1
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Jungnickel KEJ, Guelle O, Iguchi M, Dong W, Kotov V, Gabriel F, Debacker C, Dairou J, McCort-Tranchepain I, Laqtom NN, Chan SH, Ejima A, Sato K, Massa López D, Saftig P, Mehdipour AR, Abu-Remaileh M, Gasnier B, Löw C, Damme M. MFSD1 with its accessory subunit GLMP functions as a general dipeptide uniporter in lysosomes. Nat Cell Biol 2024; 26:1047-1061. [PMID: 38839979 PMCID: PMC11252000 DOI: 10.1038/s41556-024-01436-5] [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: 01/22/2024] [Accepted: 05/07/2024] [Indexed: 06/07/2024]
Abstract
The lysosomal degradation of macromolecules produces diverse small metabolites exported by specific transporters for reuse in biosynthetic pathways. Here we deorphanized the major facilitator superfamily domain containing 1 (MFSD1) protein, which forms a tight complex with the glycosylated lysosomal membrane protein (GLMP) in the lysosomal membrane. Untargeted metabolomics analysis of MFSD1-deficient mouse lysosomes revealed an increase in cationic dipeptides. Purified MFSD1 selectively bound diverse dipeptides, while electrophysiological, isotope tracer and fluorescence-based studies in Xenopus oocytes and proteoliposomes showed that MFSD1-GLMP acts as a uniporter for cationic, neutral and anionic dipeptides. Cryoelectron microscopy structure of the dipeptide-bound MFSD1-GLMP complex in outward-open conformation characterized the heterodimer interface and, in combination with molecular dynamics simulations, provided a structural basis for its selectivity towards diverse dipeptides. Together, our data identify MFSD1 as a general lysosomal dipeptide uniporter, providing an alternative route to recycle lysosomal proteolysis products when lysosomal amino acid exporters are overloaded.
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Affiliation(s)
| | - Océane Guelle
- Saints-Pères Paris Institute for the Neurosciences, Université Paris Cité, Centre National de la Recherche Scientifique, Paris, France
| | - Miharu Iguchi
- Department of Chemical Engineering, Stanford University, Stanford, CA, USA
- Department of Genetics, Stanford University, Stanford, CA, USA
- The Institute for Chemistry, Engineering and Medicine for Human Health, Stanford University, Stanford, CA, USA
| | - Wentao Dong
- Department of Chemical Engineering, Stanford University, Stanford, CA, USA
- Department of Genetics, Stanford University, Stanford, CA, USA
- The Institute for Chemistry, Engineering and Medicine for Human Health, Stanford University, Stanford, CA, USA
| | - Vadim Kotov
- Centre for Structural Systems Biology, Hamburg, Germany
- European Molecular Biology Laboratory Hamburg, Hamburg, Germany
| | - Florian Gabriel
- Centre for Structural Systems Biology, Hamburg, Germany
- European Molecular Biology Laboratory Hamburg, Hamburg, Germany
| | - Cécile Debacker
- Saints-Pères Paris Institute for the Neurosciences, Université Paris Cité, Centre National de la Recherche Scientifique, Paris, France
| | - Julien Dairou
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, CNRS UMR 8601, Université Paris Cité, Paris, France
| | - Isabelle McCort-Tranchepain
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, CNRS UMR 8601, Université Paris Cité, Paris, France
| | - Nouf N Laqtom
- Department of Chemical Engineering, Stanford University, Stanford, CA, USA
- Department of Genetics, Stanford University, Stanford, CA, USA
- The Institute for Chemistry, Engineering and Medicine for Human Health, Stanford University, Stanford, CA, USA
| | - Sze Ham Chan
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Akika Ejima
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Kenji Sato
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - David Massa López
- Institute of Biochemistry, Christian-Albrechts-University Kiel, Kiel, Germany
| | - Paul Saftig
- Institute of Biochemistry, Christian-Albrechts-University Kiel, Kiel, Germany
| | | | - Monther Abu-Remaileh
- Department of Chemical Engineering, Stanford University, Stanford, CA, USA
- Department of Genetics, Stanford University, Stanford, CA, USA
- The Institute for Chemistry, Engineering and Medicine for Human Health, Stanford University, Stanford, CA, USA
| | - Bruno Gasnier
- Saints-Pères Paris Institute for the Neurosciences, Université Paris Cité, Centre National de la Recherche Scientifique, Paris, France.
| | - Christian Löw
- Centre for Structural Systems Biology, Hamburg, Germany.
- European Molecular Biology Laboratory Hamburg, Hamburg, Germany.
| | - Markus Damme
- Institute of Biochemistry, Christian-Albrechts-University Kiel, Kiel, Germany.
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2
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Boytsov D, Madej GM, Horn G, Blaha N, Köcher T, Sitte HH, Siekhaus D, Ziegler C, Sandtner W, Roblek M. Orphan lysosomal solute carrier MFSD1 facilitates highly selective dipeptide transport. Proc Natl Acad Sci U S A 2024; 121:e2319686121. [PMID: 38507452 PMCID: PMC10990142 DOI: 10.1073/pnas.2319686121] [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: 11/10/2023] [Accepted: 02/27/2024] [Indexed: 03/22/2024] Open
Abstract
Orphan solute carrier (SLC) represents a group of membrane transporters whose exact functions and substrate specificities are not known. Elucidating the function and regulation of orphan SLC transporters is not only crucial for advancing our knowledge of cellular and molecular biology but can potentially lead to the development of new therapeutic strategies. Here, we provide evidence for the biological function of a ubiquitous orphan lysosomal SLC, the Major Facilitator Superfamily Domain-containing Protein 1 (MFSD1), which has remained phylogenetically unassigned. Targeted metabolomics revealed that dipeptides containing either lysine or arginine residues accumulate in lysosomes of cells lacking MFSD1. Whole-cell patch-clamp electrophysiological recordings of HEK293-cells expressing MFSD1 on the cell surface displayed transport affinities for positively charged dipeptides in the lower mM range, while dipeptides that carry a negative net charge were not transported. This was also true for single amino acids and tripeptides, which MFSD1 failed to transport. Our results identify MFSD1 as a highly selective lysosomal lysine/arginine/histidine-containing dipeptide exporter, which functions as a uniporter.
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Affiliation(s)
- Danila Boytsov
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, ViennaAT-1090, Austria
| | - Gregor M. Madej
- Department of Biophysics II/Structural Biology, University of Regensburg, RegensburgDE-93053, Germany
| | - Georg Horn
- Department of Biophysics II/Structural Biology, University of Regensburg, RegensburgDE-93053, Germany
| | - Nadine Blaha
- Vienna BioCenter Core Facilities, Metabolomics, Vienna BioCenter, ViennaAT-1030, Austria
| | - Thomas Köcher
- Vienna BioCenter Core Facilities, Metabolomics, Vienna BioCenter, ViennaAT-1030, Austria
| | - Harald H. Sitte
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, ViennaAT-1090, Austria
- Hourani Center for Applied Scientific Research, Al-Ahliyya Amman University, AmmanJO-19328, Jordan
- Center for Addiction Research and Science, Medical University of Vienna, ViennaAT-1090, Austria
| | - Daria Siekhaus
- Institute of Science and Technology Austria, KlosterneuburgAT-3400, Austria
| | - Christine Ziegler
- Department of Biophysics II/Structural Biology, University of Regensburg, RegensburgDE-93053, Germany
| | - Walter Sandtner
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, ViennaAT-1090, Austria
| | - Marko Roblek
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, ViennaAT-1090, Austria
- Institute of Science and Technology Austria, KlosterneuburgAT-3400, Austria
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3
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Matye D, Gunewardena S, Chen J, Wang H, Wang Y, Hasan MN, Gu L, Clayton YD, Du Y, Chen C, Friedman JE, Lu SC, Ding WX, Li T. TFEB regulates sulfur amino acid and coenzyme A metabolism to support hepatic metabolic adaptation and redox homeostasis. Nat Commun 2022; 13:5696. [PMID: 36171419 PMCID: PMC9519740 DOI: 10.1038/s41467-022-33465-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Accepted: 09/15/2022] [Indexed: 11/15/2022] Open
Abstract
Fatty liver is a highly heterogenous condition driven by various pathogenic factors in addition to the severity of steatosis. Protein insufficiency has been causally linked to fatty liver with incompletely defined mechanisms. Here we report that fatty liver is a sulfur amino acid insufficient state that promotes metabolic inflexibility via limiting coenzyme A availability. We demonstrate that the nutrient-sensing transcriptional factor EB synergistically stimulates lysosome proteolysis and methionine adenosyltransferase to increase cysteine pool that drives the production of coenzyme A and glutathione, which support metabolic adaptation and antioxidant defense during increased lipid influx. Intriguingly, mice consuming an isocaloric protein-deficient Western diet exhibit selective hepatic cysteine, coenzyme A and glutathione deficiency and acylcarnitine accumulation, which are reversed by cystine supplementation without normalizing dietary protein intake. These findings support a pathogenic link of dysregulated sulfur amino acid metabolism to metabolic inflexibility that underlies both overnutrition and protein malnutrition-associated fatty liver development.
