CARNITINE TRANSPORTER IN HUMAN DISEASE
Nicola Longo, Associate Professor
University Of Utah 75 South 2000 East Salt Lake City, Ut 84112
Grant 5R01DK053824-05 from National Institute Of Diabetes And Digestive And Kidney Diseases IRG: MEDB
Abstract: Adapted from applicant s ) ( ) Primary carnitine deficiency is an autosomal recessive disorder caused by defective carnitine transport. Carnitine is essential for fatty acid oxidation, and its deficiency results in hypoketotic hypoglycemia, skeletal and heart myopathy which are preventable by dietary carnitine. The Organic Cation Transporter with Nucleoside binding site (OCTN2) is a high-affinity carnitine transporter, which was cloned based on its homology with OCTN1 (which does not transport carnitine). Its role in carnitine deficiency was confirmed by the identification of nonsense mutations in OCTN2 in patients with early presentation of primary carnitine deficiency. The principal investigator proposes to test the hypothesis that families with primary carnitine deficiency have a spectrum of mutations in the organic cation transporter OCTN2, and that the degree of functional impairment of the transporter caused by these mutations correlates with the severity of the clinical presentation. To test this hypothesis, the following specific aims will be pursued 1) Identification of mutations in the OCTN2 gene in families with primary carnitine deficiency. 2) Expression of missense mutations identified in these patients in Chinese Hamster Ovary (CHO) cells to confirm their causative role and to characterize their effect on carnitine transport. A correlation will be established between phenotype of the proband and residual carnitine transporter activity of the relative mutant. 3) Definition of domains of OCTN2 involved in carnitine recognition and transfer by evaluating carnitine transport in chimeric transporters, created by swapping domains between homologous portions of OCTNI and OCTN2. 4) Construction of site-directed mutations in critical domains of the OCTN2 carnitine transporter and determination of their effect on carnitine transport. This research will characterize mutations responsible for primary carnitine deficiency and clarify the function of a new class of membrane transporters whose alteration may cause other types of human diseases.
Keywords: carnitine, family genetics, gene mutation, genetic disorder, inborn metabolism disorder, membrane transport protein, allosteric site, binding site, chimeric protein, mutant, sodium ion, CHO cell, clinical research, confocal scanning microscopy, human subject, site directed mutagenesis
Project start date: 2000-06-01
Project end date: 2006-05-31
5R01DK053824-05 (2003): $193500
Sponsored Links Excellgen http://Excellgen.com
THE CARNITINE TRANSPORTER IN HUMAN DISEASE
Nicola Longo, Professor Of Pediatrics
University Of Utah, 75 South 2000 East, Salt Lake City, Ut 84112
Grant 5R01DK053824-10 from National Institute Of Diabetes And Digestive And Kidney Diseases
Abstract: The objective of this project is to characterize the role of carnitine transporters in human disease. Carnitine transfers long-chain fatty acids across the mitochondrial membrane for subsequent beta oxidation. A defect in the high-affinity OCTN2 carnitine transporter causes primary carnitine deficiency characterized by hypoketotic hypoglycemia and/or skeletal/cardiac myopathy. This phenotype has now expanded with the identification of symptoms of carnitine deficiency in patients with only partially impaired carnitine transport and adult patients (age 24-37) with 2 mutations in the carnitine transporter gene completely asymptomatic. We hypothesize that this phenotypic variability can be due to unusual OCTN2 mutations, to the contribution of other carnitine transporters, or to the effect of other genes encoding proteins interacting with OCTN2 or involved in fatty acid oxidation. To test this hypothesis, we will define the effect on function of unusual OCTN2 mutations, evaluate activity and sequence of other carnitine transporters, define proteins interacting with the OCTN2 carnitine transporter and look for alterations in their genes in patients with unusual forms of carnitine deficiency. The following specific aims will be accomplished Aim 1. Study mutations in the OCTN2 carnitine