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Vyas M, Deschenes NM, Osmon KJL, Chen Z, Ahmad I, Kot S, Thompson P, Richmond C, Gray SJ, Walia JS. Efficacy of Adeno-Associated Virus Serotype 9-Mediated Gene Therapy for AB-Variant GM2 Gangliosidosis. Int J Mol Sci 2023; 24:14611. [PMID: 37834060 PMCID: PMC10572999 DOI: 10.3390/ijms241914611] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Revised: 09/06/2023] [Accepted: 09/16/2023] [Indexed: 10/15/2023] Open
Abstract
GM2 gangliosidoses are a group of neurodegenerative lysosomal storage disorders that are characterized by the accumulation of GM2 gangliosides (GM2), leading to rapid neurological decline and death. The hydrolysis of GM2 requires the specific synthesis, processing, and combination of products of three genes-HEXA, HEXB, and GM2A-within the cell's lysosomes. Mutations in these genes result in Tay-Sachs disease, Sandhoff disease, or AB-variant GM2 gangliosidosis (ABGM2), respectively. ABGM2, the rarest of the three types, is characterized by a mutation in the GM2A gene, which encodes the GM2 activator (GM2A) protein. Being a monogenic disease, gene therapy is a plausible and likely effective method of treatment for ABGM2. This study aimed at assessing the effects of administering a one-time intravenous treatment of single-stranded Adeno-associated virus serotype 9 (ssAAV9)-GM2A viral vector at a dose of 1 × 1014 vector genomes (vg) per kilogram per mouse in an ABGM2 mouse model (Gm2a-/-). ssAAV9-GM2A was administered at 1-day (neonatal) or 6-weeks of age (adult-stage). The results demonstrated that, in comparison to Gm2a-/- mice that received a vehicle injection, the treated mice had reduced GM2 accumulation within the central nervous system and had long-term persistence of vector genomes in the brain and liver. This proof-of-concept study is a step forward towards the development of a clinically therapeutic approach for the treatment of patients with ABGM2.
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Affiliation(s)
- Meera Vyas
- Centre for Neuroscience Studies, Queen’s University, Kingston, ON K7L 3N6, Canada
| | - Natalie M. Deschenes
- Centre for Neuroscience Studies, Queen’s University, Kingston, ON K7L 3N6, Canada
| | - Karlaina J. L. Osmon
- Centre for Neuroscience Studies, Queen’s University, Kingston, ON K7L 3N6, Canada
| | - Zhilin Chen
- Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, ON K7L 3N6, Canada; (Z.C.)
| | - Imtiaz Ahmad
- Centre for Neuroscience Studies, Queen’s University, Kingston, ON K7L 3N6, Canada
| | - Shalini Kot
- Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, ON K7L 3N6, Canada; (Z.C.)
| | - Patrick Thompson
- Department of Pediatrics, Queen’s University, Kingston, ON K7L 2V7, Canada;
| | - Chris Richmond
- Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, ON K7L 3N6, Canada; (Z.C.)
| | - Steven J. Gray
- Department of Pediatrics, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jagdeep S. Walia
- Centre for Neuroscience Studies, Queen’s University, Kingston, ON K7L 3N6, Canada
- Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, ON K7L 3N6, Canada; (Z.C.)
- Department of Pediatrics, Queen’s University, Kingston, ON K7L 2V7, Canada;
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Deschenes NM, Cheng C, Ryckman AE, Quinville BM, Khanal P, Mitchell M, Chen Z, Sangrar W, Gray SJ, Walia JS. Biochemical Correction of GM2 Ganglioside Accumulation in AB-Variant GM2 Gangliosidosis. Int J Mol Sci 2023; 24:ijms24119217. [PMID: 37298170 DOI: 10.3390/ijms24119217] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 05/09/2023] [Accepted: 05/15/2023] [Indexed: 06/12/2023] Open
Abstract
GM2 gangliosidosis is a group of genetic disorders that result in the accumulation of GM2 ganglioside (GM2) in brain cells, leading to progressive central nervous system (CNS) atrophy and premature death in patients. AB-variant GM2 gangliosidosis (ABGM2) arises from loss-of-function mutations in the GM2 activator protein (GM2AP), which is essential for the breakdown of GM2 in a key catabolic pathway required for CNS lipid homeostasis. In this study, we show that intrathecal delivery of self-complementary adeno-associated virus serotype-9 (scAAV9) harbouring a functional human GM2A transgene (scAAV9.hGM2A) can prevent GM2 accumulation in in GM2AP-deficient mice (Gm2a-/- mice). Additionally, scAAV9.hGM2A efficiently distributes to all tested regions of the CNS within 14 weeks post-injection and remains detectable for the lifespan of these animals (up to 104 weeks). Remarkably, GM2AP expression from the transgene scales with increasing doses of scAAV9.hGM2A (0.5, 1.0 and 2.0 × 1011 vector genomes (vg) per mouse), and this correlates with dose-dependent correction of GM2 accumulation in the brain. No severe adverse events were observed, and comorbidities in treated mice were comparable to those in disease-free cohorts. Lastly, all doses yielded corrective outcomes. These data indicate that scAAV9.hGM2A treatment is relatively non-toxic and tolerable, and biochemically corrects GM2 accumulation in the CNS-the main cause of morbidity and mortality in patients with ABGM2. Importantly, these results constitute proof-of-principle for treating ABGM2 with scAAV9.hGM2A by means of a single intrathecal administration and establish a foundation for future preclinical research.