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Affiliation(s)
- David Matye
- Harold Hamm Diabetes Center, Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Sumedha Gunewardena
- Department of Cell Biology and Physiology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Jianglei Chen
- Harold Hamm Diabetes Center, Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Huaiwen Wang
- Laboratory for Molecular Biology and Cytometry Research, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Yifeng Wang
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Mohammad Nazmul Hasan
- Harold Hamm Diabetes Center, Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Lijie Gu
- Harold Hamm Diabetes Center, Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Yung Dai Clayton
- Harold Hamm Diabetes Center, Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Yanhong Du
- Harold Hamm Diabetes Center, Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Cheng Chen
- Harold Hamm Diabetes Center, Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Jacob E Friedman
- Harold Hamm Diabetes Center, Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Shelly C Lu
- Karsh Division of Gastroenterology and Hepatology, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, 90048, USA
| | - Wen-Xing Ding
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Tiangang Li
- Harold Hamm Diabetes Center, Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA.
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4
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Rudnik S, Damme M. The lysosomal membrane-export of metabolites and beyond. FEBS J 2021; 288:4168-4182. [PMID: 33067905 DOI: 10.1111/febs.15602] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 10/01/2020] [Accepted: 10/15/2020] [Indexed: 01/01/2023]
Abstract
Lysosomes are degradative organelles in eukaryotic cells mediating the hydrolytic catabolism of various macromolecules to small basic building blocks. These low-molecular-weight metabolites are transported across the lysosomal membrane and reused in the cytoplasm and other organelles for biosynthetic pathways. Even though in the past 20 years our understanding of the lysosomal membrane regarding various transporters, other integral and peripheral membrane proteins, the lipid composition, but also its turnover has dramatically improved, there are still many unresolved questions concerning key aspects of the function of the lysosomal membrane. These include a possible function of lysosomes as a cellular storage compartment, yet unidentified transporters mediating the export such as various amino acids, mechanisms mediating the transport of lysosomal membrane proteins from the Golgi apparatus to lysosomes, and the turnover of lysosomal membrane proteins. Here, we review the current knowledge about the lysosomal membrane and identify some of the open questions that need to be solved in the future for a comprehensive and complete understanding of how lysosomes communicate with other organelles, cellular processes, and pathways.
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Affiliation(s)
- Sönke Rudnik
- Institut für Biochemie, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
| | - Markus Damme
- Institut für Biochemie, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
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5
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Tailoring acyclovir prodrugs with enhanced antiviral activity: rational design, synthesis, human plasma stability and in vitro evaluation. Amino Acids 2018; 50:1131-1143. [DOI: 10.1007/s00726-018-2590-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 05/12/2018] [Indexed: 12/14/2022]
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Cherqui S, Courtoy PJ. The renal Fanconi syndrome in cystinosis: pathogenic insights and therapeutic perspectives. Nat Rev Nephrol 2016; 13:115-131. [PMID: 27990015 DOI: 10.1038/nrneph.2016.182] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Cystinosis is an autosomal recessive metabolic disease that belongs to the family of lysosomal storage disorders. It is caused by a defect in the lysosomal cystine transporter, cystinosin, which results in an accumulation of cystine in all organs. Despite the ubiquitous expression of cystinosin, a renal Fanconi syndrome is often the first manifestation of cystinosis, usually presenting within the first year of life and characterized by the early and severe dysfunction of proximal tubule cells, highlighting the unique vulnerability of this cell type. The current therapy for cystinosis, cysteamine, facilitates lysosomal cystine clearance and greatly delays progression to kidney failure but is unable to correct the Fanconi syndrome. This Review summarizes decades of studies that have fostered a better understanding of the pathogenesis of the renal Fanconi syndrome associated with cystinosis. These studies have unraveled some of the early molecular changes that occur before the onset of tubular atrophy and identified a role for cystinosin beyond cystine transport, in endolysosomal trafficking and proteolysis, lysosomal clearance, autophagy and the regulation of energy balance. These studies have also led to the identification of new potential therapeutic targets and here, we outline the potential role of stem cell therapy for cystinosis and provide insights into the mechanism of haematopoietic stem cell-mediated kidney protection.
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Affiliation(s)
- Stephanie Cherqui
- Department of Pediatrics, Division of Genetics, University of California San Diego, 9500 Gilman Drive, MC 0734, La Jolla, California 92093-0734, USA
| | - Pierre J Courtoy
- Cell biology, de Duve Institute and Université catholique de Louvain, UCL-Brussels, 75 Avenue Hippocrate, B-1200 Brussels, Belgium
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7
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Geillinger KE, Kipp AP, Schink K, Röder PV, Spanier B, Daniel H. Nrf2 regulates the expression of the peptide transporter PEPT1 in the human colon carcinoma cell line Caco-2. Biochim Biophys Acta Gen Subj 2013; 1840:1747-54. [PMID: 24380877 DOI: 10.1016/j.bbagen.2013.12.026] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Revised: 12/20/2013] [Accepted: 12/20/2013] [Indexed: 12/30/2022]
Abstract
BACKGROUND PEPT1 is a rheogenic transport protein in the apical membrane of intestinal epithelial cells capable of transporting essentially all possible di- and tripeptides that are generated from the luminal protein breakdown. In addition, several anticancer, antimicrobial and antiviral drugs are taken up from the intestinal lumen via PEPT1 and therefore PEPT1 is a target for efficient drug delivery via prodrug approaches. Thus, understanding PEPT1 gene regulation is not only of importance for dietary adaptation but also for drug treatment. METHODS In silico analysis of the Pept1 promoter was performed using MatInspector. Pept1 promoter constructs were generated and cotransfected with an Nrf2 expression plasmid. Caco-2 cells were stimulated with Nrf2 inducers followed by electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP). Biological relevance was investigated using western blot analysis and transport activity assays. RESULTS Reporter gene assays showed transcriptional activation of the Pept1 promoter in response to Nrf2 overexpression. EMSA as well as ChIP analysis validated Nrf2 binding to the ARE located closest to the start codon (Pept1-ARE1). Induction of the Nrf2 pathway resulted in increased endogenous PEPT1 protein abundance as well as transport activity. Moreover, we demonstrate that also the induction of autophagy by MG132 resulted in elevated Nrf2 binding to Pept1-ARE1 and increased PEPT1 protein expression. CONCLUSION In summary, we identified a biologically active Nrf2 binding site within the Pept1 promoter which links Pept1 to the cellular defense program activated by Nrf2. GENERAL SIGNIFICANCE This study identifies Pept1 as an inducible target gene of the Nrf2 pathway.
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Affiliation(s)
- Kerstin E Geillinger
- ZIEL Research Center of Nutrition and Food Sciences, Biochemistry Unit, Technische Universität München, Gregor-Mendel-Str. 2, 85350 Freising, Germany.
| | - Anna P Kipp
- Department Biochemistry of Micronutrients, German Institute of Human Nutrition, Potsdam-Rehbruecke, Germany
| | - Kristin Schink
- ZIEL Research Center of Nutrition and Food Sciences, Biochemistry Unit, Technische Universität München, Gregor-Mendel-Str. 2, 85350 Freising, Germany
| | - Pia V Röder
- ZIEL Research Center of Nutrition and Food Sciences, Biochemistry Unit, Technische Universität München, Gregor-Mendel-Str. 2, 85350 Freising, Germany
| | - Britta Spanier
- ZIEL Research Center of Nutrition and Food Sciences, Biochemistry Unit, Technische Universität München, Gregor-Mendel-Str. 2, 85350 Freising, Germany
| | - Hannelore Daniel
- ZIEL Research Center of Nutrition and Food Sciences, Biochemistry Unit, Technische Universität München, Gregor-Mendel-Str. 2, 85350 Freising, Germany
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8
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Lockwood TD. Lysosomal metal, redox and proton cycles influencing the CysHis cathepsin reaction. Metallomics 2013; 5:110-24. [PMID: 23302864 DOI: 10.1039/c2mt20156a] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
In the 1930's pioneers discovered that maximal autolysis in tissue homogenates requires metal chelator, sulfhydryl reducing agent and acid pH. However, metals, reducing equivalents and protons (MR&P) have been overlooked as combined catalytic controls. Three categories of lysosomal machinery drive three distinguishable cycles importing and exporting MR&P. Zn(2+) preemptively inhibits CysHis catalysis under otherwise optimal protonation and reduction. Protein-bound cell Zn(2+) concentration is 200-2000 times the non-sequestered inhibitory concentration. Following autophagy, lysosomal proteolysis liberates much inhibitory Zn(2+). The vacuolar proton pump is the driving force for Zn(2+) export, as well as protonation of the peptidolytic mechanism. Other machinery of lysosomal cycles includes proton-driven Zn(2+) exporters (e.g. SLC11A1), Zn(2+) channels (e.g. TRPML-1), lysosomal thiol reductase, etc. The CysHis dyad is a sensor of the vacuolar environment of MR&P, an integrator of these simultaneous variables, and a catalytic responder. Rate-determination can shift between autophagic substrate acquisition (swallowing) and substrate degradation (digesting). Zn(2+) recycling from degraded proteins to new proteins is a fourth cycle that might pace lysosomal function under some conditions. Heritable insufficient or excess functions of CysHis cathepsins are associated with dysfunctional inflammation and immunity/auto-immunity, including diabetic pathogenesis.