transporter of patients with unusual phenotype of carnitine deficiency. We will exclude a possible dominant-negative effect of the mutation identified, synergistic heterozygosity with mutations in other fatty acid oxidation genes and variations in other carnitine transporters. Aim 2. Identification of proteins interacting with the carnitine transporter OCTN2 using the 2-hybrid system. Mutations in the genes identified will be sought in symptomatic patients with partial carnitine deficiency and no mutations in the carnitine transporter gene. This study will expand the phenotype of carnitine deficiency, clarify the molecular basis of unusual forms of carnitine deficiency, define the importance of intracellular protein networks in the functioning of membrane transporters, and identify the possible role of minor carnitine transporters in human disease
Keywords: 1-Propanaminium, 3-carboxy-2-hydroxy-N, N, N-trimethyl-, inner salt, (R)-; 21+ years old; Adult; Affinity; Age; Antibodies; Antimorphic mutation; Cardiac; Carnitine; Cations; Defect; Disease; Disorder; Disorder of muscle, unspecified; Dominant Negative; Dominant-Negative Mutant; Dominant-Negative Mutation; Enzymes; Genes; Genetic Alteration; Genetic Change; Genetic defect; Grant; Human, Adult; Hybrids; Hypoglycemia; Impairment; Investigators; Life; Measures; Membrane Transport Proteins; Membrane Transporters; Metabolic Diseases; Metabolic Disorder; Minor; Molecular; Muscle Disease; Muscle Disorders; Muscle disease or syndrome; Muscular Diseases; Mutation; Myopathic Conditions; Myopathic Diseases and Syndromes; Myopathic disease or syndrome; Myopathy; Myopathy, unspecified; Nonsense Mutation; OMIM; Online Mendelian Inheritance In Man; Patients; Phenotype; Precipitation; Programs (PT); Programs [Publication Type]; Proteins; Research; Research Personnel; Researchers; Role; Symptoms; System; System, LOINC Axis 4; Testing; Thesaurismosis; Two Hybrid; Variant; Variation; Yeast One Hybrid System; Yeast One/Two-Hybrid System; adult human (21+); base; disease/disorder; fatty acid oxidation; gene product; genome mutation; human disease; hypoglycemic; hypoglycemic episodes; interest; long chain fatty acid; metabolism disorder; mitochondrial membrane; muscular disorder; mutant; novel; oxidation; prevent; preventing; programs; protein expression; skeletal; social role; trafficking; yeast two hybrid system
Project start date: 2000-06-01
Project end date: 2011-05-31
Budget start date: 1-JUN-2010
Budget end date: 31-MAY-2011
5R01DK053824-10 (2010): $285598
5R01DK053824-09 (2009): $262471
5R01DK053824-07 (2007): $267828
CARNITINE TRANSPORTER IN HUMAN DISEASE
Nicola Longo, Associate Professor
Pediatricsemory University
1599 Clifton Road, 4th Floor
atlanta, Ga 30322
Grant 5R01DK053824-02 from National Institute Of Diabetes And Digestive And Kidney Diseases IRG: MEDB
Abstract: Adapted from applicant´s ) ( ) Primary carnitine deficiency is an autosomal recessive disorder caused by defective carnitine transport. Carnitine is essential for fatty acid oxidation, and its deficiency results in hypoketotic hypoglycemia, skeletal and heart myopathy which are preventable by dietary carnitine. The Organic Cation Transporter with Nucleoside binding site (OCTN2) is a high-affinity carnitine transporter, which was cloned based on its homology with OCTN1 (which does not transport carnitine). Its role in carnitine deficiency was confirmed by the identification of nonsense mutations in OCTN2 in patients with early presentation of primary carnitine deficiency. The principal investigator proposes to test the hypothesis that families with primary carnitine deficiency have a spectrum of mutations in the organic cation transporter OCTN2, and that the degree of functional impairment of the transporter caused by these mutations correlates with the severity of the clinical presentation. To test this hypothesis, the following specific aims will be pursued 1) Identification of mutations in the OCTN2 gene in families with primary carnitine deficiency. 2) Expression of missense mutations identified in these patients in Chinese Hamster Ovary (CHO) cells to confirm their causative role and to characterize their effect on carnitine transport. A correlation will be established between phenotype of the proband and residual carnitine transporter activity of the relative mutant. 3) Definition of domains of OCTN2 involved in carnitine recognition and transfer by evaluating carnitine transport in chimeric transporters, created by swapping domains between homologous portions of OCTNI and OCTN2. 4) Construction of site-directed mutations in critical domains of the OCTN2 carnitine transporter and determination of their effect on carnitine transport. This research will characterize mutations responsible for primary carnitine deficiency and clarify the function of a new class of membrane transporters whose alteration may cause other types of human diseases
