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Sigauke E, Rakheja D, Kitson K, Bennett MJ. Carnitine palmitoyltransferase II deficiency: a clinical, biochemical, and molecular review. J Transl Med 2003; 83:1543-54. [PMID: 14615409 DOI: 10.1097/01.lab.0000098428.51765.83] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Congenital deficiency of carnitine palmitoyltransferase (CPT) II has been known for at least 30 years now, and its phenotypic variability remains fascinating. Three distinct clinical entities have been described, the adult, the infantile, and the perinatal, all with an autosomal recessive inheritance pattern. The adult CPT II clinical phenotype is somewhat benign and requires additional external triggers such as high-intensity exercise before the predominantly myopathic symptoms are elicited. The perinatal and infantile forms involve multiple organ systems. The perinatal disease is the most severe form and is invariably fatal. The introduction of mass spectrometry to analyze blood acylcarnitine profiles has revolutionized the diagnosis of fatty acid oxidation disorders including CPT II deficiency. Its use in expanded neonatal screening programs has made presymptomatic diagnosis a reality. An increasing number of mutations are being identified in the CPT II gene with a distinct genotype-phenotype correlation in most cases. However, clinical variability in some patients suggests additional genetic or environmental modifiers. Herein, we present a new case of lethal perinatal CPT II deficiency with a rare missense mutation, R296Q (907G>A) associated with a previously described 25-bp deletion on the second allele. We review the clinical features, the diagnostic protocol including expanded neonatal screening, the treatment, and the biochemical and molecular basis of CPT II deficiency.
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Affiliation(s)
- Ellen Sigauke
- Department of Pathology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
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2
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Elpeleg ON, Hammerman C, Saada A, Shaag A, Golzand E, Hochner-Celnikier D, Berger I, Nadjari M. Antenatal presentation of carnitine palmitoyltransferase II deficiency. AMERICAN JOURNAL OF MEDICAL GENETICS 2001; 102:183-7. [PMID: 11477613 DOI: 10.1002/ajmg.1457] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Carnitine palmitoyl transferase (CPT) II deficiency is usually manifested around puberty by exercise induced myoglobinuria. Two Ashkenazi Jewish sibs with the rare antenatal form of CPTII deficiency are reported. On the 5th gestational month periventricular calcifications and markedly enlarged kidneys were found in both of them. The activity of CPTII in lymphocytes was undetectable and both sibs were homozygous for the 1237delAG mutation. Because of the serious consequences of homozygosity for this mutation, genotype determination of all Ashkenazi patients with the adolescent form of CPTII deficiency is warranted.
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Affiliation(s)
- O N Elpeleg
- Metabolic Disease Unit, Shaare-Zedek Medical Center, Jerusalem, Israel.
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Ramsay RR, Gandour RD, van der Leij FR. Molecular enzymology of carnitine transfer and transport. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1546:21-43. [PMID: 11257506 DOI: 10.1016/s0167-4838(01)00147-9] [Citation(s) in RCA: 255] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Carnitine (L-3-hydroxy-4-N-trimethylaminobutyric acid) forms esters with a wide range of acyl groups and functions to transport and excrete these groups. It is found in most cells at millimolar levels after uptake via the sodium-dependent carrier, OCTN2. The acylation state of the mobile carnitine pool is linked to that of the limited and compartmentalised coenzyme A pools by the action of the family of carnitine acyltransferases and the mitochondrial membrane transporter, CACT. The genes and sequences of the carriers and the acyltransferases are reviewed along with mutations that affect activity. After summarising the accepted enzymatic background, recent molecular studies on the carnitine acyltransferases are described to provide a picture of the role and function of these freely reversible enzymes. The kinetic and chemical mechanisms are also discussed in relation to the different inhibitors under study for their potential to control diseases of lipid metabolism.
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Affiliation(s)
- R R Ramsay
- Centre for Biomolecular Sciences, University of St Andrews, North Haugh, St Andrews KY16 9ST, UK.
