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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Chen J, Ma B, Yang Y, Wang B, Hao J, Zhou X. Disulfidptosis decoded: a journey through cell death mysteries, regulatory networks, disease paradigms and future directions. Biomark Res 2024; 12:45. [PMID: 38685115 PMCID: PMC11059647 DOI: 10.1186/s40364-024-00593-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2024] [Accepted: 04/23/2024] [Indexed: 05/02/2024] Open
Abstract
Cell death is an important part of the life cycle, serving as a foundation for both the orderly development and the maintenance of physiological equilibrium within organisms. This process is fundamental, as it eliminates senescent, impaired, or aberrant cells while also promoting tissue regeneration and immunological responses. A novel paradigm of programmed cell death, known as disulfidptosis, has recently emerged in the scientific circle. Disulfidptosis is defined as the accumulation of cystine by cancer cells with high expression of the solute carrier family 7 member 11 (SLC7A11) during glucose starvation. This accumulation causes extensive disulfide linkages between F-actins, resulting in their contraction and subsequent detachment from the cellular membrane, triggering cellular death. The RAC1-WRC axis is involved in this phenomenon. Disulfidptosis sparked growing interest due to its potential applications in a variety of pathologies, particularly oncology, neurodegenerative disorders, and metabolic anomalies. Nonetheless, the complexities of its regulatory pathways remain elusive, and its precise molecular targets have yet to be definitively identified. This manuscript aims to meticulously dissect the historical evolution, molecular underpinnings, regulatory frameworks, and potential implications of disulfidptosis in various disease contexts, illuminating its promise as a groundbreaking therapeutic pathway and target.
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Affiliation(s)
- Jinyu Chen
- The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, 510260, China
| | - Boyuan Ma
- The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, 510260, China
| | - Yubiao Yang
- The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, 510260, China
| | - Bitao Wang
- The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, 510260, China
| | - Jian Hao
- The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, 510260, China.
| | - Xianhu Zhou
- The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, 510260, China.
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3
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Medaer L, David D, Smits M, Levtchenko E, Sampaolesi M, Gijsbers R. Residual Cystine Transport Activity for Specific Infantile and Juvenile CTNS Mutations in a PTEC-Based Addback Model. Cells 2024; 13:646. [PMID: 38607085 PMCID: PMC11011962 DOI: 10.3390/cells13070646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2024] [Revised: 04/03/2024] [Accepted: 04/04/2024] [Indexed: 04/13/2024] Open
Abstract
Cystinosis is a rare, autosomal recessive, lysosomal storage disease caused by mutations in the gene CTNS, leading to cystine accumulation in the lysosomes. While cysteamine lowers the cystine levels, it does not cure the disease, suggesting that CTNS exerts additional functions besides cystine transport. This study investigated the impact of infantile and juvenile CTNS mutations with discrepant genotype/phenotype correlations on CTNS expression, and subcellular localisation and function in clinically relevant cystinosis cell models to better understand the link between genotype and CTNS function. Using CTNS-depleted proximal tubule epithelial cells and patient-derived fibroblasts, we expressed a selection of CTNSmutants under various promoters. EF1a-driven expression led to substantial overexpression, resulting in CTNS protein levels that localised to the lysosomal compartment. All CTNSmutants tested also reversed cystine accumulation, indicating that CTNSmutants still exert transport activity, possibly due to the overexpression conditions. Surprisingly, even CTNSmutants expression driven by the less potent CTNS and EFS promoters reversed the cystine accumulation, contrary to the CTNSG339R missense mutant. Taken together, our findings shed new light on CTNS mutations, highlighting the need for robust assessment methodologies in clinically relevant cellular models and thus paving the way for better stratification of cystinosis patients, and advocating for the development of more personalized therapy.
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Affiliation(s)
- Louise Medaer
- Laboratory of Molecular Virology and Gene Therapy, Department of Pharmacological and Pharmaceutical Sciences, Faculty of Medicine, KU Leuven, 3000 Leuven, Belgium; (L.M.); (M.S.)
| | - Dries David
- Laboratory of Molecular Virology and Gene Therapy, Department of Pharmacological and Pharmaceutical Sciences, Faculty of Medicine, KU Leuven, 3000 Leuven, Belgium; (L.M.); (M.S.)
| | - Maxime Smits
- Laboratory of Molecular Virology and Gene Therapy, Department of Pharmacological and Pharmaceutical Sciences, Faculty of Medicine, KU Leuven, 3000 Leuven, Belgium; (L.M.); (M.S.)
- Leuven Viral Vector Core, Faculty of Medicine, KU Leuven, 3000 Leuven, Belgium
| | - Elena Levtchenko
- Department of Paediatric Nephrology & Development and Regeneration, University Hospitals Leuven & KU Leuven, 3000 Leuven, Belgium;
- Department of Paediatric Nephrology, Amsterdam University Medical Centre, 1081 Amsterdam, The Netherlands
| | - Maurilio Sampaolesi
- Translational Cardiology Laboratory, Department of Development and Regeneration, Stem Cell Institute, Faculty of Medicine, KU Leuven, 3000 Leuven, Belgium;
| | - Rik Gijsbers
- Laboratory of Molecular Virology and Gene Therapy, Department of Pharmacological and Pharmaceutical Sciences, Faculty of Medicine, KU Leuven, 3000 Leuven, Belgium; (L.M.); (M.S.)
- Leuven Viral Vector Core, Faculty of Medicine, KU Leuven, 3000 Leuven, Belgium
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4
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Thiyagarajan R, Taub M. Studies with Human-Induced Pluripotent Stem Cells Reveal That CTNS Mutations Can Alter Renal Proximal Tubule Differentiation. Int J Mol Sci 2023; 24:17004. [PMID: 38069326 PMCID: PMC10707122 DOI: 10.3390/ijms242317004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 11/22/2023] [Accepted: 11/23/2023] [Indexed: 12/18/2023] Open
Abstract
Cystinosis is an autosomal recessive disease resulting from mutations in ctns, which encodes for cystinosin, a proton-coupled cystine transporter that exports cystine from lysosomes. The major clinical form, infantile cystinosis, is associated with renal failure due to the malfunctioning of the renal proximal tubule (RPT). To examine the hypothesis that the malfunctioning of the cystinotic RPT arises from defective differentiation, human-induced pluripotent stem cells (hiPSCs) were generated from human dermal fibroblasts from an individual with infantile cystinosis, as well as a normal individual. The results indicate that both the cystinotic and normal hiPSCs are pluripotent and can form embryoid bodies (EBs) with the three primordial germ layers. When the normal hiPSCs were subjected to a differentiation regime that induces RPT formation, organoids containing tubules with lumens emerged that expressed distinctive RPT proteins, including villin, the Na+/H+ Exchanger (NHE) isoform 3 (NHE3), and the NHE Regulatory Factor 1 (NHERF1). The formation of tubules with lumens was less pronounced in organoids derived from cystinotic hiPSCs, although the organoids expressed villin, NHE3, and NHERF1. These observations can be attributed to an impairment in differentiation and/or by other defects which cause cystinotic RPTs to have an increased propensity to undergo apoptosis or other types of programmed cell death.
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Affiliation(s)
- Ramkumar Thiyagarajan
- Division of Geriatric Medicine, University of Kansas Medical Center, University of Kansas, Kansas City, KS 66160, USA;
| | - Mary Taub
- Biochemistry Department, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY 14203, USA
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5
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Wang Y, Kinoshita T. The role of lipid scramblases in regulating lipid distributions at cellular membranes. Biochem Soc Trans 2023; 51:1857-1869. [PMID: 37767549 DOI: 10.1042/bst20221455] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 09/12/2023] [Accepted: 09/19/2023] [Indexed: 09/29/2023]
Abstract
Glycerophospholipids, sphingolipids and cholesterol assemble into lipid bilayers that form the scaffold of cellular membranes, in which proteins are embedded. Membrane composition and membrane protein profiles differ between plasma and intracellular membranes and between the two leaflets of a membrane. Lipid distributions between two leaflets are mediated by lipid translocases, including flippases and scramblases. Flippases use ATP to catalyze the inward movement of specific lipids between leaflets. In contrast, bidirectional flip-flop movements of lipids across the membrane are mediated by scramblases in an ATP-independent manner. Scramblases have been implicated in disrupting the lipid asymmetry of the plasma membrane, protein glycosylation, autophagosome biogenesis, lipoprotein secretion, lipid droplet formation and communications between organelles. Although scramblases in plasma membranes were identified over 10 years ago, most progress about scramblases localized in intracellular membranes has been made in the last few years. Herein, we review the role of scramblases in regulating lipid distributions in cellular membranes, focusing primarily on intracellular membrane-localized scramblases.
