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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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102
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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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103
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Sumayao R, McEvoy B, Newsholme P, McMorrow T. Lysosomal cystine accumulation promotes mitochondrial depolarization and induction of redox-sensitive genes in human kidney proximal tubular cells. J Physiol 2016; 594:3353-70. [PMID: 26915455 DOI: 10.1113/jp271858] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2015] [Accepted: 02/02/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Cystine is a disulphide amino acid that is normally generated in the lysosomes by the breakdown of cystine-containing proteins. Previously, we demonstrated that lysosomal cystine accumulation in kidney proximal tubular epithelial cells (PTECs) dramatically reduced glutathione (GSH) levels, which may result in the disruption of cellular redox balance. In the present study, we show that lysosomal cystine accumulation following CTNS gene silencing in kidney PTECs resulted in elevated intracellular reactive oxygen species production, reduced antioxidant capacity, induction of redox-sensitive proteins, altered mitochondrial integrity and augmented cell death. These alterations may represent different facets of a unique cascade leading to tubular dysfunction initiated by lysosomal cystine accumulation and may present a clear disadvantage for cystinotic PTECs in vivo. Cystine depletion by cysteamine afforded cytoprotection in CTNS knockdown cells by reducing oxidative stress, normalizing intracellular GSH and ATP content, and preserving cell viability. ABSTRACT Cystine is a disulphide amino acid that is normally generated within the lysosomes through lysosomal-based protein degradation and via extracellular uptake of free cystine. In the autosomal recessive disorder, cystinosis, a defect in the CTNS gene results in excessive lysosomal accumulation of cystine, with early kidney failure a hallmark of the disease. Previously, we demonstrated that silencing of the CTNS gene in kidney proximal tubular epithelial cells (PTECs) resulted in an increase in intracellular cystine concentration coupled with a dramatic reduction in the total GSH content. Because of the crucial role of GSH in maintaining the redox status and viability of kidney PTECs, we assessed the effects of CTNS knockdown-induced lysosomal cystine accumulation on intracellular reactive oxygen species (ROS) production, activity of classical redox-sensitive genes, mitochondrial integrity and cell viability. Our results showed that lysosomal cystine accumulation increased ROS production and solicitation to oxidative stress (OS). This was associated with the induction of classical redox-sensitive proteins, NF-κB, NRF2, HSP32 and HSP70. Cystine-loaded PTECs also displayed depolarized mitochondria, reduced ATP content and augmented apoptosis. Treatment of CTNS knockdown PTECs with the cystine-depleting agent cysteamine resulted in the normalization of OS index, increased GSH and ATP content, and preservation of cell viability. Taken together, the alterations observed in cystinotic cells may represent different facets of a cascade leading to tubular dysfunction and, in combination with cysteamine therapy, may offer a novel link for the attenuation of renal injury and preservation of functions of other organs affected in cystinosis.
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Affiliation(s)
- Rodolfo Sumayao
- Conway Institute, School of Biomolecular and Biomedical Science, University College Dublin, Dublin, Ireland
| | - Bernadette McEvoy
- Conway Institute, School of Biomolecular and Biomedical Science, University College Dublin, Dublin, Ireland
| | - Philip Newsholme
- School of Biomedical Sciences, CHIRI Biosciences Research Precinct and Faculty of Health Sciences, Curtin University, Perth, Western Australia
| | - Tara McMorrow
- Conway Institute, School of Biomolecular and Biomedical Science, University College Dublin, Dublin, Ireland
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104
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Rocca CJ, Kreymerman A, Ur SN, Frizzi KE, Naphade S, Lau A, Tran T, Calcutt NA, Goldberg JL, Cherqui S. Treatment of Inherited Eye Defects by Systemic Hematopoietic Stem Cell Transplantation. Invest Ophthalmol Vis Sci 2016; 56:7214-23. [PMID: 26540660 DOI: 10.1167/iovs.15-17107] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
PURPOSE Cystinosis is caused by a deficiency in the lysosomal cystine transporter, cystinosin (CTNS gene), resulting in cystine crystal accumulation in tissues. In eyes, crystals accumulate in the cornea causing photophobia and eventually blindness. Hematopoietic stem progenitor cells (HSPCs) rescue the kidney in a mouse model of cystinosis. We investigated the potential for HSPC transplantation to treat corneal defects in cystinosis. METHODS We isolated HSPCs from transgenic DsRed mice and systemically transplanted irradiated Ctns-/- mice. A year posttransplantation, we investigated the fate and function of HSPCs by in vivo confocal and fluorescence microscopy (IVCM), quantitative RT-PCR (RT-qPCR), mass spectrometry, histology, and by measuring the IOP. To determine the mechanism by which HSPCs may rescue disease cells, we transplanted Ctns-/- mice with Ctns-/- DsRed HSPCs virally transduced to express functional CTNS-eGFP fusion protein. RESULTS We found that a single systemic transplantation of wild-type HSPCs prevented ocular pathology in the Ctns-/- mice. Engraftment-derived HSPCs were detected within the cornea, and also in the sclera, ciliary body, retina, choroid, and lens. Transplantation of HSPC led to substantial decreases in corneal cystine crystals, restoration of normal corneal thickness, and lowered IOP in mice with high levels of donor-derived cell engraftment. Finally, we found that HSPC-derived progeny differentiated into macrophages, which displayed tunneling nanotubes capable of transferring cystinosin-bearing lysosomes to diseased cells. CONCLUSIONS To our knowledge, this is the first demonstration that HSPCs can rescue hereditary corneal defects, and supports a new potential therapeutic strategy for treating ocular pathologies.
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Affiliation(s)
- Celine J Rocca
- Department of Pediatrics Division of Genetics, University of California, San Diego, La Jolla, California, United States
| | - Alexander Kreymerman
- Shiley Eye Center, University of California, San Diego, California, United States
| | - Sarah N Ur
- Department of Pediatrics Division of Genetics, University of California, San Diego, La Jolla, California, United States
| | - Katie E Frizzi
- Department of Pathology, University of California, San Diego, California, United States
| | - Swati Naphade
- Department of Pediatrics Division of Genetics, University of California, San Diego, La Jolla, California, United States
| | - Athena Lau
- Department of Pediatrics Division of Genetics, University of California, San Diego, La Jolla, California, United States
| | - Tammy Tran
- Shiley Eye Center, University of California, San Diego, California, United States
| | - Nigel A Calcutt
- Department of Pathology, University of California, San Diego, California, United States
| | - Jeffrey L Goldberg
- Shiley Eye Center, University of California, San Diego, California, United States 4Byers Eye Institute, Stanford University, Palo Alto, California, United States
| | - Stephanie Cherqui
- Department of Pediatrics Division of Genetics, University of California, San Diego, La Jolla, California, United States
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105
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The AP-3 adaptor complex mediates sorting of yeast and mammalian PQ-loop-family basic amino acid transporters to the vacuolar/lysosomal membrane. Sci Rep 2015; 5:16665. [PMID: 26577948 PMCID: PMC4649669 DOI: 10.1038/srep16665] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 10/19/2015] [Indexed: 01/31/2023] Open
Abstract
The limiting membrane of lysosomes in animal cells and that of the vacuole in yeast
include a wide variety of transporters, but little is known about how these proteins
reach their destination membrane. The mammalian PQLC2 protein catalyzes efflux of
basic amino acids from the lysosome, and the similar Ypq1, −2, and
−3 proteins of yeast perform an equivalent function at the vacuole. We
here show that the Ypq proteins are delivered to the vacuolar membrane via the
alkaline phosphatase (ALP) trafficking pathway, which requires the AP-3 adaptor
complex. When traffic via this pathway is deficient, the Ypq proteins pass through
endosomes from where Ypq1 and Ypq2 properly reach the vacuolar membrane whereas Ypq3
is missorted to the vacuolar lumen via the multivesicular body pathway. When
produced in yeast, PQLC2 also reaches the vacuolar membrane via the ALP pathway, but
tends to sort to the vacuolar lumen if AP-3 is defective. Finally, in HeLa cells,
inhibiting the synthesis of an AP-3 subunit also impairs sorting of PQLC2 to
lysosomes. Our results suggest the existence of a conserved AP-3-dependent
trafficking pathway for proper delivery of basic amino acid exporters to the yeast
vacuole and to lysosomes of human cells.
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106
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Abstract
Lysosomes are acidic compartments filled with more than 60 different types of hydrolases. They mediate the degradation of extracellular particles from endocytosis and of intracellular components from autophagy. The digested products are transported out of the lysosome via specific catabolite exporters or via vesicular membrane trafficking. Lysosomes also contain more than 50 membrane proteins and are equipped with the machinery to sense nutrient availability, which determines the distribution, number, size, and activity of lysosomes to control the specificity of cargo flux and timing (the initiation and termination) of degradation. Defects in degradation, export, or trafficking result in lysosomal dysfunction and lysosomal storage diseases (LSDs). Lysosomal channels and transporters mediate ion flux across perimeter membranes to regulate lysosomal ion homeostasis, membrane potential, catabolite export, membrane trafficking, and nutrient sensing. Dysregulation of lysosomal channels underlies the pathogenesis of many LSDs and possibly that of metabolic and common neurodegenerative diseases.
