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Pochini L, Galluccio M, Console L, Scalise M, Eberini I, Indiveri C. Inflammation and Organic Cation Transporters Novel (OCTNs). Biomolecules 2024; 14:392. [PMID: 38672410 PMCID: PMC11048549 DOI: 10.3390/biom14040392] [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: 02/15/2024] [Revised: 03/20/2024] [Accepted: 03/21/2024] [Indexed: 04/28/2024] Open
Abstract
Inflammation is a physiological condition characterized by a complex interplay between different cells handled by metabolites and specific inflammatory-related molecules. In some pathological situations, inflammation persists underlying and worsening the pathological state. Over the years, two membrane transporters namely OCTN1 (SLC22A4) and OCTN2 (SLC22A5) have been shown to play specific roles in inflammation. These transporters form the OCTN subfamily within the larger SLC22 family. The link between these proteins and inflammation has been proposed based on their link to some chronic inflammatory diseases such as asthma, Crohn's disease (CD), and rheumatoid arthritis (RA). Moreover, the two transporters show the ability to mediate the transport of several compounds including carnitine, carnitine derivatives, acetylcholine, ergothioneine, and gut microbiota by-products, which have been specifically associated with inflammation for their anti- or proinflammatory action. Therefore, the absorption and distribution of these molecules rely on the presence of OCTN1 and OCTN2, whose expression is modulated by inflammatory cytokines and transcription factors typically activated by inflammation. In the present review, we wish to provide a state of the art on OCTN1 and OCTN2 transport function and regulation in relationships with inflammation and inflammatory diseases focusing on the metabolic signature collected in different body districts and gene polymorphisms related to inflammatory diseases.
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Affiliation(s)
- Lorena Pochini
- Laboratory of Biochemistry, Molecular Biotechnology and Molecular Biology, Department DiBEST (Biologia, Ecologia, Scienze della Terra), University of Calabria, Via Bucci 4C, 6C, 87036 Arcavacata di Rende, Italy; (M.G.); (L.C.); (M.S.)
- Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM), National Research Council (CNR), Via Amendola 122/O, 70126 Bari, Italy
| | - Michele Galluccio
- Laboratory of Biochemistry, Molecular Biotechnology and Molecular Biology, Department DiBEST (Biologia, Ecologia, Scienze della Terra), University of Calabria, Via Bucci 4C, 6C, 87036 Arcavacata di Rende, Italy; (M.G.); (L.C.); (M.S.)
| | - Lara Console
- Laboratory of Biochemistry, Molecular Biotechnology and Molecular Biology, Department DiBEST (Biologia, Ecologia, Scienze della Terra), University of Calabria, Via Bucci 4C, 6C, 87036 Arcavacata di Rende, Italy; (M.G.); (L.C.); (M.S.)
| | - Mariafrancesca Scalise
- Laboratory of Biochemistry, Molecular Biotechnology and Molecular Biology, Department DiBEST (Biologia, Ecologia, Scienze della Terra), University of Calabria, Via Bucci 4C, 6C, 87036 Arcavacata di Rende, Italy; (M.G.); (L.C.); (M.S.)
| | - Ivano Eberini
- Department of Pharmacological and Biomolecular Sciences, Università degli Studi di Milano, 20133 Milan, Italy;
| | - Cesare Indiveri
- Laboratory of Biochemistry, Molecular Biotechnology and Molecular Biology, Department DiBEST (Biologia, Ecologia, Scienze della Terra), University of Calabria, Via Bucci 4C, 6C, 87036 Arcavacata di Rende, Italy; (M.G.); (L.C.); (M.S.)
- Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM), National Research Council (CNR), Via Amendola 122/O, 70126 Bari, Italy
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Crefcoeur L, Ferdinandusse S, van der Crabben SN, Dekkers E, Fuchs SA, Huidekoper H, Janssen M, Langendonk J, Maase R, de Sain M, Rubio E, van Spronsen FJ, Vaz FM, Verschoof R, de Vries M, Wijburg F, Visser G, Langeveld M. Newborn screening for primary carnitine deficiency: who will benefit? - a retrospective cohort study. J Med Genet 2023; 60:1177-1185. [PMID: 37487700 DOI: 10.1136/jmg-2023-109206] [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: 02/26/2023] [Accepted: 06/17/2023] [Indexed: 07/26/2023]
Abstract
BACKGROUND Newborn screening (NBS) programmes identify a wide range of disease phenotypes, which raises the question whether early identification and treatment is beneficial for all. This study aims to answer this question for primary carnitine deficiency (PCD) taking into account that NBS for PCD identifies newborns with PCD and also until then undiagnosed mothers. METHODS We investigated clinical, genetic (variants in SLC22A5 gene) and functional (carnitine transport activity in fibroblasts) characteristics of all referred individuals through NBS (newborns and mothers) and clinically diagnosed patients with PCD (not through NBS). Disease phenotype in newborns was predicted using data from PCD mothers and cases published in literature with identical SLC22A5 variants. RESULTS PCD was confirmed in 19/131 referred newborns, 37/82 referred mothers and 5 clinically diagnosed patients. Severe symptoms were observed in all clinically diagnosed patients, 1 newborn and none of the mothers identified by NBS. PCD was classified as severe in all 5 clinically diagnosed patients, 3/19 newborns and 1/37 mothers; as benign in 8/19 newborns and 36/37 mothers and as unknown in 8/19 newborns. Carnitine transport activity completely separated severe phenotype from benign phenotype (median (range): 4.0% (3.5-5.0)] vs 26% (9.5-42.5), respectively). CONCLUSION The majority of mothers and a significant proportion of newborns with PCD identified through NBS are likely to remain asymptomatic without early treatment. Conversely, a small proportion of newborns with predicted severe PCD could greatly benefit from early treatment. Genetic variants and carnitine transport activity can be used to distinguish between these groups.
