Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

7-Ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (irinotecan, CPT-11) is a camptothecin prodrug that is metabolized by carboxylesterases (CE) to the active metabolite 7-ethyl-10-hydroxycamptothecin (SN-38), a topoisomerase I inhibitor. CPT-11 has shown encouraging antitumor activity against a broad spectrum of tumor types in early clinical trials, but hematopoietic and gastrointestinal toxicity limit its administration. To increase the therapeutic index of CPT-11 and to develop other prodrug analogues for enzyme/prodrug gene therapy applications, our laboratories propose to develop camptothecin prodrugs that will be activated by specific CEs. Specific analogues might then be predicted to be activated, for example, predominantly by human liver CE(hCE1), by human intestinal CE (hiCE), or in gene therapy approaches using a rabbit liver CE (rCE). This study describes a molecular modeling approach to relate the structure of rCE-activated camptothecin prodrugs with their biological activation. Comparative molecular field analysis, comparative molecular similarity index analysis, and docking studies were used to predict the biological activity of a 4-benzylpiperazine derivative of CPT-11 [7-ethyl-10-[4-(1-benzyl)-1-piperazino]carbonyloxycamptothecin (BP-CPT)] in U373MG glioma cell lines transfected with plasmids encoding rCE or hiCE. BP-CPT has been reported to be activated more efficiently than CPT-11 by a rat serum esterase activity; however, three-dimensional quantitative structure-activity relationship studies predicted that rCE would activate BP-CPT less efficiently than CPT-11. This was confirmed by both growth inhibition experiments and kinetic studies. The method is being used to design camptothecin prodrugs predicted to be activated by specific CEs.
Mol Cancer Ther 2003 Nov
PMID:Activation of a camptothecin prodrug by specific carboxylesterases as predicted by quantitative structure-activity relationship and molecular docking studies. 1461 91

Human topoisomerase I-B (Top1) efficiently relaxes DNA supercoils during basic cellular processes, and can be transformed into a DNA-damaging agent by antitumour drugs, enzyme mutations and DNA lesions. Here, we describe Gal4-Top1 chimeric proteins (GalTop) with an N-terminal truncation of Top1, and mutations of the Gal4 Zn-cluster and/or Top1 domains that impair their respective DNA-binding activities. Expression levels of chimeras were similar in yeast cells, however, GalTop conferred an increased CPT sensitivity to RAD52- yeast cells as compared to a GalTop with mutations of the Gal4 domain, showing that a functional Gal4 domain can alter in vivo functions of Top1. In vitro enzyme activity was tested with a DNA relaxation assay using negatively supercoiled plasmids with 0 to 5 Gal4 consensus motifs. Only GalTop with a functional Gal4 domain could direct DNA relaxation activity of Top1 specifically to DNA molecules containing Gal4 motifs. By using a substrate competition assay, we could demonstrate that the Gal4-anchored Top1 remains functional and efficiently relax DNA substrates in cis. The enhanced CPT sensitivity of GalTop in yeast cells may then be due to alterations of the chromatin-binding activity of Top1. The GalTop chimeras may indeed mimic a normal mechanism by which Top1 is recruited to chromatin sites in living cells. Such hybrid Top1s may be helpful in further dissecting enzyme functions, and constitute a prototype of a site-specific DNA cutter endowed with high cell lethality.
J Mol Biol 2004 Mar 19
PMID:Enhanced CPT sensitivity of yeast cells and selective relaxation of Ga14 motif-containing DNA by novel Gal4-topoisomerase I fusion proteins. 1500 48

The metabolic and genic effects induced by a 20-fold lowering of carnitine content in the heart were studied in mildronate-treated rats. In the perfused heart, the proportion of palmitate taken up then oxidized was 5-10% lower, while the triacylglycerol (TAG) formation was 100% greater than in controls. The treatment was shown to increase the maximal capacity of heart homogenates to oxidize palmitate, the mRNA level of carnitine palmitoyltransferase I (CPT-I) isoforms, the specific activity of CPT-I in subsarcolemmal mitochondria and the total carnitine content of isolated mitochondria. Concomitantly, the increased mRNA expression of lipoprotein lipase, fatty acid translocase and enzymes of TAG synthesis was associated with a 5- and 2-times increase in serum TAG and free fatty acid contents, respectively. The compartmentation of carnitine at its main functional location was expected to allow the increased CPT-I activity to ensure in vivo correct fatty acid oxidation rates. All the inductions related to fatty acid transport, oxidation and esterification most likely stem from the abundance of blood lipids providing cardiomyocytes with more fatty acids.
Mol Cell Biochem 2004 Mar
PMID:Fatty acid oxidation and related gene expression in heart depleted of carnitine by mildronate treatment in the rat. 1503 Jan 82

Phase I and II clinical trails are currently investigating the antitumor activity of cisplatin and camptothecins (CPTs; DNA topoisomerase I poisons), based on the dramatic synergistic cytotoxicity of these agents in some preclinical models. However, the mechanistic basis for this synergism is poorly understood. By exploiting the evolutionary conservation of DNA repair pathways from genetically tractable organisms such as budding and fission yeasts to mammalian cells, we demonstrate that the synergism of CPT and cisplatin requires homologous recombination. In yeast and mammalian cell lines defective for RAD52 and XRCC2/3, respectively, the combination of these agents proved antagonistic, while greater than additive activity was evident in isogenic wild-type cells. Homologous recombination appears to mediate a similar interaction of X-rays and CPT, but antagonizes the synergism of cytarabine (Ara-C) with CPT. These findings suggest that homologous recombination comprises an evolutionarily conserved determinant of cellular sensitivity when CPTs are used in combination with other therapeutics.
Mol Cancer Ther 2004 Apr
PMID:Homologous recombination is a highly conserved determinant of the synergistic cytotoxicity between cisplatin and DNA topoisomerase I poisons. 1507 82