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Affiliation(s)
- Haoxing Xu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109;
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107
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Jaradat S, Al-Rababah B, Hazza I, Akl K, Saca E, Al-Younis D. Molecular analysis of the CTNS gene in Jordanian families with nephropathic cystinosis. Nefrologia 2015; 35:547-53. [DOI: 10.1016/j.nefro.2015.09.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 06/10/2015] [Indexed: 10/22/2022] Open
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108
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Naphade S, Sharma J, Gaide Chevronnay HP, Shook MA, Yeagy BA, Rocca CJ, Ur SN, Lau AJ, Courtoy PJ, Cherqui S. Brief reports: Lysosomal cross-correction by hematopoietic stem cell-derived macrophages via tunneling nanotubes. Stem Cells 2015; 33:301-9. [PMID: 25186209 DOI: 10.1002/stem.1835] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 07/23/2014] [Indexed: 12/26/2022]
Abstract
Despite controversies on the potential of hematopoietic stem cells (HSCs) to promote tissue repair, we previously showed that HSC transplantation could correct cystinosis, a multisystemic lysosomal storage disease, caused by a defective lysosomal membrane cystine transporter, cystinosin (CTNS gene). Addressing the cellular mechanisms, we here report vesicular cross-correction after HSC differentiation into macrophages. Upon coculture with cystinotic fibroblasts, macrophages produced tunneling nanotubes (TNTs) allowing transfer of cystinosin-bearing lysosomes into Ctns-deficient cells, which exploited the same route to retrogradely transfer cystine-loaded lysosomes to macrophages, providing a bidirectional correction mechanism. TNT formation was enhanced by contact with diseased cells. In vivo, HSCs grafted to cystinotic kidneys also generated nanotubular extensions resembling invadopodia that crossed the dense basement membranes and delivered cystinosin into diseased proximal tubular cells. This is the first report of correction of a genetic lysosomal defect by bidirectional vesicular exchange via TNTs and suggests broader potential for HSC transplantation for other disorders due to defective vesicular proteins.
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Affiliation(s)
- Swati Naphade
- Division of Genetics, Department of Pediatrics, University of California, La Jolla, San Diego, California, USA
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109
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Edwards SL, Morrison LM, Yorks RM, Hoover CM, Boominathan S, Miller KG. UNC-16 (JIP3) Acts Through Synapse-Assembly Proteins to Inhibit the Active Transport of Cell Soma Organelles to Caenorhabditis elegans Motor Neuron Axons. Genetics 2015; 201:117-41. [PMID: 26354976 PMCID: PMC4566257 DOI: 10.1534/genetics.115.177345] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 06/24/2015] [Indexed: 12/31/2022] Open
Abstract
The conserved protein UNC-16 (JIP3) inhibits the active transport of some cell soma organelles, such as lysosomes, early endosomes, and Golgi, to the synaptic region of axons. However, little is known about UNC-16's organelle transport regulatory function, which is distinct from its Kinesin-1 adaptor function. We used an unc-16 suppressor screen in Caenorhabditis elegans to discover that UNC-16 acts through CDK-5 (Cdk5) and two conserved synapse assembly proteins: SAD-1 (SAD-A Kinase), and SYD-2 (Liprin-α). Genetic analysis of all combinations of double and triple mutants in unc-16(+) and unc-16(-) backgrounds showed that the three proteins (CDK-5, SAD-1, and SYD-2) are all part of the same organelle transport regulatory system, which we named the CSS system based on its founder proteins. Further genetic analysis revealed roles for SYD-1 (another synapse assembly protein) and STRADα (a SAD-1-interacting protein) in the CSS system. In an unc-16(-) background, loss of the CSS system improved the sluggish locomotion of unc-16 mutants, inhibited axonal lysosome accumulation, and led to the dynein-dependent accumulation of lysosomes in dendrites. Time-lapse imaging of lysosomes in CSS system mutants in unc-16(+) and unc-16(-) backgrounds revealed active transport defects consistent with the steady-state distributions of lysosomes. UNC-16 also uses the CSS system to regulate the distribution of early endosomes in neurons and, to a lesser extent, Golgi. The data reveal a new and unprecedented role for synapse assembly proteins, acting as part of the newly defined CSS system, in mediating UNC-16's organelle transport regulatory function.
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Affiliation(s)
- Stacey L Edwards
- Genetic Models of Disease Laboratory, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
| | - Logan M Morrison
- Genetic Models of Disease Laboratory, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
| | - Rosalina M Yorks
- Genetic Models of Disease Laboratory, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
| | - Christopher M Hoover
- Genetic Models of Disease Laboratory, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
| | - Soorajnath Boominathan
- Genetic Models of Disease Laboratory, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
| | - Kenneth G Miller
- Genetic Models of Disease Laboratory, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
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Napolitano G, Johnson JL, He J, Rocca CJ, Monfregola J, Pestonjamasp K, Cherqui S, Catz SD. Impairment of chaperone-mediated autophagy leads to selective lysosomal degradation defects in the lysosomal storage disease cystinosis. EMBO Mol Med 2015; 7:158-74. [PMID: 25586965 PMCID: PMC4328646 DOI: 10.15252/emmm.201404223] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Metabolite accumulation in lysosomal storage disorders (LSDs) results in impaired cell function and multi-systemic disease. Although substrate reduction and lysosomal overload-decreasing therapies can ameliorate disease progression, the significance of lysosomal overload-independent mechanisms in the development of cellular dysfunction is unknown for most LSDs. Here, we identify a mechanism of impaired chaperone-mediated autophagy (CMA) in cystinosis, a LSD caused by defects in the cystine transporter cystinosin (CTNS) and characterized by cystine lysosomal accumulation. We show that, different from other LSDs, autophagosome number is increased, but macroautophagic flux is not impaired in cystinosis while mTOR activity is not affected. Conversely, the expression and localization of the CMA receptor LAMP2A are abnormal in CTNS-deficient cells and degradation of the CMA substrate GAPDH is defective in Ctns−/− mice. Importantly, cysteamine treatment, despite decreasing lysosomal overload, did not correct defective CMA in Ctns−/− mice or LAMP2A mislocalization in cystinotic cells, which was rescued by CTNS expression instead, suggesting that cystinosin is important for CMA activity. In conclusion, CMA impairment contributes to cell malfunction in cystinosis, highlighting the need for treatments complementary to current therapies that are based on decreasing lysosomal overload.
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Affiliation(s)
- Gennaro Napolitano
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, USA
| | - Jennifer L Johnson
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, USA
| | - Jing He
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, USA
| | - Celine J Rocca
- Department of Pediatrics, University of California San Diego, La Jolla, CA, USA
| | - Jlenia Monfregola
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, USA
| | - Kersi Pestonjamasp
- Cancer Center Microscopy Shared Resource, University of California San Diego, La Jolla, CA, USA
| | - Stephanie Cherqui
- Department of Pediatrics, University of California San Diego, La Jolla, CA, USA
| | - Sergio D Catz
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, USA
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111
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Gaide Chevronnay HP, Janssens V, Van Der Smissen P, Liao XH, Abid Y, Nevo N, Antignac C, Refetoff S, Cherqui S, Pierreux CE, Courtoy PJ. A mouse model suggests two mechanisms for thyroid alterations in infantile cystinosis: decreased thyroglobulin synthesis due to endoplasmic reticulum stress/unfolded protein response and impaired lysosomal processing. Endocrinology 2015; 156:2349-64. [PMID: 25811319 PMCID: PMC4430621 DOI: 10.1210/en.2014-1672] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Thyroid hormones are released from thyroglobulin (Tg) in lysosomes, which are impaired in infantile/nephropathic cystinosis. Cystinosis is a lysosomal cystine storage disease due to defective cystine exporter, cystinosin. Cystinotic children develop subclinical and then overt hypothyroidism. Why hypothyroidism is the most frequent and earliest endocrine complication of cystinosis is unknown. We here defined early alterations in Ctns(-/-) mice thyroid and identified subcellular and molecular mechanisms. At 9 months, T4 and T3 plasma levels were normal and TSH was moderately increased (∼4-fold). By histology, hyperplasia and hypertrophy of most follicles preceded colloid exhaustion. Increased immunolabeling for thyrocyte proliferation and apoptotic shedding indicated accelerated cell turnover. Electron microscopy revealed endoplasmic reticulum (ER) dilation, apical lamellipodia indicating macropinocytic colloid uptake, and lysosomal cystine crystals. Tg accumulation in dilated ER contrasted with mRNA down-regulation. Increased expression of ER chaperones, glucose-regulated protein of 78 kDa and protein disulfide isomerase, associated with alternative X-box binding protein-1 splicing, revealed unfolded protein response (UPR) activation by ER stress. Decreased Tg mRNA and ER stress suggested reduced Tg synthesis. Coordinated increase of UPR markers, activating transcription factor-4 and C/EBP homologous protein, linked ER stress to apoptosis. Hormonogenic cathepsins were not altered, but lysosome-associated membrane protein-1 immunolabeling disclosed enlarged vesicles containing iodo-Tg and impaired lysosomal fusion. Isopycnic fractionation showed iodo-Tg accumulation in denser lysosomes, suggesting defective lysosomal processing and hormone release. In conclusion, Ctns(-/-) mice showed the following alterations: 1) compensated primary hypothyroidism and accelerated thyrocyte turnover; 2) impaired Tg production linked to ER stress/UPR response; and 3) altered endolysosomal trafficking and iodo-Tg processing. The Ctns(-/-) thyroid is useful to study disease progression and evaluate novel therapies.
