1
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Ferrada E, Wiedmer T, Wang WA, Frommelt F, Steurer B, Klimek C, Lindinger S, Osthushenrich T, Garofoli A, Brocchetti S, Bradberry S, Huang J, MacNamara A, Scarabottolo L, Ecker GF, Malarstig A, Superti-Furga G. Experimental and Computational Analysis of Newly Identified Pathogenic Mutations in the Creatine Transporter SLC6A8. J Mol Biol 2024; 436:168383. [PMID: 38070861 DOI: 10.1016/j.jmb.2023.168383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 11/26/2023] [Accepted: 12/01/2023] [Indexed: 12/24/2023]
Abstract
Creatine is an essential metabolite for the storage and rapid supply of energy in muscle and nerve cells. In humans, impaired metabolism, transport, and distribution of creatine throughout tissues can cause varying forms of mental disability, also known as creatine deficiency syndrome (CDS). So far, 80 mutations in the creatine transporter (SLC6A8) have been associated to CDS. To better understand the effect of human genetic variants on the physiology of SLC6A8 and their possible impact on CDS, we studied 30 missense variants including 15 variants of unknown significance, two of which are reported here for the first time. We expressed these variants in HEK293 cells and explored their subcellular localization and transport activity. We also applied computational methods to predict variant effect and estimate site-specific changes in thermodynamic stability. To explore variants that might have a differential effect on the transporter's conformers along the transport cycle, we constructed homology models of the inward facing, and outward facing conformations. In addition, we used mass-spectrometry to study proteins that interact with wild type SLC6A8 and five selected variants in HEK293 cells. In silico models of the protein complexes revealed how two variants impact the interaction interface of SLC6A8 with other proteins and how pathogenic variants lead to an enrichment of ER protein partners. Overall, our integrated analysis disambiguates the pathogenicity of 15 variants of unknown significance revealing diverse mechanisms of pathogenicity, including two previously unreported variants obtained from patients suffering from the creatine deficiency syndrome.
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Affiliation(s)
- Evandro Ferrada
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria.
| | - Tabea Wiedmer
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Wen-An Wang
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Fabian Frommelt
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Barbara Steurer
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Christoph Klimek
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Sabrina Lindinger
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | | | - Andrea Garofoli
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | | | | | - Jiahui Huang
- Department of Pharmaceutical Sciences, University of Vienna, Vienna, Austria
| | | | | | - Gerhard F Ecker
- Department of Pharmaceutical Sciences, University of Vienna, Vienna, Austria
| | - Anders Malarstig
- Pfizer Worldwide Research, Development and Medical, Stockholm, Sweden
| | - Giulio Superti-Furga
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria; Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria.
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2
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Lyons EL, Watson D, Alodadi MS, Haugabook SJ, Tawa GJ, Hannah-Shmouni F, Porter FD, Collins JR, Ottinger EA, Mudunuri US. Rare disease variant curation from literature: assessing gaps with creatine transport deficiency in focus. BMC Genomics 2023; 24:460. [PMID: 37587458 PMCID: PMC10433598 DOI: 10.1186/s12864-023-09561-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Accepted: 08/08/2023] [Indexed: 08/18/2023] Open
Abstract
BACKGROUND Approximately 4-8% of the world suffers from a rare disease. Rare diseases are often difficult to diagnose, and many do not have approved therapies. Genetic sequencing has the potential to shorten the current diagnostic process, increase mechanistic understanding, and facilitate research on therapeutic approaches but is limited by the difficulty of novel variant pathogenicity interpretation and the communication of known causative variants. It is unknown how many published rare disease variants are currently accessible in the public domain. RESULTS This study investigated the translation of knowledge of variants reported in published manuscripts to publicly accessible variant databases. Variants, symptoms, biochemical assay results, and protein function from literature on the SLC6A8 gene associated with X-linked Creatine Transporter Deficiency (CTD) were curated and reported as a highly annotated dataset of variants with clinical context and functional details. Variants were harmonized, their availability in existing variant databases was analyzed and pathogenicity assignments were compared with impact algorithm predictions. 24% of the pathogenic variants found in PubMed articles were not captured in any database used in this analysis while only 65% of the published variants received an accurate pathogenicity prediction from at least one impact prediction algorithm. CONCLUSIONS Despite being published in the literature, pathogenicity data on patient variants may remain inaccessible for genetic diagnosis, therapeutic target identification, mechanistic understanding, or hypothesis generation. Clinical and functional details presented in the literature are important to make pathogenicity assessments. Impact predictions remain imperfect but are improving, especially for single nucleotide exonic variants, however such predictions are less accurate or unavailable for intronic and multi-nucleotide variants. Developing text mining workflows that use natural language processing for identifying diseases, genes and variants, along with impact prediction algorithms and integrating with details on clinical phenotypes and functional assessments might be a promising approach to scale literature mining of variants and assigning correct pathogenicity. The curated variants list created by this effort includes context details to improve any such efforts on variant curation for rare diseases.