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Affiliation(s)
- Thomas D Lockwood
- Dept. of Pharmacology, School of Medicine, Wright State University, Dayton, Ohio 45435, USA.
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9
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Possible role of α-mannosidase and β-galactosidase in larynx cancer. Contemp Oncol (Pozn) 2012; 16:154-8. [PMID: 23788869 PMCID: PMC3687398 DOI: 10.5114/wo.2012.28795] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Revised: 10/21/2011] [Accepted: 01/19/2012] [Indexed: 12/17/2022] Open
Abstract
Background Lysosomal exoglycosidases, such as α-mannosidases (MAN) and β-galactosidases (GAL), are found in different glycoside hydrolase sequence-based families. Considerable research has proved plays the role of MAN, which play a key role in the modification and diversification of hybrid N-glycans, processes with strong cellular links to cancer. Therefore the study aim was to investigate the activities of MAN and GAL in larynx cancer compared to controls. Material and methods Larynx cancer (n = 21) and normal healthy tissue (n = 21) were collected from patients during total laryngectomy. A biopsy of macroscopically healthy tissue in the area of the lower 1/3 of omohyoid muscle was taken for frozen sections in each case and these served as controls. The release of p-nitrophenol from p-nitrophenol derivatives of MAN and GAL was used. Results In all specimens we observed significantly higher activity of investigated enzymes in larynx cancer compared with controls. The mean release of MAN from activated cells was 3.702 ±1.3245 nkat/g wet tissue compared to controls (1.614 ±0.8220 nkat/g wet tissue). The mean release of GAL from the activated cells was 3.383 ±2.1980 nkat/g wet tissue compared to controls (2.137 ±1.3685 nkat/g wet tissue). Differences in observed activity were statistically significant. Conclusion The present data indicate that MAN and GAL are significantly and consistently elevated in larynx cancer growth. It also means that catabolic reactions involving glycoproteins, glycolipids and proteoglycans may play a role in larynx cancer. Further research should also evaluate the relative importance of these particular exoglycosidases in indicating the progress of the disease in considering the spectrum of identified marker mediators.
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10
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Ma K, Hu Y, Smith DE. Influence of fed-fasted state on intestinal PEPT1 expression and in vivo pharmacokinetics of glycylsarcosine in wild-type and Pept1 knockout mice. Pharm Res 2011; 29:535-45. [PMID: 21904935 DOI: 10.1007/s11095-011-0580-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Accepted: 08/26/2011] [Indexed: 11/28/2022]
Abstract
PURPOSE To determine if fasting would affect the intestinal expression and in vivo functional activity of PEPT1 as determined after oral dosing of the dipeptide glycylsarcosine (GlySar). METHODS Systemic exposure and tissue distribution studies were performed in wild-type and Pept1 knockout mice, under fed and fasted conditions, following both intravenous and oral doses of [(14)C]GlySar at 5 nmol/g body weight. Intestinal PEPT1 expression was evaluated by real-time PCR and immunoblot analyses. RESULTS We found that expression of PEPT1 protein in the small intestine was increased ~2-fold in wild-type mice during fasted as compared to fed conditions. In agreement, systemic exposure and peak plasma concentrations of orally administered GlySar were 40 and 65% greater, respectively, in wild-type mice during fasted vs. fed state. No significant differences were observed between fed and fasted animals during PEPT1 ablation. Tissue distribution of GlySar was unchanged after oral dosing for all four treatment groups. CONCLUSIONS As little as 16 h of fasting can cause significant upregulation of PEPT1 protein expression in the small intestine, which then translates into a significant increase in in vivo oral absorption of GlySar.
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Affiliation(s)
- Ke Ma
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Michigan, Ann Arbor, Michigan, USA
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11
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Jappar D, Hu Y, Smith DE. Effect of dose escalation on the in vivo oral absorption and disposition of glycylsarcosine in wild-type and Pept1 knockout mice. Drug Metab Dispos 2011; 39:2250-7. [PMID: 21880829 DOI: 10.1124/dmd.111.041087] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
This study evaluated the in vivo absorption and disposition of glycylsarcosine (GlySar), after escalating oral doses, in wild-type and peptide transporter 1 (Pept1) knockout mice. [(3)H]GlySar was administered to mice at doses of 1, 10, 100, 1000, and 5000 nmol/g b.wt. Serial blood samples were obtained over 480 min, the plasma was harvested, and the area under the plasma concentration-time curve (AUC) was determined. It was observed that the GlySar AUC was 60, 45, and 30% lower in knockout than wild-type mice when evaluated over 2, 4, and 8 h, respectively (p < 0.01). Plasma levels of GlySar reached a plateau at 90 min in knockout mice and then rose to a second plateau at 240 min. In wild-type mice, the plasma levels rose continuously to reach a single plateau at 90 min. When partial AUC (0-120 min) was used as an indicator for rate of absorption, there was a 60% reduction in GlySar absorption rate in knockout mice compared with wild-type animals. Tissue distribution studies were also performed after 10 nmol/g oral doses of [(3)H]GlySar. When sampled 1 h after dosing, GlySar tissue concentrations were significantly lower in knockout versus wild-type mice and, with the exception of intestines, reflected differences in the systemic exposure of dipeptide between these two genotypes. Overall, PEPT1 ablation in mice resulted in significant reductions, in vivo, in the rate and extent of GlySar absorption. The AUC of GlySar was proportional to dose in both genotypes over 1 to 100 nmol/g, with minor decrements at the two highest doses.
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Affiliation(s)
- Dilara Jappar
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Michigan, Ann Arbor, MI, USA
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12
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Mallick S, Bera BK, Mondal A, Datta AK, Mandal S, Karmakar P, Ghosh AK. Kinetics and Mechanism of the Ligand Substitution Reaction of Di-μ-Hydroxobis(Bipyridyl)Dipalladium(Ii)Ion with Dipeptides in Aqueous Solution. PROGRESS IN REACTION KINETICS AND MECHANISM 2011. [DOI: 10.3184/146867811x13079836470037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The interaction of the title complex with dipeptides such as glycylglycine (Gly - Gly) and glycylglutamine (Gly-Gin) has been studied spectrophotometrically in aqueous medium as a function of [substrate complex], [ligand] and temperature at a particular pH (7.4), where the substrate complex exists predominantly as the dimeric dihydroxo-bridged species and the dipeptides are in zwitterionic form, at constant ionic strength. The reactions have been studied under pseudo-first order conditions. The reaction proceeds in a two-step-consecutive manner (A ->B ->C); where the first step is ligand-dependent and second step is ligand-independent, and is assigned to ring closure. Based on the kinetic and activation parameters, an associative interchange mechanism is proposed for the interaction processes.