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Affiliation(s)
- H P Gaide Chevronnay
- Cell Biology Unit (H.P.G.C., V.J., P.V.D.S., Y.A., C.E.P., P.J.C.), de Duve Institute and Université Catholique de Louvain, 1200 Brussels, Belgium; Departments of Medicine (X.H.L., S.R.) and Pediatrics and Genetics (S.R), The University of Chicago, Chicago, Illinois 60637; INSERM, Unité 1163 (N.N., C.A.), Hôpital Necker-Enfants Malades and Université Paris Descartes, Sorbonne Paris Cité, Institut Imagine, 75015 Paris, France; and Department of Pediatrics (S.C.), Division of Genetics, University of California, San Diego, San Diego, California 92161
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112
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La cystinose chez l’adulte : une maladie systémique. Nephrol Ther 2015; 11:152-9. [DOI: 10.1016/j.nephro.2014.12.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 12/15/2014] [Accepted: 12/15/2014] [Indexed: 11/23/2022]
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113
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Nesterova G, Williams C, Bernardini I, Gahl WA. Cystinosis: renal glomerular and renal tubular function in relation to compliance with cystine-depleting therapy. Pediatr Nephrol 2015; 30:945-51. [PMID: 25526929 DOI: 10.1007/s00467-014-3018-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 11/12/2014] [Accepted: 11/13/2014] [Indexed: 11/24/2022]
Abstract
BACKGROUND AND OBJECTIVES Nephropathic cystinosis is a lysosomal storage disorder characterized by renal tubular Fanconi syndrome in infancy and glomerular damage leading to renal failure at ∼10 years of age. Therapy with the cystine-depleting agent cysteamine postpones renal failure, but the degree of compliance with this treatment has not been correlated with preservation of kidney function. METHODS We assessed leucocyte cystine depletion by cysteamine and created the composite compliance score that incorporates the extent of leucocyte cystine depletion, as well as duration of cysteamine treatment, into a single integer. Age at renal failure was used to gauge preservation of renal function, and the Fanconi syndrome index (FSI), a measure of aminoaciduria, was used to assess renal tubular Fanconi syndrome. RESULTS Age at renal failure varied directly and linearly with the composite compliance score (y = 0.3x +8.8; R(2) = 0.61). The slope indicated that for every year of excellent cystine depletion, nearly 1 year of renal function was preserved. Age at renal failure correlated roughly with mean leucocyte cystine level, but not with mean cysteamine dosage. There was no correlation between the FSI and the composite compliance score. CONCLUSIONS Greater compliance with oral cysteamine therapy yields greater preservation of renal glomerular, but not tubular, function. Oral cysteamine therapy should be given at the maximum tolerated dose, within the recommended limits.
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Affiliation(s)
- Galina Nesterova
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA,
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114
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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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115
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Kilpatrick BS, Eden ER, Hockey LN, Futter CE, Patel S. Methods for monitoring lysosomal morphology. Methods Cell Biol 2015; 126:1-19. [PMID: 25665438 DOI: 10.1016/bs.mcb.2014.10.018] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Lysosomes are abundant organelles best known for their crucial role in macromolecule turnover. Lysosome dysfunction features in several diseases exemplified by the lysosomal storage disorders and is often associated with marked changes in lysosome structure. Lysosomal morphology may therefore serve as a sensitive readout of endocytic well-being. Here we describe methods for monitoring lysosome morphology in fixed and live cells using fluorescent probes and electron microscopy.
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Affiliation(s)
- Bethan S Kilpatrick
- Department of Cell and Developmental Biology, University College London, London, UK
| | - Emily R Eden
- Department of Cell Biology, Institute of Ophthalmology, University College London, London, UK
| | - Leanne N Hockey
- Department of Cell and Developmental Biology, University College London, London, UK
| | - Clare E Futter
- Department of Cell Biology, Institute of Ophthalmology, University College London, London, UK
| | - Sandip Patel
- Department of Cell and Developmental Biology, University College London, London, UK
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116
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Surendran K, Vitiello SP, Pearce DA. Lysosome dysfunction in the pathogenesis of kidney diseases. Pediatr Nephrol 2014; 29:2253-61. [PMID: 24217784 PMCID: PMC4018427 DOI: 10.1007/s00467-013-2652-z] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 09/29/2013] [Accepted: 10/01/2013] [Indexed: 12/18/2022]
Abstract
The lysosome, an organelle central to macromolecule degradation and recycling, plays a pivotal role in normal cell processes, ranging from autophagy to redox regulation. Not surprisingly, lysosomes are an integral part of the renal epithelial molecular machinery that facilitates normal renal physiology. Two inherited diseases that manifest as kidney dysfunction are Fabry's disease and cystinosis, each of which is caused by a primary biochemical defect at the lysosome resulting from loss-of-function mutations in genes that encode lysosomal proteins. The functions of the lysosomes in the kidney and how lysosomal dysfunction might contribute to Fabry's disease and cystinosis are discussed. Unlike most other pediatric renal diseases, therapies are available for Fabry's disease and cystinosis, but require early diagnosis. Recent analysis of ceroid neuronal lipofuscinosis type 3 (Cln3) null mice, a mouse model of lysosomal disease that is primarily associated with neurological deficits, revealed renal functional abnormalities. As current and future therapeutics increase the life-span of those suffering from diseases like neuronal ceroid lipofuscinosis, it remains a distinct possibility that many more lysosomal disorders that primarily manifest as infant and juvenile neurodegenerative diseases may also include renal disease phenotypes.
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Affiliation(s)
- Kameswaran Surendran
- Sanford Children’s Health Research Center, Sanford Research/USD, Sioux Falls, SD 57104, USA,Department of Pediatrics, Sanford School of Medicine, Sioux Falls, SD 57104, USA
| | - Seasson P. Vitiello
- Sanford Children’s Health Research Center, Sanford Research/USD, Sioux Falls, SD 57104, USA,Augustana College, Sioux Falls, SD
| | - David A. Pearce
- Sanford Children’s Health Research Center, Sanford Research/USD, Sioux Falls, SD 57104, USA,Department of Pediatrics, Sanford School of Medicine, Sioux Falls, SD 57104, USA,Corresponding Author: David A. Pearce, Sanford Research/USD, 2301 East 60th Street North, Sioux Falls, SD, 57104-0589, Telephone: 605 312-6004, FAX: 605 312-6071,
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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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118
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Shams F, Livingstone I, Oladiwura D, Ramaesh K. Treatment of corneal cystine crystal accumulation in patients with cystinosis. Clin Ophthalmol 2014; 8:2077-84. [PMID: 25336909 PMCID: PMC4199850 DOI: 10.2147/opth.s36626] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Cystinosis is a rare autosomal recessive disorder characterized by the accumulation of cystine within the cells of different organs. Infantile nephropathic cystinosis is the most common and severe phenotype. With the success of renal transplantation, these patients are now living longer and thus more long-term complications within different organs are becoming apparent. Ophthalmic manifestations range from corneal deposits of cystine crystals to pigmentary retinopathy. With increasing age, more severe ocular complications have been reported. Photophobia is a prominent symptom for patients. With prolonged survival and increasing age, this symptom, along with corneal erosions and blepharospasm, can become debilitating. This review revisits the basic pathogenesis of cystinosis, the ocular manifestations of the disease, and the treatment of corneal crystals.
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Affiliation(s)
- Fatemeh Shams
- Department of Ophthalmology, Gartnavel General Hospital, Glasgow, Scotland
| | - Iain Livingstone
- Department of Ophthalmology, Gartnavel General Hospital, Glasgow, Scotland
| | - Dilys Oladiwura
- Department of Ophthalmology, Gartnavel General Hospital, Glasgow, Scotland
| | - Kanna Ramaesh
- Department of Ophthalmology, Gartnavel General Hospital, Glasgow, Scotland
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119
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Sansanwal P, Li L, Sarwal MM. Inhibition of intracellular clusterin attenuates cell death in nephropathic cystinosis. J Am Soc Nephrol 2014; 26:612-25. [PMID: 25071085 DOI: 10.1681/asn.2013060577] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Nephropathic cystinosis, characterized by accumulation of cystine in the lysosomes, is caused by mutations in CTNS. The molecular and cellular mechanisms underlying proximal tubular dysfunction and progressive renal failure in nephropathic cystinosis are largely unclear, and increasing evidence supports the notion that cystine accumulation alone is not responsible for the end organ injury in cystinosis. We previously identified clusterin as potentially involved in nephropathic cystinosis. Here, we studied the expression of clusterin in renal proximal tubular epithelial cells obtained from patients with nephropathic cystinosis. The cytoprotective secretory form of clusterin, as evaluated by Western blot analysis, was low or absent in cystinosis cells compared with normal primary cells. Confocal microscopy revealed elevated levels of intracellular clusterin in cystinosis cells. Clusterin in cystinosis cells localized to the nucleus and cytoplasm and showed a filamentous and punctate aggresome-like pattern compared with diffuse cytoplasmic staining in normal cells. In kidney biopsy samples from patients with nephropathic cystinosis, clusterin protein expression was mainly limited to the proximal tubular cells. Furthermore, expression of clusterin overlapped with the expression of apoptotic proteins (apoptosis-inducing factor and cleaved caspase-3) and autophagy proteins (LC3 II and p62). Silencing of the clusterin gene resulted in a significant increase in cell viability and attenuation of apoptosis in cystinosis cells. Results of this study identify clusterin as a pivotal factor in the cell injury mechanism of nephropathic cystinosis and provide evidence linking cellular stress and injury to Fanconi syndrome and progressive renal injury in nephropathic cystinosis.
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Affiliation(s)
- Poonam Sansanwal
- California Pacific Medical Center Research Institute, San Francisco, California;
| | - Li Li
- Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York; and
| | - Minnie M Sarwal
- California Pacific Medical Center Research Institute, San Francisco, California; Department of Surgery, Univeristy of California, San Francisco, School of Medicine, San Francisco, California
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Abstract
Cystinosis is an autosomal recessive inherited lysosomal storage disease. It is characterized by generalized proximal tubular dysfunction known as renal Fanconi syndrome and causes end-stage renal disease by the age of about 10 years if left untreated. Extrarenal organs are also affected, including the thyroid gland, gonads, pancreas, liver, muscle, and brain. Treatment consists of administration of cysteamine, resulting in depletion of cystine that is trapped inside the lysosomes. Since cysteamine has a short half-life, it should be administered every 6 hours. Recently, a new delayed-release formulation was marketed, that should be administered every 12 hours. The first studies comparing both cysteamine formulations show comparable results regarding white blood cell cystine depletion (which serves as a measure for cystine accumulation in the body), while a slightly lower daily dose of cysteamine can be used.