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Affiliation(s)
- Natalie M Deschenes
- Centre for Neuroscience Studies, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Camilyn Cheng
- Centre for Neuroscience Studies, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Alex E Ryckman
- Centre for Neuroscience Studies, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Brianna M Quinville
- Centre for Neuroscience Studies, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Prem Khanal
- Department of Pediatrics, Queen's University, Kingston, ON K7L 2V7, Canada
| | - Melissa Mitchell
- Department of Pediatrics, Queen's University, Kingston, ON K7L 2V7, Canada
| | - Zhilin Chen
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Waheed Sangrar
- Centre for Neuroscience Studies, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Steven J Gray
- Department of Pediatrics, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jagdeep S Walia
- Centre for Neuroscience Studies, Queen's University, Kingston, ON K7L 3N6, Canada
- Department of Pediatrics, Queen's University, Kingston, ON K7L 2V7, Canada
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
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3
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Picache JA, Zheng W, Chen CZ. Therapeutic Strategies For Tay-Sachs Disease. Front Pharmacol 2022; 13:906647. [PMID: 35865957 PMCID: PMC9294361 DOI: 10.3389/fphar.2022.906647] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 06/10/2022] [Indexed: 11/13/2022] Open
Abstract
Tay-Sachs disease (TSD) is an autosomal recessive disease that features progressive neurodegenerative presentations. It affects one in 100,000 live births. Currently, there is no approved therapy or cure. This review summarizes multiple drug development strategies for TSD, including enzyme replacement therapy, pharmaceutical chaperone therapy, substrate reduction therapy, gene therapy, and hematopoietic stem cell replacement therapy. In vitro and in vivo systems are described to assess the efficacy of the aforementioned therapeutic strategies. Furthermore, we discuss using MALDI mass spectrometry to perform a high throughput screen of compound libraries. This enables discovery of compounds that reduce GM2 and can lead to further development of a TSD therapy.
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Lysosomal functions and dysfunctions: Molecular and cellular mechanisms underlying Gaucher disease and its association with Parkinson disease. Adv Drug Deliv Rev 2022; 187:114402. [DOI: 10.1016/j.addr.2022.114402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 04/28/2022] [Accepted: 06/17/2022] [Indexed: 01/18/2023]
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Osmon KJ, Thompson P, Woodley E, Karumuthil-Melethil S, Heindel C, Keimel JG, Kaemmerer WF, Gray SJ, Walia JS. Treatment of GM2 Gangliosidosis in Adult Sandhoff Mice using an Intravenous Self-Complementary Hexosaminidase Vector. Curr Gene Ther 2021; 22:262-276. [PMID: 34530708 DOI: 10.2174/1566523221666210916153051] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 07/01/2021] [Accepted: 07/16/2021] [Indexed: 11/22/2022]
Abstract
BACKGROUND GM2 gangliosidosis is a neurodegenerative, lysosomal storage disease caused by the deficiency of β-hexosaminidase A enzyme (HexA), an α/β-subunit heterodimer. A novel variant of the human hexosaminidase α-subunit, coded by HEXM, has previously been shown to form a stable homodimer, HexM, that hydrolyzes GM2 gangliosides (GM2) in vivo. MATERIALS & METHODS The current study assessed the efficacy of intravenous (IV) delivery of a self-complementary adeno-associated virus serotype 9 (scAAV9) vector incorporating the HEXM transgene, scAAV9/HEXM, including the outcomes based on the dosages provided to the Sandhoff (SD) mice. Six-week-old SD mice were injected with either 2.5E+12 vector genomes (low dose, LD) or 1.0E+13 vg (high dose, HD). We hypothesized that when examining the dosage comparison for scAAV9/HEXM in adult SD mice, the HD group would have more beneficial outcomes than the LD cohort. Assessments included survival, behavioral outcomes, vector biodistribution, and enzyme activity within the central nervous system. RESULTS Toxicity was observed in the HD cohort, with 8 of 14 mice dying within one month of the injection. As compared to untreated SD mice, which have typical survival of 16 weeks, the LD cohort and the remaining HD mice had a significant survival benefit with an average/median survival of 40.6/34.5 and 55.9/56.7 weeks, respectively. Significant behavioral, biochemical and molecular benefits were also observed. The second aim of the study was to investigate the effects of IV mannitol infusions on the biodistribution of the LD scAAV9/HEXM vector and the survival of the SD mice. Increases in both the biodistribution of the vector as well as the survival benefit (average/median of 41.6/49.3 weeks) were observed. CONCLUSION These results demonstrate the potential benefit and critical limitations of the treatment of GM2 gangliosidosis using IV delivered AAV vectors.