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Affiliation(s)
- Loek Crefcoeur
- Metabolic Diseases, Wilhelmina Children's Hospital, University Medical Centre, Utrecht, The Netherlands
- Department of Pediatrics, Division of Metabolic Disorders, Amsterdam UMC Locatie AMC, Amsterdam, The Netherlands
- Clinical Chemistry, Laboratory Genetic Metabolic Diseases, Amsterdam UMC Locatie Meibergdreef, Amsterdam, The Netherlands
| | - Sacha Ferdinandusse
- Department of Pediatrics, Division of Metabolic Disorders, Amsterdam UMC Locatie AMC, Amsterdam, The Netherlands
- Clinical Chemistry, Laboratory Genetic Metabolic Diseases, Amsterdam UMC Locatie Meibergdreef, Amsterdam, The Netherlands
| | - Saskia N van der Crabben
- Human Genetics, Amsterdam UMC Locatie Meibergdreef, Amsterdam, The Netherlands
- United for Metabolic Diseases, Amsterdam, The Netherlands
| | - Eugènie Dekkers
- Centre for Population Screening, RIVM, Bilthoven, The Netherlands
| | - Sabine A Fuchs
- Metabolic Diseases, Wilhelmina Children's Hospital, University Medical Centre, Utrecht, The Netherlands
| | - Hidde Huidekoper
- Department of Pediatrics, Center for Lysosomal and Metabolic Diseases, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Mirian Janssen
- Department of Internal Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Janneke Langendonk
- Department of Internal Medicine, Center for Lysosomal and Metabolic Diseases, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Rose Maase
- Department of Biologicals, Screening and Innovation, RIVM, Bilthoven, The Netherlands
| | - Monique de Sain
- Section Metabolic Diagnostics, Department of Genetics, Wilhelmina Children's Hospital, University Medical Centre, Utrecht, The Netherlands
| | - Estela Rubio
- Department of Pediatrics/Laboratory of Clinical Genetics, Maastricht UMC+, Maastricht, The Netherlands
| | - Francjan J van Spronsen
- Section of Metabolic Diseases, University Medical Centre Groningen, Beatrix Children's Hospital, Groningen, The Netherlands
| | - Frédéric Maxime Vaz
- Laboratory Genetic Metabolic Diseases, Amsterdam UMC, University of Amsterdam, Departments of Clinical Chemistry and Pediatrics, Core Facility Metabolomics, Emma Children's Hospital, Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam UMC Locatie Meibergdreef, Amsterdam, The Netherlands
| | - Rendelien Verschoof
- Department for Vaccine Supply and Prevention Programs, RIVM, Bilthoven, The Netherlands
| | - Maaike de Vries
- Department of Pediatrics, Amalia Children's Hospital, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Frits Wijburg
- Department of Pediatrics, Division of Metabolic Disorders, Amsterdam UMC Locatie AMC, Amsterdam, The Netherlands
| | - Gepke Visser
- Metabolic Diseases, Wilhelmina Children's Hospital, University Medical Centre, Utrecht, The Netherlands
- Department of Pediatrics, Division of Metabolic Disorders, Amsterdam UMC Locatie AMC, Amsterdam, The Netherlands
| | - Mirjam Langeveld
- Department of Endocrinology and Metabolism, Amsterdam UMC Locatie Meibergdreef, Amsterdam, The Netherlands
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Loss-of-function BK channel mutation causes impaired mitochondria and progressive cerebellar ataxia. Proc Natl Acad Sci U S A 2020; 117:6023-6034. [PMID: 32132200 DOI: 10.1073/pnas.1920008117] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Despite a growing number of ion channel genes implicated in hereditary ataxia, it remains unclear how ion channel mutations lead to loss-of-function or death of cerebellar neurons. Mutations in the gene KCNMA1, encoding the α-subunit of the BK channel have emerged as responsible for a variety of neurological phenotypes. We describe a mutation (BKG354S) in KCNMA1, in a child with congenital and progressive cerebellar ataxia with cognitive impairment. The mutation in the BK channel selectivity filter dramatically reduced single-channel conductance and ion selectivity. The BKG354S channel trafficked normally to plasma, nuclear, and mitochondrial membranes, but caused reduced neurite outgrowth, cell viability, and mitochondrial content. Small interfering RNA (siRNA) knockdown of endogenous BK channels had similar effects. The BK activator, NS1619, rescued BKG354S cells but not siRNA-treated cells, by selectively blocking the mutant channels. When expressed in cerebellum via adenoassociated virus (AAV) viral transfection in mice, the mutant BKG354S channel, but not the BKWT channel, caused progressive impairment of several gait parameters consistent with cerebellar dysfunction from 40- to 80-d-old mice. Finally, treatment of the patient with chlorzoxazone, a BK/SK channel activator, partially improved motor function, but ataxia continued to progress. These studies indicate that a loss-of-function BK channel mutation causes ataxia and acts by reducing mitochondrial and subsequently cellular viability.