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Affiliation(s)
- Yicheng Wang
- State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
- Key Laboratory of Biopharmaceutical Preparation and Delivery, Chinese Academy of Sciences, Beijing 100190, China
| | - Taroh Kinoshita
- Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan
- WPI Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan
- Center for Infectious Disease Education and Research, Osaka University, Suita, Osaka 565-0871, Japan
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6
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Kardile HB, Karkute SG, Challam C, Sharma NK, Shelake RM, Kawar PG, Patil VU, Deshmukh R, Bhardwaj V, Chourasia KN, Valluri SD. Hemibiotrophic Phytophthora infestans Modulates the Expression of SWEET Genes in Potato ( Solanum tuberosum L.). PLANTS (BASEL, SWITZERLAND) 2023; 12:3433. [PMID: 37836173 PMCID: PMC10575152 DOI: 10.3390/plants12193433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 09/02/2023] [Accepted: 09/11/2023] [Indexed: 10/15/2023]
Abstract
Sugar Efflux transporters (SWEET) are involved in diverse biological processes of plants. Pathogens have exploited them for nutritional gain and subsequently promote disease progression. Recent studies have implied the involvement of potato SWEET genes in the most devastating late blight disease caused by Phytophthora infestans. Here, we identified and designated 37 putative SWEET genes as StSWEET in potato. We performed detailed in silico analysis, including gene structure, conserved domains, and phylogenetic relationship. Publicly available RNA-seq data was harnessed to retrieve the expression profiles of SWEET genes. The late blight-responsive SWEET genes were identified from the RNA-seq data and then validated using quantitative real-time PCR. The SWEET gene expression was studied along with the biotrophic (SNE1) and necrotrophic (PiNPP1) marker genes of P. infestans. Furthermore, we explored the co-localization of P. infestans resistance loci and SWEET genes. The results indicated that nine transporter genes were responsive to the P. infestans in potato. Among these, six transporters, namely StSWEET10, 12, 18, 27, 29, and 31, showed increased expression after P. infestans inoculation. Interestingly, the observed expression levels aligned with the life cycle of P. infestans, wherein expression of these genes remained upregulated during the biotrophic phase and decreased later on. In contrast, StSWEET13, 14, and 32 didn't show upregulation in inoculated samples suggesting non-targeting by pathogens. This study underscores these transporters as prime P. infestans targets in potato late blight, pivotal in disease progression, and potential candidates for engineering blight-resistant potato genotypes.
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Affiliation(s)
- Hemant B. Kardile
- ICAR-Central Potato Research Institute, Shimla 171001, India; (N.K.S.); (V.U.P.); (V.B.)
- Department of Crop and Soil Science, 109 Crop Science Building, Oregon State University, Corvallis, OR 97331, USA
| | | | - Clarissa Challam
- ICAR-Central Potato Research Institute, Regional Station, Shillong 793009, India;
| | - Nirmal Kant Sharma
- ICAR-Central Potato Research Institute, Shimla 171001, India; (N.K.S.); (V.U.P.); (V.B.)
| | - Rahul Mahadev Shelake
- Division of Applied Life Science (BK21 Four Program), Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju 52828, Republic of Korea;
| | - Prashant Govindrao Kawar
- ICAR-Directorate of Floricultural Research, Zed Corner, Mundhwa Manjri Road, Mundhwa, Pune 411036, India;
| | - Virupaksh U. Patil
- ICAR-Central Potato Research Institute, Shimla 171001, India; (N.K.S.); (V.U.P.); (V.B.)
| | - Rupesh Deshmukh
- Department of Biotechnology, Central University of Haryana, Mahendergarh 123031, India;
| | - Vinay Bhardwaj
- ICAR-Central Potato Research Institute, Shimla 171001, India; (N.K.S.); (V.U.P.); (V.B.)
| | | | - Srikar Duttasai Valluri
- Department of Electrical Engineering and Computer Science, Oregon State University, Corvallis, OR 97331, USA;
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7
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Guo X, Schmiege P, Assafa TE, Wang R, Xu Y, Donnelly L, Fine M, Ni X, Jiang J, Millhauser G, Feng L, Li X. Structure and mechanism of human cystine exporter cystinosin. Cell 2022; 185:3739-3752.e18. [PMID: 36113465 PMCID: PMC9530027 DOI: 10.1016/j.cell.2022.08.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 07/18/2022] [Accepted: 08/17/2022] [Indexed: 01/26/2023]
Abstract
Lysosomal amino acid efflux by proton-driven transporters is essential for lysosomal homeostasis, amino acid recycling, mTOR signaling, and maintaining lysosomal pH. To unravel the mechanisms of these transporters, we focus on cystinosin, a prototypical lysosomal amino acid transporter that exports cystine to the cytosol, where its reduction to cysteine supplies this limiting amino acid for diverse fundamental processes and controlling nutrient adaptation. Cystinosin mutations cause cystinosis, a devastating lysosomal storage disease. Here, we present structures of human cystinosin in lumen-open, cytosol-open, and cystine-bound states, which uncover the cystine recognition mechanism and capture the key conformational states of the transport cycle. Our structures, along with functional studies and double electron-electron resonance spectroscopic investigations, reveal the molecular basis for the transporter's conformational transitions and protonation switch, show conformation-dependent Ragulator-Rag complex engagement, and demonstrate an unexpected activation mechanism. These findings provide molecular insights into lysosomal amino acid efflux and a potential therapeutic strategy.
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Affiliation(s)
- Xue Guo
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Philip Schmiege
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Tufa E Assafa
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95060, USA
| | - Rong Wang
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Yan Xu
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Linda Donnelly
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Michael Fine
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Xiaodan Ni
- Laboratory of Membrane Proteins and Structural Biology, Biochemistry and Biophysics Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jiansen Jiang
- Laboratory of Membrane Proteins and Structural Biology, Biochemistry and Biophysics Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Glenn Millhauser
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95060, USA.
| | - Liang Feng
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Xiaochun Li
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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8
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Structural basis for proton coupled cystine transport by cystinosin. Nat Commun 2022; 13:4845. [PMID: 35977944 PMCID: PMC9385667 DOI: 10.1038/s41467-022-32589-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 08/08/2022] [Indexed: 11/09/2022] Open
Abstract
Amino acid transporters play a key role controlling the flow of nutrients across the lysosomal membrane and regulating metabolism in the cell. Mutations in the gene encoding the transporter cystinosin result in cystinosis, an autosomal recessive metabolic disorder characterised by the accumulation of cystine crystals in the lysosome. Cystinosin is a member of the PQ-loop family of solute carrier (SLC) transporters and uses the proton gradient to drive cystine export into the cytoplasm. However, the molecular basis for cystinosin function remains elusive, hampering efforts to develop novel treatments for cystinosis and understand the mechanisms of ion driven transport in the PQ-loop family. To address these questions, we present the crystal structures of cystinosin from Arabidopsis thaliana in both apo and cystine bound states. Using a combination of in vitro and in vivo based assays, we establish a mechanism for cystine recognition and proton coupled transport. Mutational mapping and functional characterisation of human cystinosin further provide a framework for understanding the molecular impact of disease-causing mutations. Mutations in CTNS, the lysosomal cystine-proton symporter, cause cystinosis. Here authors report crystal structures of CTNS from Arabidopsis thaliana in complex with cystine, and establish the mode of ligand recognition and mechanism for proton-coupled cystine export from the lysosome.