Keywords: carnitine, family genetics, gene mutation, genetic disorder, inborn metabolism disorder, membrane transport protein allosteric site, binding site, chimeric protein, mutant, sodium ion CHO cell, clinical research, confocal scanning microscopy, human subject, site directed mutagenesis
Project start date: 2000-06-01
Project end date: 2001-08-31
5R01DK053824-02 (2001): $196403
Grants awarded to Nicola Longo
SOCIETY FOR INHERITED METABOLIC DISORDERS ANNUAL MEETING
Nicola Longo, Professor Of Pediatrics
University Of Utah, 75 South 2000 East, Salt Lake City, Ut 84112
Grant 5R13HD062129-02 from Eunice Kennedy Shriver National Institute Of Child Health & Human Development
Abstract: The Society for Inherited Metabolic Disorders (SIMD) requests support to provide scholarships for trainees to attend its annual meetings in years 2009 and 2010. The 2009 meeting will be held in conjunction with the International Congress on Inborn Errors of Metabolism in San Diego, CA, while the 2010 meeting will be held in Albuquerque, NM, in coordination with the annual meeting of the American College of Medical Genetics. Inborn errors of metabolism (IEM) are an important cause of mental retardation, cerebral palsy, neuromuscular disease, cardiac disorders, hepatic and renal dysfunction, arthritis, diabetes, growth failure, and blindness. As the wide clinical and molecular spectrum of these disorders is being elucidated, in part fueled by the development of tandem mass spectroscopy and the rapid expansion of newborn screening programs, the number of affected individuals is now known to be much larger than originally recognized. In addition, therapies are available for some conditions, yet few clinical trials have been performed to evaluate their efficacy. Thus, much remains to be done to better understand these severe disorders and develop effective treatments for them. For the U.S. to remain preeminent in this important area of research, it is essential to attract young investigators into the field. One effective mechanism to achieve this goal is to provide them with the opportunity to participate in the SIMD meeting, where they can explore the field and develop scientific ties to other established investigators. The SIMD meeting is held annually and participation, especially by young investigators, has been steadily increasing each year. The availability of NIH travel awards has been a major reason for this increase. Trainees seeking funding are required to submit an describing original research to be presented at the meeting. The organizers anticipate submission of 40 to 50 s for presentation at the annual meetings in the U.S. (2010) with two to three times that number for the international meeting (2009). Applications for travel awards will be competitively reviewed four months prior to the meeting, with the goal of making 25 annual awards of $1,000 each. Additional funds will be solicited from private sources. Women and minority applicants will be actively recruited. The Society for Inherited Metabolic Disorders (SIMD) meeting will help to train new physicians to take care of patients with disorders of the body´s biochemistry. There are very few such specialists in the country, and providing travel funds for new trainees to meet and present their research encourages them to remain in the field
