in vitro BNB model retains essential known or expected characteristics of the human BNB and has many potential applications for studies of solute, macromolecule, microbial, virus, and leukocyte interactions with this highly specialized endothelial barrier.
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14
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Abstract
Biotin is a water-soluble vitamin and serves as a coenzyme for five carboxylases in humans. Biotin is also covalently attached to distinct lysine residues in histones, affecting chromatin structure and mediating gene regulation. This review describes mammalian biotin metabolism, biotin analysis, markers of biotin status, and biological functions of biotin. Proteins such as holocarboxylase synthetase, biotinidase, and the biotin transporters SMVT and MCT1 play crucial roles in biotin homeostasis, and these roles are reviewed here. Possible effects of inadequate biotin intake, drug interactions, and inborn errors of metabolism are discussed, including putative effects on birth defects.
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Affiliation(s)
- Janos Zempleni
- Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, 316 Ruth Leverton Hall, Lincoln, NE 68583-0806, USA.
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15
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Zempleni J, Gralla M, Camporeale G, Hassan YI. Sodium-dependent multivitamin transporter gene is regulated at the chromatin level by histone biotinylation in human Jurkat lymphoblastoma cells. J Nutr 2009; 139:163-6. [PMID: 19056636 PMCID: PMC2606921 DOI: 10.3945/jn.108.091967] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The sodium-dependent multivitamin transporter (SMVT) is essential for mediating and regulating biotin entry into mammalian cells. In cells, holocarboxylase synthetase (HCS) mediates covalent binding of biotin to histones; biotinylation of lysine-12 in histone H4 (K12BioH4) causes gene repression. Here we propose a novel role for HCS in sensing and regulating levels of biotin in eukaryotic cells. We hypothesize that nuclear translocation of HCS increases in response to biotin supplementation; HCS then biotinylates histone H4 at SMVT promoters, silencing biotin transporter genes. We show that nuclear translocation of HCS is a biotin-dependent process that might involve tyrosine kinases, histone deacetylases, and histone methyltransferases in human lymphoid (Jurkat) cells. The nuclear translocation of HCS correlated with biotin concentrations in cell culture media; the relative enrichment of both HCS and K12BioH4 at SMVT promoter 1 (but not promoter 2) increased by 91% in cells cultured in medium containing 10 nmol/L biotin compared with 0.25 nmol/L biotin. This increase of K12BioH4 at the SMVT promoter was inversely linked to SMVT expression. Biotin homeostasis by HCS-dependent chromatin remodeling at the SMVT promoter 1 locus was disrupted in HCS knockdown cells, as evidenced by abnormal chromatin structure (K12BioH4 abundance) and increased SMVT expression. The findings from this study are consistent with the theory that HCS senses biotin, and that biotin regulates its own cellular uptake by participating in HCS-dependent chromatin remodeling events at the SMVT promoter 1 locus in Jurkat cells.
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Affiliation(s)
- Janos Zempleni
- Department of Nutrition and Health Sciences, University of Nebraska, Lincoln, NE 68583-0806, USA.
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Abstract
Biotin is a water-soluble vitamin that serves as an essential coenzyme for five carboxylases in mammals. Biotin-dependent carboxylases catalyze the fixation of bicarbonate in organic acids and play crucial roles in the metabolism of fatty acids, amino acids and glucose. Carboxylase activities decrease substantially in response to biotin deficiency. Biotin is also covalently attached to histones; biotinylated histones are enriched in repeat regions in the human genome and appear to play a role in transcriptional repression of genes and genome stability. Biotin deficiency may be caused by insufficient dietary uptake of biotin, drug-vitamin interactions and, perhaps, by increased biotin catabolism during pregnancy and in smokers. Biotin deficiency can also be precipitated by decreased activities of the following proteins that play critical roles in biotin homeostasis: the vitamin transporters sodium-dependent multivitamin transporter and monocarboxylate transporter 1, which mediate biotin transport in the intestine, liver and peripheral tissues, and renal reabsorption; holocarboxylase synthetase, which mediates the binding of biotin to carboxylases and histones; and biotinidase, which plays a central role in the intestinal absorption of biotin, the transport of biotin in plasma and the regulation of histone biotinylation. Symptoms of biotin deficiency include seizures, hypotonia, ataxia, dermatitis, hair loss, mental retardation, ketolactic acidosis, organic aciduria and also fetal malformations. This review focuses on the deficiencies of both biotin and biotinidase, and the medical management of such cases.