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9
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Savostyanov KV, Pushkov AA, Shchagina OA, Maltseva VV, Suleymanov EA, Zhanin IS, Mazanova NN, Fisenko AP, Mishakova PS, Polyakov AV, Balanovska EV, Zinchenko RA, Tsygin AN. Genetic Landscape of Nephropathic Cystinosis in Russian Children. Front Genet 2022; 13:863157. [PMID: 35571017 PMCID: PMC9096100 DOI: 10.3389/fgene.2022.863157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Accepted: 03/18/2022] [Indexed: 11/13/2022] Open
Abstract
Nephropathic cystinosis is a rare autosomal recessive disorder characterized by amino acid cystine accumulation and caused by biallelic mutations in the CTNS gene. The analysis methods are as follows: tandem mass spectrometry to determine the cystine concentration in polymorphonuclear blood leukocytes, Sanger sequencing for the entire coding sequence and flanking intron regions of the CTNS gene, multiplex PCR to detect a common mutation—a 57 kb deletion, and multiplex ligation-dependent probe amplification to analyze the number of exon copies in the CTNS gene. Haplotype analysis of chromosomes with major mutations was carried out using microsatellite markers D17S831, D17S1798, D17S829, D17S1828, and D17S1876. In this study, we provide clinical, biochemical, and molecular genetic characteristics of 40 Russian patients with mutations in the CTNS gene, among whom 30 patients were selected from a high-risk group of 85 people as a result of selective screening, which was carried out through cystine concentration measurement in polymorphonuclear blood leukocytes. The most common pathogenic variant, as in most described studies to date, was the 57 kb deletion, which represented 25% of all affected alleles. Previously non-described variants represented 22.5% of alleles. The founder effect in the Karachay and Chechen ethnic groups was shown for the following major variants: c.1015G > A and c.518A > G.
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Affiliation(s)
- K. V. Savostyanov
- National Medical Research Center for Children’s Health Federal State Autonomous Institution of the Ministry of Health of the Russian Federation, Moscow, Russia
- *Correspondence: K. V. Savostyanov,
| | - A. A. Pushkov
- National Medical Research Center for Children’s Health Federal State Autonomous Institution of the Ministry of Health of the Russian Federation, Moscow, Russia
| | | | - V. V. Maltseva
- National Medical Research Center for Children’s Health Federal State Autonomous Institution of the Ministry of Health of the Russian Federation, Moscow, Russia
| | | | - I. S. Zhanin
- National Medical Research Center for Children’s Health Federal State Autonomous Institution of the Ministry of Health of the Russian Federation, Moscow, Russia
| | - N. N. Mazanova
- National Medical Research Center for Children’s Health Federal State Autonomous Institution of the Ministry of Health of the Russian Federation, Moscow, Russia
| | - A. P. Fisenko
- National Medical Research Center for Children’s Health Federal State Autonomous Institution of the Ministry of Health of the Russian Federation, Moscow, Russia
| | | | | | | | | | - A. N. Tsygin
- National Medical Research Center for Children’s Health Federal State Autonomous Institution of the Ministry of Health of the Russian Federation, Moscow, Russia
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10
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Current Methods to Unravel the Functional Properties of Lysosomal Ion Channels and Transporters. Cells 2022; 11:cells11060921. [PMID: 35326372 PMCID: PMC8946281 DOI: 10.3390/cells11060921] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 03/04/2022] [Accepted: 03/05/2022] [Indexed: 02/07/2023] Open
Abstract
A distinct set of channels and transporters regulates the ion fluxes across the lysosomal membrane. Malfunctioning of these transport proteins and the resulting ionic imbalance is involved in various human diseases, such as lysosomal storage disorders, cancer, as well as metabolic and neurodegenerative diseases. As a consequence, these proteins have stimulated strong interest for their suitability as possible drug targets. A detailed functional characterization of many lysosomal channels and transporters is lacking, mainly due to technical difficulties in applying the standard patch-clamp technique to these small intracellular compartments. In this review, we focus on current methods used to unravel the functional properties of lysosomal ion channels and transporters, stressing their advantages and disadvantages and evaluating their fields of applicability.
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11
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Arginine-selective modulation of the lysosomal transporter PQLC2 through a gate-tuning mechanism. Proc Natl Acad Sci U S A 2021; 118:2025315118. [PMID: 34344826 PMCID: PMC8364130 DOI: 10.1073/pnas.2025315118] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Lysosomes degrade and recycle cell components and integrate environmental and intracellular cues to regulate cell growth, metabolism, and autophagy. The lysosomal transporter PQLC2 exports cationic amino acids from lysosomes, and under amino acid starvation, it recruits to lysosomes a signaling complex implicated in neurological diseases. In this study, we show that PQLC2 transport activity is uncoupled from the lysosomal pH gradient and other ion gradients and that it is selectively modulated by arginine through a trans-inhibition mechanism. Kinetic modeling suggests that arginine accelerates the closing of its cytosolic gate. We propose a signaling model in which PQLC2 transduces the nutrient status to its cognate complex through opposing effects of lysosomal membrane potential and cytosolic arginine on its conformational state. Lysosomes degrade excess or damaged cellular components and recycle their building blocks through membrane transporters. They also act as nutrient-sensing signaling hubs to coordinate cell responses. The membrane protein PQ-loop repeat-containing protein 2 (PQLC2; “picklock two”) is implicated in both functions, as it exports cationic amino acids from lysosomes and serves as a receptor and amino acid sensor to recruit the C9orf72/SMCR8/WDR41 complex to lysosomes upon nutrient starvation. Its transport activity is essential for drug treatment of the rare disease cystinosis. Here, we quantitatively studied PQLC2 transport activity using electrophysiological and biochemical methods. Charge/substrate ratio, intracellular pH, and reversal potential measurements showed that it operates in a uniporter mode. Thus, PQLC2 is uncoupled from the steep lysosomal proton gradient, unlike many lysosomal transporters, enabling bidirectional cationic amino acid transport across the organelle membrane. Surprisingly, the specific presence of arginine, but not other substrates (lysine, histidine), in the discharge (“trans”) compartment impaired PQLC2 transport. Kinetic modeling of the uniport cycle recapitulated the paradoxical substrate-yet-inhibitor behavior of arginine, assuming that bound arginine facilitates closing of the transporter’s cytosolic gate. Arginine binding may thus tune PQLC2 gating to control its conformation, suggesting a potential mechanism for nutrient signaling by PQLC2 to its interaction partners.
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12
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Arines FM, Hamlin AJ, Yang X, Liu YYJ, Li M. A selective transmembrane recognition mechanism by a membrane-anchored ubiquitin ligase adaptor. J Cell Biol 2021; 220:211632. [PMID: 33351099 PMCID: PMC7759299 DOI: 10.1083/jcb.202001116] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Revised: 09/10/2020] [Accepted: 10/30/2020] [Indexed: 12/30/2022] Open
Abstract
While it is well-known that E3 ubiquitin ligases can selectively ubiquitinate membrane proteins in response to specific environmental cues, the underlying mechanisms for the selectivity are poorly understood. In particular, the role of transmembrane regions, if any, in target recognition remains an open question. Here, we describe how Ssh4, a yeast E3 ligase adaptor, recognizes the PQ-loop lysine transporter Ypq1 only after lysine starvation. We show evidence of an interaction between two transmembrane helices of Ypq1 (TM5 and TM7) and the single transmembrane helix of Ssh4. This interaction is regulated by the conserved PQ motif. Strikingly, recent structural studies of the PQ-loop family have suggested that TM5 and TM7 undergo major conformational changes during substrate transport, implying that transport-associated conformational changes may determine the selectivity. These findings thus provide critical information concerning the regulatory mechanism through which transmembrane domains can be specifically recognized in response to changing environmental conditions.
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Affiliation(s)
- Felichi Mae Arines
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI
| | - Aaron Jeremy Hamlin
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI
| | - Xi Yang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI
| | - Yun-Yu Jennifer Liu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI
| | - Ming Li
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI
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13
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Jamalpoor A, Othman A, Levtchenko EN, Masereeuw R, Janssen MJ. Molecular Mechanisms and Treatment Options of Nephropathic Cystinosis. Trends Mol Med 2021; 27:673-686. [PMID: 33975805 DOI: 10.1016/j.molmed.2021.04.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 04/12/2021] [Accepted: 04/13/2021] [Indexed: 11/15/2022]
Abstract
Nephropathic cystinosis is a severe, monogenic systemic disorder that presents early in life and leads to progressive organ damage, particularly affecting the kidneys. It is caused by mutations in the CTNS gene, which encodes the lysosomal transporter cystinosin, resulting in intralysosomal accumulation of cystine. Recent studies demonstrated that the loss of cystinosin is associated with disrupted autophagy dynamics, accumulation of distorted mitochondria, and increased oxidative stress, leading to abnormal proliferation and dysfunction of kidney cells. We discuss these molecular mechanisms driving nephropathic cystinosis. Further, we consider how unravelling molecular mechanisms supports the identification and development of new strategies for cystinosis by the use of small molecules, biologicals, and genetic rescue of the disease in vitro and in vivo.