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Affiliation(s)
- Subhasis Mallick
- Department of Chemistry, University of Burdwan, Burdwan-713104, West Bengal, India
| | - Biplab K. Bera
- Department of Chemistry, University of Burdwan, Burdwan-713104, West Bengal, India
| | - Arup Mondal
- Department of Chemistry, University of Burdwan, Burdwan-713104, West Bengal, India
| | - Asok K Datta
- Department of Paediatrics, Burdwan Medical College and Hospital, Burdwan-713104, West Bengal, India
| | - Subala Mandal
- Department of Chemistry, University of Burdwan, Burdwan-713104, West Bengal, India
| | - Parnajyoti Karmakar
- Department of Chemistry, University of Burdwan, Burdwan-713104, West Bengal, India
| | - Alak K. Ghosh
- Department of Chemistry, University of Burdwan, Burdwan-713104, West Bengal, India
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Ouellette SP, Dorsey FC, Moshiach S, Cleveland JL, Carabeo RA. Chlamydia species-dependent differences in the growth requirement for lysosomes. PLoS One 2011; 6:e16783. [PMID: 21408144 PMCID: PMC3050816 DOI: 10.1371/journal.pone.0016783] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Accepted: 01/12/2011] [Indexed: 01/06/2023] Open
Abstract
Genome reduction is a hallmark of obligate intracellular pathogens such as Chlamydia, where adaptation to intracellular growth has resulted in the elimination of genes encoding biosynthetic enzymes. Accordingly, chlamydiae rely heavily on the host cell for nutrients yet their specific source is unclear. Interestingly, chlamydiae grow within a pathogen-defined vacuole that is in close apposition to lysosomes. Metabolically-labeled uninfected host cell proteins were provided as an exogenous nutrient source to chlamydiae-infected cells, and uptake and subsequent labeling of chlamydiae suggested lysosomal degradation as a source of amino acids for the pathogen. Indeed, Bafilomycin A1 (BafA1), an inhibitor of the vacuolar H+/ATPase that blocks lysosomal acidification and functions, impairs the growth of C. trachomatis and C. pneumoniae, and these effects are especially profound in C. pneumoniae. BafA1 induced the marked accumulation of material within the lysosomal lumen, which was due to the inhibition of proteolytic activities, and this response inhibits chlamydiae rather than changes in lysosomal acidification per se, as cathepsin inhibitors also inhibit the growth of chlamydiae. Finally, the addition of cycloheximide, an inhibitor of eukaryotic protein synthesis, compromises the ability of lysosomal inhibitors to block chlamydial growth, suggesting chlamydiae directly access free amino acids in the host cytosol as a preferred source of these nutrients. Thus, chlamydiae co-opt the functions of lysosomes to acquire essential amino acids.
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Affiliation(s)
- Scot P. Ouellette
- Centre for Molecular Microbiology and Infection, Division of Cell and Molecular Biology, Imperial College, London, United Kingdom
| | - Frank C. Dorsey
- Department of Cancer Biology, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, United States of America
| | - Simon Moshiach
- Department of Tumor Cell Biology and Genetics, St. Jude Children's Research Hospital, Memphis, Tennessee, United States or America
| | - John L. Cleveland
- Department of Cancer Biology, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, United States of America
| | - Rey A. Carabeo
- Centre for Molecular Microbiology and Infection, Division of Cell and Molecular Biology, Imperial College, London, United Kingdom
- * E-mail:
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Sterling KM, Roggenbeck B, Ahearn GA. Dual control of cytosolic metals by lysosomal transporters in lobster hepatopancreas. J Exp Biol 2010; 213:769-74. [DOI: 10.1242/jeb.039123] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
This study describes the membrane transport mechanisms used by lobster (Homarus americanus) hepatopancreatic epithelial lysosomes to accumulate and sequester heavy metals from the cytosol, and thereby aid in the regulation of these ions entering the animal from dietary constituents. The present investigation extends previous work describing lysosomal metal uptake by cation exchange with protons and suggests that a second, parallel, lysosomal transport process involving metal—thiol conjugates may work in conjunction with the cation antiporter to control cytoplasmic metal concentrations. Transport of 65Zn2+ by lysosomal membrane vesicles (LMV) incubated in 1 mmol l−1 glutathione (GSH) was not significantly different from metal transport in the absence of the tripeptide. However, preloading LMV with 1 mmol l−1 α-ketoglutarate (AKG), and then incubating in a medium containing 1 mmol l−1 GSH, more than doubled metal uptake, compared with vesicles equilibrated with chloride or possessing an outwardly directed chloride gradient. Kinetic analysis of lysosomal 65Zn2+ influx as a function of zinc concentration, in vesicles containing 1 mmol l−1 AKG and incubated in 1 mmol l−1 GSH, revealed the presence of a sigmoidal, low affinity, high capacity carrier process transporting the metal into the organelle. These data indicated the possible presence of an organic anion exchanger in lobster lysosomal membranes. Western blot analysis of LMV with a rabbit anti-rat OAT1 antibody showed the presence of an orthologous OAT1-like protein (approximate molecular mass of 80 kDa) signal from these membranes. These results, and those published previously, suggest the occurrence of two metal transporters on hepatopancreatic membranes, a high affinity, low capacity cation antiporter and a low affinity, high capacity organic anion exchanger. Together these two systems have the potential to regulate cytoplasmic metals over a wide concentration range.
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Affiliation(s)
- K. M. Sterling
- Department of Biology, 1 UNF Drive, University of North Florida, Jacksonville, FL 32224, USA
| | - B. Roggenbeck
- Department of Biology, 1 UNF Drive, University of North Florida, Jacksonville, FL 32224, USA
| | - G. A. Ahearn
- Department of Biology, 1 UNF Drive, University of North Florida, Jacksonville, FL 32224, USA
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15
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Brandsch M, Knütter I, Bosse-Doenecke E. Pharmaceutical and pharmacological importance of peptide transporters. J Pharm Pharmacol 2010; 60:543-85. [DOI: 10.1211/jpp.60.5.0002] [Citation(s) in RCA: 179] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
AbstractPeptide transport is currently a prominent topic in membrane research. The transport proteins involved are under intense investigation because of their physiological importance in protein absorption and also because peptide transporters are possible vehicles for drug delivery. Moreover, in many tissues peptide carriers transduce peptidic signals across membranes that are relevant in information processing. The focus of this review is on the pharmaceutical relevance of the human peptide transporters PEPT1 and PEPT2. In addition to their physiological substrates, both carriers transport many β-lactam antibiotics, valaciclovir and other drugs and prodrugs because of their sterical resemblance to di- and tripeptides. The primary structure, tissue distribution and substrate specificity of PEPT1 and PEPT2 have been well characterized. However, there is a dearth of knowledge on the substrate binding sites and the three-dimensional structure of these proteins. Until this pivotal information becomes available by X-ray crystallography, the development of new drug substrates relies on classical transport studies combined with molecular modelling. In more than thirty years of research, data on the interaction of well over 700 di- and tripeptides, amino acid and peptide derivatives, drugs and prodrugs with peptide transporters have been gathered. The aim of this review is to put the reports on peptide transporter-mediated drug uptake into perspective. We also review the current knowledge on pharmacogenomics and clinical relevance of human peptide transporters. Finally, the reader's attention is drawn to other known or proposed human peptide-transporting proteins.
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Affiliation(s)
- Matthias Brandsch
- Membrane Transport Group, Biozentrum of the Martin-Luther-University Halle-Wittenberg, D-06120 Halle, Germany
| | - Ilka Knütter
- Membrane Transport Group, Biozentrum of the Martin-Luther-University Halle-Wittenberg, D-06120 Halle, Germany
| | - Eva Bosse-Doenecke
- Institute of Biochemistry/Biotechnology, Faculty of Science I, Martin-Luther-University Halle-Wittenberg, D-06120 Halle, Germany
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16
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Peck RF, Shiflett AM, Schwartz KJ, McCann A, Hajduk SL, Bangs JD. The LAMP-like protein p67 plays an essential role in the lysosome of African trypanosomes. Mol Microbiol 2008; 68:933-46. [PMID: 18430083 DOI: 10.1111/j.1365-2958.2008.06195.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
RNAi knockdown was employed to study the function of p67, a lysosome-associated membrane protein (LAMP)-like type I transmembrane lysosomal glycoprotein in African trypanosomes. Conditional induction of p67 dsRNA resulted in specific approximately 90% reductions in de novo p67 synthesis in both mammalian bloodstream and procyclic insect-stage parasites. Bloodstream cell growth was severely retarded with extensive death after > 24 h of induction. Biosynthetic trafficking of residual p67, and of the soluble lysosomal protease trypanopain, were unimpaired. Endocytosis of tomato lectin, a surrogate receptor-mediated cargo, was only mildly impaired (approximately 20%), but proper lysosomal targeting was unaffected. p67 ablation had dramatic effects on lysosomal morphology with gross enlargement (four- to fivefold) and internal membrane profiles reminiscent of autophagic vacuoles. Ablation of p67 expression rendered bloodstream trypanosomes refractory to lysis by human trypanolytic factor (TLF), a lysosomally activated host innate immune mediator. Similar effects on lysosomal morphology and TLF sensitivity were also obtained by two pharmacological agents that neutralize lysosomal pH--chloroquine and bafilomycin A1. Surprisingly, however, lysosomal pH was not affected in ablated cells suggesting that other physiological alterations must account for increased resistance to TLF. These results indicate p67 plays an essential role in maintenance of normal lysosomal structure and physiology in bloodstream-stage African trypanosomes.