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Affiliation(s)
- Janos Zempleni
- Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, NE 68586, USA, Tel.: +1 402 472 3270, ,
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Pendini NR, Bailey LM, Booker GW, Wilce MC, Wallace JC, Polyak SW. Microbial biotin protein ligases aid in understanding holocarboxylase synthetase deficiency. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:973-82. [DOI: 10.1016/j.bbapap.2008.03.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Revised: 03/16/2008] [Accepted: 03/26/2008] [Indexed: 11/16/2022]
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Peluso I, Fina D, Caruso R, Stolfi C, Caprioli F, Fantini MC, Caspani G, Grossi E, Di Iorio L, Paone FM, Pallone F, Monteleone G. Lactobacillus paracasei subsp. paracasei B21060 suppresses human T-cell proliferation. Infect Immun 2007; 75:1730-7. [PMID: 17242060 PMCID: PMC1865705 DOI: 10.1128/iai.01172-06] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Recent studies have shown that probiotics are beneficial in T-cell-mediated inflammatory diseases. The molecular mechanism by which probiotics work remains elusive, but accumulating evidence indicates that probiotics can modulate immune cell responses. Since T cells express receptors for bacterial products or components, we examined whether different strains of lactobacilli directly regulate the functions of human T cells. CD4(+) T cells were isolated from blood and intestinal lamina propria (LP) of normal individuals and patients with inflammatory bowel disease (IBD). Mononuclear cells were also isolated from Peyer's patches. Cells were activated with anti-CD3/CD2/CD28 in the presence or absence of Lactobacillus paracasei subsp. paracasei B21060, L. paracasei subsp. paracasei F19, or L. casei subsp. casei DG. Cell proliferation and death, Foxp3, intracellular pH, and cytokine production were evaluated by flow cytometry. We showed that L. paracasei subsp. paracasei B21060 but neither L. paracasei subsp. paracasei F19 nor L. casei subsp. casei DG inhibited blood CD4(+) T-cell growth. This effect was associated with no change in cell survival, expression of Foxp3, or production of gamma interferon, interleukin-4 (IL-4), IL-5, and IL-10. L. paracasei subsp. paracasei B21060-mediated blockade of CD4(+) T-cell proliferation required a viable bacterium and was associated with decreased MCT-1 expression and low intracellular pH. L. paracasei subsp. paracasei B21060 also inhibited the growth of Peyer's patch mononuclear cells, normal lymphocytes, and IBD CD4(+) LP lymphocytes without affecting cytokine production. The data show that L. paracasei subsp. paracasei B21060 blocks T-cell growth, thus suggesting a mechanism by which these probiotics could interfere with T-cell-driven immune responses.
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Affiliation(s)
- Ilaria Peluso
- Dipartimento di Medicina Interna, Università Tor Vergata, Via Montpellier 1, 00133 Rome, Italy
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Alkemade A, Friesema EC, Kuiper GG, Wiersinga WM, Swaab DF, Visser TJ, Fliers E. Novel neuroanatomical pathways for thyroid hormone action in the human anterior pituitary. Eur J Endocrinol 2006; 154:491-500. [PMID: 16498064 DOI: 10.1530/eje.1.02111] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE An increasing number of proteins appear to be involved in thyroid hormone feedback action at the level of the anterior pituitary, but the cell types expressing these proteins are largely unknown. The aim of the present study was to identify cell types in the human anterior pituitary that express type II and type III deiodinase (D2 and D3), the recently described thyroid hormone transporter (MCT8) and thyroid hormone receptor (TR) isoforms by means of double-labeling immunocytochemistry. RESULTS We found TR isoforms to be expressed most prominently in gonadotropes and - although to a lesser extent - in thyrotropes, corticotropes, lactotropes and somatotropes. D3 staining showed a distribution pattern that was remarkably similar. By contrast, D2 immunoreactivity was observed exclusively in folliculostellate (FS) cells showing coexpression with human leukocyte antigen (HLA), a marker of major histocompatibility complex (MHC)-class II. MCT8 immunostaining was present in FS cells without HLA coexpression. CONCLUSIONS From these results, we propose a novel neuroanatomical model for thyroid hormone feedback on the human pituitary, with a central role for FS cells in thyroid hormone activation, which thus play an important role in the suppression of TSH secretion by circulating thyroxine (T(4)).