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Affiliation(s)
- Amer Jamalpoor
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, 3584, CG, Utrecht, The Netherlands
| | - Amr Othman
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, 3584, CG, Utrecht, The Netherlands
| | - Elena N Levtchenko
- Department of Pediatric Nephrology & Growth and Regeneration, University Hospitals Leuven & KU Leuven, Leuven, Belgium
| | - Rosalinde Masereeuw
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, 3584, CG, Utrecht, The Netherlands.
| | - Manoe J Janssen
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, 3584, CG, Utrecht, The Netherlands.
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14
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Kobayashi S, Harada Y, Homma T, Yokoyama C, Fujii J. Characterization of a rat monoclonal antibody raised against ferroptotic cells. J Immunol Methods 2020; 489:112912. [PMID: 33189725 DOI: 10.1016/j.jim.2020.112912] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 10/16/2020] [Accepted: 11/09/2020] [Indexed: 01/03/2023]
Abstract
Ferroptosis is regulated, non-apoptotic cell death in which ferrous iron and lipid peroxidation products play essential roles. While the ferroptotic pathway is now becoming unveiled, it is difficult to determine its involvement in situ because no unique marker for ferroptotic cells is known. In this study, we report on raising a rat monoclonal antibody against mouse-derived Hepa 1-6 cells that had been cultivated in cystine-deprived media. Binding of the resulting antibody, designated as FerAb, increased during advancing ferroptosis which was caused, not only by cystine deprivation but also treatment with erastin or RSL3, while apoptotic cell death induced by a staurosporine treatment had no effect on the binding. The FerAb was found to bind to 4-hydroxy-2-nonenal (HNE)-modified bovine serum albumin, but no specific protein was detected in ferroptotic cells in an immunoblot analysis. These results indicate that non-proteinaceous, HNE-like structural moiety was part of the antigen for FerAb, although the binding profiles of FerAb to ferroptotic cells were different from those of the currently available anti-HNE antibody. Immunocytological detection revealed inhomogenous staining within cells and partial co-localization with peripheral mitochondria and other cellular components. FerAb was found to be applicable for ferroptotic cells in other mouse cells and cultured human cells that were examined. Thus, the properties of the rat monoclonal antibody FerAb established in this study promise to be useful for the characterization of ferroptotic cell death.
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Affiliation(s)
- Sho Kobayashi
- Department of Biochemistry and Molecular Biology, Graduate School of Medical Science, Yamagata University, Japan
| | - Yumi Harada
- Department of Biochemical Engineering, Graduate School of Science and Engineering, Yamagata University, Yonezawa, Yamagata 992-8510, Japan
| | - Takujiro Homma
- Department of Biochemistry and Molecular Biology, Graduate School of Medical Science, Yamagata University, Japan
| | - Chikako Yokoyama
- Department of Biochemical Engineering, Graduate School of Science and Engineering, Yamagata University, Yonezawa, Yamagata 992-8510, Japan
| | - Junichi Fujii
- Department of Biochemistry and Molecular Biology, Graduate School of Medical Science, Yamagata University, Japan.
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15
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Eriksen J, Li F, Edwards RH. The mechanism and regulation of vesicular glutamate transport: Coordination with the synaptic vesicle cycle. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183259. [PMID: 32147354 DOI: 10.1016/j.bbamem.2020.183259] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 03/02/2020] [Accepted: 03/02/2020] [Indexed: 01/30/2023]
Abstract
The transport of classical neurotransmitters into synaptic vesicles generally relies on a H+ electrochemical gradient (∆μH+). Synaptic vesicle uptake of glutamate depends primarily on the electrical component ∆ψ as the driving force, rather than the chemical component ∆pH. However, the vesicular glutamate transporters (VGLUTs) belong to the solute carrier 17 (SLC17) family, which includes closely related members that function as H+ cotransporters. Recent work has also shown that the VGLUTs undergo allosteric regulation by H+ and Cl-, and exhibit an associated Cl- conductance. These properties appear to coordinate VGLUT activity with the large ionic shifts that accompany the rapid recycling of synaptic vesicles driven by neural activity. Recent structural information also suggests common mechanisms that underlie the apparently divergent function of SLC17 family members, and that confer allosteric regulation.
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Affiliation(s)
- Jacob Eriksen
- Department of Physiology, UCSF School of Medicine, United States of America; Department of Neurology, UCSF School of Medicine, United States of America
| | - Fei Li
- Department of Physiology, UCSF School of Medicine, United States of America; Department of Neurology, UCSF School of Medicine, United States of America
| | - Robert H Edwards
- Department of Physiology, UCSF School of Medicine, United States of America; Department of Neurology, UCSF School of Medicine, United States of America.
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16
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A PQ-loop protein Ypq2 is involved in the exchange of arginine and histidine across the vacuolar membrane of Saccharomyces cerevisiae. Sci Rep 2019; 9:15018. [PMID: 31636363 PMCID: PMC6803629 DOI: 10.1038/s41598-019-51531-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 09/30/2019] [Indexed: 11/08/2022] Open
Abstract
In nutrient-rich conditions, basic amino acids are actively accumulated into the vacuoles by H+-coupled transporters in Saccharomyces cerevisiae. In addition to the H+-coupled systems, the existence of an exchanger for arginine and histidine was indicated by kinetic analysis using isolated vacuolar membrane vesicles; however, the gene(s) involved in the activity has not been identified. Here, we show that the uptake activity of arginine driven by an artificially imposed histidine gradient decreased significantly by the disruption of the gene encoding vacuolar PQ-loop protein Ypq2, but not by those of Ypq1 and Ypq3. The exchange activity was restored by the expression of YPQ2. Furthermore, the substitution of a conserved proline residue, Pro29, in Ypq2 greatly decreased the exchange activity. These results suggest that Ypq2 is responsible for the exchange activity of arginine and histidine across the vacuolar membrane, and the conserved proline residue in the PQ-loop motif is required for the activity.
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17
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Fujii J, Homma T, Kobayashi S. Ferroptosis caused by cysteine insufficiency and oxidative insult. Free Radic Res 2019; 54:969-980. [PMID: 31505959 DOI: 10.1080/10715762.2019.1666983] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Free iron has long been assumed to be a deteriorating factor in an oxidative insult and was recently found to be directly associated with ferroptosis, a specific type of cell death. The free iron-involved production of lipid peroxides activates the fatal pathway, resulting in nonapoptotic, programed cell death. Lipid peroxides appear to destroy membrane integrity, leading to cell rupture. Glutathione (GSH) is a major redox molecule that functions to protect against ferroptosis by its ability to donate an electron to glutathione peroxidase 4 (GPX4), the sole enzyme that reduces phospholipid hydroperoxides. The availability of free cysteine (Cys) determines the levels of GSH synthesis, and, hence, its deprivation causes ferroptosis. Free iron is provided via ferritinophagy, the chaperone-mediated autophagic degradation of ferritin, but GPX4 also undergoes degradation via chaperone-mediated autophagy. Activated Nrf2 and ATF4 induce the expression of the cystine transporter xCT to cope with ferroptosis. To the contrary, the excessive activation of p53 induces ferroptosis by suppressing the expression of xCT in genetic and nongenetic manners. It therefore appears that xCT functions as the gatekeeper for determining cellular survival by regulating the availability of Cys in the cell. The issue of the extent of involvement of ferroptosis in an in vivo situation largely remains ambiguous. Establishing tools for specifying ferroptotic cells in situ would facilitate our understanding of its roles in pathogenesis.