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Knottnerus SJG, Bleeker JC, Wüst RCI, Ferdinandusse S, IJlst L, Wijburg FA, Wanders RJA, Visser G, Houtkooper RH. Disorders of mitochondrial long-chain fatty acid oxidation and the carnitine shuttle. Rev Endocr Metab Disord 2018; 19:93-106. [PMID: 29926323 PMCID: PMC6208583 DOI: 10.1007/s11154-018-9448-1] [Citation(s) in RCA: 178] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Mitochondrial fatty acid oxidation is an essential pathway for energy production, especially during prolonged fasting and sub-maximal exercise. Long-chain fatty acids are the most abundant fatty acids in the human diet and in body stores, and more than 15 enzymes are involved in long-chain fatty acid oxidation. Pathogenic mutations in genes encoding these enzymes result in a long-chain fatty acid oxidation disorder in which the energy homeostasis is compromised and long-chain acylcarnitines accumulate. Symptoms arise or exacerbate during catabolic situations, such as fasting, illness and (endurance) exercise. The clinical spectrum is very heterogeneous, ranging from hypoketotic hypoglycemia, liver dysfunction, rhabdomyolysis, cardiomyopathy and early demise. With the introduction of several of the long-chain fatty acid oxidation disorders (lcFAOD) in newborn screening panels, also asymptomatic individuals with a lcFAOD are identified. However, despite early diagnosis and dietary therapy, a significant number of patients still develop symptoms emphasizing the need for individualized treatment strategies. This review aims to function as a comprehensive reference for clinical and laboratory findings for clinicians who are confronted with pediatric and adult patients with a possible diagnosis of a lcFAOD.
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Affiliation(s)
- Suzan J G Knottnerus
- Dutch Fatty Acid Oxidation Expertise Center, Department of Metabolic Diseases, Wilhelmina Children's Hospital, University Medical Center Utrecht, Lundlaan 6, 3584, EA, Utrecht, The Netherlands
- Dutch Fatty Acid Oxidation Expertise Center, Laboratory Genetic Metabolic Diseases, Departments of Clinical Chemistry and Pediatrics, Emma Children's Hospital, Academic Medical Center, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands
| | - Jeannette C Bleeker
- Dutch Fatty Acid Oxidation Expertise Center, Department of Metabolic Diseases, Wilhelmina Children's Hospital, University Medical Center Utrecht, Lundlaan 6, 3584, EA, Utrecht, The Netherlands
- Dutch Fatty Acid Oxidation Expertise Center, Laboratory Genetic Metabolic Diseases, Departments of Clinical Chemistry and Pediatrics, Emma Children's Hospital, Academic Medical Center, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands
| | - Rob C I Wüst
- Dutch Fatty Acid Oxidation Expertise Center, Laboratory Genetic Metabolic Diseases, Departments of Clinical Chemistry and Pediatrics, Emma Children's Hospital, Academic Medical Center, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands
| | - Sacha Ferdinandusse
- Dutch Fatty Acid Oxidation Expertise Center, Laboratory Genetic Metabolic Diseases, Departments of Clinical Chemistry and Pediatrics, Emma Children's Hospital, Academic Medical Center, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands
| | - Lodewijk IJlst
- Dutch Fatty Acid Oxidation Expertise Center, Laboratory Genetic Metabolic Diseases, Departments of Clinical Chemistry and Pediatrics, Emma Children's Hospital, Academic Medical Center, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands
| | - Frits A Wijburg
- Dutch Fatty Acid Oxidation Expertise Center, Laboratory Genetic Metabolic Diseases, Departments of Clinical Chemistry and Pediatrics, Emma Children's Hospital, Academic Medical Center, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands
| | - Ronald J A Wanders
- Dutch Fatty Acid Oxidation Expertise Center, Laboratory Genetic Metabolic Diseases, Departments of Clinical Chemistry and Pediatrics, Emma Children's Hospital, Academic Medical Center, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands
| | - Gepke Visser
- Dutch Fatty Acid Oxidation Expertise Center, Department of Metabolic Diseases, Wilhelmina Children's Hospital, University Medical Center Utrecht, Lundlaan 6, 3584, EA, Utrecht, The Netherlands.