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Affiliation(s)
- Karlaina Jl Osmon
- Centre for Neuroscience Studies, Queen's University, Kingston, Ontario. Canada
| | - Patrick Thompson
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario. Canada
| | - Evan Woodley
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario. Canada
| | | | - Cliff Heindel
- Gene Therapy Center, University of North Carolina, Chapel Hill, North Carolina. United States
| | - John G Keimel
- New Hope Research Foundation, North Oaks, Minnesota. United States
| | | | - Steven J Gray
- Gene Therapy Center, University of North Carolina, Chapel Hill, North Carolina. United States
| | - Jagdeep S Walia
- Centre for Neuroscience Studies, Queen's University, Kingston, Ontario. Canada
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In silico analysis of the effects of disease-associated mutations of β-hexosaminidase A in Tay‒Sachs disease. J Genet 2020. [DOI: 10.1007/s12041-020-01208-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Efficacy of a Bicistronic Vector for Correction of Sandhoff Disease in a Mouse Model. MOLECULAR THERAPY-METHODS & CLINICAL DEVELOPMENT 2018; 12:47-57. [PMID: 30534578 PMCID: PMC6279944 DOI: 10.1016/j.omtm.2018.10.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Accepted: 10/23/2018] [Indexed: 12/01/2022]
Abstract
GM2 gangliosidoses are a family of severe neurodegenerative disorders resulting from a deficiency in the β-hexosaminidase A enzyme. These disorders include Tay-Sachs disease and Sandhoff disease, caused by mutations in the HEXA gene and HEXB gene, respectively. The HEXA and HEXB genes are required to produce the α and β subunits of the β-hexosaminidase A enzyme, respectively. Using a Sandhoff disease mouse model, we tested for the first time the potential of a comparatively lower dose (2.04 × 1013 vg/kg) of systemically delivered single-stranded adeno-associated virus 9 expressing both human HEXB and human HEXA cDNA under the control of a single promoter with a P2A-linked bicistronic vector design to correct the neurological phenotype. A bicistronic design allows maximal overexpression and secretion of the Hex A enzyme. Neonatal mice were injected with either this ssAAV9-HexB-P2A-HexA vector or a vehicle solution via the superficial temporal vein. An increase in survival of 56% compared with vehicle-injected controls and biochemical analysis of the brain tissue and serum revealed an increase in enzyme activity and a decrease in brain GM2 ganglioside buildup. This is a proof-of-concept study showing the “correction efficacy” of a bicistronic AAV9 vector delivered intravenously for GM2 gangliosidoses. Further studies with higher doses are warranted.
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Hunter CD, Guo T, Daskhan G, Richards MR, Cairo CW. Synthetic Strategies for Modified Glycosphingolipids and Their Design as Probes. Chem Rev 2018; 118:8188-8241. [DOI: 10.1021/acs.chemrev.8b00070] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Carmanah D. Hunter
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Tianlin Guo
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Gour Daskhan
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Michele R. Richards
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Christopher W. Cairo
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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9
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Osmon KJL, Woodley E, Thompson P, Ong K, Karumuthil-Melethil S, Keimel JG, Mark BL, Mahuran D, Gray SJ, Walia JS. Systemic Gene Transfer of a Hexosaminidase Variant Using an scAAV9.47 Vector Corrects GM2 Gangliosidosis in Sandhoff Mice. Hum Gene Ther 2017; 27:497-508. [PMID: 27199088 DOI: 10.1089/hum.2016.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
GM2 gangliosidosis is a group of neurodegenerative diseases caused by β-hexosaminidase A (HexA) enzyme deficiency. There is currently no cure. HexA is composed of two similar, nonidentical subunits, α and β, which must interact with the GM2 activator protein (GM2AP), a substrate-specific cofactor, to hydrolyze GM2 ganglioside. Mutations in either subunit or the activator can result in the accumulation of GM2 ganglioside within neurons throughout the central nervous system. The resulting neuronal cell death induces the primary symptoms of the disease: motor impairment, seizures, and sensory impairments. This study assesses the long-term effects of gene transfer in a Sandhoff (β-subunit knockout) mouse model. The study utilized a modified human β-hexosaminidase α-subunit (μ-subunit) that contains critical sequences from the β-subunit that enables formation of a stable homodimer (HexM) and interaction with GM2AP to hydrolyze GM2 ganglioside. We investigated a self-complementary adeno-associated viral (scAAV) vector expressing HexM, through intravenous injections of the neonatal mice. We monitored one cohort for 8 weeks and another cohort long-term for survival benefit, behavioral, biochemical, and molecular analyses. Untreated Sandhoff disease (SD) control mice reached a humane endpoint at approximately 15 weeks, whereas treated mice had a median survival age of 40 weeks, an approximate 2.5-fold survival advantage. On behavioral tests, the treated mice outperformed their knockout age-matched controls and perform similarly to the heterozygous controls. Through the enzymatic and GM2 ganglioside analyses, we observed a significant decrease in the GM2 ganglioside level, even though the enzyme levels were not significantly increased. Molecular analyses revealed a global distribution of the vector between brain and spinal cord regions. In conclusion, the neonatal delivery of a novel viral vector expressing the human HexM enzyme is effective in ameliorating the SD mouse phenotype for long-term. Our data could have implications not only for treatment of SD but also for Tay-Sachs disease (α-subunit deficiency) and similar brain disorders.