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Affiliation(s)
- Junichi Fujii
- Department of Biochemistry and Molecular Biology, Graduate School of Medical Science, Yamagata University, Yamagata City, Japan
| | - Takujiro Homma
- Department of Biochemistry and Molecular Biology, Graduate School of Medical Science, Yamagata University, Yamagata City, Japan
| | - Sho Kobayashi
- Department of Biochemistry and Molecular Biology, Graduate School of Medical Science, Yamagata University, Yamagata City, Japan
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18
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Kandasamy P, Gyimesi G, Kanai Y, Hediger MA. Amino acid transporters revisited: New views in health and disease. Trends Biochem Sci 2018; 43:752-789. [PMID: 30177408 DOI: 10.1016/j.tibs.2018.05.003] [Citation(s) in RCA: 252] [Impact Index Per Article: 42.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Revised: 05/23/2018] [Accepted: 05/25/2018] [Indexed: 02/09/2023]
Abstract
Amino acid transporters (AATs) are membrane-bound transport proteins that mediate transfer of amino acids into and out of cells or cellular organelles. AATs have diverse functional roles ranging from neurotransmission to acid-base balance, intracellular energy metabolism, and anabolic and catabolic reactions. In cancer cells and diabetes, dysregulation of AATs leads to metabolic reprogramming, which changes intracellular amino acid levels, contributing to the pathogenesis of cancer, obesity and diabetes. Indeed, the neutral amino acid transporters (NATs) SLC7A5/LAT1 and SLC1A5/ASCT2 are likely involved in several human malignancies. However, a clinical therapy that directly targets AATs has not yet been developed. The purpose of this review is to highlight the structural and functional diversity of AATs, their diverse physiological roles in different tissues and organs, their wide-ranging implications in human diseases and the emerging strategies and tools that will be necessary to target AATs therapeutically.
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Affiliation(s)
- Palanivel Kandasamy
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland
| | - Gergely Gyimesi
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland
| | - Yoshikatsu Kanai
- Division of Bio-system Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan.
| | - Matthias A Hediger
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland.
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19
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Jentsch TJ, Pusch M. CLC Chloride Channels and Transporters: Structure, Function, Physiology, and Disease. Physiol Rev 2018; 98:1493-1590. [DOI: 10.1152/physrev.00047.2017] [Citation(s) in RCA: 214] [Impact Index Per Article: 35.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
CLC anion transporters are found in all phyla and form a gene family of eight members in mammals. Two CLC proteins, each of which completely contains an ion translocation parthway, assemble to homo- or heteromeric dimers that sometimes require accessory β-subunits for function. CLC proteins come in two flavors: anion channels and anion/proton exchangers. Structures of these two CLC protein classes are surprisingly similar. Extensive structure-function analysis identified residues involved in ion permeation, anion-proton coupling and gating and led to attractive biophysical models. In mammals, ClC-1, -2, -Ka/-Kb are plasma membrane Cl−channels, whereas ClC-3 through ClC-7 are 2Cl−/H+-exchangers in endolysosomal membranes. Biological roles of CLCs were mostly studied in mammals, but also in plants and model organisms like yeast and Caenorhabditis elegans. CLC Cl−channels have roles in the control of electrical excitability, extra- and intracellular ion homeostasis, and transepithelial transport, whereas anion/proton exchangers influence vesicular ion composition and impinge on endocytosis and lysosomal function. The surprisingly diverse roles of CLCs are highlighted by human and mouse disorders elicited by mutations in their genes. These pathologies include neurodegeneration, leukodystrophy, mental retardation, deafness, blindness, myotonia, hyperaldosteronism, renal salt loss, proteinuria, kidney stones, male infertility, and osteopetrosis. In this review, emphasis is laid on biophysical structure-function analysis and on the cell biological and organismal roles of mammalian CLCs and their role in disease.
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Affiliation(s)
- Thomas J. Jentsch
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany; and Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genova, Italy
| | - Michael Pusch
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany; and Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genova, Italy
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20
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Deshpande AA, Shukla A, Bachhawat AK. A Genetic Screen for Investigating the Human Lysosomal CystineTransporter, Cystinosin. Sci Rep 2018; 8:3442. [PMID: 29467429 PMCID: PMC5821828 DOI: 10.1038/s41598-018-21483-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 02/06/2018] [Indexed: 11/09/2022] Open
Abstract
Cystinosin, a lysosomal transporter is involved in the efflux of cystine from the lysosome to the cytosol. Mutations in the human cystinosin gene (CTNS) cause cystinosis, a recessive autosomal disorder. Studies on cystinosin have been limited by the absence of a robust genetic screen. In the present study we have developed a dual strategy for evaluating cystinosin function that is amenable to rapid genetic analysis. We show that human cystinosin expressed in this yeast confers growth on cystine when the protein is mistargeted to the plasma membrane by the deletion of the C-terminal targeting signal, GYQDL. We also screened a vacuolar protein sorting deletion library, and subsequently created multiple vps deletion mutants for kinetic studies. The double deletion, vps1Δvps17Δ, greatly enhanced uptake. This enabled validation by kinetic studies, including first studies on the WT CTNS protein (that contained the GYQDL motif). Using this screen we isolated several gain of function mutants, G131S/D, G309S/D, A137V, G197R, S270T, L274F and S312N showing enhanced growth on low concentrations of cystine. Kinetic analysis yielded insights into the role of the residues (including one of the patient mutations, G197R). The results indicate that the screen could be effectively used for interrogating and understanding the CTNS protein.
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Affiliation(s)
- Anup Arunrao Deshpande
- Indian Institute of Science and Education Research Mohali, Sector 81, Knowledge City, SAS Nagar, Punjab, India
| | - Anuj Shukla
- Indian Institute of Science and Education Research Mohali, Sector 81, Knowledge City, SAS Nagar, Punjab, India
| | - Anand Kumar Bachhawat
- Indian Institute of Science and Education Research Mohali, Sector 81, Knowledge City, SAS Nagar, Punjab, India.
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21
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Lee J, Kang E, Kobayashi S, Homma T, Sato H, Seo H, Fujii J. The viability of primary hepatocytes is maintained under a low cysteine-glutathione redox state with a marked elevation in ophthalmic acid production. Exp Cell Res 2017; 361:178-191. [DOI: 10.1016/j.yexcr.2017.10.017] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2017] [Revised: 10/17/2017] [Accepted: 10/20/2017] [Indexed: 12/22/2022]
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22
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DeCoursey TE, Morgan D, Musset B, Cherny VV. Insights into the structure and function of HV1 from a meta-analysis of mutation studies. J Gen Physiol 2017; 148:97-118. [PMID: 27481712 PMCID: PMC4969798 DOI: 10.1085/jgp.201611619] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 06/30/2016] [Indexed: 01/26/2023] Open
Abstract
The voltage-gated proton channel (HV1) is a widely distributed, proton-specific ion channel with unique properties. Since 2006, when genes for HV1 were identified, a vast array of mutations have been generated and characterized. Accessing this potentially useful resource is hindered, however, by the sheer number of mutations and interspecies differences in amino acid numbering. This review organizes all existing information in a logical manner to allow swift identification of studies that have characterized any particular mutation. Although much can be gained from this meta-analysis, important questions about the inner workings of HV1 await future revelation.
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Affiliation(s)
- Thomas E DeCoursey
- Department of Molecular Biophysics and Physiology, Rush University, Chicago, IL 60612
| | - Deri Morgan
- Department of Molecular Biophysics and Physiology, Rush University, Chicago, IL 60612
| | - Boris Musset
- Institut für Physiologie, PMU Klinikum Nürnberg, 90419 Nürnberg, Germany
| | - Vladimir V Cherny
- Department of Molecular Biophysics and Physiology, Rush University, Chicago, IL 60612
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23
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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: 94] [Impact Index Per Article: 11.8] [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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Bellomo F, Taranta A, Petrini S, Venditti R, Rocchetti MT, Rega LR, Corallini S, Gesualdo L, De Matteis MA, Emma F. Carboxyl-Terminal SSLKG Motif of the Human Cystinosin-LKG Plays an Important Role in Plasma Membrane Sorting. PLoS One 2016; 11:e0154805. [PMID: 27148969 PMCID: PMC4858208 DOI: 10.1371/journal.pone.0154805] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Accepted: 04/19/2016] [Indexed: 11/18/2022] Open
Abstract
Cystinosin mediates an ATP-dependent cystine efflux from lysosomes and causes, if mutated, nephropathic cystinosis, a rare inherited lysosomal storage disease. Alternative splicing of the last exon of the cystinosin sequence produces the cystinosin-LKG isoform that is characterized by a different C-terminal region causing changes in the subcellular distribution of the protein. We have constructed RFP-tagged proteins and demonstrated by site-directed mutagenesis that the carboxyl-terminal SSLKG sequence of cystinosin-LKG is an important sorting motif that is required for efficient targeting the protein to the plasma membrane, where it can mediate H+ coupled cystine transport. Deletion of the SSLKG sequence reduced cystinosin-LKG expression in the plasma membrane and cystine transport by approximately 30%, and induced significant accumulation of the protein in the Golgi apparatus and in lysosomes. Cystinosin-LKG, unlike the canonical isoform, also moves to the lysosomes by the indirect pathway, after endocytic retrieval from the plasma membrane, mainly by a clathrin-mediated endocytosis. Nevertheless, silencing of AP-2 triggers the clathrin-independent endocytosis, showing the complex adaptability of cystinosin-LKG trafficking.