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Abstract
The mitochondrial carnitine system plays an obligatory role in beta-oxidation of long-chain fatty acids by catalyzing their transport into the mitochondrial matrix. This transport system consists of the malonyl-CoA sensitive carnitine palmitoyltransferase I (CPT-I) localized in the mitochondrial outer membrane, the carnitine:acylcarnitine translocase, an integral inner membrane protein, and carnitine palmitoyltransferase II localized on the matrix side of the inner membrane. Carnitine palmitoyltransferase I is subject to regulation at the transcriptional level and to acute control by malonyl-CoA. The N-terminal domain of CPT-I is essential for malonyl-CoA inhibition. In liver CPT-I activity is also regulated by changes in the enzyme's sensitivity to malonyl-CoA. As fluctuations in tissue malonyl-CoA content are parallel with changes in acetyl-CoA carboxylase activity, which in turn is under the control of 5'-AMP-activated protein kinase, the CPT-I/malonyl-CoA system is part of a fuel sensing gauge, turning off and on fatty acid oxidation depending on the tissue's energy demand. Additional mechanism(s) of short-term control of CPT-I activity are emerging. One proposed mechanism involves phosphorylation/dephosphorylation dependent direct interaction of cytoskeletal components with the mitochondrial outer membrane or CPT-I. We have proposed that contact sites between the outer and inner mitochondrial membranes form a microenvironment which facilitates the carnitine transport system. In addition, this system includes the long-chain acyl-CoA synthetase and porin as components.
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Affiliation(s)
- J Kerner
- Department of Veterans Affairs Medical Center, Case Western Reserve University, Cleveland, OH 44106, USA
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Wieser T, Deschauer M, Zierz S. Genetics of carnitine palmitoyltransferase II deficiencies. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2000; 466:339-45. [PMID: 10709661 DOI: 10.1007/0-306-46818-2_39] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Affiliation(s)
- T Wieser
- Klinik und Poliklinik für Neurologie, Martin-Luther-Universität Halle/Wittenberg, Halle/S., Germany.
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Cohen I, Girard J, Prip-Buus C. Biogenesis of the rat liver mitochondrial carnitine palmitoyltransferase I. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2000; 466:1-16. [PMID: 10709623 DOI: 10.1007/0-306-46818-2_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Affiliation(s)
- I Cohen
- Endocrinologie, Métabolisme et Développement CNRS UPR1524, Meudon, France
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Peluso G, Nicolai R, Reda E, Benatti P, Barbarisi A, Calvani M. Cancer and anticancer therapy-induced modifications on metabolism mediated by carnitine system. J Cell Physiol 2000; 182:339-50. [PMID: 10653600 DOI: 10.1002/(sici)1097-4652(200003)182:3<339::aid-jcp4>3.0.co;2-b] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
An efficient regulation of fuel metabolism in response to internal and environmental stimuli is a vital task that requires an intact carnitine system. The carnitine system, comprehensive of carnitine, its derivatives, and proteins involved in its transformation and transport, is indispensable for glucose and lipid metabolism in cells. Two major functions have been identified for the carnitine system: (1) to facilitate entry of long-chain fatty acids into mitochondria for their utilization in energy-generating processes; (2) to facilitate removal from mitochondria of short-chain and medium-chain fatty acids that accumulate as a result of normal and abnormal metabolism. In cancer patients, abnormalities of tumor tissue as well as nontumor tissue metabolism have been observed. Such abnormalities are supposed to contribute to deterioration of clinical status of patients, or might induce cancerogenesis by themselves. The carnitine system appears abnormally expressed both in tumor tissue, in such a way as to greatly reduce fatty acid beta-oxidation, and in nontumor tissue. In this view, the study of the carnitine system represents a tool to understand the molecular basis underlying the metabolism in normal and cancer cells. Some important anticancer drugs contribute to dysfunction of the carnitine system in nontumor tissues, which is reversed by carnitine treatment, without affecting anticancer therapeutic efficacy. In conclusion, a more complex approach to mechanisms that underlie tumor growth, which takes into account the altered metabolic pathways in cancer disease, could represent a challenge for the future of cancer research.
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Affiliation(s)
- G Peluso
- Institute of Protein Biochemistry and Enzymology (I.B.P.E.) CNR, Naples, Italy.