Keywords: Affect; American; Area; Arthritis; Award; Biochemistry; Blindness; Cardiac Diseases; Cardiac Disorders; Cerebral Palsy; Chemistry, Biological; Clinical; Clinical Trials; Clinical Trials, Unspecified; Congresses; Country; Development; Diabetes Mellitus; Disease; Disorder; Dysfunction; FLR; Failure (biologic function); Functional disorder; Funding; Generalized Growth; Genetics, Medical; Goals; Growth; Heart Diseases; Hepatic; Hereditary; Hereditary Metabolic Disorder; Inborn Errors of Metabolism; Individual; Inherited; International; Investigators; Kidney; Mass Spectrum; Mass Spectrum Analysis; Medical Genetics; Mental Retardation; Metabolic Diseases; Metabolic Disorder; Metabolism, Inborn Errors; Minority; Molecular; NIH; National Institutes of Health; National Institutes of Health (U.S.); Neonatal Screening; Neuromuscular Diseases; Newborn Infant Screening; Patient Care; Patient Care Delivery; Photometry/Spectrum Analysis, Mass; Physicians; Physiopathology; Programs (PT); Programs [Publication Type]; Recruitment Activity; Research; Research Personnel; Researchers; Scholarship; Societies; Source; Specialist; Spectrometry, Mass; Spectroscopy, Mass; Spectrum Analyses, Mass; Spectrum Analysis, Mass; Thesaurismosis; Time; Tissue Growth; Training; Travel; United States National Institutes of Health; Urinary System, Kidney; Woman; ing; arthritic; clinical investigation; college; diabetes; disease/disorder; effective therapy; failure; heart disorder; inborn metabolism disorder; meetings; metabolism disorder; myoneural disorder; neuromuscular disorder; newborn screening; ontogeny; pathophysiology; programs; recruit; renal
Relevance: The Society for Inherited Metabolic Disorders (SIMD) meeting will help to train new physicians to take care of patients with disorders of the body´s biochemistry. There are very few such specialists in the country and providing travel funds for new trainees to meet and present their research encourages them to remain in the field
Project start date: 2009-07-14
Project end date: 2011-02-28
Budget start date: 1-MAR-2010
Budget end date: 28-FEB-2011
PFA/PA: PA-08-149
5R13HD062129-02 (2010): $11000
ANAPLEROTIC THERAPY IN PROPIONIC ACIDEMIA
Nicola Longo, Professor Of Pediatrics
University Of Utah, 75 South 2000 East, Salt Lake City, Ut 84112
Grant 5R21DK077415-02 from National Institute Of Diabetes And Digestive And Kidney Diseases
Abstract: The objective of this project is to define whether nutritional supplements capable of filling-up the citric acid cycle (anaplerotic therapy) can improve hyperammonemia, glutamine levels, and outcome in patients with propionic acidemia. Propionic acidemia is a rare recessive disorder caused by deficiency of propionyl CoA carboxylase. Deficient activity of propionyl CoA carboxylase impairs the supply of succinyl CoA to the citric acid cycle. Affected patients develop hyperammonemia at birth that recurs during episodes of metabolic decompensation. The investigators have found that plasma levels of glutamine/glutamate are reduced in patients with propionic acidemia and decrease, rather than increase, with hyperammonemia. Since a-ketoglutarate is the main source of endogenous glutamate/glutamine synthesis, their hypothesis is that chronic hyperammonemia in patients with propionic acidemia is due to a functional insufficiency of the citric acid (Krebs) cycle with defective production of a-ketoglutarate. The basic deficiency of intermediates of the Krebs cycle could decrease production of ATP and explain the low muscle tone, progressive organ dysfunction, and poor outcome of patients with propionic acidemia. To test this hypothesis, the investigators will determine whether dietary supplementation with a-ketoglutarate precursors (in the form of ornithine a-ketoglutarate, glutamine, or citrate) can improve plasma ammonia and overall outcome in patients with propionic acidemia. The current therapy of propionic acidemia is based on restriction of precursors of propionic acid (methionine, valine, isoleucine, threonine, odd chain fatty acids, cholesterol) and administration of carnitine to help remove toxic organic acids. This therapy is not effective in preventing the long-term complications of the disease, even in children identified at birth by newborn screening. Thus this research will test a completely new way of treating patients with severe and disabling metabolic disorders using replacement of downstream products involved in the generation of energy (ATP). This approach, if effective, could be extended to a number of other diseases, including other organic acidemias and mitochondrial disorders