- Dutch Fatty Acid Oxidation Expertise Center, Laboratory Genetic Metabolic Diseases, Departments of Clinical Chemistry and Pediatrics, Emma Children's Hospital, Academic Medical Center, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands.
| | - Riekelt H Houtkooper
- Dutch Fatty Acid Oxidation Expertise Center, Laboratory Genetic Metabolic Diseases, Departments of Clinical Chemistry and Pediatrics, Emma Children's Hospital, Academic Medical Center, Meibergdreef 9, 1105, AZ, Amsterdam, The Netherlands.
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Frigeni M, Balakrishnan B, Yin X, Calderon FRO, Mao R, Pasquali M, Longo N. Functional and molecular studies in primary carnitine deficiency. Hum Mutat 2017; 38:1684-1699. [PMID: 28841266 DOI: 10.1002/humu.23315] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 08/13/2017] [Accepted: 08/17/2017] [Indexed: 12/30/2022]
Abstract
Primary carnitine deficiency is caused by a defect in the OCTN2 carnitine transporter encoded by the SLC22A5 gene. It can cause hypoketotic hypoglycemia or cardiomyopathy in children, and sudden death in children and adults. Fibroblasts from affected patients have reduced carnitine transport. We evaluated carnitine transport in fibroblasts from 358 subjects referred for possible carnitine deficiency. Carnitine transport was reduced to 20% or less of normal in fibroblasts of 140 out of 358 subjects. Sequencing of the 10 exons and flanking regions of the SLC22A5 gene in 95 out of 140 subjects identified causative variants in 84% of the alleles. The missense variants identified in our patients and others previously reported (n = 92) were expressed in CHO cells. Carnitine transport was impaired by 73 out of 92 variants expressed. Prediction algorithms (Polyphen-2, SIFT) correctly predicted the functional effects of expressed variants in about 80% of cases. These results indicate that mutations in the coding region of the SLC22A5 gene cannot be identified in about 16% of the alleles causing primary carnitine deficiency. Prediction algorithms failed to determine the functional effects of amino acid substitutions in this transmembrane protein in about 20% of cases. Therefore, functional studies in fibroblasts remain the best strategy to confirm or exclude a diagnosis of primary carnitine deficiency.
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Affiliation(s)
- Marta Frigeni
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, Utah
| | - Bijina Balakrishnan
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, Utah
| | - Xue Yin
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, Utah
| | - Fernanda R O Calderon
- ARUP Institute for Clinical and Experimental Pathology®, ARUP Laboratories, Salt Lake City, Utah.,Department of Pathology, University of Utah, Salt Lake City, Utah
| | - Rong Mao
- ARUP Institute for Clinical and Experimental Pathology®, ARUP Laboratories, Salt Lake City, Utah.,Department of Pathology, University of Utah, Salt Lake City, Utah
| | - Marzia Pasquali
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, Utah.,ARUP Institute for Clinical and Experimental Pathology®, ARUP Laboratories, Salt Lake City, Utah.,Department of Pathology, University of Utah, Salt Lake City, Utah
| | - Nicola Longo
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, Utah.,ARUP Institute for Clinical and Experimental Pathology®, ARUP Laboratories, Salt Lake City, Utah.,Department of Pathology, University of Utah, Salt Lake City, Utah
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6
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Longo N, Frigeni M, Pasquali M. Carnitine transport and fatty acid oxidation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2422-35. [PMID: 26828774 DOI: 10.1016/j.bbamcr.2016.01.023] [Citation(s) in RCA: 454] [Impact Index Per Article: 56.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 01/27/2016] [Accepted: 01/28/2016] [Indexed: 12/14/2022]
Abstract
Carnitine is essential for the transfer of long-chain fatty acids across the inner mitochondrial membrane for subsequent β-oxidation. It can be synthesized by the body or assumed with the diet from meat and dairy products. Defects in carnitine biosynthesis do not routinely result in low plasma carnitine levels. Carnitine is accumulated by the cells and retained by kidneys using OCTN2, a high affinity organic cation transporter specific for carnitine. Defects in the OCTN2 carnitine transporter results in autosomal recessive primary carnitine deficiency characterized by decreased intracellular carnitine accumulation, increased losses of carnitine in the urine, and low serum carnitine levels. Patients can present early in life with hypoketotic hypoglycemia and hepatic encephalopathy, or later in life with skeletal and cardiac myopathy or sudden death from cardiac arrhythmia, usually triggered by fasting or catabolic state. This disease responds to oral carnitine that, in pharmacological doses, enters cells using the amino acid transporter B(0,+). Primary carnitine deficiency can be suspected from the clinical presentation or identified by low levels of free carnitine (C0) in the newborn screening. Some adult patients have been diagnosed following the birth of an unaffected child with very low carnitine levels in the newborn screening. The diagnosis is confirmed by measuring low carnitine uptake in the patients' fibroblasts or by DNA sequencing of the SLC22A5 gene encoding the OCTN2 carnitine transporter. Some mutations are specific for certain ethnic backgrounds, but the majority are private and identified only in individual families. Although the genotype usually does not correlate with metabolic or cardiac involvement in primary carnitine deficiency, patients presenting as adults tend to have at least one missense mutation retaining residual activity. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.