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Affiliation(s)
- Ronald F Peck
- Department of Medical Microbiology & Immunology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA
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17
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Sagné C, Gasnier B. Molecular physiology and pathophysiology of lysosomal membrane transporters. J Inherit Metab Dis 2008; 31:258-66. [PMID: 18425435 DOI: 10.1007/s10545-008-0879-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2008] [Revised: 02/19/2008] [Accepted: 02/20/2008] [Indexed: 10/22/2022]
Abstract
In contrast to lysosomal hydrolytic enzymes, the lysosomal membrane remains poorly characterized. In particular, although the genetic study of cystinosis and sialic acid storage disorders led to the identification of two lysosomal transporters for cystine and sialic acids, respectively, ten years ago, most transporters responsible for exporting lysosomal hydrolysis products to the cytosol are still unknown at the molecular level. However, two lines of investigation recently started to fill this gap in the knowledge of lysosomal biology. First, novel proteomic approaches are now able to provide a reliable inventory of lysosomal membrane proteins. On the other hand, a novel functional approach based on intracellular trafficking mechanisms allows direct transport measurement in whole cells by redirecting recombinant lysosomal transporters to the cell surface. After surveying the current state of knowledge in this field, the review focuses on the sialic acid transporter sialin and shows how recent functional data using the above whole-cell approach shed new light on the pathogenesis of sialic acid storage disorders by revealing the existence of a residual transport activity associated with Salla disease.
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Affiliation(s)
- C Sagné
- Institut de Biologie Physico-Chimique, Centre National de la Recherche Scientifique, Université Paris 7 Denis Diderot, Paris, France
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18
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Li K, Xu L, Kulkarni AA, Perkins DI, Haworth IS, Davies DL. Ethanol inhibits functional activity of the human intestinal dipeptide transporter hPepT1 expressed in Xenopus oocytes. Alcohol Clin Exp Res 2008; 32:777-84. [PMID: 18336632 DOI: 10.1111/j.1530-0277.2008.00636.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND The pathological effects of high alcohol (ethanol) consumption on gastrointestinal and hepatic systems are well recognized. However, the effects of ethanol intake on gastric and intestinal absorption and transport systems remain unclear. The present study investigates the effects of ethanol on the human peptide transporter 1 (hPepT1) which mediates the transport of di-and tripeptides as well as several orally administered peptidomimetic drugs such as beta-lactam antibiotics (e.g., penicillin), angiotensin-converting enzyme inhibitors, the anti-neoplastic agent bestatin, and prodrugs of acyclovir. METHODS Xenopus oocytes were injected with hPepT1 cRNA and incubated for 3 to 10 days. Currents induced by glycyl-sarcosine (Gly-Sar), Ala-Ala (dipeptides), penicillin and enalapril measured in the presence or absence of ethanol were determined using an 8-channel 2-electrode voltage clamp system, with a membrane potential of -70 mV and 11 voltage steps of 100 milliseconds (from +50 mV to -150 mV in -20 mV increments). RESULTS Ethanol (200 mM) inhibited Gly-Sar and Ala-Ala currents by 42 and 30%, respectively, with IC(50)s of 184 and 371 mM, respectively. Ethanol reduced maximal transport capacity (I(max)) of hPepT1 for Gly-Sar without affecting Gly-Sar binding affinity (K(0.5) and Hill coefficient). Penicillin- and enalapril-induced currents were significantly less than those induced by dipeptides and were not inhibited by ethanol. CONCLUSION Ethanol significantly reduced transport of dipeptides via a reduction in transport capacity, rather than competing for binding sites in hPepT1. Ethanol inhibition or alteration of transport function may be a primary causative factor contributing to both the nutritional deficits as well as the immunological deficiencies that many alcoholics experience including alcohol liver disease and brain damage.
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Affiliation(s)
- Kaixun Li
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California 90033, USA.
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19
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Biegel A, Gebauer S, Brandsch M, Neubert K, Thondorf I. Structural requirements for the substrates of the H+/peptide cotransporter PEPT2 determined by three-dimensional quantitative structure-activity relationship analysis. J Med Chem 2006; 49:4286-96. [PMID: 16821788 DOI: 10.1021/jm0601811] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The renal type H(+)/peptide cotransporter PEPT2 has a substantial influence on the in vivo disposition of dipeptides and tripeptides as well as peptide-like drugs within the body, particularly in kidney, lung, and the brain. The comparative molecular similarity indices analysis (CoMSIA) method was applied to identify those regions in the substrate structures that are responsible for recognition and for differences in affinity. We have developed a comprehensive 3D quantitative structure-activity relationship (3D-QSAR) model based on 83 compounds that is able to explain and predict the binding affinities of new PEPT2 substrates. This 3D-QSAR model possesses a high predictive power (q(2) = 0.755; r(2) = 0.893). An additional 3D-QSAR model based on the same compounds was generated and correlated with affinity data of the intestinal H(+)/peptide cotransporter PEPT1. By comparing the CoMSIA contour plots, differences in selectivity between the intestinal and the renal type peptide carrier become evident.
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Affiliation(s)
- Annegret Biegel
- Department of Biochemistry/Biotechnology, Institute of Biochemistry, Martin-Luther-University Halle-Wittenberg, D-06099 Halle, Germany
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20
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Biegel A, Knütter I, Hartrodt B, Gebauer S, Theis S, Luckner P, Kottra G, Rastetter M, Zebisch K, Thondorf I, Daniel H, Neubert K, Brandsch M. The renal type H+/peptide symporter PEPT2: structure-affinity relationships. Amino Acids 2006; 31:137-56. [PMID: 16868651 DOI: 10.1007/s00726-006-0331-0] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2005] [Accepted: 01/04/2006] [Indexed: 10/24/2022]
Abstract
The H(+)/peptide cotransporter PEPT2 is expressed in a variety of organs including kidney, lung, brain, mammary gland, and eye. PEPT2 substrates are di- and tripeptides as well as peptidomimetics, such as beta-lactam antibiotics. Due to the presence of PEPT2 at the bronchial epithelium, the aerosolic administration of peptide-like drugs might play a major role in future treatment of various pulmonary and systemic diseases. Moreover, PEPT2 has a significant influence on the in vivo disposition and half-life time of peptide-like drugs within the body, particularly in kidney and brain. PEPT2 is known to have similar but not identical structural requirements for substrate recognition and transport compared to PEPT1, its intestinal counterpart. In this review we compiled available affinity constants of 352 compounds, measured at different mammalian tissues and expression systems and compare the data whenever possible with those of PEPT1.
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Affiliation(s)
- A Biegel
- Institute of Biochemistry, Department of Biochemistry/Biotechnology, Martin-Luther-University Halle-Wittenberg, Halle, Germany
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21
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Boonen M, Hamer I, Boussac M, Delsaute AF, Flamion B, Garin J, Jadot M. Intracellular localization of p40, a protein identified in a preparation of lysosomal membranes. Biochem J 2006; 395:39-47. [PMID: 16367739 PMCID: PMC1409702 DOI: 10.1042/bj20051647] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Unlike lysosomal soluble proteins, few lysosomal membrane proteins have been identified. Rat liver lysosomes were purified by centrifugation on a Nycodenz density gradient. The most hydrophobic proteins were extracted from the lysosome membrane preparation and were identified by MS. We focused our attention on a protein of approx. 40 kDa, p40, which contains seven to ten putative transmembrane domains and four lysosomal consensus sorting motifs in its sequence. Knowing that preparations of lysosomes obtained by centrifugation always contain contaminant membranes, we combined biochemical and morphological methods to analyse the subcellular localization of p40. The results of subcellular fractionation of mouse liver homogenates validate the lysosomal residence of p40. In particular, a density shift of lysosomes induced by Triton WR-1339 similarly affected the distributions of p40 and beta-galactosidase, a lysosomal marker protein. We confirmed by fluorescence microscopy on eukaryotic cells transfected with p40 or p40-GFP (green fluorescent protein) constructs that p40 is localized in lysosomes. A first molecular characterization of p40 in transfected Cos-7 cells revealed that it is an unglycosylated protein tightly associated with membranes. Taken together, our results strongly support the hypothesis that p40 is an authentic lysosomal membrane protein.