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Affiliation(s)
- Karlaina J L Osmon
- 1 Centre for Neuroscience Studies, Queen's University , Kingston, Ontario, Canada
| | - Evan Woodley
- 2 Department of Biomedical and Molecular Sciences, Queen's University , Kingston, Ontario, Canada
| | - Patrick Thompson
- 3 Medical Genetics/Departments of Pediatrics, Queen's University , Kingston, Ontario, Canada
| | - Katalina Ong
- 3 Medical Genetics/Departments of Pediatrics, Queen's University , Kingston, Ontario, Canada
| | | | - John G Keimel
- 5 New Hope Research Foundation , North Oaks, Minnesota
| | - Brian L Mark
- 6 Department of Microbiology, University of Manitoba , Winnipeg, Manitoba, Canada
| | - Don Mahuran
- 7 Genetics and Genome Biology, SickKids, Toronto, Ontario, Canada .,8 Department of Laboratory Medicine and Pathology, University of Toronto , Toronto, Ontario, Canada
| | - Steven J Gray
- 4 Gene Therapy Center, University of North Carolina , Chapel Hill, North Carolina.,9 Department of Ophthalmology, University of North Carolina , Chapel Hill, North Carolina
| | - Jagdeep S Walia
- 1 Centre for Neuroscience Studies, Queen's University , Kingston, Ontario, Canada .,2 Department of Biomedical and Molecular Sciences, Queen's University , Kingston, Ontario, Canada .,3 Medical Genetics/Departments of Pediatrics, Queen's University , Kingston, Ontario, Canada
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Construction of a hybrid β-hexosaminidase subunit capable of forming stable homodimers that hydrolyze GM2 ganglioside in vivo. MOLECULAR THERAPY-METHODS & CLINICAL DEVELOPMENT 2016; 3:15057. [PMID: 26966698 PMCID: PMC4774620 DOI: 10.1038/mtm.2015.57] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 12/17/2015] [Indexed: 02/07/2023]
Abstract
Tay-Sachs or Sandhoff disease result from mutations in either the evolutionarily related HEXA or HEXB genes encoding respectively, the α- or β-subunits of β-hexosaminidase A (HexA). Of the three Hex isozymes, only HexA can interact with its cofactor, the GM2 activator protein (GM2AP), and hydrolyze GM2 ganglioside. A major impediment to establishing gene or enzyme replacement therapy based on HexA is the need to synthesize both subunits. Thus, we combined the critical features of both α- and β-subunits into a single hybrid µ-subunit that contains the α-subunit active site, the stable β-subunit interface and unique areas in each subunit needed to interact with GM2AP. To facilitate intracellular analysis and the purification of the µ-homodimer (HexM), CRISPR-based genome editing was used to disrupt the HEXA and HEXB genes in a Human Embryonic Kidney 293 cell line stably expressing the µ-subunit. In association with GM2AP, HexM was shown to hydrolyze a fluorescent GM2 ganglioside derivative both in cellulo and in vitro. Gene transfer studies in both Tay-Sachs and Sandhoff mouse models demonstrated that HexM expression reduced brain GM2 ganglioside levels.
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11
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Huang FT, Han YB, Feng Y, Yang GY. A facile method for controlling the reaction equilibrium of sphingolipid ceramide N-deacylase for lyso-glycosphingolipid production. J Lipid Res 2015; 56:1836-42. [PMID: 26130766 DOI: 10.1194/jlr.d061176] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Indexed: 11/20/2022] Open
Abstract
Lyso-glycosphingolipids (lyso-GSLs), the N-deacylated forms of glycosphingolipids (GSLs), are important synthetic intermediates for the preparation of GSL analogs. Although lyso-GSLs can be produced by hydrolyzing natural GSLs using sphingolipid ceramide N-deacylase (SCDase), the yield for this reaction is usually low because SCDase also catalyzes the reverse reaction, ultimately establishing an equilibrium between hydrolysis and synthesis. In the present study, we developed an efficient method for controlling the reaction equilibrium by introducing divalent metal cation and detergent in the enzymatic reaction system. In the presence of both Ca(2+) and taurodeoxycholate hydrate, the generated fatty acids were precipitated by the formation of insoluble stearate salts and pushing the reaction equilibrium toward hydrolysis. The yield of GM1 hydrolysis can be achieved as high as 96%, with an improvement up to 45% compared with the nonoptimized condition. In preparative scale, 75 mg of lyso-GM1 was obtained from 100 mg of GM1 with a 90% yield, which is the highest reported yield to date. The method can also be used for the efficient hydrolysis of a variety of GSLs and sphingomyelin. Thus, this method should serve as a facile, easily scalable, and general tool for lyso-GSL production to facilitate further GSL research.
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Affiliation(s)
- Feng-Tao Huang
- State Key Laboratory of Microbial Metabolism and Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Yun-Bin Han
- State Key Laboratory of Microbial Metabolism and Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Yan Feng
- State Key Laboratory of Microbial Metabolism and Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Guang-Yu Yang
- State Key Laboratory of Microbial Metabolism and Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China Shanghai Collaborative Innovation Center for Biomanufacturing (SCICB), East China University of Science and Technology, Shanghai 200237, China
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12
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Tropak MB, Zhang J, Yonekawa S, Rigat BA, Aulakh VS, Smith MR, Hwang HJ, Ciufolini MA, Mahuran DJ. Pyrimethamine Derivatives: Insight into Binding Mechanism and Improved Enhancement of Mutant β-N-acetylhexosaminidase Activity. J Med Chem 2015; 58:4483-93. [PMID: 25984755 DOI: 10.1021/jm5017895] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In order to identify structural features of pyrimethamine (5-(4-chlorophenyl)-6-ethylpyrimidine-2,4-diamine) that contribute to its inhibitory activity (IC50 value) and chaperoning efficacy toward β-N-acetylhexosaminidase, derivatives of the compound were synthesized that differ at the positions bearing the amino, ethyl, and chloro groups. Whereas the amino groups proved to be critical to its inhibitory activity, a variety of substitutions at the chloro position only increased its IC50 by 2-3-fold. Replacing the ethyl group at the 6-position with butyl or methyl groups increased IC50 more than 10-fold. Surprisingly, despite its higher IC50, a derivative lacking the chlorine atom in the para-position was found to enhance enzyme activity in live patient cells a further 25% at concentrations >100 μM, while showing less toxicity. These findings demonstrate the importance of the phenyl group in modulating the chaperoning efficacy and toxicity profile of the derivatives.