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Affiliation(s)
- Erica L Lyons
- Advanced Biomedical Computational Science, Frederick National Laboratory for Cancer Research, Frederick, MD, 21702, USA
| | - Daniel Watson
- Advanced Biomedical Computational Science, Frederick National Laboratory for Cancer Research, Frederick, MD, 21702, USA
| | - Mohammad S Alodadi
- Advanced Biomedical Computational Science, Frederick National Laboratory for Cancer Research, Frederick, MD, 21702, USA
| | - Sharie J Haugabook
- Division of Preclinical Innovation, Therapeutic Development Branch, Therapeutics for Rare and Neglected Diseases (TRND) Program, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Gregory J Tawa
- Division of Preclinical Innovation, Therapeutic Development Branch, Therapeutics for Rare and Neglected Diseases (TRND) Program, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Fady Hannah-Shmouni
- Division of Translational Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Forbes D Porter
- Division of Translational Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Jack R Collins
- Advanced Biomedical Computational Science, Frederick National Laboratory for Cancer Research, Frederick, MD, 21702, USA
| | - Elizabeth A Ottinger
- Division of Preclinical Innovation, Therapeutic Development Branch, Therapeutics for Rare and Neglected Diseases (TRND) Program, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD, 20892, USA.
| | - Uma S Mudunuri
- Advanced Biomedical Computational Science, Frederick National Laboratory for Cancer Research, Frederick, MD, 21702, USA.
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3
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Mustafa NM, Elabd NE, Selim LA, Abdou DM, Griffin JL. Creatine Deficiency Syndromes: Comparison of Screening Methods and Characterization of Four Novel Intronic Variants. Clin Chim Acta 2022; 536:70-76. [PMID: 36130657 DOI: 10.1016/j.cca.2022.09.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 09/04/2022] [Accepted: 09/05/2022] [Indexed: 11/28/2022]
Abstract
BACKGROUND Cerebral creatine deficiency syndromes (CCDS) are disorders affecting creatine synthesis or transport. Several methods have been developed to measure creatine and guanidinoacetate (GAA) in different body fluids including methods based on gas chromatography-mass spectrometry (GC-MS) and High-pressure liquid chromatography mass spectrometry (HPLC-MS). The diagnosis of CCDS is then confirmed by sequencing of creatine biosynthesis genes guanidinoacetate methyltransferase (GAMT) and Arginine: glycine amidinotransferase (GATM) and creatine transporter gene solute carrier family 6 member 8 (SLC6A8) or by functional enzymatic assay. The aim of the current study was to find the most reliable and accurate screening method for CCDS by comparing methods using Nuclear Magnetic Resonance spectroscopy (NMR), GC-MS and HPLC-MS. Additionally, this study was performed to estimate the prevalence of CCDS in a cohort of Egyptian patients and potentially to discover novel variants. SUBJECTS AND METHODS The study was conducted on 150 subjects with clinical signs and symptoms consistent with CCDS. Metabolic profiling of urine samples was performed using three techniques: 1) GC-MS 2) Ultra high-pressure (or performance) liquid chromatography - Tandem Mass Spectrometry (UHPLC- MS/MS) and 3) NMR. RESULTS The linearity of peak areas for creatine and GAA by UHPLC-MS/MS and NMR covered and exceeded the ranges normally found in urine. The limit of quantification and the inter-day precision results for creatine and GAA were more robust by UHPLC-MS/MS than NMR. Ten cases were identified as being positive for CCDS by our analytical approaches and underwent next generation sequencing (NGS) for GAMT, GATM and SLC6A8 genes. NGS was performed and confirmed one patient with one likely Pathogenic variant in GAMT gene: (NC_000019.10:g.1401317C > G, NP_000147.1:p.Ala54Pro). Additionally, we describe four novel intronic variants in the GATM gene: c.1043-357del and c.1043-357_1043-356insT, and were predicted to activate cryptic acceptor site with potential alteration of splicing, c.979-227G > A was found to significantly alter the Exon Splice Enhancer (ESE) xon Splice Silencer (ESS) motifs ratio and c.1042 + 262del which was found to have no implications on splicing. CONCLUSIONS Both UHPLC-MS/MS and NMR spectroscopy are comparable to GC-MS in screening for CCDS. Nonetheless, the UHPLC-MS/MS method had better performance than NMR spectroscopy. Additionally, Sequencing of the full length of GATM, GAMT, and SLC6A8 genes is needed to identify intronic variants that could cause CCDS via affecting splice sites.
