Differential Regulation of Carnitine Palmitoyltransferase-I Gene Isoforms (CPT-I α and CPT-Iβ ) in the Rat Heart

Carnitine palmitoyltransferase I (CPT I) catalyses the transfer of long chain fatty acids to carnitine for translocation across the mitochondrial inner membrane. The cDNAs of two isoforms of CPT I, termed the hepatic and muscle isoforms, have been cloned. Expression of the hepatic CPT I gene (L-CPT I) is subject to developmental, hormonal and tissue specific regulation. We have cloned the promoter of the L-CPT I gene from a rat genomic library. In the L-CPT I gene, there are two exons 5ʹ to the exon containing the ATG that initiates translation. Exon 1 and the 5ʹ end of exon 2 contain sequences that were not previously described in the rat L-CPT I cDNA. There is an alternatively spliced form of the L-CPT I mRNA in which exon 2 is skipped. The proximal promoter of the L-CPT I gene is extremely GC rich and does not contain a TATA box. There are several putative Sp1 binding sites near the transcriptional start site. A 190 base pair fragment of the promoter can efficiently drive transcription of luciferase and CAT (chloramphenicol acetyltransferase) reporter genes transiently transfected into HepG2 cells. Sequences in both the first intron and the promoter contribute to basal expression. Our results provide the foundation for further studies into the regulation of L-CPTI gene expression.

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Regulation of hepatic carnitine palmitoyltransferase I (CPT‐I) gene expression by the peroxisomal proliferator activated receptor gamma coactivator (PGC‐1β)

The FASEB Journal ◽

10.1096/fasebj.20.5.a955-b ◽

2006 ◽

Vol 20 (5) ◽

Author(s):

Prabodh Sadana ◽

Yi Zhang ◽

Shulan Song ◽

Geroge A Cook ◽

Marshall B Elam ◽

...

Keyword(s):

Gene Expression ◽

Carnitine Palmitoyltransferase ◽

Carnitine Palmitoyltransferase I ◽

Cpt I ◽

I Gene

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Long-chain fatty acids regulate liver carnitine palmitoyltransferase I gene (L-CPT I) expression through a peroxisome-proliferator-activated receptor α (PPARα)-independent pathway

Biochemical Journal ◽

10.1042/bj3540189 ◽

2001 ◽

Vol 354 (1) ◽

pp. 189-197 ◽

Cited By ~ 59

Author(s):

Jean-Francç;ois LOUET ◽

Florence CHATELAIN ◽

Jean-Francç;ois DECAUX ◽

Edwards A. PARK ◽

Claude KOHL ◽

...

Keyword(s):

Gene Expression ◽

Carnitine Palmitoyltransferase ◽

Dietary Lipids ◽

Lipid Lowering ◽

Peroxisome Proliferator ◽

Peroxisome Proliferator Activated Receptor ◽

Carnitine Palmitoyltransferase I ◽

Cpt I ◽

I Gene ◽

Long Chain

Liver carnitine palmitoyltransferase I (L-CPT I) catalyses the transfer of long-chain fatty acid (LCFA) for translocation across the mitochondrial membrane. Expression of the L-CPT I gene is induced by LCFAs as well as by lipid-lowering compounds such as clofibrate. Previous studies have suggested that the peroxisome-proliferator-activated receptor α (PPARα) is a common mediator of the transcriptional effects of LCFA and clofibrate. We found that free LCFAs rather than acyl-CoA esters are the signal metabolites responsible for the stimulation of L-CPT I gene expression. Using primary culture of hepatocytes we found that LCFAs failed to stimulate L-CPT I gene expression both in wild-type and PPARα-null mice. These results suggest that the PPARα-knockout mouse does not represent a suitable model for the regulation of L-CPT I gene expression by LCFAs in the liver. Finally, we determined that clofibrate stimulates L-CPT I through a classical direct repeat 1 (DR1) motif in the promoter of the L-CPT I gene while LCFAs induce L-CPT I via elements in the first intron of the gene. Our results demonstrate that LCFAs can regulate gene expression through PPARα-independent pathways and suggest that the regulation of gene expression by dietary lipids is more complex than previously proposed.

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Expression of novel isoforms of carnitine palmitoyltransferase I (CPT-1) generated by alternative splicing of the CPT-Iβ gene

Biochemical Journal ◽

10.1042/bj3340225 ◽

1998 ◽

Vol 334 (1) ◽

pp. 225-231 ◽

Cited By ~ 11

Author(s):

Geng-Sheng YU ◽

Yi-Chun LU ◽

Tod GULICK

Keyword(s):

Alternative Splicing ◽

Donor Site ◽

Carnitine Palmitoyltransferase ◽

Membrane Topology ◽

Splice Donor Site ◽

The Novel ◽

Pcr Screening ◽

Mitochondrial Fatty Acid ◽

Carnitine Palmitoyltransferase I ◽

Cpt I

Carnitine palmitoyltransferase I (CPT-I) catalyses the rate-determining step in mitochondrial fatty acid β-oxidation. The enzyme has two cognate structural genes that are preferentially expressed in liver (α) or fat and muscle (β). We hypothesized the existence of additional isoforms in heart to account for unique kinetic characteristics of enzyme activity in this tissue. Hybridization and PCR screening of a human cardiac cDNA library revealed the expression of two novel CPT-I isoforms generated by alternative splicing of the CPT-Iβ transcript, in addition to the β and α cDNA species previously described. Ribonuclease protection and reverse transcriptase-mediated PCR assays confirmed the presence of mRNA species of each splicing variant in heart, skeletal muscle and liver, with differing relative concentrations in the tissues. The novel splicing variants omit exons or utilize a cryptic splice donor site within an exon. Deduced polypeptide sequences of the novel enzymes include omissions in the region of putative membrane-spanning and malonyl-CoA regulatory domains compared with the previously described CPT-Is, implying that the encoded enzymes will exhibit unique features with respect to outer mitochondrial membrane topology and response to physiological and pharmacological inhibitors.