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Affiliation(s)
- Nicola Longo
- Division of Medical Genetics, Department of Pediatrics, University of Utah, Salt Lake City, UT, USA; Department of Pathology, University of Utah, and ARUP Laboratories, 500 Chipeta Way, Salt Lake City, UT, USA.
| | - Marta Frigeni
- Division of Medical Genetics, Department of Pediatrics, University of Utah, Salt Lake City, UT, USA
| | - Marzia Pasquali
- Department of Pathology, University of Utah, and ARUP Laboratories, 500 Chipeta Way, Salt Lake City, UT, USA
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Toh DSL, Cheung FSG, Murray M, Pern TK, Lee EJD, Zhou F. Functional Analysis of Novel Variants in the Organic Cation/Ergothioneine Transporter 1 Identified in Singapore Populations. Mol Pharm 2013; 10:2509-16. [DOI: 10.1021/mp400193r] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Dorothy Su Lin Toh
- Faculty of Pharmacy, University of Sydney, NSW 2006, Australia
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 119245
| | | | - Michael Murray
- Faculty of Pharmacy, University of Sydney, NSW 2006, Australia
- Discipline of Pharmacology, School
of Medical Sciences, The University of Sydney, NSW 2006, Australia
| | - Tan Kuan Pern
- Bioinformatics Institute, Agency for Science, Technology and Research (A*STAR), Singapore 138632
| | - Edmund Jon Deoon Lee
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 119245
| | - Fanfan Zhou
- Faculty of Pharmacy, University of Sydney, NSW 2006, Australia
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Shibbani K, Fahed AC, Al-Shaar L, Arabi M, Nemer G, Bitar F, Majdalani M. Primary carnitine deficiency: novel mutations and insights into the cardiac phenotype. Clin Genet 2013; 85:127-37. [PMID: 23379544 DOI: 10.1111/cge.12112] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 01/22/2013] [Indexed: 11/28/2022]
Abstract
Solute carrier family 22 member 5 (SLC22A5) encodes a sodium-dependent ion transporter responsible for shuffling carnitine across the plasma membrane. This process provides energy for the heart, among other organs allowing beta-oxidation of fatty acids. Mutations in SLC22A5 result in primary carnitine deficiency (PCD), a disorder that manifests with cardiac, skeletal, or metabolic symptoms. We hereby describe two novel mutations in SLC22A5 in two Lebanese families associated exclusively with a cardiac phenotype. The frequency of the cardiac, metabolic and skeletal symptoms in PCD patients remains undefined. All the reported eight PCD patients belonging to five different Lebanese families have an exclusive cardiac phenotype. Carnitine levels appear to be directly linked to the type and position of the mutation and the severity of the phenotypic presentation does not seem to be associated with serum carnitine levels. A comprehensive review of 61 literature-reported PCD cases revealed an exclusive cardiac manifestation frequency at 62.3% with a very low likelihood of simultaneous occurrence of cardiac and metabolic manifestation.
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Affiliation(s)
- K Shibbani
- Department of Biochemistry and Molecular Genetics, American University of Beirut, Beirut, Lebanon
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9
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Kilic M, Ozgül RK, Coşkun T, Yücel D, Karaca M, Sivri HS, Tokatli A, Sahin M, Karagöz T, Dursun A. Identification of mutations and evaluation of cardiomyopathy in Turkish patients with primary carnitine deficiency. JIMD Rep 2011; 3:17-23. [PMID: 23430869 DOI: 10.1007/8904_2011_36] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2010] [Revised: 03/31/2011] [Accepted: 04/01/2011] [Indexed: 12/13/2022] Open
Abstract
Primary systemic carnitine deficiency (SCD) is an autosomal recessive disorder caused by defective cellular carnitine transport. Patients usually present with predominant metabolic or cardiac manifestations. SCD is caused by mutations in the organic cation/carnitine transporter OCTN2 (SLC22A5) gene. Mutation analysis of SLC22A5 gene was carried out in eight Turkish patients from six families. Six patients presented with signs and symptoms of heart failure, cardiomyopathy, and low plasma carnitine levels, five of them with concurrent anemia. A patient with dilated cardiomyopathy had also facial dysmorphia, microcephaly, and developmental delay. Tandem MS analyses in siblings of the patients revealed two more cases with low plasma carnitine levels. SCD diagnosis was confirmed in these two cases by mutation screening. These two cases were asymptomatic but echocardiography revealed left ventricular dilatation in one of them. Carnitine treatment was started before the systemic signs and symptoms developed in these patients. Mean value of serum carnitine levels of the patients was 2.63±1.92μmol/L at the time of diagnosis. After 1year of treatment, carnitine values increased to 16.62±5.11 (p<0.001) and all responded to carnitine supplementation clinically. Mutation screening of the OCTN2 gene study in the patients revealed two novel (p.G411V, p.G152R), and four previously identified mutations (p.R254X, p.R282X, p.R289X, p.T337Pfs12X). Early recognition and carnitine supplementation can be lifesaving in this inborn error of fatty acid oxidation.