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Affiliation(s)
- Marielle Boonen
- *URΦM, Laboratoire de Chimie Physiologique, Facultés Universitaires Notre-Dame de la Paix, B-5000 Namur, Belgium
| | - Isabelle Hamer
- *URΦM, Laboratoire de Chimie Physiologique, Facultés Universitaires Notre-Dame de la Paix, B-5000 Namur, Belgium
| | - Muriel Boussac
- †Laboratoire de Chimie des Protéines, CEA/INSERM/UJF, F-38054 Grenoble, France
| | - Anne-Françoise Delsaute
- *URΦM, Laboratoire de Chimie Physiologique, Facultés Universitaires Notre-Dame de la Paix, B-5000 Namur, Belgium
| | - Bruno Flamion
- ‡URΦM, Laboratoire de Physiologie/Pharmacologie, Facultés Universitaires Notre-Dame de la Paix, B-5000 Namur, Belgium
| | - Jérôme Garin
- †Laboratoire de Chimie des Protéines, CEA/INSERM/UJF, F-38054 Grenoble, France
| | - Michel Jadot
- *URΦM, Laboratoire de Chimie Physiologique, Facultés Universitaires Notre-Dame de la Paix, B-5000 Namur, Belgium
- To whom correspondence should be addressed (email )
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Bhardwaj RK, Herrera-Ruiz D, Eltoukhy N, Saad M, Knipp GT. The functional evaluation of human peptide/histidine transporter 1 (hPHT1) in transiently transfected COS-7 cells. Eur J Pharm Sci 2005; 27:533-42. [PMID: 16289537 DOI: 10.1016/j.ejps.2005.09.014] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2005] [Accepted: 09/22/2005] [Indexed: 10/25/2022]
Abstract
Recently, the expression of the human peptide/histidine transporter (hPHT1, SLC15A4) mRNA was observed in the GI tract and in Caco-2 cells, suggesting that it may participate in the intestinal absorption of peptide-based agents. This study aims to elucidate the: (i) protein expression pattern of hPHT1 (SLC15A4) in human small intestine; (ii) cloning of the hPHT1 full-length sequence; (iii) functional characterization of hPHT1 in transiently transfected COS-7 cells. The expression of hPHT1 was measured using Western blot and immunohistochemical analysis. The hPHT1 full-sequence was amplified from BeWo cells, inserted into the pcDNA3.1-V5/His TOPO plasmid and transiently transfected into COS-7 cells to investigate the uptake kinetics of [3H]histidine and [3H]carnosine. Time, pH and sodium-dependent uptake studies were performed in mock (empty vector) and hPHT1-COS-7 cells. Results demonstrated hPHT1 protein expression in different intestinal regions. Histidine and carnosine uptake was linear in hPHT1-COS-7 cells over 15 min and was found to be pH-dependent. These substrates and valacyclovir showed significantly higher uptake at pH 5.0 in the hPHT1 transients when contrasted to the mock COS-7 cells, whereas glycylsarcosine uptake was significantly lower and unaffected by pH. Other di- and tripeptides also showed affinity for hPHT1. This study presents the initial functional characterization, the protein expression of the hPHT1 transporter and provides insight into a potentially different route for increasing peptide and peptide-based drug transport.
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Affiliation(s)
- Rajinder K Bhardwaj
- Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, 160 Frelinghuysen Road, Piscataway, NJ 08854-8022, USA
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23
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Nielsen CU, Brodin B, Jørgensen FS, Frokjaer S, Steffansen B. Human peptide transporters: therapeutic applications. Expert Opin Ther Pat 2005. [DOI: 10.1517/13543776.12.9.1329] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Abstract
The lysosomal catabolism of glycoproteins is part of the normal turnover of cellular constituents and the cellular homeostasis of glycosylation. Glycoproteins are delivered to lysosomes for catabolism either by endocytosis from outside the cell or by autophagy within the cell. Once inside the lysosome, glycoproteins are broken down by a combination of proteases and glycosidases, with the characteristic properties of soluble lysosomal hydrolases. The proteases consist of a mixture of endopeptidases and exopeptidases, which act in concert to produce a mixture of amino acids and dipeptides, which are transported across the lysosomal membrane into the cytosol by a combination of diffusion and carrier-mediated transport. Although the glycans of all mature glycoproteins are probably degraded in lysosomes, the breakdown of N-linked glycans has been studied most intensively. The catabolic pathways for high-mannose, hybrid, and complex glycans have been established. They are bidirectional with concurrent sequential removal of monosaccharides from the nonreducing end by exoglycosidases and proteolysis and digestion of the carbohydrate-polypeptide linkage at the reducing end. The process is initiated by the removal of any core and peripheral fucose, which is a prerequisite for the action of the peptide N-glycanase aspartylglucosaminidase, which hydrolyzes the glycan-peptide bond. This enzyme also requires free alpha carboxyl and amino groups on the asparagine residue, implying extensive prior proteolysis. The catabolism of O-linked glycans has not been studied so intensively, but many lysosomal glycosidases appear to act on the same linkages whether they are in N- or O-linked glycans, glycosaminoglycans, or glycolipids. The monosaccharides liberated during the breakdown of N- and O-linked glycans are transported across the lysosomal membrane into the cytosol by a combination of diffusion and carrier-mediated transport. Defects in these pathways lead to lysosomal storage diseases. The structures of some of the oligosaccharides that accumulate in these diseases are not digestion intermediates in the lysosomal catabolic pathways but correspond to intermediates in the biosynthetic pathway for N-linked glycans, suggesting another route of delivery of glycans to the lysosome. Incorrectly folded or glycosylated proteins that are rejected by the quality control mechanism are broken down in the ER and cytoplasm and the end product of the cytosolic degradation of N-glycans is delivered to the lysosomes. This route is enhanced in cells actively secreting glycoproteins or producing increased amounts of aberrant glycoproteins. Thus interaction between the lysosome and proteasome is important for the regulation of the biosynthesis and distribution of N-linked glycoproteins. Another example of the extralysosomal function of lysosomal enzymes is the release of lysosomal proteases into the cytosol to initiate the lysosomal pathway of apoptosis.
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Affiliation(s)
- Bryan Winchester
- Institute of Child Health at Great Ormond Street Hospital, University College London, 30 Guilford Street, London WC1N 1EH, U.K
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26
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Klemba M, Gluzman I, Goldberg DE. A Plasmodium falciparum dipeptidyl aminopeptidase I participates in vacuolar hemoglobin degradation. J Biol Chem 2004; 279:43000-7. [PMID: 15304495 DOI: 10.1074/jbc.m408123200] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Intraerythrocytic growth of the human malaria parasite Plasmodium falciparum requires the catabolism of large amounts of host cell hemoglobin. Endoproteolytic digestion of hemoglobin to short oligopeptides occurs in an acidic organelle called the food vacuole. How amino acids are generated from these peptides is not well understood. To gain insight into this process, we have studied a plasmodial ortholog of the lysosomal exopeptidase cathepsin C. The plasmodial enzyme dipeptidyl aminopeptidase 1 (DPAP1) was enriched from parasite extract by two different approaches and was shown to possess hydrolytic activity against fluorogenic dipeptide substrates. To localize DPAP1 we created a transgenic parasite line expressing a chromosomally encoded DPAP1-green fluorescent protein fusion. Green fluorescent protein fluorescence was observed in the food vacuole of live transgenic parasites, and anti-DPAP1 antibody labeled the food vacuole in parasite cryosections. Together these data implicate DPAP1 in the generation of dipeptides from hemoglobin-derived oligopeptides. To assess the significance of DPAP1, we attempted to ablate DPAP1 activity from blood stage parasites by truncating the chromosomal DPAP1-coding sequence. The inability to disrupt the coding sequence indicates that DPAP1 is important for asexual proliferation. The proenzyme form of DPAP1 was found to accumulate in the parasitophorous vacuole of mature parasites. This observation suggests a trafficking route for DPAP1 through the parasitophorous vacuole to the food vacuole.
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Affiliation(s)
- Michael Klemba
- Department of Medicine, Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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27
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Ocheltree SM, Keep RF, Shen H, Yang D, Hughes BA, Smith DE. Preliminary investigation into the expression of proton-coupled oligopeptide transporters in neural retina and retinal pigment epithelium (RPE): lack of functional activity in RPE plasma membranes. Pharm Res 2004; 20:1364-72. [PMID: 14567629 DOI: 10.1023/a:1025741723724] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE To determine the expression and functional activity of proton-coupled oligopeptide transporters (POT) in retinal pigment epithelial (RPE) cells. METHODS RT-PCR was used to probe the presence of POT mRNA in freshly isolated bovine RPE (BRPE) and human RPE (HRPE) cells, a human RPE cell line (ARPE-19), and human and bovine neural retina. [14C]GlySar uptake was used to characterize POT activity in cultured ARPE-19 cells and freshly isolated BRPE cell sheet suspensions. RESULTS PHT1 mRNA was expressed in BRPE, HRPE, ARPE-19, and bovine and human neural retina. In contrast, PEPT2 and PHT2 were expressed only in bovine and human retina, and PEPT1 could not be detected. GlySar exhibited a linear uptake over 6 h at pH values of 6.0 and 7.4, with greater uptake at pH 7.4 (p < 0.01). GlySar uptake did not exhibit saturability (5-2000 microM) and was unchanged when studied in the presence of 1 mM L-histidine. In contrast, GlySar uptake was significantly decreased when studied at 4 degrees C or in the presence of endocytic inhibitors at 37 degrees C (p < 0.01). Studies in BRPE cell sheet suspensions validated the results obtained in ARPE-19 cells and strongly suggested the absence of POT on the apical and basolateral membranes of RPE. CONCLUSIONS PHT1 mRNA is present in native bovine and human RPE and a human RPE cell line. However, the data argue against PHT1 being expressed on plasma membranes of RPE. Overall, GlySar appears to be taken up by RPE cells via a low-affinity, endocytic process.
