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Sachs W, Sachs M, Krüger E, Zielinski S, Kretz O, Huber TB, Baranowsky A, Westermann LM, Voltolini Velho R, Ludwig NF, Yorgan TA, Di Lorenzo G, Kollmann K, Braulke T, Schwartz IV, Schinke T, Danyukova T, Pohl S, Meyer-Schwesinger C. Distinct Modes of Balancing Glomerular Cell Proteostasis in Mucolipidosis Type II and III Prevent Proteinuria. J Am Soc Nephrol 2020; 31:1796-1814. [PMID: 32641396 DOI: 10.1681/asn.2019090960] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 04/14/2020] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND The mechanisms balancing proteostasis in glomerular cells are unknown. Mucolipidosis (ML) II and III are rare lysosomal storage disorders associated with mutations of the Golgi-resident GlcNAc-1-phosphotransferase, which generates mannose 6-phosphate residues on lysosomal enzymes. Without this modification, lysosomal enzymes are missorted to the extracellular space, which results in lysosomal dysfunction of many cell types. Patients with MLII present with severe skeletal abnormalities, multisystemic symptoms, and early death; the clinical course in MLIII is less progressive. Despite dysfunction of a major degradative pathway, renal and glomerular involvement is rarely reported, suggesting organ-specific compensatory mechanisms. METHODS MLII mice were generated and compared with an established MLIII model to investigate the balance of protein synthesis and degradation, which reflects glomerular integrity. Proteinuria was assessed in patients. High-resolution confocal microscopy and functional assays identified proteins to deduce compensatory modes of balancing proteostasis. RESULTS Patients with MLII but not MLIII exhibited microalbuminuria. MLII mice showed lysosomal enzyme missorting and several skeletal alterations, indicating that they are a useful model. In glomeruli, both MLII and MLIII mice exhibited reduced levels of lysosomal enzymes and enlarged lysosomes with abnormal storage material. Nevertheless, neither model had detectable morphologic or functional glomerular alterations. The models rebalance proteostasis in two ways: MLII mice downregulate protein translation and increase the integrated stress response, whereas MLIII mice upregulate the proteasome system in their glomeruli. Both MLII and MLIII downregulate the protein complex mTORC1 (mammalian target of rapamycin complex 1) signaling, which decreases protein synthesis. CONCLUSIONS Severe lysosomal dysfunction leads to microalbuminuria in some patients with mucolipidosis. Mouse models indicate distinct compensatory pathways that balance proteostasis in MLII and MLIII.
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Affiliation(s)
- Wiebke Sachs
- Institute of Cellular and Integrative Physiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Marlies Sachs
- Institute of Cellular and Integrative Physiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Elke Krüger
- Institute of Medical Biochemistry and Molecular Biology, University Medicine Greifswald, Greifswald, Germany
| | - Stephanie Zielinski
- Institute of Cellular and Integrative Physiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Oliver Kretz
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Tobias B Huber
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Anke Baranowsky
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Lena Marie Westermann
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Renata Voltolini Velho
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Nataniel Floriano Ludwig
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.,Postgraduate Program in Genetics and Molecular Biology, Department of Genetics, Federal University of Rio Grande do Sul, Porto Alegre, Brazil
| | - Timur Alexander Yorgan
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Giorgia Di Lorenzo
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Katrin Kollmann
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Thomas Braulke
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Ida Vanessa Schwartz
- Postgraduate Program in Genetics and Molecular Biology, Department of Genetics, Federal University of Rio Grande do Sul, Porto Alegre, Brazil
| | - Thorsten Schinke
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Tatyana Danyukova
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Sandra Pohl
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Catherine Meyer-Schwesinger
- Institute of Cellular and Integrative Physiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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Tüysüz B, Ercan-Sencicek AG, Canpolat N, Koparır A, Yılmaz S, Kılıçaslan I, Gülez B, Bilguvar K, Günel M. Renal involvement in patients with mucolipidosis IIIalpha/beta: Causal relation or co-occurrence? Am J Med Genet A 2016; 170A:1187-95. [PMID: 26749367 DOI: 10.1002/ajmg.a.37543] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 12/21/2015] [Indexed: 11/07/2022]
Abstract
Mucolipidosis IIIalpha/beta (MLIIIalpha/beta) is a rare lysosomal storage disorder characterized by childhood onset of flexion contractures of fingers, joint stiffness in the shoulders, hips, and knees, and mild short stature. Recessive mutations in the GNPTAB gene have been associated with MLIIIalpha/beta. We present five children aged 9-16 years from a large kindred family whose serum activities of several lysosomal enzymes were significantly elevated. Whole exome sequencing followed by confirmation by Sanger sequencing identified a novel homozygous missense mutation (c.22 A > G; p.R8G) in the GNPTAB gene in all affected subjects. The five patients initially presented with flexion contractures of fingers followed by stiffnes of large joints. Only two affected boys also had a nephrotic-range proteinuria. Renal biopsy showed focal segmental glomerulosclerosis and foamy appearance of glomerular visceral epithelial cells which were compatible with storage disease. No other known causes of proteinuria could be detected by both laboratory and biopsy findings. There was no known family history of hereditary kidney disease, and healthy siblings and parents had normal renal function and urinalysis. These findings suggest that the renal involvement probably due to MLIIIalpha/beta, although it can still be present by coincidence in the two affected patients.