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Affiliation(s)
- M Kilic
- Department of Pediatrics, Metabolism and Nutrition Unit, Hacettepe University, Ankara, Turkey,
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Abstract
Lipid storage myopathy (LSM) is pathologically characterized by prominent lipid accumulation in muscle fibers due to lipid dysmetabolism. Although extensive molecular studies have been performed, there are only four types of genetically diagnosable LSMs: primary carnitine deficiency (PCD), multiple acyl-coenzyme A dehydrogenase deficiency (MADD), neutral lipid storage disease with ichthyosis, and neutral lipid storage disease with myopathy. Making an accurate diagnosis, by specific laboratory tests including genetic analyses, is important for LSM as some of the patients are treatable: individuals with PCD show dramatic improvement with high-dose oral L-carnitine supplementation and increasing evidence indicates that MADD due to ETFDH mutations is riboflavin responsive.
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Filippo CADS, Ardon O, Longo N. Glycosylation of the OCTN2 carnitine transporter: study of natural mutations identified in patients with primary carnitine deficiency. Biochim Biophys Acta Mol Basis Dis 2010; 1812:312-20. [PMID: 21126579 DOI: 10.1016/j.bbadis.2010.11.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Revised: 11/14/2010] [Accepted: 11/19/2010] [Indexed: 12/30/2022]
Abstract
Primary carnitine deficiency is caused by impaired activity of the Na(+)-dependent OCTN2 carnitine/organic cation transporter. Carnitine is essential for entry of long-chain fatty acids into mitochondria and its deficiency impairs fatty acid oxidation. Most missense mutations identified in patients with primary carnitine deficiency affect putative transmembrane or intracellular domains of the transporter. Exceptions are the substitutions P46S and R83L located in an extracellular loop close to putative glycosylation sites (N57, N64, and N91) of OCTN2. P46S and R83L impaired glycosylation and maturation of OCTN2 transporters to the plasma membrane. We tested whether glycosylation was essential for the maturation of OCTN2 transporters to the plasma membrane. Substitution of each of the three asparagine (N) glycosylation sites with glutamine (Q) decreased carnitine transport. Substitution of two sites at a time caused a further decline in carnitine transport that was fully abolished when all three glycosylation sites were substituted by glutamine (N57Q/N64Q/N91Q). Kinetic analysis of carnitine and sodium-stimulated carnitine transport indicated that all substitutions decreased the Vmax for carnitine transport, but N64Q/N91Q also significantly increased the Km toward carnitine, indicating that these two substitutions affected regions of the transporter important for substrate recognition. Western blot analysis confirmed increased mobility of OCTN2 transporters with progressive substitutions of asparagines 57, 64 and/or 91 with glutamine. Confocal microscopy indicated that glutamine substitutions caused progressive retention of OCTN2 transporters in the cytoplasm, up to full retention (such as that observed with R83L) when all three glycosylation sites were substituted. Tunicamycin prevented OCTN2 glycosylation, but it did not impair maturation to the plasma membrane. These results indicate that OCTN2 is physiologically glycosylated and that the P46S and R83L substitutions impair this process. Glycosylation does not affect maturation of OCTN2 transporters to the plasma membrane, but the 3 asparagines that are normally glycosylated are located in a region important for substrate recognition and turnover rate.
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12
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Klaassen CD, Aleksunes LM. Xenobiotic, bile acid, and cholesterol transporters: function and regulation. Pharmacol Rev 2010; 62:1-96. [PMID: 20103563 PMCID: PMC2835398 DOI: 10.1124/pr.109.002014] [Citation(s) in RCA: 558] [Impact Index Per Article: 39.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Transporters influence the disposition of chemicals within the body by participating in absorption, distribution, and elimination. Transporters of the solute carrier family (SLC) comprise a variety of proteins, including organic cation transporters (OCT) 1 to 3, organic cation/carnitine transporters (OCTN) 1 to 3, organic anion transporters (OAT) 1 to 7, various organic anion transporting polypeptide isoforms, sodium taurocholate cotransporting polypeptide, apical sodium-dependent bile acid transporter, peptide transporters (PEPT) 1 and 2, concentrative nucleoside transporters (CNT) 1 to 3, equilibrative nucleoside transporter (ENT) 1 to 3, and multidrug and toxin extrusion transporters (MATE) 1 and 2, which mediate the uptake (except MATEs) of organic anions and cations as well as peptides and nucleosides. Efflux transporters of the ATP-binding cassette superfamily, such as ATP-binding cassette transporter A1 (ABCA1), multidrug resistance proteins (MDR) 1 and 2, bile salt export pump, multidrug resistance-associated proteins (MRP) 1 to 9, breast cancer resistance protein, and ATP-binding cassette subfamily G members 5 and 8, are responsible for the unidirectional export of endogenous and exogenous substances. Other efflux transporters [ATPase copper-transporting beta polypeptide (ATP7B) and ATPase class I type 8B member 1 (ATP8B1) as well as organic solute transporters (OST) alpha and beta] also play major roles in the transport of some endogenous chemicals across biological membranes. This review article provides a comprehensive overview of these transporters (both rodent and human) with regard to tissue distribution, subcellular localization, and substrate preferences. Because uptake and efflux transporters are expressed in multiple cell types, the roles of transporters in a variety of tissues, including the liver, kidneys, intestine, brain, heart, placenta, mammary glands, immune cells, and testes are discussed. Attention is also placed upon a variety of regulatory factors that influence transporter expression and function, including transcriptional activation and post-translational modifications as well as subcellular trafficking. Sex differences, ontogeny, and pharmacological and toxicological regulation of transporters are also addressed. Transporters are important transmembrane proteins that mediate the cellular entry and exit of a wide range of substrates throughout the body and thereby play important roles in human physiology, pharmacology, pathology, and toxicology.