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Affiliation(s)
- Naira M Mustafa
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK; Department of Chemical Pathology, Faculty of Medicine, Cairo University, Egypt.
| | - Nevine E Elabd
- Department of Chemical Pathology, Faculty of Medicine, Cairo University, Egypt
| | - Laila A Selim
- Department of Paediatrics, Neurology and Metabolic Division, Faculty of Medicine, Cairo University, Egypt; Inherited Metabolic Disease Unit, Centre of Social and Preventive Medicine, Cairo University, Egypt
| | - Doaa M Abdou
- Department of Chemical Pathology, Faculty of Medicine, Cairo University, Egypt
| | - Julian L Griffin
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK; Biomolecular Medicine, Department of Metabolism, Digestion and Reproduction, Imperial College, London, UK; The Rowett Institute, Foresterhill Campus, University of Aberdeen, Aberdeen, UK
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4
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Shen M, Yang G, Chen Z, Yang K, Dong H, Yin C, Cheng Y, Zhang C, Gu F, Yang Y, Tian Y. Identification of novel variations in SLC6A8 and GAMT genes causing cerebral creatine deficiency syndrome. Clin Chim Acta 2022; 532:29-36. [PMID: 35588794 DOI: 10.1016/j.cca.2022.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 04/24/2022] [Accepted: 05/05/2022] [Indexed: 11/03/2022]
Abstract
Cerebral creatine deficiency syndromes (CCDSs) are a group of rare mendelian disorders mainly characterized by intellectual disability, movement anomaly, behavior disorder and seizures. SLC6A8, GAMT, and GATM are known genes responsible for CCDS. In this study, seven pediatric patients with developmental delay were recruited and submitted to a series of clinical evaluation, laboratory testing, and genetic analysis. The clinical manifestations and core biochemical indications of each child were basically consistent with the diagnosis of CCDS. Genetic diagnosis determined that all patients were positive for SLC6A8 or GAMT variation. A total of 12 variants were identified in this cohort, including six novel ones. The frequency of these variants, the Revel scores and the conservatism of the affected amino acids support their pathogenicity. Our findings expanded the mutation spectrum of CCDS disorders, and provided solid evidence for the counseling to affected families.
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Affiliation(s)
- Ming Shen
- Research Center for Translational Medicine Laboratory, Medical Innovation Research Division of Chinese PLA General Hospital, Beijing, China
| | - Guangming Yang
- Research Center for Translational Medicine Laboratory, Medical Innovation Research Division of Chinese PLA General Hospital, Beijing, China
| | - Zhehui Chen
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Kai Yang
- Prenatal Diagnosis Center, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing, China
| | - Hui Dong
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Chengliang Yin
- Medical Big Data Research Center, Medical Innovation Research Division of Chinese People's Liberation Army General Hospital, Beijing, China
| | - Yuxuan Cheng
- Birth Defects Prevention and Control Technology Research Center, Medical Research and Innovation Department, Chinese PLA General Hospital, Beijing, China
| | - Chunyan Zhang
- Birth Defects Prevention and Control Technology Research Center, Medical Research and Innovation Department, Chinese PLA General Hospital, Beijing, China
| | - Fangyan Gu
- Clinical Biobank Center, Medical Innovation Research Division of Chinese PLA General Hospital, Beijing, China
| | - Yanling Yang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Yaping Tian
- Birth Defects Prevention and Control Technology Research Center, Medical Research and Innovation Department, Chinese PLA General Hospital, Beijing, China
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5
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Morey K, Hallinan B, Cecil KM. Case report: Clinical and magnetic resonance spectroscopy presentation of a female severely affected with X-linked creatine transporter deficiency. Radiol Case Rep 2022; 17:1115-1119. [PMID: 35169411 PMCID: PMC8829519 DOI: 10.1016/j.radcr.2022.01.053] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 01/18/2022] [Accepted: 01/19/2022] [Indexed: 11/30/2022] Open
Abstract
Creatine transporter deficiency is an X-linked genetic disorder caused by a variant in the SLC6A8 gene located on the X chromosome (Xq28). This condition varies in severity with features often including intellectual disabilities, speech delay, autistic features, attention deficit hyperactivity and gastrointestinal issues. While creatine transporter deficiency primarily affects males, females may also demonstrate severe phenotypes. However, screening of creatine transporter deficiency in females can be especially difficult as urine creatine/creatinine screenings often have values falling within normative ranges. Also, females may not demonstrate the characteristic reduction of creatine concentrations in the brain visualized with in vivo proton magnetic resonance spectroscopy. Identification typically results from exome sequencing. In this report, we present the clinical, imaging, and spectroscopy features of a heterozygous female with a severe presentation of creatine transporter deficiency.