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Cohen I, Kohl C, McGarry JD, Girard J, Prip-Buus C. The N-terminal domain of rat liver carnitine palmitoyltransferase 1 mediates import into the outer mitochondrial membrane and is essential for activity and malonyl-CoA sensitivity. J Biol Chem 1998; 273:29896-904. [PMID: 9792707 DOI: 10.1074/jbc.273.45.29896] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The rat liver carnitine palmitoyltransferase 1 (L-CPT1), an integral outer mitochondrial membrane (OMM) protein, is the key regulatory enzyme of fatty acid oxidation and is inhibited by malonyl-CoA. In vitro import of L-CPT1 into the OMM requires the presence of mitochondrial receptors and is stimulated by ATP but is membrane potential-independent. Its N-terminal domain (residues 1-150), which contains two transmembrane segments, possesses all of the information for mitochondrial targeting and OMM insertion. Deletion of this domain abrogates protein targeting, whereas its fusion to non-OMM-related proteins results in their mitochondrial targeting and OMM insertion in a manner similar to L-CPT1. Functional analysis of chimeric CPTs expressed in Saccharomyces cerevisiae shows that this domain also mediates in vivo protein insertion into the OMM. When the malonyl-CoA-insensitive CPT2 was anchored at the OMM either by a specific OMM signal anchor sequence (pOM29) or by the N-terminal domain of L-CPT1, its activity remains insensitive to malonyl-CoA inhibition. This indicates that malonyl-CoA sensitivity is an intrinsic property of L-CPT1 and that its N-terminal domain cannot confer malonyl-CoA sensitivity to CPT2. Replacement of the N-terminal domain by pOM29 results in a less folded and less active protein, which is also malonyl-CoA-insensitive. Thus, in addition to its role in mitochondrial targeting and OMM insertion, the N-terminal domain of L-CPT1 is essential to maintain an optimal conformation for both catalytic function and malonyl-CoA sensitivity.
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Affiliation(s)
- I Cohen
- Endocrinologie, Métabolisme, et Développement, CNRS-UPR 1524, 9 Rue J. Hetzel, 92190 Meudon, France
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Abstract
Carnitine functions as a substrate for a family of enzymes, carnitine acyltransferases, involved in acyl-coenzyme A metabolism and as a carrier for long-chain fatty acids into mitochondria. Carnitine biosynthesis and/or dietary carnitine fulfill the body's requirement for carnitine. To date, a genetic disorder of carnitine biosynthesis has not been described. A genetic defect in the high-affinity plasma membrane carnitine-carrier(in) leads to renal carnitine wasting and primary carnitine deficiency. Myopathic carnitine deficiency could be due to an increase in efflux moderated by the carnitine-carrier(out). Defects in the carnitine transport system for fatty acids in mitochondria have been described and are being examined at the molecular and pathophysiological levels. the nutritional management of these disorders includes a high-carbohydrate, low-fat diet and avoidance of those events that promote fatty acid oxidation, such as fasting, prolonged exercise, and cold. Large-dose carnitine treatment is effective in systemic carnitine deficiency.
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Affiliation(s)
- J Kerner
- Department of Veteran Affairs Medical Center, Department of Nutrition, Cleveland, USA
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McGarry JD, Brown NF. The mitochondrial carnitine palmitoyltransferase system. From concept to molecular analysis. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 244:1-14. [PMID: 9063439 DOI: 10.1111/j.1432-1033.1997.00001.x] [Citation(s) in RCA: 1170] [Impact Index Per Article: 43.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
First conceptualized as a mechanism for the mitochondrial transport of long-chain fatty acids in the early 1960s, the carnitine palmitoyltransferase (CPT) system has since come to be recognized as a pivotal component of fuel homeostasis. This is by virtue of the unique sensitivity of the outer membrane CPT I to the simple molecule, malonyl-CoA. In addition, both CPT I and the inner membrane enzyme, CPT II, have proved to be loci of inherited defects, some with disastrous consequences. Early efforts using classical approaches to characterize the CPT proteins in terms of structure/function/regulatory relationships gave rise to confusion and protracted debate. By contrast, recent application of molecular biological tools has brought major enlightenment at an exponential pace. Here we review some key developments of the last 20 years that have led to our current understanding of the physiology of the CPT system, the structure of the CPT isoforms, the chromosomal localization of their respective genes, and the identification of mutations in the human population.