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Affiliation(s)
- Beyhan Tüysüz
- Department of Pediatric Genetics, Cerrahpasa Medical School, Istanbul University, Istanbul, Turkey
| | | | - Nur Canpolat
- Department of Pediatric Nephrology, Cerrahpasa Medical School, Istanbul University, Istanbul, Turkey
| | - Asuman Koparır
- Department of Pediatric Genetics, Cerrahpasa Medical School, Istanbul University, Istanbul, Turkey
| | - Saliha Yılmaz
- Department of Neurosurgery, Program on Neurogenetics, Yale School of Medicine, New Haven, Connecticut
| | - Işın Kılıçaslan
- Department of Pathology, Istanbul Medical School, Istanbul University, Istanbul, Turkey
| | - Burcu Gülez
- Department of Neurosurgery, Program on Neurogenetics, Yale School of Medicine, New Haven, Connecticut
| | - Kaya Bilguvar
- Department of Neurosurgery, Program on Neurogenetics, Yale School of Medicine, New Haven, Connecticut
| | - Murat Günel
- Department of Neurosurgery, Program on Neurogenetics, Yale School of Medicine, New Haven, Connecticut
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Cystinosis: practical tools for diagnosis and treatment. Pediatr Nephrol 2011; 26:205-15. [PMID: 20734088 PMCID: PMC3016220 DOI: 10.1007/s00467-010-1627-6] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2010] [Revised: 07/05/2010] [Accepted: 07/07/2010] [Indexed: 02/07/2023]
Abstract
Cystinosis is the major cause of inherited Fanconi syndrome, and should be suspected in young children with failure to thrive and signs of renal proximal tubular damage. The diagnosis can be missed in infants, because not all signs of renal Fanconi syndrome are present during the first months of life. In older patients cystinosis can mimic idiopathic nephrotic syndrome due to focal and segmental glomerulosclerosis. Measuring elevated white blood cell cystine content is the corner stone for the diagnosis. The diagnosis is confirmed by molecular analysis of the cystinosin gene. Corneal cystine crystals are invariably present in all patients with cystinosis after the age of 1 year. Treatment with the cystine depleting drug cysteamine should be initiated as soon as possible and continued lifelong to prolong renal function survival and protect extra-renal organs. This educational feature provides practical tools for the diagnosis and treatment of cystinosis.
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Wilmer MJ, Emma F, Levtchenko EN. The pathogenesis of cystinosis: mechanisms beyond cystine accumulation. Am J Physiol Renal Physiol 2010; 299:F905-16. [PMID: 20826575 DOI: 10.1152/ajprenal.00318.2010] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Renal proximal tubules are highly sensitive to ischemic and toxic insults and are affected in diverse genetic disorders, of which nephropathic cystinosis is the most common. The disease is caused by mutations in the CTNS gene, encoding the lysosomal cystine transporter cystinosin, and is characterized by accumulation of cystine in the lysosomes throughout the body. In the majority of the patients, this leads to generalized proximal tubular dysfunction (also called DeToni-Debré-Fanconi syndrome) in the first year and progressive renal failure during the first decade. Extrarenal organs are affected by cystinosis as well, with clinical symptoms manifesting mostly after 10 yr of age. The cystine-depleting agent cysteamine significantly improves life expectancy of patients with cystinosis, but offers no cure, pointing to the complexity of the disease mechanism. In this review, current knowledge on the pathogenesis of cystinosis is described and placed in perspective of future research.
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Affiliation(s)
- Martijn J Wilmer
- Dept. of Pediatric Nephrology, Univ. Hospitals Leuven, Herestraat 49, 3000 Leuven, Belgium
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