Keywords: 0-11 years old; 1-Propanaminium, 3-carboxy-2-hydroxy-N, N, N-trimethyl-, inner salt, (R)-; 2, 5-Diaminopentanoic Acid; Affect; Ammonia; Birth; Blood Plasma; Carnitine; Child; Child Youth; Children (0-21); Cholest-5-en-3-ol (3beta)-; Cholesterol; Chronic; Citrate; Citrates; Citric Acid; Citric Acid Cycle; Diet Supplement; Dietary Supplementation; Dietary Supplements; Disease; Disorder; Dysfunction; Fatty Acids; Functional disorder; Generations; Gln; Glutamates; Glutamine; Human, Child; Hyperammonemia; Investigators; Isoleucine; Isoleucine, L-Isomer; Krebs Cycle; L-Glutamate; L-Glutamine; L-Isoleucine; L-Methionine; L-Threonine; L-Valine; Metabolic; Metabolic Diseases; Metabolic Disorder; Methionine; Methionine, L-Isomer; Mitochondrial Diseases; Mitochondrial Disorders; Muscle Tonus; Neonatal Screening; Newborn Infant Screening; Numbers; Nutritional Supplement; Organ; Ornithine; Outcome; Parturition; Patients; Physiopathology; Plasma; Production; Propionic Acids; Propionic acid; Propionyl-CoA Carboxylase; Propionyl-Coenzyme A Carboxylase; Q. Levoglutamide; Research; Research Personnel; Researchers; Reticuloendothelial System, Serum, Plasma; Serum, Plasma; Source; TCA cycle; Testing; Thesaurismosis; Threonine; Tricarboxylic Acid Cycle; Valine; base; children; coenzyme A, S-(hydrogen butanedioate); disease/disorder; ethylformic acid; improved; ketotic glycinemia; ketotic hyperglycinemia; metabolism disorder; methylmalonyl-CoA decarboxylase; mitochondrial disease/disorder; muscle tone; newborn screening; organic acid; pathophysiology; prevent; preventing; propanoic acid; propionic acidemia; propionyl coA carboxylase deficiency; succinyl-CoA; succinyl-coenzyme A; youngster
Project start date: 2007-08-15
Project end date: 2010-06-30
Budget start date: 1-JUL-2008
Budget end date: 30-JUN-2010
PFA/PA: PAR-06-342
5R21DK077415-02 (2008): $0
1R21DK077415-01A1 (2007): $224250
THE CARNITINE TRANSPORTER IN HUMAN DISEASE
Nicola Longo, Associate Professor
University Of Utah 75 South 2000 East Salt Lake City, Ut 84112
Grant 2R01DK053824-06A2 from National Institute Of Diabetes And Digestive And Kidney Diseases IRG: ZRG1
Abstract: The objective of this project is to characterize the role of carnitine transporters in human disease. Carnitine transfers long-chain fatty acids across the mitochondrial membrane for subsequent beta oxidation. A defect in the high-affinity OCTN2 carnitine transporter causes primary carnitine deficiency characterized by hypoketotic hypoglycemia and/or skeletal/cardiac myopathy. This phenotype has now expanded with the identification of symptoms of carnitine deficiency in patients with only partially impaired carnitine transport and adult patients (age 24-37) with 2 mutations in the carnitine transporter gene completely asymptomatic. We hypothesize that this phenotypic variability can be due to unusual OCTN2 mutations, to the contribution of other carnitine transporters, or to the effect of other genes encoding proteins interacting with OCTN2 or involved in fatty acid oxidation. To test this hypothesis, we will define the effect on function of unusual OCTN2 mutations, evaluate activity and sequence of other carnitine transporters, define proteins interacting with the OCTN2 carnitine transporter and look for alterations in their genes in patients with unusual forms of carnitine deficiency. The following specific aims will be accomplished Aim 1. Study mutations in the OCTN2 carnitine transporter of patients with unusual phenotype of carnitine deficiency. We will exclude a possible dominant-negative effect of the mutation identified, synergistic heterozygosity with mutations in other fatty acid oxidation genes and variations in other carnitine transporters. Aim 2. Identification of proteins interacting with the carnitine transporter OCTN2 using the 2-hybrid system. Mutations in the genes identified will be sought in symptomatic patients with partial carnitine deficiency and no mutations in the carnitine transporter gene. This study will expand the phenotype of carnitine deficiency, clarify the molecular basis of unusual forms of carnitine deficiency, define the importance of intracellular protein networks in the functioning of membrane transporters, and identify the possible role of minor carnitine transporters in human disease.