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Affiliation(s)
- Katherine Morey
- Summer Undergraduate Research Fellowship Program, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
- Department of Radiology, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, 3333 Burnet Avenue, MLC 5033, Cincinnati, OH 45229, USA
| | - Barbara Hallinan
- Department of Pediatrics, Division of Neurology, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Kim M. Cecil
- Department of Radiology, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, 3333 Burnet Avenue, MLC 5033, Cincinnati, OH 45229, USA
- Corresponding author.
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6
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Farr CV, El-Kasaby A, Freissmuth M, Sucic S. The Creatine Transporter Unfolded: A Knotty Premise in the Cerebral Creatine Deficiency Syndrome. Front Synaptic Neurosci 2020; 12:588954. [PMID: 33192443 PMCID: PMC7644880 DOI: 10.3389/fnsyn.2020.588954] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 09/18/2020] [Indexed: 12/16/2022] Open
Abstract
Creatine provides cells with high-energy phosphates for the rapid reconstitution of hydrolyzed adenosine triphosphate. The eponymous creatine transporter (CRT1/SLC6A8) belongs to a family of solute carrier 6 (SLC6) proteins. The key role of CRT1 is to translocate creatine across tissue barriers and into target cells, such as neurons and myocytes. Individuals harboring mutations in the coding sequence of the human CRT1 gene develop creatine transporter deficiency (CTD), one of the pivotal underlying causes of cerebral creatine deficiency syndrome. CTD encompasses an array of clinical manifestations, including severe intellectual disability, epilepsy, autism, development delay, and motor dysfunction. CTD is characterized by the absence of cerebral creatine, which implies an indispensable role for CRT1 in supplying the brain cells with creatine. CTD-associated variants dramatically reduce or abolish creatine transport activity by CRT1. Many of these are point mutations that are known to trigger folding defects, leading to the retention of encoded CRT1 proteins in the endoplasmic reticulum and precluding their delivery to the cell surface. Misfolding of several related SLC6 transporters also gives rise to detrimental pathologic conditions in people; e.g., mutations in the dopamine transporter induce infantile parkinsonism/dystonia, while mutations in the GABA transporter 1 cause treatment-resistant epilepsy. In some cases, folding defects are amenable to rescue by small molecules, known as pharmacological and chemical chaperones, which restore the cell surface expression and transport activity of the previously non-functional proteins. Insights from the recent molecular, animal and human case studies of CTD add toward our understanding of this complex disorder and reveal the wide-ranging effects elicited upon CRT1 dysfunction. This grants novel therapeutic prospects for the treatment of patients afflicted with CTD, e.g., modifying the creatine molecule to facilitate CRT1-independent entry into brain cells, or correcting folding-deficient and loss-of-function CTD variants using pharmacochaperones and/or allosteric modulators. The latter justifies a search for additional compounds with a capacity to correct mutation-specific defects.