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Affiliation(s)
- Michael B Tropak
- †Genetics and Genome Biology, SickKids, PGCRL 686 Bay Street, Toronto, Ontario M5G 0A4, Canada
| | - Jianmin Zhang
- ‡Department of Chemistry, University of British Columbia, 2036 Main Mall Vancouver, British Columbia V6T 1Z1, Canada
| | - Sayuri Yonekawa
- †Genetics and Genome Biology, SickKids, PGCRL 686 Bay Street, Toronto, Ontario M5G 0A4, Canada
| | - Brigitte A Rigat
- †Genetics and Genome Biology, SickKids, PGCRL 686 Bay Street, Toronto, Ontario M5G 0A4, Canada
| | - Virender S Aulakh
- ‡Department of Chemistry, University of British Columbia, 2036 Main Mall Vancouver, British Columbia V6T 1Z1, Canada
| | - Matthew R Smith
- ‡Department of Chemistry, University of British Columbia, 2036 Main Mall Vancouver, British Columbia V6T 1Z1, Canada
| | - Hee-Jong Hwang
- ‡Department of Chemistry, University of British Columbia, 2036 Main Mall Vancouver, British Columbia V6T 1Z1, Canada
| | - Marco A Ciufolini
- ‡Department of Chemistry, University of British Columbia, 2036 Main Mall Vancouver, British Columbia V6T 1Z1, Canada
| | - Don J Mahuran
- †Genetics and Genome Biology, SickKids, PGCRL 686 Bay Street, Toronto, Ontario M5G 0A4, Canada.,§Department of Laboratory Medicine and Pathology, University of Toronto, Medical Science Building, 1 King's College Circle, 6th Floor, Toronto, Ontario M5S 1A8, Canada
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13
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Renvoisé B, Chang J, Singh R, Yonekawa S, FitzGibbon EJ, Mankodi A, Vanderver A, Schindler A, Toro C, Gahl WA, Mahuran DJ, Blackstone C, Pierson TM. Lysosomal abnormalities in hereditary spastic paraplegia types SPG15 and SPG11. Ann Clin Transl Neurol 2014; 1:379-389. [PMID: 24999486 PMCID: PMC4078876 DOI: 10.1002/acn3.64] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Objective Hereditary spastic paraplegias (HSPs) are among the most genetically diverse inherited neurological disorders, with over 70 disease loci identified (SPG1-71) to date. SPG15 and SPG11 are clinically similar, autosomal recessive disorders characterized by progressive spastic paraplegia along with thin corpus callosum, white matter abnormalities, cognitive impairment, and ophthalmologic abnormalities. Furthermore, both have been linked to early-onset parkinsonism. Methods We describe two new cases of SPG15 and investigate cellular changes in SPG15 and SPG11 patient-derived fibroblasts, seeking to identify shared pathogenic themes. Cells were evaluated for any abnormalities in cell division, DNA repair, endoplasmic reticulum, endosomes, and lysosomes. Results Fibroblasts prepared from patients with SPG15 have selective enlargement of LAMP1-positive structures, and they consistently exhibited abnormal lysosomal storage by electron microscopy. A similar enlargement of LAMP1-positive structures was also observed in cells from multiple SPG11 patients, though prominent abnormal lysosomal storage was not evident. The stabilities of the SPG15 protein spastizin/ZFYVE26 and the SPG11 protein spatacsin were interdependent. Interpretation Emerging studies implicating these two proteins in interactions with the late endosomal/lysosomal adaptor protein complex AP-5 are consistent with shared abnormalities in lysosomes, supporting a converging mechanism for these two disorders. Recent work with Zfyve26−/− mice revealed a similar phenotype to human SPG15, and cells in these mice had endolysosomal abnormalities. SPG15 and SPG11 are particularly notable among HSPs because they can also present with juvenile parkinsonism, and this lysosomal trafficking or storage defect may be relevant for other forms of parkinsonism associated with lysosomal dysfunction.
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Affiliation(s)
- Benoît Renvoisé
- Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Jaerak Chang
- Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Rajat Singh
- Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Sayuri Yonekawa
- Research Institute, Hospital for Sick Children and University of Toronto, Toronto, ON, Canada
| | - Edmond J FitzGibbon
- Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - Ami Mankodi
- Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Adeline Vanderver
- Department of Neurology, Children's National Medical Center, Washington, DC, USA
| | - Alice Schindler
- Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Camilo Toro
- Office of the Clinical Director, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA ; NIH Undiagnosed Diseases Program, National Institutes of Health, Office of Rare Diseases Research and National Human Genome Research Institute, Bethesda, MD, USA
| | - William A Gahl
- Office of the Clinical Director, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA ; NIH Undiagnosed Diseases Program, National Institutes of Health, Office of Rare Diseases Research and National Human Genome Research Institute, Bethesda, MD, USA
| | - Don J Mahuran
- Research Institute, Hospital for Sick Children and University of Toronto, Toronto, ON, Canada
| | - Craig Blackstone
- Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Tyler Mark Pierson
- Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA ; NIH Undiagnosed Diseases Program, National Institutes of Health, Office of Rare Diseases Research and National Human Genome Research Institute, Bethesda, MD, USA ; Departments of Pediatrics and Neurology, and the Regenerative Medicine Institute, Cedars- Sinai Medical Center, Los Angeles, CA, USA
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Pharmacological chaperoning: a primer on mechanism and pharmacology. Pharmacol Res 2014; 83:10-9. [PMID: 24530489 DOI: 10.1016/j.phrs.2014.01.005] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 01/29/2014] [Indexed: 12/26/2022]
Abstract
Approximately forty percent of diseases are attributable to protein misfolding, including those for which genetic mutation produces misfolding mutants. Intriguingly, many of these mutants are not terminally misfolded since native-like folding, and subsequent trafficking to functional locations, can be induced by target-specific, small molecules variably termed pharmacological chaperones, pharmacoperones, or pharmacochaperones (PCs). PC targets include enzymes, receptors, transporters, and ion channels, revealing the breadth of proteins that can be engaged by ligand-assisted folding. The purpose of this review is to provide an integrated primer of the diverse mechanisms and pharmacology of PCs. In this regard, we examine the structural mechanisms that underlie PC rescue of misfolding mutants, including the ability of PCs to act as surrogates for defective intramolecular interactions and, at the intermolecular level, overcome oligomerization deficiencies and dominant negative effects, as well as influence the subunit stoichiometry of heteropentameric receptors. Not surprisingly, PC-mediated structural correction of misfolding mutants normalizes interactions with molecular chaperones that participate in protein quality control and forward-trafficking. A variety of small molecules have proven to be efficacious PCs and the advantages and disadvantages of employing orthostatic antagonists, active-site inhibitors, orthostatic agonists, and allosteric modulator PCs are considered. Also examined is the possibility that several therapeutic agents may have unrecognized activity as PCs, and this chaperoning activity may mediate/contribute to therapeutic action and/or account for adverse effects. Lastly, we explore evidence that pharmacological chaperoning exploits intrinsic ligand-assisted folding mechanisms. Given the widespread applicability of PC rescue of mutants associated with protein folding disorders, both in vitro and in vivo, the therapeutic potential of PCs is vast. This is most evident in the treatment of lysosomal storage disorders, cystic fibrosis, and nephrogenic diabetes insipidus, for which proof of principle in humans has been demonstrated.