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Affiliation(s)
- Francesco Bellomo
- Department of Nephrology-Urology, Division of Nephrology and Dialysis, Bambino Gesù Children’s Hospital and Research Institute, Rome, Italy
- * E-mail:
| | - Anna Taranta
- Department of Nephrology-Urology, Division of Nephrology and Dialysis, Bambino Gesù Children’s Hospital and Research Institute, Rome, Italy
| | - Stefania Petrini
- Confocal Microscopy Core Facility, Bambino Gesù Children’s Hospital and Research Institute, Rome, Italy
| | - Rossella Venditti
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli (NA), Italy
| | - Maria Teresa Rocchetti
- Department of Emergency and Organ Transplantation (DETO), Nephrology, Dialysis and Transplantation Unit, University of Bari Aldo Moro, Bari, Italy
| | - Laura Rita Rega
- Department of Nephrology-Urology, Division of Nephrology and Dialysis, Bambino Gesù Children’s Hospital and Research Institute, Rome, Italy
| | - Serena Corallini
- Department of Nephrology-Urology, Division of Nephrology and Dialysis, Bambino Gesù Children’s Hospital and Research Institute, Rome, Italy
| | - Loreto Gesualdo
- Department of Emergency and Organ Transplantation (DETO), Nephrology, Dialysis and Transplantation Unit, University of Bari Aldo Moro, Bari, Italy
| | | | - Francesco Emma
- Department of Nephrology-Urology, Division of Nephrology and Dialysis, Bambino Gesù Children’s Hospital and Research Institute, Rome, Italy
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25
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Salazar A, Keusgen M, von Hagen J. Amino acids in the cultivation of mammalian cells. Amino Acids 2016; 48:1161-71. [PMID: 26832172 PMCID: PMC4833841 DOI: 10.1007/s00726-016-2181-8] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Accepted: 01/18/2016] [Indexed: 11/29/2022]
Abstract
Amino acids are crucial for the cultivation of mammalian cells. This importance of amino acids was realized soon after the development of the first cell lines, and a solution of a mixture of amino acids has been supplied to cultured cells ever since. The importance of amino acids is further pronounced in chemically defined mammalian cell culture media, making the consideration of their biological and chemical properties necessary. Amino acids concentrations have been traditionally adjusted to their cellular consumption rates. However, since changes in the metabolic equilibrium of amino acids can be caused by changes in extracellular concentrations, metabolomics in conjunction with flux balance analysis is being used in the development of culture media. The study of amino acid transporters is also gaining importance since they control the intracellular concentrations of these molecules and are influenced by conditions in cell culture media. A better understanding of the solubility, stability, dissolution kinetics, and interactions of these molecules is needed for an exploitation of these properties in the development of dry powdered chemically defined media for mammalian cells. Due to the complexity of these mixtures however, this has proven to be challenging. Studying amino acids in mammalian cell culture media will help provide a better understanding of how mammalian cells in culture interact with their environment. It would also provide insight into the chemical behavior of these molecules in solutions of complex mixtures, which is important in the understanding of the contribution of individual amino acids to protein structure.
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Affiliation(s)
- Andrew Salazar
- Institute of Pharmaceutical Chemistry, University of Marburg, 35032, Marburg, Germany.
- Biopharm Materials & Technologies R&D, Merck Lifescience, 64293, Darmstadt, Germany.
| | - Michael Keusgen
- Institute of Pharmaceutical Chemistry, University of Marburg, 35032, Marburg, Germany
| | - Jörg von Hagen
- Biopharm Materials & Technologies R&D, Merck Lifescience, 64293, Darmstadt, Germany
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Endo-lysosomal dysfunction in human proximal tubular epithelial cells deficient for lysosomal cystine transporter cystinosin. PLoS One 2015; 10:e0120998. [PMID: 25811383 PMCID: PMC4374958 DOI: 10.1371/journal.pone.0120998] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 02/09/2015] [Indexed: 12/11/2022] Open
Abstract
Nephropathic cystinosis is a lysosomal storage disorder caused by mutations in the CTNS gene encoding cystine transporter cystinosin that results in accumulation of amino acid cystine in the lysosomes throughout the body and especially affects kidneys. Early manifestations of the disease include renal Fanconi syndrome, a generalized proximal tubular dysfunction. Current therapy of cystinosis is based on cystine-lowering drug cysteamine that postpones the disease progression but offers no cure for the Fanconi syndrome. We studied the mechanisms of impaired reabsorption in human proximal tubular epithelial cells (PTEC) deficient for cystinosin and investigated the endo-lysosomal compartments of cystinosin-deficient PTEC by means of light and electron microscopy. We demonstrate that cystinosin-deficient cells had abnormal shape and distribution of the endo-lysosomal compartments and impaired endocytosis, with decreased surface expression of multiligand receptors and delayed lysosomal cargo processing. Treatment with cysteamine improved surface expression and lysosomal cargo processing but did not lead to a complete restoration and had no effect on the abnormal morphology of endo-lysosomal compartments. The obtained results improve our understanding of the mechanism of proximal tubular dysfunction in cystinosis and indicate that impaired protein reabsorption can, at least partially, be explained by abnormal trafficking of endosomal vesicles.
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Jaehme M, Guskov A, Slotboom DJ. The twisted relation between Pnu and SWEET transporters. Trends Biochem Sci 2015; 40:183-8. [PMID: 25757400 DOI: 10.1016/j.tibs.2015.02.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 01/30/2015] [Accepted: 02/11/2015] [Indexed: 02/02/2023]
Abstract
The evolutionary relation between sugar and vitamin transporters from the SWEET and Pnu families is unclear. They have similar 3D structures, but differ in the topology of their secondary structure elements, and lack significant sequence similarity. Here we analyze the structures and sequences of different members of the SWEET and Pnu transporter families and propose an evolutionary pathway by which they may have diverged from a common ancestor. A 3D domain swapping event can explain the topological differences between the families, as well as the puzzling observation that a highly conserved and essential sequence motif of the SWEET family (the PQ loop) is absent from the Pnu transporters.
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Affiliation(s)
- Michael Jaehme
- University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute, Groningen, The Netherlands
| | - Albert Guskov
- University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute, Groningen, The Netherlands
| | - Dirk Jan Slotboom
- University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute, Groningen, The Netherlands.
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28
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Emma F, Nesterova G, Langman C, Labbé A, Cherqui S, Goodyer P, Janssen MC, Greco M, Topaloglu R, Elenberg E, Dohil R, Trauner D, Antignac C, Cochat P, Kaskel F, Servais A, Wühl E, Niaudet P, Van't Hoff W, Gahl W, Levtchenko E. Nephropathic cystinosis: an international consensus document. Nephrol Dial Transplant 2014; 29 Suppl 4:iv87-94. [PMID: 25165189 DOI: 10.1093/ndt/gfu090] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Cystinosis is caused by mutations in the CTNS gene (17p13.2), which encodes for a lysosomal cystine/proton symporter termed cystinosin. It is the most common cause of inherited renal Fanconi syndrome in young children. Because of its rarity, the diagnosis and specific treatment of cystinosis are frequently delayed, which has a significant impact on the overall prognosis. In this document, we have summarized expert opinions on several aspects of the disease to improve knowledge and provide guidance for diagnosis and treatment.