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Affiliation(s)
| | | | | | - Sonja Sucic
- Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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7
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Rostami P, Hosseinpour S, Ashrafi MR, Alizadeh H, Garshasbi M, Tavasoli AR. Primary creatine deficiency syndrome as a potential missed diagnosis in children with psychomotor delay and seizure: case presentation with two novel variants and literature review. Acta Neurol Belg 2020; 120:511-516. [PMID: 31222513 DOI: 10.1007/s13760-019-01168-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Accepted: 06/06/2019] [Indexed: 11/24/2022]
Abstract
Creatine is the main source of energy for the brain. Primary creatine deficiency syndromes (PCDSs) are inborn error of metabolism of creatine synthesis. Symptoms of central nervous system involvement are the most common clinical manifestations in these disorders. We reviewed medical records of all genetically confirmed patients diagnosed by whole exome sequencing who were referred to Myelin and Neurodegenerative Disorders Clinic, Children's Medical Center, Tehran, Iran, from May 2016 to Dec 2018. A literature review was conducted on clinical and genomic variability of PCDS to compare our patients with previously reported cases. We report two patients with creatine deficiency among a cohort of 550 registered cases out of which 200 patients had a genetically confirmed neurodegenerative disorder diagnosis. The main complain in the first patient with creatine transporter (CRTR) deficiency was seizure and genetic study in this patient identified a novel hemizygote variant of "c.92 > T; p.Pro31Leu" in the first exon of SLC6A8 gene. The second patient with guanidinoacetate methyltransferase (GAMT) deficiency had an unknown motor and speech delay as the striking manifestation and molecular assay revealed a novel homozygote variant of "c.134G > A; p.Trp45*" in the first exon of GAMT gene. PCDSs usually are associated with nonspecific neurologic symptoms. The first presented case had a mean delayed diagnosis of 5 years. Therefore, in children with unexplained neurologic features including developmental delay and/or regression, mental disability and repeated seizures without any significant findings in metabolic studies, PCDSs can be considered as a differential diagnosis and molecular analysis can be helpful for the precise diagnosis and treatment.
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Affiliation(s)
- Parastoo Rostami
- Division of Pediatric Endocrinology and Metabolism, Growth and Development Research Center, Children's Medical Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Sareh Hosseinpour
- Myelin Disorders Clinic (Iranian Neurometabolic Registry), Pediatric Neurology Division, Children's Medical Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Mahmoud Reza Ashrafi
- Myelin Disorders Clinic (Iranian Neurometabolic Registry), Pediatric Neurology Division, Children's Medical Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Houman Alizadeh
- Division of Pediatric Radiology, Department of Pediatrics, Children's Medical Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Masoud Garshasbi
- Department of Medical Genetics, Faculty of Medical Sciences, Tarbiat Modares University, Teheran, Iran.
| | - Ali Reza Tavasoli
- Myelin Disorders Clinic (Iranian Neurometabolic Registry), Pediatric Neurology Division, Children's Medical Center, Tehran University of Medical Sciences, Tehran, Iran.
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8
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Rescue by 4-phenylbutyrate of several misfolded creatine transporter-1 variants linked to the creatine transporter deficiency syndrome. Neuropharmacology 2019; 161:107572. [PMID: 30885608 DOI: 10.1016/j.neuropharm.2019.03.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 03/07/2019] [Accepted: 03/11/2019] [Indexed: 12/15/2022]
Abstract
Diseases arising from misfolding of SLC6 transporters have been reported over recent years, e.g. folding-deficient mutants of the dopamine transporter and of the glycine transporter-2 cause infantile/juvenile Parkinsonism dystonia and hyperekplexia, respectively. Mutations in the coding sequence of the human creatine transporter-1 (hCRT-1/SLC6A8) gene result in a creatine transporter deficiency syndrome, which varies in its clinical manifestation from epilepsy, mental retardation, autism, development delay and motor dysfunction to gastrointestinal symptoms. Some of the mutations in hCRT-1 occur at residues, which are highly conserved across the SLC6 family. Here, we examined 16 clinically relevant hCRT-1 variants to verify the conjecture that they were misfolded and that this folding defect was amenable to correction. Confocal microscopy