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Affiliation(s)
- Curtis D Klaassen
- Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, 3901 Rainbow Blvd., Kansas City, KS 66160-7417, USA.
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Maternal systemic primary carnitine deficiency uncovered by newborn screening: clinical, biochemical, and molecular aspects. Genet Med 2010; 12:19-24. [PMID: 20027113 DOI: 10.1097/gim.0b013e3181c5e6f7] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Systemic primary carnitine deficiency is an autosomal recessive disorder of the carnitine cycle caused by mutations in the SLC22A5 gene that encodes the carnitine transporter, organic cation transporter. Systemic primary carnitine deficiency typically presents in childhood with either metabolic decompensation or cardiomyopathy. We report five families in which low free carnitine levels in the infants' newborn screening have led to the diagnosis of maternal systemic primary carnitine deficiency. METHODS Blood samples from the infants and /or their family members were used to extract the DNA. The entire coding regions of the SLC22A5 gene were sequenced. The clinical data were obtained from the referring metabolic specialists. RESULT Sequencing the SLC22A5 gene allowed molecular confirmation with identification of three novel mutations: c.1195C>T (p.R399W), c.1324_1325GC>AT (p.A442I), and c.43G>T (p.G15W). All infants were asymptomatic at the time of diagnosis, and one was found to have systemic primary carnitine deficiency. Three mothers are asymptomatic, one had decreased stamina during pregnancy, and one has mild fatigability and developed preeclampsia. DISCUSSION These findings provide further evidence that systemic primary carnitine deficiency presents with a broad clinical spectrum from a metabolic decompensation in infancy to an asymptomatic adult. The maternal systemic primary carnitine deficiency was uncovered by the newborn screening results supporting the previous notion that newborn screening can identify some of the maternal inborn errors of metabolism. It also emphasizes the importance of maternal evaluation after identification of a low free carnitine level in the newborn screening.
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Zhang W, Miao J, Zhang G, Liu R, Zhang D, Wan Q, Yu Y, Zhao G, Li Z. Muscle carnitine deficiency: adult onset lipid storage myopathy with sensory neuropathy. Neurol Sci 2009; 31:61-4. [DOI: 10.1007/s10072-009-0128-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Accepted: 08/21/2009] [Indexed: 11/28/2022]
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Organic cation/carnitine transporter family expression patterns in adult murine heart. Pathol Res Pract 2009; 205:395-402. [DOI: 10.1016/j.prp.2008.12.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2008] [Revised: 10/26/2008] [Accepted: 12/17/2008] [Indexed: 11/22/2022]
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Lamhonwah AM, Hawkins CE, Tam C, Wong J, Mai L, Tein I. Expression patterns of the organic cation/carnitine transporter family in adult murine brain. Brain Dev 2008; 30:31-42. [PMID: 17576045 DOI: 10.1016/j.braindev.2007.05.005] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2006] [Revised: 04/30/2007] [Accepted: 05/01/2007] [Indexed: 12/16/2022]
Abstract
UNLABELLED Organic cation/carnitine transporters transport carnitine, drugs, and xenobiotics (e.g. choline, acetylcarnitine, betaine, valproic acid), and are expressed in muscle, heart, blood vessels, kidney, gut, etc. OBJECTIVE To characterize expression patterns of mOctn1, -2 and -3 in murine brain. METHODS We applied our transporter-specific antibodies to mOctn1, -2 and -3, followed by 2 0 antibody and DAB peroxidase detection to serial adult murine brain sections counterstained with hematoxylin. RESULTS All three transporters showed strong expression in the external plexiform layer of the olfactory bulb and in olfactory nerve, the molecular layer and neuronal processes of input fibres extending vertically in motor cortex, in the dendritic arborization of the cornu ammonis and dendate gyrus (hippocampus), neuronal processes in the arcuate nucleus (hypothalamus), choroid plexus cells, and neuronal cell bodies and dendrites of cranial nerve nuclei V and VII. In the cerebellum, all three transporters were strongly expressed in dendritic processes of Purkinje cells, but Octn1 and -2 were expressed more strongly than Octn3 in Purkinje cell bodies. In spinal cord, Octn1, -2 and -3 were prominent in axons and dendritic end-arborizations of spinal cord neurons in both ascending and descending white matter tracts, whereas Octn3 was also strongly expressed in grey matter, specifically in anterior horn cell bodies. Octn3 was weakly expressed in glomerular layer neuronal cell bodies of olfactory bulb. CONCLUSIONS hOCTN2 deficiency presents with carnitine-responsive cardiomyopathy, myopathy and hypoglycemic, hypoketotic coma with strokes, seizures and delays. In mouse, Octn1, -2 and -3 are expressed in many regions throughout the central nervous system with a pattern suggestive of roles in modulating cerebral bioenergetics and in acetylcholine generation for neurotransmission in olfactory, satiety, limbic, memory, motor and sensory functions. This distribution may play a role in the pattern of neurological injury that occurs in hOCTN2 deficiency during catabolic episodes of hypoglycemic, hypoketotic encephalopathy and which may manifest with cognitive impairment, hypotonia and seizures.