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Affiliation(s)
- Scott M Ocheltree
- Department of Pharmaceutical Sciences, The University of Michigan, Ann Arbor, Michigan 48109-1065, USA
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Kulkarni AA, Haworth IS, Uchiyama T, Lee VHL. Analysis of Transmembrane Segment 7 of the Dipeptide Transporter hPepT1 by Cysteine-scanning Mutagenesis. J Biol Chem 2003; 278:51833-40. [PMID: 14532279 DOI: 10.1074/jbc.m308356200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To investigate the involvement of transmembrane segment 7 (TMS7) of hPepT1 in forming the putative central aqueous channel through which the substrate traverses, we individually mutated each of the 21 amino acids in TMS7 to a cysteine and analyzed the mutated transporters using the scanning cysteine accessibility method. Y287C- and M292C-hPepT1 did not express at the plasma membrane. Out of the remaining 19 transporters, three (F293C-, L296C-, and F297C-hPepT1) showed negligible glycyl-sarcosine (gly-sar) uptake activity and may play an important role in defining the overall hPepT1 structure. K278C-hPepT1 showed approximately 40% activity and the 15 other transporters exhibited more than 50% gly-sar uptake when compared with wild type (WT)-hPepT1. Gly-sar uptake for the 16 active transporters containing cysteine mutations was then measured in the presence of 2.5 mM 2-aminoethyl methanethiosulfonate hydrobromide (MTSEA) or 1 mM [2-(trimethylammonium) ethyl] methanethiosulfonate bromide (MTSET). Gly-sar uptake was significantly inhibited for each of the 16 single cysteine mutants in the presence of 2.5 mM MTSEA. In contrast, significant inhibition of uptake was only observed for K278C-, M279C-, V280C-, T281C-, M284C-, L286C-, P291C-, and D298C-hPepT1 in the presence of 1 mM MTSET. MTSET modification of R282C-hPepT1 resulted in a significant increase in gly-sar uptake. To investigate this further, we mutated WT-hPepT1 to R282A-, R282E-, and R282K-hPepT1. R282E-hPepT1 showed a 43% reduction in uptake activity, whereas R282A- and R282K-hPepT1 had activities comparable with WT-hPepT1, suggesting a role for the Arg-282 positive charge in substrate translocation. Most of the amino acids that were MTSET-sensitive upon cysteine mutation, including R282C, are located toward the intracellular end of TMS7. Hence, our results suggest that TMS7 of hPepT1 is relatively solvent-accessible along most of its length but that the intracellular end of the transmembrane domain is particularly so. From a structure-function perspective, we speculate that the extracellular end of TMS7 may shift following substrate binding, providing the basis for channel opening and substrate translocation.
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Affiliation(s)
- Ashutosh A Kulkarni
- Department of Pharmaceutical Sciences, University of Southern California, Los Angeles, California 90089-9121, USA
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Chavez-Crooker P, Garrido N, Pozo P, Ahearn GA. Copper transport by lobster (Homarus americanus) hepatopancreatic lysosomes. Comp Biochem Physiol C Toxicol Pharmacol 2003; 135:107-18. [PMID: 12860049 DOI: 10.1016/s1532-0456(03)00103-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Lysosomes are known centers for sequestration of calcium and a variety of heavy metals in many invertebrate tissues, and as a result of this compartmentalization these organelles perform important detoxification roles in the animals involved. The present investigation uses a centrifugation method to isolate and purify hepatopancreatic lysosomes from the American lobster, Homarus americanus. Purified lysosomal preparations were used to characterize membrane transport mechanisms in these organelles for transferring and sequestering cytoplasmic copper following its absorption across the plasma membrane from dietary constituents. The copper-specific fluorescent dye, Phen Green, was employed to quantify transmembrane fluxes of this metal as has been recently used to investigate copper movements across hepatopancreatic mitochondrial and plasma membranes. Results indicated the presence of a vanadate-sensitive, calcium-stimulated, copper ATPase in the membranes of these organelles that displayed high affinity carrier-mediated transport kinetics and may significantly contribute to organismic copper homeostasis. Together with a putative bafilomycin-sensitive V-ATPase in the membrane of the same organelles, importing hydrogen ions into the organellar interior, this copper ATPase may function as part of a physiological mechanism for precipitate formation between metallic cations and anions. These ionic precipitate complexes may then act as a sink for excess metals and thereby reduce the circulating concentrations of these elements.
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Affiliation(s)
- Pamela Chavez-Crooker
- Laboratory of Biotechnology and Molecular Biology, Facultad Recursos del Mar, Universidad de Antofagasta, Casilla 170 Antofagasta, Chile
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Bernardini F, Warburton MJ. Lysosomal degradation of cholecystokinin-(29-33)-amide in mouse brain is dependent on tripeptidyl peptidase-I: implications for the degradation and storage of peptides in classical late-infantile neuronal ceroid lipofuscinosis. Biochem J 2002; 366:521-9. [PMID: 12038963 PMCID: PMC1222804 DOI: 10.1042/bj20020467] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2002] [Revised: 05/13/2002] [Accepted: 05/31/2002] [Indexed: 11/17/2022]
Abstract
Tripeptidyl peptidase-I (TPP-I) is a lysosomal exopeptidase which removes tripeptides from the N-terminus of small peptides. Mutations in the TPP-I gene result in a lethal neurodegenerative disease, classical late-infantile neuronal ceroid lipofuscinosis (CLN2). This disease is characterized by the accumulation of proteinaceous and autofluorescent material within the lysosomes of neurons, which undergo massive cell death during the course of the disease. The absence of TPP-I may result in the lysosomal accumulation of small peptides and proteins, which eventually compromises lysosomal functions critical to the survival of neurons. To investigate the metabolism of small peptides, we have studied the degradation of cholecystokinin-(29-33)-amide (GWMDF-NH2; cholecystokinin C-terminal pentapeptide) by lysosomal fractions isolated from mouse brain and several other tissues. GWMDF-NH2 is cleaved at only one peptide bond by brain lysosomes, to produce GWM and DF-NH2. Inhibitor studies demonstrate that this reaction is catalysed by TPP-I. In contrast, lysosomal fractions from other mouse tissues additionally cleave a second peptide bond to produce GW and MDF-NH2. Inhibitor studies indicate that this reaction is catalysed by dipeptidyl peptidase-I (DPP-I; cathepsin C). Inhibitors of TPP-I are sufficient to completely block the degradation of GWMDF-NH2 by brain, but inhibitors of both TPP-I and DPP-I are required to completely inhibit the degradation of GWMDF-NH2 by other mouse tissues. Enzyme assays confirm the low activity of DPP-I in brain. An unrelated neuropeptide, neuromedin B, is degraded by a pathway that is partially dependent on TPP-I. These results indicate that TPP-I is required for the partial or complete digestion of certain neuropeptides by brain lysosomes. In the absence of TPP-I, neuropeptides or their degradation products will accumulate in brain lysosomes and may contribute to the pathogenesis of CLN2. Other tissues are spared because they express another peptidase, DPP-I, which has extensive activity on peptides and can compensate for the loss of TPP-I.
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Affiliation(s)
- Francesca Bernardini
- Department of Cellular Pathology, St. George's Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK
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31
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Brodin B, Nielsen CU, Steffansen B, Frøkjaer S. Transport of peptidomimetic drugs by the intestinal Di/tri-peptide transporter, PepT1. PHARMACOLOGY & TOXICOLOGY 2002; 90:285-96. [PMID: 12403049 DOI: 10.1034/j.1600-0773.2002.900601.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The apical membrane of small intestinal enterocytes possess an uptake system for di- and tripeptides. The physiological function of the system is to transport small peptides resulting from digestion of dietary protein. Moreover, due to the broad substrate specificity of the system, it is also capable of transporting a number of orally administered peptidomimetic drugs. Absorbed peptides may be hydrolysed in the cells due to the high peptidase activity present in the cytosol. Peptidomimetic drugs may, if resistant to the cellular enzyme activity, pass the basolateral membrane via a basolateral peptide transport mechanism and enter the systemic circulation. As the number of new peptide and peptidomimetic drugs are rapidly increasing, the peptide transport system has gained increasing attention as a possible drug delivery system for small peptides and peptide-like compounds. In this paper we give an updated introduction to the transport system and discuss the substrate characteristics of the di/tri-peptide transporter system with special emphasis on chemically modified substrates and prodrugs.