imaging revealed that the heterologously expressed YFP-tagged mutant CRTs were trapped in the endoplasmic reticulum (ER), co-localised with the ER-resident chaperone calnexin. In contrast, the wild type hCRT-1 reached the plasma membrane. Preincubation of transiently transfected HEK293 cells with the chemical chaperone 4-phenylbutyrate (4-PBA) restored ER export and surface expression of as well as substrate uptake by several folding-deficient CRT-1 mutants. A representative mutant (hCRT-1-P544L) was expressed in rat primary hippocampal neurons to verify pharmacochaperoning in a target cell: 4-PBA promoted the delivery of hCRT-1-P544L to the neurite extensions. These observations show that several folding-deficient hCRT-1 mutants can be rescued. This proof-of-principle justifies the search for additional pharmacochaperones to restore folding of 4PBA-unresponsive hCRT-1 mutants. Finally, 4-PBA is an approved drug in paediatric use: this provides a rationale for translating the current insights into clinical trials. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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9
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Joncquel-Chevalier Curt M, Bout MA, Fontaine M, Kim I, Huet G, Bekri S, Morin G, Moortgat S, Moerman A, Cuisset JM, Cheillan D, Vamecq J. Functional assessment of creatine transporter in control and X-linked SLC6A8-deficient fibroblasts. Mol Genet Metab 2018; 123:463-471. [PMID: 29478817 DOI: 10.1016/j.ymgme.2018.02.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Revised: 02/15/2018] [Accepted: 02/15/2018] [Indexed: 01/01/2023]
Abstract
Creatine transporter is currently the focus of renewed interest with emerging roles in brain neurotransmission and physiology, and the bioenergetics of cancer metastases. We here report on amendments of a standard creatine uptake assay which might help clinical chemistry laboratories to extend their current range of measurements of creatine and metabolites in body fluids to functional enzyme explorations. In this respect, short incubation times and the use of a stable-isotope-labeled substrate (D3-creatine) preceded by a creatine wash-out step from cultured fibroblast cells by removal of fetal bovine serum (rich in creatine) from the incubation medium are recommended. Together, these measures decreased, by a first order of magnitude, creatine concentrations in the incubation medium at the start of creatine-uptake studies and allowed to functionally discriminate between 4 hemizygous male and 4 heterozygous female patients with X-linked SLC6A8 deficiency, and between this cohort of eight patients and controls. The functional assay corroborated genetic diagnosis of SLC6A8 deficiency. Gene anomalies in our small cohort included splicing site (c.912G > A [p.Ile260_Gln304del], c.778-2A > G and c.1495 + 2 T > G), substitution (c.407C > T) [p.Ala136Val] and deletion (c.635_636delAG [p.Glu212Valfs*84] and c.1324delC [p.Gln442Lysfs*21]) variants with reduced creatine transporter function validating their pathogenicity, including that of a previously unreported c.1324delC variant. The present assay adaptations provide an easy, reliable and discriminative manner for exploring creatine transporter activity and disease variations. It might apply to drug testing or other evaluations in the genetic and metabolic horizons covered by the emerging functions of creatine and its transporter, in a way, however, requiring and completed by additional studies on female patients and blood-brain barrier permeability properties of selected compounds. As a whole, the proposed assay of creatine transporter positively adds to currently existing measurements of this transporter activity, and determining on a large scale the extent of its exact suitability to detect female patients should condition in the future its transfer in clinical practice.
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MESH Headings
- Adolescent
- Brain Diseases, Metabolic, Inborn/genetics
- Brain Diseases, Metabolic, Inborn/metabolism
- Brain Diseases, Metabolic, Inborn/pathology
- Case-Control Studies
- Child
- Child, Preschool
- Cohort Studies
- Creatine/deficiency
- Creatine/genetics
- Creatine/metabolism
- Female
- Fibroblasts/metabolism
- Fibroblasts/pathology
- Follow-Up Studies
- Humans
- Infant
- Male
- Mental Retardation, X-Linked/genetics
- Mental Retardation, X-Linked/metabolism
- Mental Retardation, X-Linked/pathology
- Mutation
- Nerve Tissue Proteins/deficiency
- Nerve Tissue Proteins/genetics
- Plasma Membrane Neurotransmitter Transport Proteins/deficiency
- Plasma Membrane Neurotransmitter Transport Proteins/genetics
- Plasma Membrane Neurotransmitter Transport Proteins/metabolism
- Prognosis
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Affiliation(s)
- Marie Joncquel-Chevalier Curt