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Affiliation(s)
- J D McGarry
- Department of Internal Medicine and Biochemistry, University of Texas Southwestern Medical Center, Dallas 75235-9135, USA
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Esser V, Brown NF, Cowan AT, Foster DW, McGarry JD. Expression of a cDNA isolated from rat brown adipose tissue and heart identifies the product as the muscle isoform of carnitine palmitoyltransferase I (M-CPT I). M-CPT I is the predominant CPT I isoform expressed in both white (epididymal) and brown adipocytes. J Biol Chem 1996; 271:6972-7. [PMID: 8636126 DOI: 10.1074/jbc.271.12.6972] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We set out to determine if the cDNA encoding a carnitine palmitoyltransferase (CPT)-like protein recently isolated from rat brown adipose tissue (BAT) by Yamazaki et al. (Yamazaki, N., Shinohara, Y., Shima, A., and Terada, H. (1995) FEBS Lett. 363, 41-45) actually encodes the muscle isoform of mitochondrial CPT I (M-CPT I). To this end, a cDNA essentially identical to the original BAT clone was isolated from a rat heart library. When expressed in COS cells, the novel cDNA and our previously described cDNA for rat liver CPT I (L-CPT I) gave rise to products with the same kinetic characteristics (sensitivity to malonyl-CoA and Km for carnitine) as CPT I in skeletal muscle and liver mitochondria, respectively. When labeled with [3H]etomoxir, recombinant L-CPT I and putative M-CPT I, although having approximately the same predicated masses (88.2 kDa), migrated differently on SDS gels, as did CPT I from liver and muscle mitochondria. The same was true for the products of in vitro transcription and translation of the L-CPT I and putative M-CPT I cDNAs. We conclude that the BAT cDNA does in fact encode M-CPT I. Northern blots using L- and M-CPT I cDNA probes revealed the presence of L-CPT I mRNA in liver and heart and its absence from skeletal muscle and BAT. M-CPT I mRNA, which was absent from liver, was readily detected in skeletal muscle and was particularly strong in heart and BAT. Whereas the signal for L-CPT I was more abundant than that for M-CPT I in RNA isolated from whole epididymal fat pad, this was reversed in purified adipocytes from this source. These findings, coupled with the kinetic properties and migration profiles on SDS gels of CPT I in brown and white adipocytes, indicate that the muscle form of the enzyme is the dominant, if not exclusive, species in both cell types.
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Affiliation(s)
- V Esser
- Department of Internal Medicine, Gifford Laboratories, Center for Diabetes Research, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9135, USA
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Brown N, Anderson R, Caplan S, Foster D, McGarry J. Catalytically important domains of rat carnitine palmitoyltransferase II as determined by site-directed mutagenesis and chemical modification. Evidence for a critical histidine residue. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)32288-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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Abstract
The mouse carnitine palmitoyltransferase II gene has been isolated and its genomic structure determined. The gene contained five exons, including an unusually long 1305-nt exon 4. The exon/intron boundaries were sequenced and conformed to the consensus splice junction sequences. The transcription start site was determined from adult mouse heart mRNA by primer extension analysis and confirmed by 5' rapid amplification of cDNA ends. A promoter that differs from the previously published promoter for the carnitine palmitoyltransferase II gene was isolated and sequenced. When placed in a mammalian expression vector, this promoter was shown to drive the chloramphenicol acetyltransferase gene in mouse hepatoma cells. This new promoter is the major driver of carnitine palmitoyltransferase II gene expression in heart and may also be active in liver.
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Affiliation(s)
- B D Gelb
- Department of Pediatrics, Mount Sinai School of Medicine, New York, New York 10029
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Esser V, Britton C, Weis B, Foster D, McGarry J. Cloning, sequencing, and expression of a cDNA encoding rat liver carnitine palmitoyltransferase I. Direct evidence that a single polypeptide is involved in inhibitor interaction and catalytic function. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53392-5] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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