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Affiliation(s)
- Martine Tp Besouw
- Department of Pediatric Nephrology, University Hospitals Leuven, Belgium ; Laboratory of Pediatrics, Catholic University Leuven, Leuven, Belgium
| | - Elena N Levtchenko
- Department of Pediatric Nephrology, University Hospitals Leuven, Belgium ; Laboratory of Pediatrics, Catholic University Leuven, Leuven, Belgium
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121
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Rocca CJ, Ur SN, Harrison F, Cherqui S. rAAV9 combined with renal vein injection is optimal for kidney-targeted gene delivery: conclusion of a comparative study. Gene Ther 2014; 21:618-28. [PMID: 24784447 PMCID: PMC4047163 DOI: 10.1038/gt.2014.35] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 03/03/2014] [Accepted: 03/14/2014] [Indexed: 12/19/2022]
Abstract
Effective gene therapy strategies for the treatment of kidney disorders remain elusive. We report an optimized kidney-targeted gene delivery strategy using recombinant adeno-associated virus (rAAV) administered via retrograde renal vein injection in mice. Renal vein injection of rAAV consistently resulted in superior kidney transduction compared with tail vein injection using as little as half the tail vein dose. We compared rAAV5, 6, 8 and 9, containing either green fluorescent protein (GFP) or luciferase reporter genes driven by the Cytomegalovirus promoter. We demonstrated that although rAAV6 and 8 injected via renal vein transduced the kidney, transgene expression was mainly restricted to the medulla. Transgene expression was systematically low after rAAV5 injection, attributed to T-cell immune response, which could be overcome by transient immunosuppression. However, rAAV9 was the only serotype that permitted high-transduction efficiency of both the cortex and medulla. Moreover, both the glomeruli and tubules were targeted, with a higher efficiency within the glomeruli. To improve the specificity of kidney-targeted gene delivery with rAAV9, we used the parathyroid hormone receptor 'kidney-specific' promoter. We obtained a more efficient transgene expression within the kidney, and a significant reduction in other tissues. Our work represents the first comprehensive and clinically relevant study for kidney gene delivery.
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Affiliation(s)
- Céline J. Rocca
- Department of Pediatrics, Division of Genetics, University of California, San Diego, 9500 Gilman drive, MC 0734, La Jolla, California 92093-0734, USA
| | - Sarah N. Ur
- Department of Pediatrics, Division of Genetics, University of California, San Diego, 9500 Gilman drive, MC 0734, La Jolla, California 92093-0734, USA
| | - Frank Harrison
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Stephanie Cherqui
- Department of Pediatrics, Division of Genetics, University of California, San Diego, 9500 Gilman drive, MC 0734, La Jolla, California 92093-0734, USA
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122
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Carnitine Profile and Effect of Suppletion in Children with Renal Fanconi Syndrome due to Cystinosis. JIMD Rep 2014; 16:25-30. [PMID: 24798266 DOI: 10.1007/8904_2014_312] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2013] [Revised: 03/17/2014] [Accepted: 03/19/2014] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Cystinosis is an autosomal recessive disorder marked by intralysosomal cystine accumulation. Patients present with generalized proximal tubular dysfunction called renal Fanconi syndrome. Urinary carnitine loss results in plasma and muscle carnitine deficiency, but no clinical signs of carnitine deficiency have been described. Also, the optimal dose of carnitine supplementation is undefined. This study aimed to determine whether currently recommended carnitine doses result in adequate correction of plasma carnitine. METHODS Five cystinosis patients with renal Fanconi syndrome, aged 2-18 years, were included. L-carnitine was prescribed 50 mg/kg/day since diagnosis: median 36 (range 18-207) months. Total and free plasma and urine carnitine and carnitine profiles were measured at study onset, after stopping L-carnitine for 3 months and 3 months after reintroducing L-carnitine 50 mg/kg/day. RESULTS At study onset, plasma free carnitine was normal in all patients, total carnitine (1/5), acetylcarnitine (3/5), and several short- and medium-chain acylcarnitines ≤10 carbons (5/5) were increased indicating carnitine over-supplementation. Three months after cessation, carnitine profiles normalized and 3/5 patients showed plasma carnitine deficiency. Three months after reintroduction, plasma free carnitine normalized in all patients, however, carnitine profiles were disturbed in 4/5 patients. Urine free carnitine, acetylcarnitine, and acylcarnitines ≤10 carbons were increased in all patients independent of carnitine supplementation. CONCLUSION Administration of recommended doses L-carnitine (50 mg/kg/day) resulted in over-supplementation. Although the drug is considered to be rather safe, long-term effects of over-supplementation remain unknown warranting cautious use of high doses. Plasma carnitine profile might be used as a monitor, to prevent overdosing.
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123
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Gaide Chevronnay HP, Janssens V, Van Der Smissen P, N'Kuli F, Nevo N, Guiot Y, Levtchenko E, Marbaix E, Pierreux CE, Cherqui S, Antignac C, Courtoy PJ. Time course of pathogenic and adaptation mechanisms in cystinotic mouse kidneys. J Am Soc Nephrol 2014; 25:1256-69. [PMID: 24525030 DOI: 10.1681/asn.2013060598] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Cystinosis, a main cause of Fanconi syndrome, is reproduced in congenic C57BL/6 cystinosin knockout (KO) mice. To identify the sequence of pathogenic and adaptation mechanisms of nephropathic cystinosis, we defined the onset of Fanconi syndrome in KO mice between 3 and 6 months of age and analyzed the correlation with structural and functional changes in proximal tubular cells (PTCs), with focus on endocytosis of ultrafiltrated disulfide-rich proteins as a key source of cystine. Despite considerable variation between mice at the same age, typical event sequences were delineated. At the cellular level, amorphous lysosomal inclusions preceded cystine crystals and eventual atrophy without crystals. At the nephron level, lesions started at the glomerulotubular junction and then extended distally. In situ hybridization and immunofluorescence revealed progressive loss of expression of megalin, cubilin, sodium-glucose cotransporter 2, and type IIa sodium-dependent phosphate cotransporter, suggesting apical dedifferentiation accounting for Fanconi syndrome before atrophy. Injection of labeled proteins revealed that defective endocytosis in S1 PTCs led to partial compensatory uptake by S3 PTCs, suggesting displacement of endocytic load and injury by disulfide-rich cargo. Increased PTC apoptosis allowed luminal shedding of cystine crystals and was partially compensated for by tubular proliferation. We conclude that lysosomal storage triggered by soluble cystine accumulation induces apical PTC dedifferentiation, which causes transfer of the harmful load of disulfide-rich proteins to more distal cells, possibly explaining longitudinal progression of swan-neck lesions. Furthermore, our results suggest that subsequent adaptation mechanisms include lysosomal clearance of free and crystalline cystine into urine and ongoing tissue repair.
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Affiliation(s)
| | - Virginie Janssens
- Cell Biology Unit, de Duve Institute and Université Catholique de Louvain, Brussels, Belgium
| | - Patrick Van Der Smissen
- Cell Biology Unit, de Duve Institute and Université Catholique de Louvain, Brussels, Belgium
| | - Francisca N'Kuli
- Cell Biology Unit, de Duve Institute and Université Catholique de Louvain, Brussels, Belgium
| | - Nathalie Nevo
- Inserm, U574, Hôpital Necker-Enfants Malades and Université Paris Descartes, Sorbonne Paris Cité, Institut Imagine, Paris, France
| | - Yves Guiot
- Pathology Department, Saint-Luc University Clinics, Brussels, Belgium
| | - Elena Levtchenko
- Department of Pediatric Nephrology, University Hospitals Leuven, Leuven, Belgium; and
| | - Etienne Marbaix
- Cell Biology Unit, de Duve Institute and Université Catholique de Louvain, Brussels, Belgium; Pathology Department, Saint-Luc University Clinics, Brussels, Belgium
| | - Christophe E Pierreux
- Cell Biology Unit, de Duve Institute and Université Catholique de Louvain, Brussels, Belgium
| | - Stéphanie Cherqui
- Department of Pediatrics, Division of Genetics, University of California, San Diego, California
| | - Corinne Antignac
- Inserm, U574, Hôpital Necker-Enfants Malades and Université Paris Descartes, Sorbonne Paris Cité, Institut Imagine, Paris, France
| | - Pierre J Courtoy
- Cell Biology Unit, de Duve Institute and Université Catholique de Louvain, Brussels, Belgium
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Abstract
Amino acid (AA) transporters may act as sensors, as well as carriers, of tissue nutrient supplies. This review considers recent advances in our understanding of the AA-sensing functions of AA transporters in both epithelial and nonepithelial cells. These transporters mediate AA exchanges between extracellular and intracellular fluid compartments, delivering substrates to intracellular AA sensors. AA transporters on endosomal (eg, lysosomal) membranes may themselves function as intracellular AA sensors. AA transporters at the cell surface, particularly those for large neutral AAs such as leucine, interact functionally with intracellular nutrient-signaling pathways that regulate metabolism: for example, the mammalian target of rapamycin complex 1 (mTORC1) pathway, which promotes cell growth, and the general control non-derepressible (GCN) pathway, which is activated by AA starvation. Under some circumstances, upregulation of AA transporter expression [notably a leucine transporter, solute carrier 7A5 (SLC7A5)] is required to initiate AA-dependent activation of the mTORC1 pathway. Certain AA transporters may have dual receptor-transporter functions, operating as "transceptors" to sense extracellular (or intracellular) AA availability upstream of intracellular signaling pathways. New opportunities for nutritional therapy may include targeting of AA transporters (or mechanisms that upregulate their expression) to promote protein-anabolic signals for retention or recovery of lean tissue mass.