Keywords: carnitine, gene mutation, genetic disorder, inborn metabolism disorder, membrane transport protein, molecular pathology, protein structure function, binding site, fatty acid, oxidation, protein localization, protein protein interaction, CHO cell, clinical research, confocal scanning microscopy, human genetic material tag, human subject, site directed mutagenesis, yeast two hybrid system
Project start date: 2000-06-01
Project end date: 2011-05-31
2R01DK053824-06A2 (2006): $275828
MUTANT INSULIN REC IN GROWTH RESTRICTION
Nicola Longo, Associate Professor
Emory University 1599 Clifton Road, 4th Floor Atlanta, Ga 30322
Grant 5M01RR000039-390533 from National Center For Research Resources
Abstract: No research subjects are admitted to the GCRC under this protocol. It utilizes the Molecular Cell Biology Laboratory only. The Lab Supervisor transforms and stores immortal Epstein-Barr virus lymphoblast cell lines from patient samples sent directly to the lab. The cell lines then serve as a permanent DNA/RNA resource, as well as an in vitro model system for molecular genetics investigations.
Keywords: cell bank /registry, cell line, cell transformation, insulin, postnatal growth disorder, Epstein Barr virus, lymphoblast, human genetic material tag
Project start date: 1998-12-01
Project end date: 1999-11-30
REGULATION OF ION FLUXES BY THE INSULIN RECEPTOR
Nicola Longo, Associate Professor
Emory University 1599 Clifton Road, 4th Floor Atlanta, Ga 30322
Grant 5R29DK048742-05 from National Institute Of Diabetes And Digestive And Kidney Diseases IRG: END
Abstract: Changes in ion fluxes represent one of the earliest events activated by the interaction of insulin with its receptor. This proposal wants to define the molecular mechanism by which the insulin receptor modifies ion fluxes in target cells. It will be tested if the kinase activity of the receptor is required for insulin stimulation of ion fluxes and if the insulin receptor modifies the phosphorylation and/or subcellular distribution of ion transporters. To test these hypotheses, this study will define 1. The effect of insulin on K fluxes and Na/K homeostasis in cells expressing normal insulin receptors, focusing on insulin effect on the Na,K-ATPase and the Na/K/Cl cotransporter. 2. Insulin stimulation of ion fluxes and Na/K homeostasis in cells with activated or defective insulin receptor kinase to determine whether the kinase activity of the receptor is required for the stimulation of ion fluxes. 3. The molecular mechanism by which insulin activates ion transporters, and specifically, whether insulin recruits preformed ion transporters on the plasma membrane and/or affects their phosphorylation. This will be determined by a combined approach involving measurement of insulin-induced changes in ouabain binding and biotin labeling of ion transporters on the plasma membrane of intact cells, Western blot analysis on subcellular fractions (using antibodies specific for each transporter and anti- phosphotyrosine antibodies), immunoprecipitation of 32P-transporters, phosphoamino acid analysis and tryptic phosphopeptide mapping. 4. Insulin stimulation of the alpha1, alpha2, and beta1 isoforms of Na,K- ATPase after their transfection into mammalian cells. The great abundance of Na,K-pumps in transfected cells should facilitate the study of changes of insulin-induced changes in their phosphorylation and subcellular distribution. Very little is currently known on the molecular mechanism(s) by which insulin regulates ion fluxes. Ion transport across the plasma membrane by the Na,K-ATPase is an energy-requiring process whose reduction has been implicated in the pathogenesis of human obesity. In addition, changes in insulin-stimulated ion fluxes contribute to acute and long-term complications of diabetes. This study will define the molecular mechanism by which insulin modifies ion fluxes and Na,K-ATPase activity and may allow the design of better therapy to prevent obesity and acute or chronic complications of diabetes.