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Dietary Fatty Acids Influence the Activity and Metabolic Control of Mitochondrial Carnitine Palmitoyltransferase I in Rat Heart and Skeletal Muscle

Journal of Nutrition ◽

10.1093/jn/127.11.2142 ◽

1997 ◽

Vol 127 (11) ◽

pp. 2142-2150 ◽

Cited By ~ 99

Author(s):

Glen W. Power ◽

Eric A. Newsholme

Keyword(s):

Skeletal Muscle ◽

Fatty Acids ◽

Metabolic Control ◽

Rat Heart ◽

Carnitine Palmitoyltransferase ◽

Dietary Fatty Acids ◽

Carnitine Palmitoyltransferase I

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Cold acclimation increases carnitine palmitoyltransferase I activity in oxidative muscle of striped bass

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1994.266.2.r405 ◽

1994 ◽

Vol 266 (2) ◽

pp. R405-R412 ◽

Cited By ~ 3

Author(s):

K. J. Rodnick ◽

B. D. Sidell

Keyword(s):

Cold Acclimation ◽

Striped Bass ◽

Fatty Acyl ◽

Thermal Acclimation ◽

Carnitine Palmitoyltransferase ◽

Malonyl Coa ◽

Red Muscle ◽

Carnitine Palmitoyltransferase I ◽

Cpt I ◽

Long Chain

The effect of thermal acclimation on the activity of carnitine palmitoyltransferase I (CPT I), the rate-limiting enzyme for beta-oxidation of long-chain fatty acids, was determined in oxidative red muscle of striped bass (Morone saxatilis) acclimated at 5 or 25 degrees C. As observed in mammalian tissues, malonyl-CoA potently inhibited CPT I activity of mitochondria. Inhibition by malonyl-CoA required inclusions of both bovine serum albumin (BSA) and palmitoyl-CoA in the reaction media. Because BSA binds long-chain fatty acyl-CoAs, this observation suggests that free fatty acyl-CoAs may disrupt mitochondrial membranes and affect the CPT I protein. Cold acclimation increased citrate synthase activity 1.6-fold and total CPT activity 2-fold in homogenates of red muscle; free carnitine increased 62%, and specific activity of CPT I in mitochondria increased 2-fold. No differences were observed between cold- and warm-acclimated fish in substrate-binding properties of CPT I at an assay temperature of 15 degrees C, as judged by the Michaelis constant (Km) for carnitine (0.11 +/- 0.02 vs. 0.13 +/- 0.02 mM) or inhibition of CPT I, as determined by the half-maximal inhibition concentration (IC50) for malonyl-CoA (0.14 +/- 0.05 vs. 0.09 +/- 0.03 microM). Thermal sensitivity of CPT I (Q10 = 2.91 +/- 0.12 vs. 3.02 +/- 0.20) and preference of CPT I for different long-chain fatty acyl-CoA substrates (16:1-CoA = 16:0-CoA > 18:1-CoA) were not altered by thermal acclimation.(ABSTRACT TRUNCATED AT 250 WORDS)

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Regulation of liver carnitine palmitoyltransferase I gene expression by hormones and fatty acids

Biochemical Society Transactions ◽

10.1042/bst0290310 ◽

2001 ◽

Vol 29 (2) ◽

pp. 310-316 ◽

Cited By ~ 61

Author(s):

J.-F. Louet ◽

C. Le May ◽

J.-P. Pégorier ◽

J.-F. Decaux ◽

J. Girard

Keyword(s):

Fatty Acids ◽

Gene Transcription ◽

Peroxisome Proliferator ◽

Gene Encoding ◽

First Intron ◽

Transcriptional Effect ◽

Carnitine Palmitoyltransferase I ◽

Responsive Element ◽

Cpt I ◽

I Gene

This brief review focuses on the transcriptional regulation of liver carnitine palmitoyltransferase I (L-CPT I) by pancreatic and thyroid hormones and by long-chain fatty acids (LCFA). Both glucagon and 3,3′,5-tri-iodothyronine (T3) enhanced the transcription of the gene encoding L-CPT I, whereas insulin had the opposite effect. Interestingly, the transcriptional effect of T3 required, in addition to the thyroid-responsive element, the co-operation of a sequence located in the first intron of L-CPT I gene. Non-esterified fatty acids rather than acyl-CoA ester or intramitochondrial metabolite were responsible for the transcriptional effect on the gene encoding LCPT I. It was shown that LCFA and peroxisome proliferators stimulated L-CPT I gene transcription by distinct mechanisms. Peroxisome proliferator stimulated L-CPT I gene transcription through a peroxisome-proliferator-responsive element (PPRE) located at -2846 bp, whereas LCFA induced L-CPT I gene transcription through a peroxisome-proliferator-activated receptor α (PPARα)-independent mechanism owing to a sequence located in the first intron of the gene.

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