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Affiliation(s)
- Peter M Taylor
- Division of Cell Signalling & Immunology, College of Life Sciences, University of Dundee, Dundee, United Kingdom
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125
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An organelle gatekeeper function for Caenorhabditis elegans UNC-16 (JIP3) at the axon initial segment. Genetics 2013; 194:143-61. [PMID: 23633144 DOI: 10.1534/genetics.112.147348] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Neurons must cope with extreme membrane trafficking demands to produce axons with organelle compositions that differ dramatically from those of the cell soma and dendrites; however, the mechanism by which they accomplish this is not understood. Here we use electron microscopy and quantitative imaging of tagged organelles to show that Caenorhabditis elegans axons lacking UNC-16 (JIP3/Sunday Driver) accumulate Golgi, endosomes, and lysosomes at levels up to 10-fold higher than wild type, while ER membranes are largely unaffected. Time lapse microscopy of tagged lysosomes in living animals and an analysis of lysosome distributions in various regions of unc-16 mutant axons revealed that UNC-16 inhibits organelles from escaping the axon initial segment (AIS) and moving to the distal synaptic part of the axon. Immunostaining of native UNC-16 in C. elegans neurons revealed a localized concentration of UNC-16 at the initial segment, although UNC-16 is also sparsely distributed in distal regions of axons, including the synaptic region. Organelles that escape the AIS in unc-16 mutants show bidirectional active transport within the axon commissure that occasionally deposits them in the synaptic region, where their mobility decreases and they accumulate. These results argue against the long-standing, untested hypothesis that JIP3/Sunday Driver promotes anterograde organelle transport in axons and instead suggest an organelle gatekeeper model in which UNC-16 (JIP3/Sunday Driver) selectively inhibits the escape of Golgi and endosomal organelles from the AIS. This is the first evidence for an organelle gatekeeper function at the AIS, which could provide a regulatory node for controlling axon organelle composition.
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126
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Cherqui S. Is genetic rescue of cystinosis an achievable treatment goal? Nephrol Dial Transplant 2013; 29:522-8. [PMID: 23861466 DOI: 10.1093/ndt/gft270] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Cystinosis is an autosomal recessive metabolic disease that belongs to the family of lysosomal storage disorders. The defective gene is CTNS, which encodes the lysosomal cystine transporter, cystinosin. Cystine accumulates in all tissues and leads to organ damage including end-stage renal disease. In this review, we outline the studies that support that genetic rescue of cystinosis could be an achievable goal, even though cystinosis is a multi-compartmental disease and cystinosin an intracellular transmembrane protein. Using the mouse model of cystinosis, the Ctns(-/-) mice, we showed that transplanted hematopoietic stem cells (HSCs) were able to act as vehicles for the delivery of a functional Ctns gene to the different organs and led to the significant decrease of the tissue cystine content and tissue preservation. Ex vivo gene-modified Ctns(-/-) HSC transplantation using a lentiviral vector containing CTNS complementary DNA (cDNA) was also successful in the Ctns(-/-) mice and built the foundations for a clinical trial for autologous HSC transplantation for cystinosis. The capacity of HSCs for rescuing non-hematopoietic disease is controversial, and new insights into regenerative medicine could be gained from unraveling the underlying mechanism of action.
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Affiliation(s)
- Stephanie Cherqui
- Department of Pediatrics, Division of Genetics, University of California, San Diego, La Jolla, California, USA
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127
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Widger LR, Siegler MA, Goldberg DP. Sulfide Oxidation by O 2: Synthesis, Structure and Reactivity of Novel Sulfide-Incorporated Fe(II) Bis(imino)pyridine Complexes. Polyhedron 2013; 58:179-189. [PMID: 23878411 PMCID: PMC3712537 DOI: 10.1016/j.poly.2013.01.043] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The unsymmetrical iron(II) bis(imino)pyridine complexes [FeII(LN3SMe)(H2O)3](OTf)2 (1), and [FeII(LN3SMe)Cl2] (2) were synthesized and their reactivity with O2 was examined. Complexes 1 and 2 were characterized by single crystal X-ray crystallography, LDI-MS, 1H-NMR and elemental analysis. The LN3SMe ligand was designed to incorporate a single sulfide donor and relies on the bis(imino)pyridine scaffold. This scaffold was selected for its ease of synthesis and its well-precedented ability to stabilize Fe(II) ions. Complexes 1 and 2 ware prepared via a metal-assisted template reaction from the unsymmetrical pyridyl ketone precursor 2-(O=CMe)-6-(2,6-(iPr2-C6H3N=CMe)-C5H3N. Reaction of 1 with O2 was shown to afford the S-oxygenated sulfoxide complex [Fe(LN3S(O)Me)(OTf)]2+(3), whereas compound 2, under the same reaction conditions, afforded the corresponding sulfone complex [Fe(LN3S(O2)Me)Cl]2+ (4).
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Affiliation(s)
- Leland R Widger
- Department of Chemistry, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218
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Schwake M, Schröder B, Saftig P. Lysosomal membrane proteins and their central role in physiology. Traffic 2013; 14:739-48. [PMID: 23387372 DOI: 10.1111/tra.12056] [Citation(s) in RCA: 165] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 02/01/2013] [Accepted: 02/06/2013] [Indexed: 12/19/2022]
Abstract
The lysosomal membrane was thought for a long time to primarily act as a physical barrier separating the luminal acidic milieu from the cytoplasmic environment. Meanwhile, it has been realized that unique lysosomal membranes play essential roles in a number of cellular events ranging from phagocytosis, autophagy, cell death, virus infection to membrane repair. This review provides an overview about the most interesting emerging functions of lysosomal membrane proteins and how they contribute to health and disease. Their importance is exemplified by their role in acidification, transport of metabolites and ions across the membrane, intracellular transport of hydrolases and the regulation of membrane fusion events. Studies in patient cells, non-mammalian model organisms and knockout mice contributed to our understanding of how the different lysosomal membrane proteins affect cellular homeostasis, developmental processes as well as tissue functions. Because these proteins are central for the biogenesis of this compartment they are also considered as attractive targets to modulate the lysosomal machinery in cases where impaired lysosomal degradation leads to cellular pathologies. We are only beginning to understand the complex composition and function of these proteins which are tightly linked to processes occurring throughout the endocytic and biosynthetic pathways.
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Affiliation(s)
- Michael Schwake
- Institut für Biochemie, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, D-24098, Kiel, Germany
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129
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Upregulation of the Rab27a-dependent trafficking and secretory mechanisms improves lysosomal transport, alleviates endoplasmic reticulum stress, and reduces lysosome overload in cystinosis. Mol Cell Biol 2013; 33:2950-62. [PMID: 23716592 DOI: 10.1128/mcb.00417-13] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Cystinosis is a lysosomal storage disorder caused by the accumulation of the amino acid cystine due to genetic defects in the CTNS gene, which encodes cystinosin, the lysosomal cystine transporter. Although many cellular dysfunctions have been described in cystinosis, the mechanisms leading to these defects are not well understood. Here, we show that increased lysosomal overload induced by accumulated cystine leads to cellular abnormalities, including vesicular transport defects and increased endoplasmic reticulum (ER) stress, and that correction of lysosomal transport improves cellular function in cystinosis. We found that Rab27a was expressed in proximal tubular cells (PTCs) and partially colocalized with the lysosomal marker LAMP-1. The expression of Rab27a but not other small GTPases, including Rab3 and Rab7, was downregulated in kidneys from Ctns-/- mice and in human PTCs from cystinotic patients. Using total internal reflection fluorescence microscopy, we found that lysosomal transport is impaired in Ctns-/- cells. Ctns-/- cells showed significant ER expansion and a marked increase in the unfolded protein response-induced chaperones Grp78 and Grp94. Upregulation of the Rab27a-dependent vesicular trafficking mechanisms rescued the defective lysosomal transport phenotype and reduced ER stress in cystinotic cells. Importantly, reconstitution of lysosomal transport mediated by Rab27a led to decreased lysosomal overload, manifested as reduced cystine cellular content. Our data suggest that upregulation of the Rab27a-dependent lysosomal trafficking and secretory pathways contributes to the correction of some of the cellular defects induced by lysosomal overload in cystinosis, including ER stress.
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130
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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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131
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Harrison F, Yeagy BA, Rocca CJ, Kohn DB, Salomon DR, Cherqui S. Hematopoietic stem cell gene therapy for the multisystemic lysosomal storage disorder cystinosis. Mol Ther 2012; 21:433-44. [PMID: 23089735 DOI: 10.1038/mt.2012.214] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Cystinosis is an autosomal recessive metabolic disease that belongs to the family of lysosomal storage disorders (LSDs). The defective gene is CTNS encoding the lysosomal cystine transporter, cystinosin. Cystine accumulates in all tissues and leads to organ damage including end-stage renal disease. Using the Ctns(-/-) murine model for cystinosis, we tested the use of hematopoietic stem and progenitor cells (HSPC) genetically modified to express a functional CTNS transgene using a self-inactivating-lentiviral vector (SIN-LV). We showed that transduced cells were capable of decreasing cystine content in all tissues and improved kidney function. Transduced HSPC retained their differentiative capabilities, populating all tissue compartments examined and allowing long-term expression of the transgene. Direct correlation between the levels of lentiviral DNA present in the peripheral blood and the levels present in tissues were demonstrated, which could be useful to follow future patients. Using a new model of cystinosis, the DsRed Ctns(-/-) mice, and a LV driving the expression of the fusion protein cystinosin-enhanced green fluorescent protein (eGFP), we showed that cystinosin was transferred from CTNS-expressing cells to Ctns-deficient adjacent cells in vitro and in vivo. This transfer led to cystine decreases in Ctns-deficient cells in vitro. These data suggest that the mechanism of cross-correction is possible in cystinosis.