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Affiliation(s)
- Francesco Emma
- Division of Nephrology and Dialysis, Bambino Gesu` Children's Hospital - IRCCS, Rome, Italy
| | - Galina Nesterova
- Section on Human Biochemical Genetics, Human Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892-1851, USA
| | - Craig Langman
- Kidney Diseases, Feinberg School of Medicine, Northwestern University and the Ann and Robert H Lurie Children's Hospital of Chicago, Chicago, IL, USA
| | - Antoine Labbé
- Quinze-Vingts National Ophthalmology Hospital, Paris and Versailles Saint-Quentin-en-Yvelines University, Versailles, France Clinical Investigations Center, INSERM 503, Quinze-Vingts National Ophthalmology Hospital, Paris, France
| | - Stephanie Cherqui
- Division of Genetics, Department of Pediatrics, University of California, San Diego, La Jolla, CA, USA
| | - Paul Goodyer
- Department of Pediatrics, McGill University, Montreal Children's Hospital, Montreal, Québec, Canada
| | - Mirian C Janssen
- Department of Internal Medicine, Radboud University Medical Centre Nijmegen, Nijmegen, The Netherlands
| | - Marcella Greco
- Division of Nephrology and Dialysis, Bambino Gesu` Children's Hospital - IRCCS, Rome, Italy
| | - Rezan Topaloglu
- Division of Pediatric Nephrology, Department of Pediatrics, Hacettepe University Faculty of Medicine, Ankara, Turkey
| | - Ewa Elenberg
- Renal Service, Texas Children's Hospital, Baylor College of Medicine, Houston, TX, USA
| | - Ranjan Dohil
- Department of Pediatrics, Rady Children's Hospital, San Diego, University of California San Diego, San Diego, CA, USA
| | - Doris Trauner
- Department of Neurosciences, University of California, San Diego, School of Medicine, San Diego, CA, USA
| | - Corinne Antignac
- Laboratory of Inherited Kidney Diseases, Inserm UMR 1163, Paris, France Paris Descartes-Sorbonne Paris Cité University, Imagine Institute, Paris, France APHP, Department of Genetics, Necker Hospital, Paris, France
| | - Pierre Cochat
- Centre de référence des maladies rénales rares, Hospices Civils de Lyon and Université Claude-Bernard Lyon 1, Lyon, France
| | - Frederick Kaskel
- Pediatric Nephrology, Children's Hospital at Montefiore, Bronx, NY, USA
| | - Aude Servais
- Department of Adult Nephrology, Hôpital Necker-Enfants Malades, APHP, Paris Descartes University, Paris, France
| | - Elke Wühl
- Division of Pediatric Nephrology, Center of Pediatrics and Adolescent Medicine, University of Heidelberg, Heidelberg, Germany
| | - Patrick Niaudet
- Université Paris Descartes, Hôpital Necker-Enfants Malades, Paris 75015, France
| | | | - William Gahl
- Section on Human Biochemical Genetics, Human Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892-1851, USA
| | - Elena Levtchenko
- Department of Pediatric Nephrology and Growth and Regeneration, University Hospitals Leuven, Katholieke Universiteit Leuven, Leuven, Belgium
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29
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Zheng X, Liang Y, He Q, Yao R, Bao W, Bao L, Wang Y, Wang Z. Current models of mammalian target of rapamycin complex 1 (mTORC1) activation by growth factors and amino acids. Int J Mol Sci 2014; 15:20753-69. [PMID: 25402640 PMCID: PMC4264194 DOI: 10.3390/ijms151120753] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 09/24/2014] [Accepted: 10/29/2014] [Indexed: 01/09/2023] Open
Abstract
Mammalian target of rapamycin (mTOR), which is now referred to as mechanistic target of rapamycin, integrates many signals, including those from growth factors, energy status, stress, and amino acids, to regulate cell growth and proliferation, protein synthesis, protein degradation, and other physiological and biochemical processes. The mTOR-Rheb-TSC-TBC complex co-localizes to the lysosome and the phosphorylation of TSC-TBC effects the dissociation of the complex from the lysosome and activates Rheb. GTP-bound Rheb potentiates the catalytic activity of mTORC1. Under conditions with growth factors and amino acids, v-ATPase, Ragulator, Rag GTPase, Rheb, hVps34, PLD1, and PA have important but disparate effects on mTORC1 activation. In this review, we introduce five models of mTORC1 activation by growth factors and amino acids to provide a comprehensive theoretical foundation for future research.
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Affiliation(s)
- Xu Zheng
- College of Life Sciences, Inner Mongolia University, Hohhot 010021, China.
| | - Yan Liang
- College of Life Sciences, Inner Mongolia University, Hohhot 010021, China.
| | - Qiburi He
- College of Life Sciences, Inner Mongolia University, Hohhot 010021, China.
| | - Ruiyuan Yao
- College of Life Sciences, Inner Mongolia University, Hohhot 010021, China.
| | - Wenlei Bao
- College of Life Sciences, Inner Mongolia University, Hohhot 010021, China.
| | - Lili Bao
- College of Life Sciences, Inner Mongolia University, Hohhot 010021, China.
| | - Yanfeng Wang
- College of Life Sciences, Inner Mongolia University, Hohhot 010021, China.
| | - Zhigang Wang
- College of Life Sciences, Inner Mongolia University, Hohhot 010021, China.
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30
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Sekito T, Nakamura K, Manabe K, Tone J, Sato Y, Murao N, Kawano-Kawada M, Kakinuma Y. Loss of ATP-dependent lysine uptake in the vacuolar membrane vesicles of Saccharomyces cerevisiae ypq1∆ mutant. Biosci Biotechnol Biochem 2014; 78:1199-202. [PMID: 25229858 DOI: 10.1080/09168451.2014.918489] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Saccharomyces cerevisiae Ypq1p is a vacuolar membrane protein of the PQ-loop protein family. We found that ATP-dependent uptake activities of amino acids by vacuolar membrane vesicles were impaired by ypq1∆ mutation. Loss of lysine uptake was most remarkable, and the uptake was recovered by overproduction of Ypq1p. Ypq1p is thus involved in transport of amino acids into vacuoles.
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Affiliation(s)
- Takayuki Sekito
- a Faculty of Agriculture, Department of Applied Bioresource Science , Ehime University , Matsuyama , Japan
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31
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DeCoursey TE, Hosler J. Philosophy of voltage-gated proton channels. J R Soc Interface 2014; 11:20130799. [PMID: 24352668 PMCID: PMC3899857 DOI: 10.1098/rsif.2013.0799] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 11/22/2013] [Indexed: 02/02/2023] Open
Abstract
In this review, voltage-gated proton channels are considered from a mainly teleological perspective. Why do proton channels exist? What good are they? Why did they go to such lengths to develop several unique hallmark properties such as extreme selectivity and ΔpH-dependent gating? Why is their current so minuscule? How do they manage to be so selective? What is the basis for our belief that they conduct H(+) and not OH(-)? Why do they exist in many species as dimers when the monomeric form seems to work quite well? It is hoped that pondering these questions will provide an introduction to these channels and a way to logically organize their peculiar properties as well as to understand how they are able to carry out some of their better-established biological functions.
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Affiliation(s)
- Thomas E. DeCoursey
- Department of Molecular Biophysics and Physiology, Rush University, 1750 West Harrison, Chicago, IL 60612, USA
| | - Jonathan Hosler
- Department of Biochemistry, University of Mississippi Medical Center, Jackson, MS 39216, USA
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32
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Anne C, Gasnier B. Vesicular neurotransmitter transporters: mechanistic aspects. CURRENT TOPICS IN MEMBRANES 2014; 73:149-74. [PMID: 24745982 DOI: 10.1016/b978-0-12-800223-0.00003-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Secondary transporters driven by a V-type H⁺-ATPase accumulate nonpeptide neurotransmitters into synaptic vesicles. Distinct transporter families are involved depending on the neurotransmitter. Monoamines and acetylcholine on the one hand, and glutamate and ATP on the other hand, are accumulated by SLC18 and SLC17 transporters, respectively, which belong to the major facilitator superfamily (MFS). GABA and glycine accumulate through a common SLC32 transporter from the amino acid/polyamine/organocation (APC) superfamily. Although crystallographic structures are not yet available for any vesicular transporter, homology modeling studies of MFS-type vesicular transporters based on distantly related bacterial structures recently provided significant advances, such as the characterization of substrate-binding pockets or the identification of spatial clusters acting as hinge points during the alternating-access cycle. However, several basic issues, such as the ion stoichiometry of vesicular amino acid transporters, remain unsettled.
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Affiliation(s)
- Christine Anne
- Université Paris Descartes, Sorbonne Paris Cité, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8192, Centre Universitaire des Saints-Pères, Paris, France
| | - Bruno Gasnier
- Université Paris Descartes, Sorbonne Paris Cité, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8192, Centre Universitaire des Saints-Pères, Paris, France.