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15
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Chaperone therapy for GM2 gangliosidosis: effects of pyrimethamine on β-hexosaminidase activity in Sandhoff fibroblasts. Mol Neurobiol 2013; 50:159-67. [PMID: 24356898 DOI: 10.1007/s12035-013-8605-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 12/08/2013] [Indexed: 12/20/2022]
Abstract
Sphingolipidoses are inherited genetic diseases due to mutations in genes encoding proteins involved in the lysosomal catabolism of sphingolipids. Despite a low incidence of each individual disease, altogether, the number of patients involved is relatively high and resolutive approaches for treatment are still lacking. The chaperone therapy is one of the latest pharmacological approaches to these storage diseases. This therapy allows the mutated protein to escape its natural removal and to increase its quantity in lysosomes, thus partially restoring the metabolic functions. Sandhoff disease is an autosomal recessive inherited disorder resulting from β-hexosaminidase deficiency and characterized by large accumulation of GM2 ganglioside in brain. No enzymatic replacement therapy is currently available, and the use of inhibitors of glycosphingolipid biosynthesis for substrate reduction therapy, although very promising, is associated with serious side effects. The chaperone pyrimethamine has been proposed as a very promising drug in those cases characterized by a residual enzyme activity. In this review, we report the effect of pyrimethamine on the recovery of β-hexosaminidase activity in cultured fibroblasts from Sandhoff patients.
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16
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Boustany RMN. Lysosomal storage diseases--the horizon expands. NATURE REVIEWS. NEUROLOGY 2013. [PMID: 23938739 DOI: 10.1038/nrneurol.2013.163]] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Since the discovery of the lysosome in 1955, advances have been made in understanding the key roles and functions of this organelle. The concept of lysosomal storage diseases (LSDs)--disorders characterized by aberrant, excessive storage of cellular material in lysosomes--developed following the discovery of α-glucosidase deficiency as the cause of Pompe disease in 1963. Great strides have since been made in understanding the pathobiology of LSDs and the neuronal ceroid lipofuscinoses (NCLs). The NCLs are neurodegenerative disorders that display symptoms of cognitive and motor decline, seizures, blindness, early death, and accumulation of lipofuscin in various cell types, and also show some similarities to 'classic' LSDs. Defective lysosomal storage can occur in many cell types, but the CNS and PNS are particularly vulnerable to LSDs and NCLs, being affected in two-thirds of these disorders. Most LSDs are inherited in an autosomal recessive manner, with the exception of X-linked Hunter disease, Fabry disease and Danon disease, and a variant type of adult NCL (Kuf disease). This Review provides a summary of known LSDs, and the pathways affected in these disorders. Existing therapies and barriers to development of novel and improved treatments for LSDs and NCLs are also discussed.
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Affiliation(s)
- Rose-Mary Naaman Boustany
- Department of Paediatrics and Adolescent Medicine, Biochemistry and Molecular Genetics, American University of Beirut, PO Box 11-0236, Riad El-Solh, 1107 2020, Beirut, Lebanon.
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Abstract
Since the discovery of the lysosome in 1955, advances have been made in understanding the key roles and functions of this organelle. The concept of lysosomal storage diseases (LSDs)--disorders characterized by aberrant, excessive storage of cellular material in lysosomes--developed following the discovery of α-glucosidase deficiency as the cause of Pompe disease in 1963. Great strides have since been made in understanding the pathobiology of LSDs and the neuronal ceroid lipofuscinoses (NCLs). The NCLs are neurodegenerative disorders that display symptoms of cognitive and motor decline, seizures, blindness, early death, and accumulation of lipofuscin in various cell types, and also show some similarities to 'classic' LSDs. Defective lysosomal storage can occur in many cell types, but the CNS and PNS are particularly vulnerable to LSDs and NCLs, being affected in two-thirds of these disorders. Most LSDs are inherited in an autosomal recessive manner, with the exception of X-linked Hunter disease, Fabry disease and Danon disease, and a variant type of adult NCL (Kuf disease). This Review provides a summary of known LSDs, and the pathways affected in these disorders. Existing therapies and barriers to development of novel and improved treatments for LSDs and NCLs are also discussed.
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Affiliation(s)
- Rose-Mary Naaman Boustany
- Department of Paediatrics and Adolescent Medicine, Biochemistry and Molecular Genetics, American University of Beirut, PO Box 11-0236, Riad El-Solh, 1107 2020, Beirut, Lebanon.