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Affiliation(s)
- Frank Harrison
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California, USA
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132
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Iglesias DM, El-Kares R, Taranta A, Bellomo F, Emma F, Besouw M, Levtchenko E, Toelen J, van den Heuvel L, Chu L, Zhao J, Young YK, Eliopoulos N, Goodyer P. Stem cell microvesicles transfer cystinosin to human cystinotic cells and reduce cystine accumulation in vitro. PLoS One 2012; 7:e42840. [PMID: 22912749 PMCID: PMC3418268 DOI: 10.1371/journal.pone.0042840] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 07/11/2012] [Indexed: 11/25/2022] Open
Abstract
Cystinosis is a rare disease caused by homozygous mutations of the CTNS gene, encoding a cystine efflux channel in the lysosomal membrane. In Ctns knockout mice, the pathologic intralysosomal accumulation of cystine that drives progressive organ damage can be reversed by infusion of wildtype bone marrow-derived stem cells, but the mechanism involved is unclear since the exogeneous stem cells are rarely integrated into renal tubules. Here we show that human mesenchymal stem cells, from amniotic fluid or bone marrow, reduce pathologic cystine accumulation in co-cultured CTNS mutant fibroblasts or proximal tubular cells from cystinosis patients. This paracrine effect is associated with release into the culture medium of stem cell microvesicles (100–400 nm diameter) containing wildtype cystinosin protein and CTNS mRNA. Isolated stem cell microvesicles reduce target cell cystine accumulation in a dose-dependent, Annexin V-sensitive manner. Microvesicles from stem cells expressing CTNSRed transfer tagged CTNS protein to the lysosome/endosome compartment of cystinotic fibroblasts. Our observations suggest that exogenous stem cells may reprogram the biology of mutant tissues by direct microvesicle transfer of membrane-associated wildtype molecules.
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Affiliation(s)
- Diana M. Iglesias
- Department of Pediatrics, Montreal Children's Hospital Research Institute, McGill University, Montréal, Québec, Canada
| | - Reyhan El-Kares
- Department of Pediatrics, Montreal Children's Hospital Research Institute, McGill University, Montréal, Québec, Canada
| | - Anna Taranta
- U.O.C. di Nefrologia e Dialisi, Ospedale Pediatrico Bambino Gesù, Rome, Italy
| | - Francesco Bellomo
- U.O.C. di Nefrologia e Dialisi, Ospedale Pediatrico Bambino Gesù, Rome, Italy
| | - Francesco Emma
- U.O.C. di Nefrologia e Dialisi, Ospedale Pediatrico Bambino Gesù, Rome, Italy
| | - Martine Besouw
- Department of Pediatric Nephrology University Hospitals Leuven, Laboratory of Pediatrics, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Elena Levtchenko
- Department of Pediatric Nephrology University Hospitals Leuven, Laboratory of Pediatrics, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Jaan Toelen
- Department of Pediatric Nephrology University Hospitals Leuven, Laboratory of Pediatrics, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Lambertus van den Heuvel
- Department of Pediatric Nephrology University Hospitals Leuven, Laboratory of Pediatrics, Katholieke Universiteit Leuven, Leuven, Belgium
| | - LeeLee Chu
- Department of Pediatrics, Montreal Children's Hospital Research Institute, McGill University, Montréal, Québec, Canada
| | - Jing Zhao
- Lady Davis Institute for Medical Research, Jewish General Hospital, Montréal, Québec, Canada
| | - Yoon Kow Young
- Lady Davis Institute for Medical Research, Jewish General Hospital, Montréal, Québec, Canada
| | - Nicoletta Eliopoulos
- Lady Davis Institute for Medical Research, Jewish General Hospital, Montréal, Québec, Canada
- Division of Surgical Research, Department of Surgery, McGill University, Montréal, Québec, Canada
- Department of Oncology, McGill University, Montréal, Québec, Canada
| | - Paul Goodyer
- Department of Pediatrics, Montreal Children's Hospital Research Institute, McGill University, Montréal, Québec, Canada
- * E-mail:
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133
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Liu B, Du H, Rutkowski R, Gartner A, Wang X. LAAT-1 is the lysosomal lysine/arginine transporter that maintains amino acid homeostasis. Science 2012; 337:351-4. [PMID: 22822152 PMCID: PMC3432903 DOI: 10.1126/science.1220281] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Defective catabolite export from lysosomes results in lysosomal storage diseases in humans. Mutations in the cystine transporter gene CTNS cause cystinosis, but other lysosomal amino acid transporters are poorly characterized at the molecular level. Here, we identified the Caenorhabditis elegans lysosomal lysine/arginine transporter LAAT-1. Loss of laat-1 caused accumulation of lysine and arginine in enlarged, degradation-defective lysosomes. In mutants of ctns-1 (C. elegans homolog of CTNS), LAAT-1 was required to reduce lysosomal cystine levels and suppress lysosome enlargement by cysteamine, a drug that alleviates cystinosis by converting cystine to a lysine analog. LAAT-1 also maintained availability of cytosolic lysine/arginine during embryogenesis. Thus, LAAT-1 is the lysosomal lysine/arginine transporter, which suggests a molecular explanation for how cysteamine alleviates a lysosomal storage disease.
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Affiliation(s)
- Bin Liu
- Graduate Program in Chinese Academy of Medical Sciences and Peking Union Medical College, China
- National Institute of Biological Sciences, No. 7 Science Park Road, Zhongguancun Life Science Park, Beijing, 102206, China
| | - Hongwei Du
- State Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
- Graduate School, Chinese Academy of Sciences, Beijing, 100039, China
- National Institute of Biological Sciences, No. 7 Science Park Road, Zhongguancun Life Science Park, Beijing, 102206, China
| | - Rachael Rutkowski
- Wellcome Trust Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee, DD1 5EH, United Kingdom
| | - Anton Gartner
- Wellcome Trust Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dundee, DD1 5EH, United Kingdom
| | - Xiaochen Wang
- National Institute of Biological Sciences, No. 7 Science Park Road, Zhongguancun Life Science Park, Beijing, 102206, China
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134
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Jaenecke I, Boissel JP, Lemke M, Rupp J, Gasnier B, Closs EI. A chimera carrying the functional domain of the orphan protein SLC7A14 in the backbone of SLC7A2 mediates trans-stimulated arginine transport. J Biol Chem 2012; 287:30853-60. [PMID: 22787143 DOI: 10.1074/jbc.m112.350322] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In human skin fibroblasts, a lysosomal transport system specific for cationic amino acids has been described and named system c. We asked if SLC7A14 (solute carrier family 7 member A14), an orphan protein assigned to the SLC7 subfamily of cationic amino acid transporters (CATs) due to sequence homology, may represent system c. Fusion proteins between SLC7A14 and enhanced GFP localized to intracellular vesicles, co-staining with the lysosomal marker LysoTracker(®). To perform transport studies, we first tried to redirect SLC7A14 to the plasma membrane (by mutating putative lysosomal targeting motifs) but without success. We then created a chimera carrying the backbone of human (h) CAT-2 and the protein domain of SLC7A14 corresponding to the so-called "functional domain" of the hCAT proteins, a protein stretch of 81 amino acids that determines the apparent substrate affinity, sensitivity to trans-stimulation, and (as revealed in this study) pH dependence. The chimera mediated arginine transport and exhibited characteristics similar but not identical to hCAT-2A (the low affinity hCAT-2 isoform). Western blot and microscopic analyses confirmed localization of the chimera in the plasma membrane of Xenopus laevis oocytes. Noticeably, arginine transport by the hCAT-2/SLC7A14 chimera was pH-dependent, trans-stimulated, and inhibited by α-trimethyl-L-lysine, properties assigned to lysosomal transport system c in human skin fibroblasts. Expression analysis showed strong expression of SLC7A14 mRNA in these cells. Taken together, these data strongly suggest that SLC7A14 is a lysosomal transporter for cationic amino acids.
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Affiliation(s)
- Isabel Jaenecke
- Department of Pharmacology, University Medical Center of the Johannes Gutenberg University, 55131 Mainz, Germany
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135
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Chiaverini C, Sillard L, Flori E, Ito S, Briganti S, Wakamatsu K, Fontas E, Berard E, Cailliez M, Cochat P, Foulard M, Guest G, Niaudet P, Picardo M, Bernard FX, Antignac C, Ortonne JP, Ballotti R. Cystinosin is a melanosomal protein that regulates melanin synthesis. FASEB J 2012; 26:3779-89. [PMID: 22649030 DOI: 10.1096/fj.11-201376] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Cystinosis is a rare autosomal recessive disease characterized by cystine crystal accumulation leading to multiorgan dysfunctions and caused by mutation in CTNS. CTNS encodes cystinosin, a cystine/H(+) symporter that exports cystine out of the lysosomes. Patients with cystinosis frequently exhibit blond hair and fair complexion, suggesting an alteration in melanogenesis. However, the pigmentation singularities of these patients have not been studied, and the role of cystinosin in melanogenesis has remained unknown. In our study, a clinical evaluation of 27 patients with cystinosis showed that 44% had a cutaneous pigmentation dilution compared to their relatives. Analysis of the hair melanin content in these patients by HPLC demonstrated a 50% decrease in eumelanin (4360 vs. 9360 ng/mg), and a 2-fold increase in pheomelanin (53 vs. 20 ng/mg), the yellow/red pigments. Cystinosin-deficient mice also showed a 4-fold increase in hair pheomelanin content. In vitro studies showed that cystinosin was located at melanosomes. CTNS silencing led to a 75% reduction of melanin synthesis that was caused by a degradation of tyrosinase by lysosomal proteases. Our results objectify the pigmentation defect in patients with cystinosis. We also identify the role of CTNS in melanogenesis and add a new gene to the list of the genes involved in the control of skin and hair pigmentation.