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Affiliation(s)
- Anneke Alkemade
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, The Netherlands
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Murray CM, Hutchinson R, Bantick JR, Belfield GP, Benjamin AD, Brazma D, Bundick RV, Cook ID, Craggs RI, Edwards S, Evans LR, Harrison R, Holness E, Jackson AP, Jackson CG, Kingston LP, Perry MWD, Ross ARJ, Rugman PA, Sidhu SS, Sullivan M, Taylor-Fishwick DA, Walker PC, Whitehead YM, Wilkinson DJ, Wright A, Donald DK. Monocarboxylate transporter MCT1 is a target for immunosuppression. Nat Chem Biol 2006; 1:371-6. [PMID: 16370372 DOI: 10.1038/nchembio744] [Citation(s) in RCA: 202] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Current immunosuppressive therapies act on T lymphocytes by modulation of cytokine production, modulation of signaling pathways or by inhibition of the enzymes of nucleotide biosynthesis. We have identified a previously unknown series of immunomodulatory compounds that potently inhibit human and rat T lymphocyte proliferation in vitro and in vivo in immune-mediated animal models of disease, acting by a novel mechanism. Here we identify the target of these compounds, the monocarboxylate transporter MCT1 (SLC16A1), using a strategy of photoaffinity labeling and proteomic characterization. We show that inhibition of MCT1 during T lymphocyte activation results in selective and profound inhibition of the extremely rapid phase of T cell division essential for an effective immune response. MCT1 activity, however, is not required for many stages of lymphocyte activation, such as cytokine production, or for most normal physiological functions. By pursuing a chemistry-led target identification strategy, we have discovered that MCT1 is a previously unknown target for immunosuppressive therapy and have uncovered an unsuspected role for MCT1 in immune biology.
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Affiliation(s)
- Clare M Murray
- Department of Discovery BioScience, AstraZeneca R&D Charnwood, Bakewell Road, Loughborough, Leicestershire LE11 5RH, UK
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Abstract
Evidence is emerging that biotin participates in processes other than classical carboxylation reactions. Specifically, novel roles for biotin in cell signaling, gene expression, and chromatin structure have been identified in recent years. Human cells accumulate biotin by using both the sodium-dependent multivitamin transporter and monocarboxylate transporter 1. These transporters and other biotin-binding proteins partition biotin to compartments involved in biotin signaling: cytoplasm, mitochondria, and nuclei. The activity of cell signals such as biotinyl-AMP, Sp1 and Sp3, nuclear factor (NF)-kappaB, and receptor tyrosine kinases depends on biotin supply. Consistent with a role for biotin and its catabolites in modulating these cell signals, greater than 2000 biotin-dependent genes have been identified in various human tissues. Many biotin-dependent gene products play roles in signal transduction and localize to the cell nucleus, consistent with a role for biotin in cell signaling. Posttranscriptional events related to ribosomal activity and protein folding may further contribute to effects of biotin on gene expression. Finally, research has shown that biotinidase and holocarboxylase synthetase mediate covalent binding of biotin to histones (DNA-binding proteins), affecting chromatin structure; at least seven biotinylation sites have been identified in human histones. Biotinylation of histones appears to play a role in cell proliferation, gene silencing, and the cellular response to DNA repair. Roles for biotin in cell signaling and chromatin structure are consistent with the notion that biotin has a unique significance in cell biology.
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Affiliation(s)
- Janos Zempleni
- Department of Nutrition and Health Sciences and Departments of Biochemistry and Animal Science, University of Nebraska at Lincoln, Nebraska 68583-0806, USA.
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Pacheco-Alvarez D, Solórzano-Vargas RS, González-Noriega A, Michalak C, Zempleni J, León-Del-Río A. Biotin availability regulates expression of the sodium-dependent multivitamin transporter and the rate of biotin uptake in HepG2 cells. Mol Genet Metab 2005; 85:301-7. [PMID: 15905112 DOI: 10.1016/j.ymgme.2005.04.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2005] [Revised: 04/07/2005] [Accepted: 04/07/2005] [Indexed: 11/21/2022]
Abstract
In human cells, biotin is essential to maintain metabolic homeostasis and as regulator of gene expression. The enzyme holocarboxylase synthetase (HCS) transforms biotin into its active form 5'-biotinyl-AMP and this compound is used to biotinylate five biotin-dependent carboxylases or to activate a soluble guanylate cyclase (sGC) and a cGMP-dependent protein kinase (PKG). The HCS-sGC-PKG pathway is responsible for maintaining the mRNA levels of enzymes involved in biotin utilization including HCS, carboxylases, and a biotin carrier known as sodium-dependent multivitamin transporter (SMVT). To understand the role of SMVT in the control of biotin utilization, we have studied the effect of biotin availability on SMVT protein and mRNA expression levels in HepG2 cells by Western blot analysis and rtPCR, respectively; and their functional impact on the rate of [3H]biotin uptake in human cells. Our results showed that human HepG2 cells grown in a biotin-deficient medium have a lower rate of biotin uptake than normal cells. The impairment in biotin uptake is associated with a reduction in the amount of both SMVT protein mass and mRNA levels. Transfection of HepG2 cells with a vector containing a luciferase reporter gene under the control of the rat SMVT promoter demonstrated that its transcriptional activity is regulated by biotin availability through activation of the HCS-sGC-PKG pathway. Our results support the proposed role of SMVT in the altruistic regulation of biotin utilization in liver cells that has been associated with sparing biotin depletion of the brain.