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33
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Lee CP, Wirtz M, Hell R. Evidence for Several Cysteine Transport Mechanisms in the Mitochondrial Membranes of Arabidopsis thaliana. ACTA ACUST UNITED AC 2013; 55:64-73. [DOI: 10.1093/pcp/pct155] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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34
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Thoene J, Goss T, Witcher M, Mullet J, N'Kuli F, Van Der Smissen P, Courtoy P, Hahn SH. In vitro correction of disorders of lysosomal transport by microvesicles derived from baculovirus-infected Spodoptera cells. Mol Genet Metab 2013; 109:77-85. [PMID: 23465695 DOI: 10.1016/j.ymgme.2013.01.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 01/24/2013] [Accepted: 01/24/2013] [Indexed: 01/29/2023]
Abstract
Infection of Spodoptera frugiperda (Sf9) cells by baculovirus (BV) is well established for transgene expression of soluble proteins, but few correctly folded transmembrane proteins have been so produced. We here report the use of the BV/Sf9 (BVES) method for the expression and transfer, via microvesicles, of the exclusive lysosomal exporters for cystine and sialic acid, human cystinosin and sialin. These proteins and their mRNA are released into the culture medium as very low-density microvesicles (~1.05 g/ml), which do not label for lysobisphosphatidic acid. The presence of the human transgene proteins in the vesicles was confirmed by western blotting and confirmed and quantified by mass spectrometry. Addition of vesicles to cultures of human fibroblast lines deficient in either cystinosin or sialin produced a progressive depletion of stored lysosomal cystine or sialic acid, respectively. The depletion effect was slow (T1/2 ~48 h), saturable (down to ~40% of initial after 4 days) and stable (>one week). Surprisingly, BV infection of Spodoptera appeared to induce expression and release into microvesicles of the insect orthologue of cystinosin, but not of sialin. We conclude that BVES is an effective method to express and transfer functional transmembrane proteins so as to study their properties in mammalian cells, and has a generic potential for transport protein replacement therapy.
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Affiliation(s)
- Jess Thoene
- Department of Pediatric Genetics, University of Michigan, Ann Arbor, MI 48109-5629, USA.
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35
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Yaffe D, Radestock S, Shuster Y, Forrest LR, Schuldiner S. Identification of molecular hinge points mediating alternating access in the vesicular monoamine transporter VMAT2. Proc Natl Acad Sci U S A 2013; 110:E1332-41. [PMID: 23530208 PMCID: PMC3625309 DOI: 10.1073/pnas.1220497110] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Vesicular monoamine transporter 2 (VMAT2) catalyzes transport of monoamines into storage vesicles in a process that involves exchange of the charged monoamine with two protons. VMAT2 is a member of the DHA12 family of multidrug transporters that belongs to the major facilitator superfamily (MFS) of secondary transporters. Here we present a homology model of VMAT2, which has the standard MFS fold, that is, with two domains of six transmembrane helices each which are related by twofold pseudosymmetry and whose axis runs normal to the membrane and between the two halves. Demonstration of the essential role of a membrane-embedded glutamate and confirmation of the existence of a hydrogen bond probably involved in proton transport provide experimental evidence that validates some of the predictions inherent to the model. Moreover, we show the essential role of residues at two anchor points between the two bundles. These residues appear to function as molecular hinge points about which the two six transmembrane-helix bundles flex and straighten to open and close the pathways on either side of the membrane as required for transport. Polar residues that create a hydrogen bond cluster form one of the anchor points of VMAT2. The other results from hydrophobic interactions. Residues at the anchor points are strongly conserved in other MFS transporters in one way or another, suggesting that interactions at these locations will be critical in most, if not all, MFS transporters.
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Affiliation(s)
- Dana Yaffe
- Department of Biological Chemistry, Alexander A. Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel; and
| | - Sebastian Radestock
- Computational Structural Biology Group, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany
| | - Yonatan Shuster
- Department of Biological Chemistry, Alexander A. Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel; and
| | - Lucy R. Forrest
- Computational Structural Biology Group, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany
| | - Shimon Schuldiner
- Department of Biological Chemistry, Alexander A. Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel; and
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36
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Jewell JL, Guan KL. Nutrient signaling to mTOR and cell growth. Trends Biochem Sci 2013; 38:233-42. [PMID: 23465396 DOI: 10.1016/j.tibs.2013.01.004] [Citation(s) in RCA: 274] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Revised: 01/03/2013] [Accepted: 01/08/2013] [Indexed: 12/25/2022]
Abstract
The mammalian target of rapamycin (mTOR) is a conserved protein kinase involved in a multitude of cellular processes including cell growth. Increased mTOR activation is observed in multiple human cancers and inhibition of mTOR has proven efficacious in numerous clinical trials. mTOR comprises two complexes, termed mTORC1 and mTORC2. Both complexes respond to growth factors, whereas only mTORC1 is controlled by nutrients, such as glucose and amino acids. Since the discovery of mTOR, extensive studies have intricately detailed the molecular mechanisms by which mTORC1 is regulated. Somewhat paradoxically, amino acid (AA)-induced mTORC1 activation -arguably the most essential stimulus leading to mTORC1 activation - is the least understood. Here we review the current knowledge of nutrient-dependent regulation of mTORC1.
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Affiliation(s)
- Jenna L Jewell
- Department of Pharmacology and Moores Cancer Center, University of California at San Diego, La Jolla, CA 92093, USA
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37
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Heptahelical protein PQLC2 is a lysosomal cationic amino acid exporter underlying the action of cysteamine in cystinosis therapy. Proc Natl Acad Sci U S A 2012; 109:E3434-43. [PMID: 23169667 DOI: 10.1073/pnas.1211198109] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Cystinosin, the lysosomal cystine exporter defective in cystinosis, is the founding member of a family of heptahelical membrane proteins related to bacteriorhodopsin and characterized by a duplicated motif termed the PQ loop. PQ-loop proteins are more frequent in eukaryotes than in prokaryotes; except for cystinosin, their molecular function remains elusive. In this study, we report that three yeast PQ-loop proteins of unknown function, Ypq1, Ypq2, and Ypq3, localize to the vacuolar membrane and are involved in homeostasis of cationic amino acids (CAAs). We also show that PQLC2, a mammalian PQ-loop protein closely related to yeast Ypq proteins, localizes to lysosomes and catalyzes a robust, electrogenic transport that is selective for CAAs and strongly activated at low extracytosolic pH. Heterologous expression of PQLC2 at the yeast vacuole rescues the resistance phenotype of an ypq2 mutant to canavanine, a toxic analog of arginine efficiently transported by PQLC2. Finally, PQLC2 transports a lysine-like mixed disulfide that serves as a chemical intermediate in cysteamine therapy of cystinosis, and PQLC2 gene silencing trapped this intermediate in cystinotic cells. We conclude that PQLC2 and Ypq1-3 proteins are lysosomal/vacuolar exporters of CAAs and suggest that small-molecule transport is a conserved feature of the PQ-loop protein family, in agreement with its distant similarity to SWEET sugar transporters and to the mitochondrial pyruvate carrier. The elucidation of PQLC2 function may help improve cysteamine therapy. It may also clarify the origin of CAA abnormalities in Batten disease.
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38
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Efeyan A, Zoncu R, Sabatini DM. Amino acids and mTORC1: from lysosomes to disease. Trends Mol Med 2012; 18:524-33. [PMID: 22749019 DOI: 10.1016/j.molmed.2012.05.007] [Citation(s) in RCA: 310] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Revised: 05/22/2012] [Accepted: 05/23/2012] [Indexed: 12/24/2022]
Abstract
The mechanistic target of rapamycin (mTOR) kinase controls growth and metabolism, and its deregulation underlies the pathogenesis of many diseases, including cancer, neurodegeneration, and diabetes. mTOR complex 1 (mTORC1) integrates signals arising from nutrients, energy, and growth factors, but how exactly these signals are propagated await to be fully understood. Recent findings have placed the lysosome, a key mediator of cellular catabolism, at the core of mTORC1 regulation by amino acids. A multiprotein complex that includes the Rag GTPases, Ragulator, and the v-ATPase forms an amino acid-sensing machinery on the lysosomal surface that affects the decision between cell growth and catabolism at multiple levels. The involvement of a catabolic organelle in growth signaling may have important implications for our understanding of mTORC1-related pathologies.
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Affiliation(s)
- Alejo Efeyan
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, MA 02142, USA
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