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Affiliation(s)
- Christine Chiaverini
- Institut National de Santé et de Recherche Médical (INSERM), U1065, Centre Méditerranéen de Médecine Moléculaire, Equipe 1, Biology and Pathology of Melanocytes, Nice, France
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136
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Abstract
Cystinosis as a clinical entity is a progressive dysfunction of multiple organs caused by the accumulation of cystine in the tissues, leading, for example, to end-stage renal failure, diabetes, hypothyroidism, myopathy, and central nervous system deterioration. Brodin-Sartorius and colleagues present a long-term study on the impact of cysteamine therapy on these complications. The data show that cysteamine improves the outcome and complications of cystinosis but does not prevent them.
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137
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Taranta A, Petrini S, Citti A, Boldrini R, Corallini S, Bellomo F, Levtchenko E, Emma F. Distribution of cystinosin-LKG in human tissues. Histochem Cell Biol 2012; 138:351-63. [PMID: 22544350 DOI: 10.1007/s00418-012-0958-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/13/2012] [Indexed: 12/31/2022]
Abstract
Nephropathic cystinosis is multisystemic progressive disorder caused by mutations of CTNS gene that encodes for the lysosomal cystine co-transporter cystinosin, and for a less abundant isoform termed cystinosin-LKG, which is expressed in not only lysosomes but also other cell compartments. To overcome the absence of high-quality antibodies against cystinosin, we have obtained a rabbit antiserum against cystinosin-LKG and have analyzed in human tissues the expression of the two known cystinosin isoforms by RT-PCR, and the expression of cystinosin-LKG by immunohistochemistry. In most tissues, CTNS-LKG represents 5-20 % of CTNS transcripts, with the exception of the testis that expresses both isoforms in equal proportions. Cystinosin-LKG was found to be highly expressed in renal tubular cells, pancreatic islets of Langerhans, Leydig cells of the testis, mucoserous glands of the bronchial wall, melanocytes and keratinocytes. These results are parallel with many features of cystinosis, such as early onset Fanconi syndrome, male infertility, diabetes mellitus and hypopigmentation. Intermediate expression levels were of the LKG isoform observed in the gastro-intestinal tract and thyroid glands; low levels of expression were observed in the brain, skeletal and cardiac muscles.
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Affiliation(s)
- Anna Taranta
- Division of Nephrology, Department of Nephrology and Urology, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy.
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138
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Hippert C, Ibanes S, Serratrice N, Court F, Malecaze F, Kremer EJ, Kalatzis V. Corneal transduction by intra-stromal injection of AAV vectors in vivo in the mouse and ex vivo in human explants. PLoS One 2012; 7:e35318. [PMID: 22523585 PMCID: PMC3327666 DOI: 10.1371/journal.pone.0035318] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Accepted: 03/14/2012] [Indexed: 12/13/2022] Open
Abstract
The cornea is a transparent, avascular tissue that acts as the major refractive surface of the eye. Corneal transparency, assured by the inner stroma, is vital for this role. Disruption in stromal transparency can occur in some inherited or acquired diseases. As a consequence, light entering the eye is blocked or distorted, leading to decreased visual acuity. Possible treatment for restoring transparency could be via viral-based gene therapy. The stroma is particularly amenable to this strategy due to its immunoprivileged nature and low turnover rate. We assayed the potential of AAV vectors to transduce keratocytes following intra-stromal injection in vivo in the mouse cornea and ex vivo in human explants. In murine and human corneas, we transduced the entire stroma using a single injection, preferentially targeted keratocytes and achieved long-term gene transfer (up to 17 months in vivo in mice). Of the serotypes tested, AAV2/8 was the most promising for gene transfer in both mouse and man. Furthermore, transgene expression could be transiently increased following aggression to the cornea.
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Affiliation(s)
- Claire Hippert
- Institut de Génétique Moléculaire de Montpellier, CNRS, Montpellier, France
- Universités Montpellier I & II, Montpellier, France
| | - Sandy Ibanes
- Institut de Génétique Moléculaire de Montpellier, CNRS, Montpellier, France
- Universités Montpellier I & II, Montpellier, France
| | - Nicolas Serratrice
- Institut de Génétique Moléculaire de Montpellier, CNRS, Montpellier, France
- Universités Montpellier I & II, Montpellier, France
| | - Franck Court
- Institut de Génétique Moléculaire de Montpellier, CNRS, Montpellier, France
- Universités Montpellier I & II, Montpellier, France
| | - François Malecaze
- Inserm U563, Toulouse, France
- Département d'Ophtalmologie, Hôpital Purpan, Toulouse, France
| | - Eric J. Kremer
- Institut de Génétique Moléculaire de Montpellier, CNRS, Montpellier, France
- Universités Montpellier I & II, Montpellier, France
| | - Vasiliki Kalatzis
- Institut de Génétique Moléculaire de Montpellier, CNRS, Montpellier, France
- Universités Montpellier I & II, Montpellier, France
- * E-mail:
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139
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Ito S, Wakamatsu K. Diversity of human hair pigmentation as studied by chemical analysis of eumelanin and pheomelanin. J Eur Acad Dermatol Venereol 2012; 25:1369-80. [PMID: 22077870 DOI: 10.1111/j.1468-3083.2011.04278.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Hair colour is one of the most conspicuous phenotypes in humans, ranging from black, brown, blond to red. This diversity arises mostly from the quantity and ratio of the black-dark brown eumelanin and the reddish-brown pheomelanin. To study the chemical basis underlying the diversity of hair colour, we have developed several chemical methods to quantify those two pigments. Alkaline H(2) O(2) oxidation affords pyrrole-2,3,5-tricarboxylic acid (PTCA) as a eumelanin marker and thiazole-2,4,5-tricarboxylic acid (TTCA) as a pheomelanin marker. Pheomelanin can also be analysed as 4-amino-3-hydroxyphenylalanine (4-AHP) after hydroiodic acid hydrolysis. Using those methods, we evaluated the contents of eumelanin and pheomelanin (the 'chemical' phenotype) in human hairs of black, dark brown, brown, light brown, blond and red colour (the 'visual' phenotype). Eumelanin contents decrease in that order, with a trace but constant level of pheomelanin, except for red hair which contains about equal levels of pheomelanin and eumelanin. Thus, the chemical phenotype correlates well with the visual phenotype. The genotype of melanocortin-1 receptor (MC1R), a gene regulating the red hair phenotype, is predictive of hair melanin expressed as the log value of eumelanin to pheomelanin ratio, with a dosage effect evident. Hair melanin contents were also analysed in patients with various hypopigmentary disorders including Hermansky-Pudlak syndrome, Menkes disease, proopiomelanocortin deficiency, cystinosis, malnutrition and trace metal deficiency. The chemical phenotype helped evaluate the precise effects of each disease on pigmentation. In studies of human hair, the chemical phenotype will find more and more application as an objective measure of pigmentation.
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Affiliation(s)
- S Ito
- Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi, Japan.
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140
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Saudek V. Cystinosin, MPDU1, SWEETs and KDELR belong to a well-defined protein family with putative function of cargo receptors involved in vesicle trafficking. PLoS One 2012; 7:e30876. [PMID: 22363504 PMCID: PMC3281891 DOI: 10.1371/journal.pone.0030876] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Accepted: 12/22/2011] [Indexed: 12/26/2022] Open
Abstract
Classification of proteins into families based on remote homology often helps prediction of their biological function. Here we describe prediction of protein cargo receptors involved in vesicle formation and protein trafficking. Hidden Markov model profile-to-profile searches in protein databases using endoplasmic reticulum lumen protein retaining receptors (KDEL, Erd2) as query reveal a large and diverse family of proteins with seven transmembrane helices and common topology and, most likely, similar function. Their coding genes exist in all eukaryota and in several prokaryota. Some are responsible for metabolic diseases (cystinosis, congenital disorder of glycosylation), others are candidate genes for genetic disorders (cleft lip and palate, certain forms of cancer) or solute uptake and efflux (SWEETs) and many have not yet been assigned a function. Comparison with the properties of KDEL receptors suggests that the family members could be involved in protein trafficking and serve as cargo receptors. This prediction sheds new light on a range of biologically, medically and agronomically important proteins and could open the way to discovering the function of many genes not yet annotated. Experimental testing is suggested.
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Affiliation(s)
- Vladimir Saudek
- University of Cambridge Metabolic Research Labs, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, United Kingdom.
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141
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Molecular pathogenesis of sialic acid storage diseases: insight gained from four missense mutations and a putative polymorphism of human sialin. Biol Cell 2012; 100:551-9. [DOI: 10.1042/bc20070166] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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142
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Mechanism of proton/substrate coupling in the heptahelical lysosomal transporter cystinosin. Proc Natl Acad Sci U S A 2012; 109:E210-7. [PMID: 22232659 DOI: 10.1073/pnas.1115581109] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Secondary active transporters use electrochemical gradients provided by primary ion pumps to translocate metabolites or drugs "uphill" across membranes. Here we report the ion-coupling mechanism of cystinosin, an unusual eukaryotic, proton-driven transporter distantly related to the proton pump bacteriorhodopsin. In humans, cystinosin exports the proteolysis-derived dimeric amino acid cystine from lysosomes and is impaired in cystinosis. Using voltage-dependence analysis of steady-state and transient currents elicited by cystine and neutralization-scanning mutagenesis of conserved protonatable residues, we show that cystine binding is coupled to protonation of a clinically relevant aspartate buried in the membrane. Deuterium isotope substitution experiments are consistent with an access of this aspartate from the lysosomal lumen through a deep proton channel. This aspartate lies in one of the two PQ-loop motifs shared by cystinosin with a set of eukaryotic membrane proteins of unknown function and is conserved in about half of them, thus suggesting that other PQ-loop proteins may translocate protons.