- Department of Biochemistry and Molecular Biology, Laboratory of Hormonology, Metabolism-Nutrition & Oncology (HMNO), Center of Biology and Pathology (CBP) Pierre-Marie Degand, CHRU, Lille, France
| | - Marie-Adélaïde Bout
- Department of Biochemistry and Molecular Biology, Laboratory of Hormonology, Metabolism-Nutrition & Oncology (HMNO), Center of Biology and Pathology (CBP) Pierre-Marie Degand, CHRU, Lille, France
| | - Monique Fontaine
- Department of Biochemistry and Molecular Biology, Laboratory of Hormonology, Metabolism-Nutrition & Oncology (HMNO), Center of Biology and Pathology (CBP) Pierre-Marie Degand, CHRU, Lille, France
| | - Isabelle Kim
- Department of Biochemistry and Molecular Biology, Laboratory of Hormonology, Metabolism-Nutrition & Oncology (HMNO), Center of Biology and Pathology (CBP) Pierre-Marie Degand, CHRU, Lille, France
| | - Guillemette Huet
- Cell Culture Department, Center of Biology-Pathology, CHRU Lille, F-59000 Lille, France
| | - Soumeya Bekri
- Inserm U1245, UNIROUEN, Normandie Univ, Normandy Centre for Genomic and Personalized Medicine, France.Department of Metabolic Biochemistry, Rouen University Hospital, Rouen, France
| | - Gilles Morin
- EA 4666, Département de génétique, Université de Picardie-Jules-Verne, CHU d'Amiens, 80054 Amiens, France
| | - Stéphanie Moortgat
- Centre de Génétique Humaine, Institut de Pathologie et de Génétique, Charleroi, Gosselies, Belgium
| | - Alexandre Moerman
- Service de Génétique Clinique Guy Fontaine, Hôpital Jeanne de Flandre, CHRU Lille, 59037 Lille, France
| | - Jean-Marie Cuisset
- Service de Neurologie Infantile, Hôpital Roger Salengro, CHRU Lille, 59037 Lille, France
| | - David Cheillan
- Hospices Civils de Lyon, Service de Biochimie et Biologie Moléculaire Grand Est, Centre de Biologie et de Pathologie Est, 69677 Bron, France and Université de Lyon, INSERM U1060, CarMen; Medical Reference Center for Inherited Metabolic Diseases, Jeanne de Flandre Hospital, CHRU Lille, France
| | - Joseph Vamecq
- Department of Biochemistry and Molecular Biology, Laboratory of Hormonology, Metabolism-Nutrition & Oncology (HMNO), Center of Biology and Pathology (CBP) Pierre-Marie Degand, CHRU, Lille, France; Inserm, Lille, France; Université de Lyon, INSERM U1060 CarMeN, Lyon, France.; Univ. Lille, RADEME - Maladies RAres du Développement et du Métabolisme : du phénotype au génotype et à la Fonction, Lille, EA 7364, France.
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10
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Asjad HMM, Nasrollahi-Shirazi S, Sucic S, Freissmuth M, Nanoff C. Relax, Cool Down and Scaffold: How to Restore Surface Expression of Folding-Deficient Mutant GPCRs and SLC6 Transporters. Int J Mol Sci 2017; 18:ijms18112416. [PMID: 29135937 PMCID: PMC5713384 DOI: 10.3390/ijms18112416] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2017] [Revised: 11/11/2017] [Accepted: 11/12/2017] [Indexed: 01/01/2023] Open
Abstract
Many diseases arise from mutations, which impair protein folding. The study of folding-deficient variants of G protein-coupled receptors and solute carrier 6 (SLC6) transporters has shed light on the folding trajectory, how it is monitored and how misfolding can be remedied. Reducing the temperature lowers the energy barrier between folding intermediates and thereby eliminates stalling along the folding trajectory. For obvious reasons, cooling down is not a therapeutic option. One approach to rescue misfolded variants is to use membrane-permeable orthosteric ligands. Antagonists of GPCRs are—in many instances—effective pharmacochaperones: they restore cell surface expression provided that they enter cells and bind to folding intermediates. Pharmacochaperoning of SLC6 transporters is less readily achieved because the ionic conditions in the endoplasmic reticulum (ER) are not conducive to binding of typical inhibitors. The second approach is to target the heat-shock protein (HSP) relay, which monitors the folding trajectory on the cytosolic side. Importantly, orthosteric ligands and HSP-inhibitors are not mutually exclusive. In fact, pharmacochaperones and HSP-inhibitors can act in an additive or synergistic manner. This was exemplified by rescuing disease-causing, folding-deficient variants of the human dopamine transporters with the HSP70 inhibitor pifithrin-μ and the pharmacochaperone noribogaine in Drosophila melanogaster.
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Affiliation(s)
- H M Mazhar Asjad
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria.
| | - Shahrooz Nasrollahi-Shirazi
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria.
| | - Sonja Sucic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria.
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria.
| | - Christian Nanoff
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria.