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Affiliation(s)
- Birger Brodin
- Centre for Drug Design and Transport, Department of Pharmaceutics, Royal Danish School of Pharmacy, Universitetsparken 2, Copenhagen, Denmark.
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32
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Sakata K, Yamashita T, Maeda M, Moriyama Y, Shimada S, Tohyama M. Cloning of a lymphatic peptide/histidine transporter. Biochem J 2001; 356:53-60. [PMID: 11336635 PMCID: PMC1221811 DOI: 10.1042/0264-6021:3560053] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Although peptide transport across the plasma membrane has been characterized well in the kidney and the intestine, the functional relevance of this transport in other organs has not been addressed. Here we report the cloning of a cDNA for a novel peptide/histidine transporter found in the rat (rPHT2), whose mRNA is expressed mainly in the lymphatic system. rPHT2 encodes a protein of 582 amino acids and showed 49% identity with the brain PHT (PHT1) [Yamashita, Shimada, Guo, Sato, Kohmura, Hayakawa, Takagi and Tohyama (1997) J. Biol. Chem. 272, 10205-10211]. rPHT2 mRNA was abundant in lung, spleen and thymus, and detected faintly in brain, liver, adrenal gland and heart by Northern-blot analysis and reverse transcriptase PCR (RT-PCR). Intense signals for the gene were found in immunocytes using in situ hybridization. Ectopic expression of rPHT2 protein in HEK-293T cells and BHK cells was not found on the cell surface, but was found on the lysosomal membrane using light- and electron-microscopic analysis. Recombinant rPHT2 protein reconstituted into liposomes showed proton-dependent transport activity with histidine and histidyl-leucine. These findings suggest that rPHT2 is involved in the protein catabolic pathway in the lymphatic system.
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Affiliation(s)
- K Sakata
- Department of Anatomy and Neuroscience, Graduate School of Medicine Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
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Sun D, Landowski CP, Chu X, Wallsten R, Fleisher D, Amidon GL, Komorowski TE. Drug inhibition of Gly-Sar uptake and hPepT1 localization using hPepT1-GFP fusion protein. AAPS PHARMSCI 2001; 3:E2. [PMID: 11741253 PMCID: PMC2751234 DOI: 10.1208/ps030102] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
An hPepT1-GFP fusion construct was made to study drug inhibition of dipeptide uptake and apical, basolateral, or subcellular hPepT1 localization. The hPepT1 stop codon was mutated by polymerase chain reaction and was subsequently cloned into the pEGFP-N1 vector. The hPepT1-GFP fusion construct was then transfected into Caco-2 and HeLa cells, and drug inhibition was studied by inhibiting 3H-Gly-Sar uptake. Western blot analysis was used to determine hPepT1-GFP expression levels and confocal microscopy was used to examine the localization. Both anti-hPepT1 antibody and anti-GFP antibody recognized a 120-kd hPepT1-GFP fusion protein in the transfected cells. The 3H-Gly-Sar uptake in transfected HeLa cells was enhanced more than 20 times compared with the control. Valacyclovir (5 mmol/L) was able to completely inhibit 3H-Gly-Sar uptake in these transfected cells. Confocal microscopy showed that the hPepT1-GFP mainly localized in the Caco-2 cell apical membrane, but was present throughout the entire HeLa cell membranes. The hPepT1-GFP fusion protein was not found in either early endosome or lysosome of Caco-2 cells under normal conditions; however, it was detected in some subsets of lysosomes and early endosomes in phorbol 12-myristate 13-acetate (PMA)-treated Caco-2 cells.
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Affiliation(s)
- Duxin Sun
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Michigan, 48109-1065 Ann Arbor, MI
| | - Christopher P. Landowski
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Michigan, 48109-1065 Ann Arbor, MI
| | - Xiaoyan Chu
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Michigan, 48109-1065 Ann Arbor, MI
| | - Richard Wallsten
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Michigan, 48109-1065 Ann Arbor, MI
| | - David Fleisher
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Michigan, 48109-1065 Ann Arbor, MI
| | - Gordon L. Amidon
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Michigan, 48109-1065 Ann Arbor, MI
| | - Thomas E. Komorowski
- Michigan Diabetes Research and Training Center, University of Michigan, 48109 Ann Arbor, MI
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Zhou X, Thamotharan M, Gangopadhyay A, Serdikoff C, Adibi SA. Characterization of an oligopeptide transporter in renal lysosomes. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1466:372-8. [PMID: 10825457 DOI: 10.1016/s0005-2736(00)00201-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Renal lysosomes play a major role in catabolism of plasma proteins. Final products of this catabolism include dipeptides and tripeptides that must be exported to the cytosol for hydrolysis. The aim of the present study was to determine whether an oligopeptide transporter is present in the renal lysosomal membrane that could mediate this export. The existence of an oligopeptide transporter was probed with the uptake of glycylglutamine (Gly-Gln) by membrane vesicles prepared from renal lysosomes. Kinetic analysis showed the presence of a single transporter with a K(m) of 8.77 mM for the uptake of Gly-Gln. The Gly-Gln uptake was energized by the imposition of an inwardly directed proton gradient (pH(out) 5.0/pH(in) 7.3) and membrane potential (outside positive/inside negative) resulting in overshoot. The Gly-Gln uptake was inhibited by the presence of dipeptides and tripeptides, but not amino acids. Western blot analysis of lysosomal membrane proteins with Pept-1 (an oligopeptide transporter) antibody as the probe showed the presence of an immunoreactive protein. This immunoreaction was abolished when the antiserum was preabsorbed with the Pept-1 epitope (0.5 microg/ml). In conclusion, the present data show the existence of a low-affinity dipeptide transporter in the renal lysosomal membrane that appears to belong to the Pept family of transporters. The function of this transporter appears to be to prevent accumulation of dipeptides in renal lysosomes.
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Affiliation(s)
- X Zhou
- Clinical Nutrition Research Unit, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
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Abstract
In the group of lysosomal storage diseases, transport disorders occupy a special place because they represent rare examples of inborn errors of metabolism caused by a defect of an intracellular membrane transporter. In particular, two disorders are caused by a proven defect in carrier-mediated transport of metabolites: cystinosis and the group of sialic acid storage disorders (SASD). The recent identification of the gene mutations for both disorders will improve patient diagnosis and shed light on new physiological mechanisms of intracellular trafficking.
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Affiliation(s)
- G M Mancini
- Department of Clinical Genetics, Erasmus University, Rotterdam, The Netherlands.
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Bockman DE, Ganapathy V, Oblak TG, Leibach FH. Localization of peptide transporter in nuclei and lysosomes of the pancreas. INTERNATIONAL JOURNAL OF PANCREATOLOGY : OFFICIAL JOURNAL OF THE INTERNATIONAL ASSOCIATION OF PANCREATOLOGY 1997; 22:221-5. [PMID: 9444554 DOI: 10.1007/bf02788388] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
CONCLUSIONS These studies show for the first time the localization of a H+/peptide cotrasporter in nuclei of vascular smooth muscle cells and Schwann cells and its localization in lysosomes of the exocrine pancreas. It is likely that the transporter functions to move small peptides from the lysosome to the cytoplasm following intralysosomal protein degradation. The nature of the transporter function in the nucleus remains to be determined, including the possibility that peptide signaling molecules may be transmitted between nucleus and cytoplasm. BACKGROUND PEPT1 transports di- and tripeptides through plasma membranes. Peptides are cotransported with H+, thus deriving the energy for the active transport process from an electrochemical H+ gradient. The main regions in which PEPT1 has been thought to function are the plasma membranes of the small intestinal epithelial cells for absorption of protein digestion products and in the kidney tubules for recovery of small peptides from the glomerular filtrate. METHODS Pancreas was removed from rats and quick frozen with liquid nitrogen. Frozen sections were fixed in cold acetone. Sections were incubated with primary antibody against PEPT1, followed by a secondary antibody conjugated with fluorescein, then examined with a fluorescence microscope. RESULTS Three major structures were immunopositive with the antibody to PEPT1: the nuclei of smooth muscle cells in the wall of arterioles, the nuclei of Schwann cells in unmyelinated pancreatic nerves, and lysosomes in acinar cells.
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Affiliation(s)
- D E Bockman
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta 30912-2000, USA
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