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Simpson JL, Nien CJ, Flynn KJ, Jester JV. Evaluation of topical cysteamine therapy in the CTNS(-/-) knockout mouse using in vivo confocal microscopy. Mol Vis 2011; 17:2649-54. [PMID: 22065917 PMCID: PMC3209421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Accepted: 09/29/2011] [Indexed: 11/20/2022] Open
Abstract
PURPOSE The purpose of this study was to assess the ability of quantitative in vivo confocal microscopy (CM) to detect changes in cystine crystal volume in the cystinosisn (Ctns(-/-))mouse cornea following topical cysteamine therapy. METHODS Fifteen Ctns(-/-) mice were sequentially followed using in vivo CM from 3 to 10 months of age. In a second experiment, five mice receiving topical cysteamine eyedrops (0.55%) for 4 weeks were compared to five untreated mice. The volume of corneal cystine crystals was determined by thresholding and counting high intensity pixels in the in vivo CM scans and dividing by the stromal volume to calculate a crystal volume index (CVI). RESULTS Corneal crystals progressively increased in density with age, reaching a peak density at 6-8 months and showing a 70 fold increase in CVI. Eyes treated with cysteamine drops showed significantly less crystal accumulation compared to control eyes (p<0.001) with only a 15% increase in treated eyes (p=ns) compared to 173% increase (p<0.04) for untreated eyes. CONCLUSIONS Measurement of CVI shows that there is a progressive increase in cystine crystal volume up to 8 months of age and that cysteamine eyedrops significantly inhibits progression in the Ctns(-/-) mouse. These findings are similar to those seen clinically in patients with cystinosis, and suggest that measurement of CVI in the Ctns(-/-) mouse may be used as a model to develop novel therapeutic strategies for treating corneal cystinosis.
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Savalas LRT, Gasnier B, Damme M, Lübke T, Wrocklage C, Debacker C, Jézégou A, Reinheckel T, Hasilik A, Saftig P, Schröder B. Disrupted in renal carcinoma 2 (DIRC2), a novel transporter of the lysosomal membrane, is proteolytically processed by cathepsin L. Biochem J 2011; 439:113-28. [PMID: 21692750 DOI: 10.1042/bj20110166] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
DIRC2 (Disrupted in renal carcinoma 2) has been initially identified as a breakpoint-spanning gene in a chromosomal translocation putatively associated with the development of renal cancer. The DIRC2 protein belongs to the MFS (major facilitator superfamily) and has been previously detected by organellar proteomics as a tentative constituent of lysosomal membranes. In the present study, lysosomal residence of overexpressed as well as endogenous DIRC2 was shown by several approaches. DIRC2 is proteolytically processed into a N-glycosylated N-terminal and a non-glycosylated C-terminal fragment respectively. Proteolytic cleavage occurs in lysosomal compartments and critically depends on the activity of cathepsin L which was found to be indispensable for this process in murine embryonic fibroblasts. The cleavage site within DIRC2 was mapped between amino acid residues 214 and 261 using internal epitope tags, and is presumably located within the tentative fifth intralysosomal loop, assuming the typical MFS topology. Lysosomal targeting of DIRC2 was demonstrated to be mediated by a N-terminal dileucine motif. By disrupting this motif, DIRC2 can be redirected to the plasma membrane. Finally, in a whole-cell electrophysiological assay based on heterologous expression of the targeting mutant at the plasma membrane of Xenopus oocytes, the application of a complex metabolic mixture evokes an outward current associated with the surface expression of full-length DIRC2. Taken together, these data strongly support the idea that DIRC2 is an electrogenic lysosomal metabolite transporter which is subjected to and presumably modulated by limited proteolytic processing.
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Brodin-Sartorius A, Tête MJ, Niaudet P, Antignac C, Guest G, Ottolenghi C, Charbit M, Moyse D, Legendre C, Lesavre P, Cochat P, Servais A. Cysteamine therapy delays the progression of nephropathic cystinosis in late adolescents and adults. Kidney Int 2011; 81:179-89. [PMID: 21900880 DOI: 10.1038/ki.2011.277] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Nephropathic cystinosis is a multisystem autosomal recessive disease caused by cystine accumulation, which is usually treated by oral cysteamine. In order to determine long-term effects of this therapy, we enrolled 86 adult patients (mean age 26.7 years) diagnosed with nephropathic cystinosis, 75 of whom received cysteamine. Therapy was initiated at a mean age of 9.9 years with a mean duration of 17.4 years. By last follow-up, 78 patients had end-stage renal disease (mean age 11.1 years), 62 had hypothyroidism (mean age 13.4), 48 developed diabetes (mean age 17.1 years), and 32 had neuromuscular disorders (mean age 23.3 years). Initiating cysteamine therapy before 5 years of age significantly decreased the incidence and delayed the onset of end-stage renal disease, and significantly delayed the onset of hypothyroidism, diabetes, and neuromuscular disorders. The development of diabetes and hypothyroidism was still significantly delayed, however, in patients in whom therapy was initiated after 5 years of age, compared with untreated patients. The life expectancy was significantly improved in cysteamine-treated versus untreated patients. Thus, cysteamine decreases and delays the onset of complications and improves life expectancy in cystinosis. Hence, cysteamine therapy should be introduced as early as possible during childhood and maintained lifelong.
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Simpson J, Nien CJ, Flynn K, Jester B, Cherqui S, Jester J. Quantitative in vivo and ex vivo confocal microscopy analysis of corneal cystine crystals in the Ctns knockout mouse. Mol Vis 2011; 17:2212-20. [PMID: 21897743 PMCID: PMC3164685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Accepted: 08/11/2011] [Indexed: 11/09/2022] Open
Abstract
PURPOSE The purpose of this study was to assess the ability of quantitative in vivo confocal microscopy to characterize the natural history and detect changes in crystal volume in corneas from a novel animal model of cystinosis, the cystinosin (Ctns(-/-)) mouse. METHODS Two Ctns(-/-) mice and one C57Bl/6 mouse were examined at each of the following time points: 2, 3, 5, 7, 10, 12, and 14 months of age. In vivo confocal microscopy scans were performed in 4 different regions of the cornea per eye. After, animals were sacrificed and cornea blocks evaluated for cell morphology using phalloidin and lymphocytic infiltration using CD45 antibodies by ex vivo confocal microscopy. Cystine crystal content in the cornea was measured by calculating the pixel intensity of the crystals divided by the stromal volume using Metamorph Image Processing Software. RESULTS Corneal crystals were identified in Ctns(-/-) eyes beginning at 3 months of age and increased in density until 7-12 months, at which time animals begin to succumb to the disease and corneas become scarred and neovascularized. Older Ctns(-/-) mice (7 months and older) showed the presence of cell infiltrates that stained positively for CD45 associated with progressive keratocyte disruption. Finally, at 12 months of age, decreased cell density and endothelial distortion were detected. CONCLUSIONS Confocal microscopy identified corneal crystals starting at 3 month old Ctns(-/-) eyes. Cystine crystals induce inflammatory and immune response with aging associated with loss of keratocyte and endothelial cells. These findings suggest that the Ctns(-/-) mouse can be used as a model for developing and evaluating potential alternative therapies for corneal cystinosis.
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Affiliation(s)
- Jennifer Simpson
- Gavin Herbert Eye Institute, University of California, Irvine CA
| | - Chyong Jy Nien
- Gavin Herbert Eye Institute, University of California, Irvine CA
| | - Kevin Flynn
- Gavin Herbert Eye Institute, University of California, Irvine CA
| | - Brian Jester
- Gavin Herbert Eye Institute, University of California, Irvine CA
| | | | - James Jester
- Gavin Herbert Eye Institute, University of California, Irvine CA
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Min-Oo G, Gros P. Genetic analysis in mice identifies cysteamine as a novel partner for artemisinin in the treatment of malaria. Mamm Genome 2011; 22:486-94. [DOI: 10.1007/s00335-011-9316-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Accepted: 01/21/2011] [Indexed: 11/29/2022]
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Abstract
Amino acids are essential building blocks of all mammalian cells. In addition to their role in protein synthesis, amino acids play an important role as energy fuels, precursors for a variety of metabolites and as signalling molecules. Disorders associated with the malfunction of amino acid transporters reflect the variety of roles that they fulfil in human physiology. Mutations of brain amino acid transporters affect neuronal excitability. Mutations of renal and intestinal amino acid transporters affect whole-body homoeostasis, resulting in malabsorption and renal problems. Amino acid transporters that are integral parts of metabolic pathways reduce the function of these pathways. Finally, amino acid uptake is essential for cell growth, thereby explaining their role in tumour progression. The present review summarizes the involvement of amino acid transporters in these roles as illustrated by diseases resulting from transporter malfunction.
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Ito S, Wakamatsu K. Human hair melanins: what we have learned and have not learned from mouse coat color pigmentation. Pigment Cell Melanoma Res 2011; 24:63-74. [PMID: 20726950 DOI: 10.1111/j.1755-148x.2010.00755.x] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Hair pigmentation is one of the most conspicuous phenotypes in humans. Melanocytes produce two distinct types of melanin pigment: brown to black, indolic eumelanin and yellow to reddish brown, sulfur-containing pheomelanin. Biochemically, the precursor tyrosine and the key enzyme tyrosinase and the tyrosinase-related proteins are involved in eumelanogenesis, while only the additional presence of cysteine is necessary for pheomelanogenesis. Other important proteins involved in melanogenesis include P protein, MATP protein, α-MSH, agouti signaling protein (ASIP), MC1R (the receptor for MSH and ASIP), and SLC7A11, a cystine transporter. Many studies have examined the effects of loss-of-function mutations of those proteins on mouse coat color pigmentation. In contrast, much less is known regarding the effects of mutations of the corresponding proteins on human hair pigmentation except for MC1R polymorphisms that lead to pheomelanogenesis. This perspective will discuss what we have/have not learned from mouse coat color pigmentation, with special emphasis on the significant roles of pH and the level of cysteine in melanosomes in controlling melanogenesis. Based on these data, a hypothesis is proposed to explain the diversity of human hair pigmentation.
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Affiliation(s)
- Shosuke Ito
- Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi, Japan.
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