Keywords: biological signal transduction, insulin, insulin receptor, ion transport, sodium potassium exchanging ATPase, cell type, membrane potential, membrane transport protein, phosphorylation, potassium, protein isoform, protein tyrosine kinase, receptor binding, receptor expression, sodium, CHO cell, adipocyte, immunoprecipitation, mutant, northern blotting, rubidium, site directed mutagenesis, transfection, western blotting
Project start date: 1995-09-01
Project end date: 2001-08-31
5R29DK048742-05 (1999): $117077
Sponsored Links Excellgen http://Excellgen.com
5R29DK048742-04 (1998): $112216
5R29DK048742-03 (1997): $107561
CARNITINE TRANSPORTER IN HUMAN DISEASE
Nicola Longo, Associate Professor
Pediatricsemory University
1599 Clifton Road, 4th Floor
atlanta, Ga 30322
Grant 1R01DK053824-01A2 from National Institute Of Diabetes And Digestive And Kidney Diseases IRG: MEDB
Abstract: Adapted from applicant´s ) ( ) Primary carnitine deficiency is an autosomal recessive disorder caused by defective carnitine transport. Carnitine is essential for fatty acid oxidation, and its deficiency results in hypoketotic hypoglycemia, skeletal and heart myopathy which are preventable by dietary carnitine. The Organic Cation Transporter with Nucleoside binding site (OCTN2) is a high-affinity carnitine transporter, which was cloned based on its homology with OCTN1 (which does not transport carnitine). Its role in carnitine deficiency was confirmed by the identification of nonsense mutations in OCTN2 in patients with early presentation of primary carnitine deficiency. The principal investigator proposes to test the hypothesis that families with primary carnitine deficiency have a spectrum of mutations in the organic cation transporter OCTN2, and that the degree of functional impairment of the transporter caused by these mutations correlates with the severity of the clinical presentation. To test this hypothesis, the following specific aims will be pursued 1) Identification of mutations in the OCTN2 gene in families with primary carnitine deficiency. 2) Expression of missense mutations identified in these patients in Chinese Hamster Ovary (CHO) cells to confirm their causative role and to characterize their effect on carnitine transport. A correlation will be established between phenotype of the proband and residual carnitine transporter activity of the relative mutant. 3) Definition of domains of OCTN2 involved in carnitine recognition and transfer by evaluating carnitine transport in chimeric transporters, created by swapping domains between homologous portions of OCTNI and OCTN2. 4) Construction of site-directed mutations in critical domains of the OCTN2 carnitine transporter and determination of their effect on carnitine transport. This research will characterize mutations responsible for primary carnitine deficiency and clarify the function of a new class of membrane transporters whose alteration may cause other types of human diseases
Keywords: carnitine, family genetics, gene mutation, genetic disorder, inborn metabolism disorder, membrane transport protein allosteric site, binding site, chimeric protein, mutant, sodium ion CHO cell, clinical research, confocal scanning microscopy, human subject, site directed mutagenesis
Project start date: 2000-06-01
Project end date: 2004-05-31
1R01DK053824-01A2 (2000): $219032
REGULATION OF ION FLUXES BY THE INSULIN RECEPTOR
Nicola Longo, Associate Professor
Emory University 1599 Clifton Road, 4th Floor Atlanta, Ga 30322
Grant 5R29DK048742-02 from National Institute Of Diabetes And Digestive And Kidney Diseases IRG: END
Project start date: 1995-09-01
Project end date: 2000-08-31
5R29DK048742-02 (1996): $103092