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18
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Sinici I, Yonekawa S, Tkachyova I, Gray SJ, Samulski RJ, Wakarchuk W, Mark BL, Mahuran DJ. In cellulo examination of a beta-alpha hybrid construct of beta-hexosaminidase A subunits, reported to interact with the GM2 activator protein and hydrolyze GM2 ganglioside. PLoS One 2013; 8:e57908. [PMID: 23483939 PMCID: PMC3587417 DOI: 10.1371/journal.pone.0057908] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Accepted: 01/29/2013] [Indexed: 11/19/2022] Open
Abstract
The hydrolysis in lysosomes of GM2 ganglioside to GM3 ganglioside requires the correct synthesis, intracellular assembly and transport of three separate gene products; i.e., the alpha and beta subunits of heterodimeric beta-hexosaminidase A, E.C. # 3.2.1.52 (encoded by the HEXA and HEXB genes, respectively), and the GM2-activator protein (GM2AP, encoded by the GM2A gene). Mutations in any one of these genes can result in one of three neurodegenerative diseases collectively known as GM2 gangliosidosis (HEXA, Tay-Sachs disease, MIM # 272800; HEXB, Sandhoff disease, MIM # 268800; and GM2A, AB-variant form, MIM # 272750). Elements of both of the hexosaminidase A subunits are needed to productively interact with the GM2 ganglioside-GM2AP complex in the lysosome. Some of these elements have been predicted from the crystal structures of hexosaminidase and the activator. Recently a hybrid of the two subunits has been constructed and reported to be capable of forming homodimers that can perform this reaction in vivo, which could greatly simplify vector-mediated gene transfer approaches for Tay-Sachs or Sandhoff diseases. A cDNA encoding a hybrid hexosaminidase subunit capable of dimerizing and hydrolyzing GM2 ganglioside could be incorporated into a single vector, whereas packaging both subunits of hexosaminidase A into vectors, such as adeno-associated virus, would be impractical due to size constraints. In this report we examine the previously published hybrid construct (H1) and a new more extensive hybrid (H2), with our documented in cellulo (live cell- based) assay utilizing a fluorescent GM2 ganglioside derivative. Unfortunately when Tay-Sachs cells were transfected with either the H1 or H2 hybrid construct and then were fed the GM2 derivative, no significant increase in its turnover was detected. In vitro assays with the isolated H1 or H2 homodimers confirmed that neither was capable of human GM2AP-dependent hydrolysis of GM2 ganglioside.
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Affiliation(s)
- Incilay Sinici
- Department of Biochemistry, Hacettepe University, Faculty of Medicine, Ankara, Turkey
| | - Sayuri Yonekawa
- Genetics and Genome Biology, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Ilona Tkachyova
- Genetics and Genome Biology, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Steven J. Gray
- Gene Therapy Center, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - R. Jude Samulski
- Gene Therapy Center, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Warren Wakarchuk
- Ryerson University, Department of Chemistry and Biology, Toronto, Canada
| | - Brian L. Mark
- Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Don J. Mahuran
- Genetics and Genome Biology, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
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Fan X, Tkachyova I, Sinha A, Rigat B, Mahuran D. Characterization of the biosynthesis, processing and kinetic mechanism of action of the enzyme deficient in mucopolysaccharidosis IIIC. PLoS One 2011; 6:e24951. [PMID: 21957468 PMCID: PMC3177862 DOI: 10.1371/journal.pone.0024951] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Accepted: 08/22/2011] [Indexed: 11/18/2022] Open
Abstract
Heparin acetyl-CoA:alpha-glucosaminide N-acetyltransferase (N-acetyltransferase, EC 2.3.1.78) is an integral lysosomal membrane protein containing 11 transmembrane domains, encoded by the HGSNAT gene. Deficiencies of N-acetyltransferase lead to mucopolysaccharidosis IIIC. We demonstrate that contrary to a previous report, the N-acetyltransferase signal peptide is co-translationally cleaved and that this event is required for its intracellular transport to the lysosome. While we confirm that the N-acetyltransferase precursor polypeptide is processed in the lysosome into a small amino-terminal alpha- and a larger ß- chain, we further characterize this event by identifying the mature amino-terminus of each chain. We also demonstrate this processing step(s) is not, as previously reported, needed to produce a functional transferase, i.e., the precursor is active. We next optimize the biochemical assay procedure so that it remains linear as N-acetyltransferase is purified or protein-extracts containing N-acetyltransferase are diluted, by the inclusion of negatively charged lipids. We then use this assay to demonstrate that the purified single N-acetyltransferase protein is both necessary and sufficient to express transferase activity, and that N-acetyltransferase functions as a monomer. Finally, the kinetic mechanism of action of purified N-acetyltransferase was evaluated and found to be a random sequential mechanism involving the formation of a ternary complex with its two substrates; i.e., N-acetyltransferase does not operate through a ping-pong mechanism as previously reported. We confirm this conclusion by demonstrating experimentally that no acetylated enzyme intermediate is formed during the reaction.