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Affiliation(s)
- Diana Pacheco-Alvarez
- Department of Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico D.F. 04510, Mexico
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Baron JM, Heise R, Blaner WS, Neis M, Joussen S, Dreuw A, Marquardt Y, Saurat JH, Merk HF, Bickers DR, Jugert FK. Retinoic Acid and its 4-Oxo Metabolites are Functionally Active in Human Skin Cells In Vitro. J Invest Dermatol 2005; 125:143-53. [PMID: 15982314 DOI: 10.1111/j.0022-202x.2005.23791.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Retinoic acid exerts a variety of effects on gene transcription that regulate growth, differentiation, and inflammation in normal and neoplastic skin cells. Because there is a lack of information regarding the influence of metabolic transformation of retinoids on their pharmacologic effects in skin, we have analyzed the functional activity of all-trans-, 9-cis-, and 13-cis-retinoic acid and their 4-oxo-metabolites in normal human epidermal keratinocytes (NHEKs) and dermal fibroblasts using gene and protein expression profiling techniques, including cDNA microarrays, two-dimensional gel electrophoresis, and MALDI-MS. It was previously thought that the 4-oxo-metabolites of RA are inert catabolic end-products but our results indicate instead that they display strong and isomer-specific transcriptional regulatory activity in both NHEKs and dermal fibroblasts. Microarray and proteomic analyses identified a number of novel genes/gene products that are influenced by RA treatment of NHEKs or fibroblasts, including genes for enzymes catalyzing biotransformation of retinoids, corticosteroids, and antioxidants and structural and transport proteins known to be essential for homeostasis. Our results expand current knowledge regarding retinoic acid action within skin cells and the target tissue/cell regulatory systems that are important for modulating the physiological and pharmacological effects of this important class of dermatological drugs.
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Affiliation(s)
- Jens M Baron
- Department of Dermatology and Allergology, University Hospital of the RWTH, Aachen, Germany.
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Vlasova TI, Stratton SL, Wells AM, Mock NI, Mock DM. Biotin deficiency reduces expression of SLC19A3, a potential biotin transporter, in leukocytes from human blood. J Nutr 2005; 135:42-7. [PMID: 15623830 PMCID: PMC1307527 DOI: 10.1093/jn/135.1.42] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In evaluating potential indicators of biotin status, we quantitated the expression of biotin-related genes in leukocytes from human blood of normal subjects before and after inducing marginal biotin deficiency. Biotin deficiency was induced experimentally by feeding an egg-white diet for 28 d. Gene expression was quantitated for the following biotin-related proteins: methylcrotonyl-CoA carboxylase chains A (MCCA) and B (MCCB); propionyl-CoA carboxylase chains A (PCCA) and B (PCCB); pyruvate carboxylase (PC); acetyl-CoA carboxylase isoforms A (ACCA) and B (ACCB); holocarboxylase synthetase (HCS); biotinidase; and 2 potential biotin transporters: sodium-dependent multivitamin transporter (SMVT) and solute carrier family 19 member 3 (SLC19A3). For 7 subjects who successfully completed the study, the abundance of the specific mRNAs was determined by quantitative real-time RT-PCR at d 0 and 28. At d 28, SLC19A3 expression had decreased to 33% of d 0 (P < 0.02 by two-tailed, paired t test). Expression of MCCA, PCCA, PC, ACCA, ACCB, HCS, biotinidase, and SMVT decreased to approximately 80% of d 0 (P < 0.05). Expression of the MCCB and PCCB chains that do not carry the biotin-binding motif did not change significantly; we speculate that expression of the biotin-binding chains of biotin-dependent carboxylases is more responsive to biotin status changes. These data provide evidence that expression of SLC19A3 is a relatively sensitive indicator of marginal biotin deficiency.
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Affiliation(s)
| | | | | | - Nell I. Mock
- Biochemistry & Molecular Biology
- General Clinical Research Center; and
| | - Donald M. Mock
- General Clinical Research Center; and
- Biochemistry & Molecular Biology and Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR
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