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11
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Neuroimaging of Pediatric Metabolic Disorders with Emphasis on Diffusion-Weighted Imaging and MR Spectroscopy: A Pictorial Essay. CURRENT RADIOLOGY REPORTS 2017. [DOI: 10.1007/s40134-017-0251-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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12
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Zhu DS, Yu L, Li M, Han L, Huang XX, Wang XQ, Yang XL, Zhu Y, Zhou XJ, Guan YT. High serum creatinine is associated with reduction of vision impaired in patients with NMOSD. J Neuroimmunol 2017; 310:32-37. [PMID: 28778442 DOI: 10.1016/j.jneuroim.2017.06.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 05/25/2017] [Accepted: 06/12/2017] [Indexed: 12/13/2022]
Abstract
Serum creatinine (SCR) has been found to be neuroprotective in neurodegenerative disease. However, whether SCR is a protective factor for vision impaired in neuromyelitis optica spectrum disorder (NMOSD) is unclear. This study to determine the relationship between SCR level and vision impaired in NMOSD patients through multivariate-adjusted linear regression analyses. Our result showed that high level of SCR was associated with a low occurrence of vision impaired, and the association was independent after adjustment for confounding risk factors and hierarchical analysis. Therefore, these results demonstrated that higher SCR level is a protective factor of vision impaired in male NMOSD patients.
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Affiliation(s)
- De-Sheng Zhu
- Department of Neurology, Renji Hospital, School of medicine, Shanghai Jiaotong University, Shanghai 200127, China
| | - Lu Yu
- Department of Neurology, Changhai Hospital, Second Military Medical University, Shanghai 200366, China
| | - Mei Li
- Department of Neurology, Changhai Hospital, Second Military Medical University, Shanghai 200366, China
| | - Lu Han
- Department of Neurology, Changhai Hospital, Second Military Medical University, Shanghai 200366, China
| | - Xin-Xin Huang
- Department of Neurology, Changhai Hospital, Second Military Medical University, Shanghai 200366, China
| | - Xiao-Qing Wang
- Department of Neurology, Changhai Hospital, Second Military Medical University, Shanghai 200366, China
| | - Xiao-Li Yang
- Department of Neurology, The Fifth People's Hospital of Shanghai, Fudan University, Shanghai 200011, China
| | - Ying Zhu
- Department of Neurology, Renji Hospital, School of medicine, Shanghai Jiaotong University, Shanghai 200127, China
| | - Xia-Jun Zhou
- Department of Neurology, Renji Hospital, School of medicine, Shanghai Jiaotong University, Shanghai 200127, China
| | - Yang-Tai Guan
- Department of Neurology, Renji Hospital, School of medicine, Shanghai Jiaotong University, Shanghai 200127, China.
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13
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Freissmuth M, Stockner T, Sucic S. SLC6 Transporter Folding Diseases and Pharmacochaperoning. Handb Exp Pharmacol 2017; 245:249-270. [PMID: 29086036 DOI: 10.1007/164_2017_71] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The human genome encodes 19 genes of the solute carrier 6 (SLC6) family; non-synonymous changes in the coding sequence give rise to mutated transporters, which are misfolded and thus cause diseases in the affected individuals. Prominent examples include mutations in the transporters for dopamine (DAT, SLC6A3), for creatine (CT1, SLC6A8), and for glycine (GlyT2, SLC6A5), which result in infantile dystonia, mental retardation, and hyperekplexia, respectively. Thus, there is an obvious unmet medical need to identify compounds, which can remedy the folding deficit. The pharmacological correction of folding defects was originally explored in mutants of the serotonin transporter (SERT, SLC6A4), which were created to study the COPII-dependent export from the endoplasmic reticulum. This led to the serendipitous discovery of the pharmacochaperoning action of ibogaine. Ibogaine and its metabolite noribogaine also rescue several disease-relevant mutants of DAT. Because the pharmacology of DAT and SERT is exceptionally rich, it is not surprising that additional compounds have been identified, which rescue folding-deficient mutants. These compounds are not only of interest for restoring DAT function in the affected children. They are also likely to serve as useful tools to interrogate the folding trajectory of the transporter. This is likely to initiate a virtuous cycle: if the principles underlying folding of SLC6 transporters are understood, the design of pharmacochaperones ought to be facilitated.
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Affiliation(s)
- Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria.
| | - Thomas Stockner
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Sonja Sucic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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