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Affiliation(s)
- Xiaolian Fan
- Genetics and Genome Biology Program, The Hospital For Sick Children, Toronto, Canada
| | - Ilona Tkachyova
- Genetics and Genome Biology Program, The Hospital For Sick Children, Toronto, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
| | - Ankit Sinha
- Genetics and Genome Biology Program, The Hospital For Sick Children, Toronto, Canada
| | - Brigitte Rigat
- Genetics and Genome Biology Program, The Hospital For Sick Children, Toronto, Canada
| | - Don Mahuran
- Genetics and Genome Biology Program, The Hospital For Sick Children, Toronto, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
- * E-mail:
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Valenzano KJ, Khanna R, Powe AC, Boyd R, Lee G, Flanagan JJ, Benjamin ER. Identification and characterization of pharmacological chaperones to correct enzyme deficiencies in lysosomal storage disorders. Assay Drug Dev Technol 2011; 9:213-35. [PMID: 21612550 PMCID: PMC3102255 DOI: 10.1089/adt.2011.0370] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Many human diseases result from mutations in specific genes. Once translated, the resulting aberrant proteins may be functionally competent and produced at near-normal levels. However, because of the mutations, the proteins are recognized by the quality control system of the endoplasmic reticulum and are not processed or trafficked correctly, ultimately leading to cellular dysfunction and disease. Pharmacological chaperones (PCs) are small molecules designed to mitigate this problem by selectively binding and stabilizing their target protein, thus reducing premature degradation, facilitating intracellular trafficking, and increasing cellular activity. Partial or complete restoration of normal function by PCs has been shown for numerous types of mutant proteins, including secreted proteins, transcription factors, ion channels, G protein-coupled receptors, and, importantly, lysosomal enzymes. Collectively, lysosomal storage disorders (LSDs) result from genetic mutations in the genes that encode specific lysosomal enzymes, leading to a deficiency in essential enzymatic activity and cellular accumulation of the respective substrate. To date, over 50 different LSDs have been identified, several of which are treated clinically with enzyme replacement therapy or substrate reduction therapy, although insufficiently in some cases. Importantly, a wide range of in vitro assays are now available to measure mutant lysosomal enzyme interaction with and stabilization by PCs, as well as subsequent increases in cellular enzyme levels and function. The application of these assays to the identification and characterization of candidate PCs for mutant lysosomal enzymes will be discussed in this review. In addition, considerations for the successful in vivo use and development of PCs to treat LSDs will be discussed.
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Bateman KS, Cherney MM, Mahuran DJ, Tropak M, James MNG. Crystal structure of β-hexosaminidase B in complex with pyrimethamine, a potential pharmacological chaperone. J Med Chem 2011; 54:1421-9. [PMID: 21265544 DOI: 10.1021/jm101443u] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
β-Hexosaminidases (β-hex) are a group of glycosyl hydrolase isozymes that break down neutral and sialylated glycosphingolipids in the lysosomes, thereby preventing their buildup in neuronal cells. Some mutants of β-hex have decreased folding stability that results in adult-onset forms of lysosomal storage diseases. However, prevention of the harmful accumulation of glycolipids only requires 10% of wild-type activity. Pyrimethamine (PYR) is a potential pharmacological chaperone that works by stabilizing these mutant enzymes sufficiently to allow more β-hex to arrive in the lysosome, where it can carry out its function. An X-ray structure of the complex between human β-hexosaminidase B (HexB) and PYR has been determined to 2.8 Å. PYR binds to the active site of HexB where several favorable van der Waals contacts and hydrogen bonds are introduced. Small adjustments of the enzyme structure are required to accommodate the ligand, and details of the inhibition and stabilization properties of PYR are discussed.
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Affiliation(s)
- Katherine S Bateman
- Department of Biochemistry, 4-29 Medical Sciences Building, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
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22
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Clarke JTR, Mahuran DJ, Sathe S, Kolodny EH, Rigat BA, Raiman JA, Tropak MB. An open-label Phase I/II clinical trial of pyrimethamine for the treatment of patients affected with chronic GM2 gangliosidosis (Tay-Sachs or Sandhoff variants). Mol Genet Metab 2011; 102:6-12. [PMID: 20926324 PMCID: PMC3019177 DOI: 10.1016/j.ymgme.2010.09.004] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Revised: 09/11/2010] [Accepted: 09/13/2010] [Indexed: 11/21/2022]
Abstract
Late-onset GM2 gangliosidosis is an autosomal recessive, neurodegenerative, lysosomal storage disease, caused by deficiency of ß-hexosaminidase A (Hex A), resulting from mutations in the HEXA (Tay-Sachs variant) or the HEXB (Sandhoff variant) genes. The enzyme deficiency in many patients with juvenile or adult onset forms of the disease results from the production of an unstable protein, which becomes targeted for premature degradation by the quality control system of the smooth endoplasmic reticulum and is not transported to lysosomes. In vitro studies have shown that many mutations in either the α or β subunit of Hex A can be partially rescued, i.e. enhanced levels of both enzyme protein and activity in lysosomes, following the growth of patient cells in the presence of the drug, pyrimethamine. The objectives of the present clinical trial were to establish the tolerability and efficacy of the treatment of late-onset GM2 gangliosidosis patients with escalating doses of pyrimethamine, to a maximum of 100 mg per day, administered orally in a single daily dose, over a 16-week period . The primary objective, tolerability, was assessed by regular clinical examinations, along with a panel of hematologic and biochemical studies. Although clinical efficacy could not be assessed in this short trial, treatment efficacy was evaluated by repeated measurements of leukocyte Hex A activity, expressed relative to the activity of lysosomal ß-glucuronidase. A total of 11 patients were enrolled, 8 males and 3 females, aged 23 to 50 years. One subject failed the initial screen, another was omitted from analysis because of the large number of protocol violations, and a third was withdrawn very early as a result of adverse events which were not drug-related. For the remaining 8 subjects, up to a 4-fold enhancement of Hex A activity at doses of 50 mg per day or less was observed. Additionally marked individual variations in the pharmacokinetics of the drug among the patients were noted. However, the study also found that significant side effects were experienced by most patients at or above 75 mg pyrimethamine per day. We concluded that pyrimethamine treatment enhances leukocyte Hex A activity in patients with late-onset GM2 gangliosidosis at doses lower than those associated with unacceptable side effects. Further plans are underway to extend these trials and to develop methods to assess clinical efficacy.
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Affiliation(s)
- Joe T R Clarke
- Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada.
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