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Affiliation(s)
- Anne Marie Lamhonwah
- Division of Neurology, Department of Pediatrics, The Hospital for Sick Children, 555 University Avenue, University of Toronto, Toronto, Ont., Canada M5G 1X8
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Amat di San Filippo C, Pasquali M, Longo N. Pharmacological rescue of carnitine transport in primary carnitine deficiency. Hum Mutat 2006; 27:513-23. [PMID: 16652335 DOI: 10.1002/humu.20314] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Primary carnitine deficiency is a recessive disorder caused by heterogeneous mutations in the SLC22A5 gene encoding the OCTN2 carnitine transporter. Here we extend mutational analysis to eight new families with this disorder. To determine the mechanism by which missense mutations impaired carnitine transport, the OCTN2 transporter was tagged with the green fluorescent protein and expressed in CHO cells. Analysis by confocal microscopy indicated that several missense mutants (M1I, R169W, T232 M, G242 V, S280F, R282Q, W283R, A301D, W351R, R399Q, T440 M, E452 K, and T468R) matured normally to the plasma membrane. By contrast, other mutations (including R19P, DeltaF22, R83L, S280F, P398L, Y447C, and A142S/R488 H) caused significant retention of the mutant OCTN2 transporter in the cytoplasm. Failed maturation to the plasma membrane is a common mechanism in disorders affecting membrane transporters/ion channels, including cystic fibrosis. To correct this defect, we tested whether drugs reducing the efficiency of protein degradation in the endoplasmic reticulum (ER) (phenylbutyrate, curcumin) or capable of binding the OCTN2 carnitine transporter (verapamil, quinidine) could improve carnitine transport. Prolonged incubation with phenylbutyrate, quinidine, and verapamil partially stimulated carnitine transport, while curcumin was ineffective. These results indicate that OCTN2 mutations can affect carnitine transport by impairing maturation of transporters to the plasma membrane. Pharmacological therapy can be effective in partially restoring activity of mutant transporters.
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Longo N, Amat di San Filippo C, Pasquali M. Disorders of carnitine transport and the carnitine cycle. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2006; 142C:77-85. [PMID: 16602102 PMCID: PMC2557099 DOI: 10.1002/ajmg.c.30087] [Citation(s) in RCA: 327] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Carnitine plays an essential role in the transfer of long-chain fatty acids across the inner mitochondrial membrane. This transfer requires enzymes and transporters that accumulate carnitine within the cell (OCTN2 carnitine transporter), conjugate it with long chain fatty acids (carnitine palmitoyl transferase 1, CPT1), transfer the acylcarnitine across the inner plasma membrane (carnitine-acylcarnitine translocase, CACT), and conjugate the fatty acid back to Coenzyme A for subsequent beta oxidation (carnitine palmitoyl transferase 2, CPT2). Deficiency of the OCTN2 carnitine transporter causes primary carnitine deficiency, characterized by increased losses of carnitine in the urine and decreased carnitine accumulation in tissues. Patients can present with hypoketotic hypoglycemia and hepatic encephalopathy, or with skeletal and cardiac myopathy. This disease responds to carnitine supplementation. Defects in the liver isoform of CPT1 present with recurrent attacks of fasting hypoketotic hypoglycemia. The heart and the muscle, which express a genetically distinct form of CPT1, are usually unaffected. These patients can have elevated levels of plasma carnitine. CACT deficiency presents in most cases in the neonatal period with hypoglycemia, hyperammonemia, and cardiomyopathy with arrhythmia leading to cardiac arrest. Plasma carnitine levels are extremely low. Deficiency of CPT2 present more frequently in adults with rhabdomyolysis triggered by prolonged exercise. More severe variants of CPT2 deficiency present in the neonatal period similarly to CACT deficiency associated or not with multiple congenital anomalies. Treatment for deficiency of CPT1, CPT2, and CACT consists in a low-fat diet supplemented with medium chain triglycerides that can be metabolized by mitochondria independently from carnitine, carnitine supplements, and avoidance of fasting and sustained exercise.
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Affiliation(s)
- Nicola Longo
- Division of Medical Genetics, Department of Pediatrics, University of Utah, 2C412 SOM, 50 North Medical Drive, Salt Lake City, UT, USA.
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