Liver carnitine palmitoyltransferase I (CPT I) deficiency is a rare disorder of hepatic mitochondrial long-chain fatty acid oxidation. It characteristically presents with symptoms associated with failure of ketogenesis (hypoketotic hypoglycemia). The disorder is due to mutations in the CPT 1A gene for which few patients have been characterized. We present here four novel mutations in five patients from four families with severe enzyme deficiency. Three of these are missense mutations (G465W, R316G, and F343V) and the fourth a nonsense mutation (R160X). Other than small Inuit and Hutterite populations in Canada and the Northern plains, there is complete heterogeneity of disease-causing mutations within CPT I deficient families with each demonstrating unique mutations. Because there are no easily recognizable disease-specific metabolite markers, diagnostic confirmation of this disorder requires a combination of enzymatic analysis and whole gene sequencing.
Mol Genet Metab 2004 May
PMID:Novel mutations in CPT 1A define molecular heterogeneity of hepatic carnitine palmitoyltransferase I deficiency. 1511 Mar 23

Peroxisome proliferator-activated receptor (PPAR) alpha is a nuclear receptor implicated in several physiological processes such as lipid and lipoprotein metabolism, glucose homeostasis, and the inflammatory response. PPARalpha is activated by natural fatty acids and synthetic compounds like fibrates. PPARalpha activity has been shown to be modulated by its phosphorylation status. PPARalpha is phosphorylated by kinases such as the MAPKs and cAMP-activated protein kinase A. In this report, we show that protein kinase C (PKC) inhibition impairs ligand-activated PPARalpha transcriptional activity. Furthermore, PKC inhibition decreases PPARalpha ligand-induction of its target genes including PPARalpha itself and carnitine palmitoyltransferase I. By contrast, PKC inhibition enhances PPARalpha transrepression properties as demonstrated using the fibrinogen-beta gene as model system. Finally, PKC inhibition decreases PPARalpha phosphorylation activity of hepatocyte cell extracts. In addition, PPARalpha purified protein is phosphorylated in vitro by recombinant PKCalpha and betaII. The replacement of serines 179 and 230 by alanine residues reduces the phosphorylation of the PPARalpha protein. The PPARalpha S179A-S230A protein displays an impaired ligand-induced transactivation activity and an enhanced trans-repression activity. Altogether, our data indicate that the PKC signaling pathway acts as a molecular switch dissociating the transactivation and transrepression functions of PPARalpha, which involved phosphorylation of serines 179 and 230.
Mol Endocrinol 2004 Aug
PMID:The protein kinase C signaling pathway regulates a molecular switch between transactivation and transrepression activity of the peroxisome proliferator-activated receptor alpha. 1513 Dec 57

Hepatic mitochondrial outer membrane carnitine palmitoyltransferase I (CPT I) and mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (HMG-CoA synthase) enzymes play a key role in regulation of fatty acid oxidation and in ketogenic pathways, respectively. Their expression are regulated by fatty acids mainly by the peroxisome proliferator-activated receptor alpha (PPARalpha). To investigate possible mechanisms through which cancer alters the lipid metabolism, we analyzed by Northern blot, the mRNA relative abundance of these proteins in liver from healthy and DMBA-induced mammary tumor-bearing rats fed a low or high corn oil diet. Serum levels of lipids, body weight and mass were also determined. Whereas mRNA steady-state levels of CPT I and mit HMG-CoA synthase were unaffected by the presence of the extra-hepatic tumor, the cancer state seemed to modify the regulation of the expression of these genes by high fat diet. We hypothesize that putative changes in PPARalpha mRNA levels could have contributed to such alterations. These results, together with changes in serum lipid profiles, body weight and mass, indicate fat mobilization and non-enhanced oxidation rates despite a high-fat feeding. This effect of the cancer state could be related to tumor aggressiveness and suggest a preferential redirection of long-chain fatty acids into energetic and specific pathways of the cancer cells.
Int J Mol Med 2004 Aug
PMID:Influence of DMBA-induced mammary cancer on the liver CPT I, mit HMG-CoA synthase and PPARalpha mRNA expression in rats fed a low or high corn oil diet. 1525 79

Carnitine status in humans is reported to vary according to body composition, gender, and diet. Plasma carnitine concentration positively correlates with the dietary intake of carnitine. The content of carnitine in foodstuff is based on old and inadequate methodology. Nevertheless, dietary carnitine is important. The molecular biology of the enzymes of carnitine biosynthesis has recently been accomplished. Carnitine biosynthesis requires pathways in different tissues and is an efficient system. Overall biosynthesis is determined by the availability of trimethyllysine from tissue proteins. Carnitine deficiency resulting from a defect in biosynthesis has yet to be reported. The role of carnitine in long-chain fatty acid oxidation is well defined. Recent evidence supports a role for the voltage-dependent anion channel in the transport of acyl-CoAs through the mitochondrial outer membrane. The mitochondrial outer membrane carnitine palmitoyltransferase-I in liver can be phosphorylated and when phosphorylated the sensitivity to malonyl-CoA is greatly decreased. This may explain the change in sensitivity of liver carnitine palmitoyltransferase-I observed during fasting and diabetes. Recently reported data clarify the role of carnitine and the carnitine transport system in the interplay between peroxisomes and mitochondrial fatty acid oxidation. Lastly, the buffering of the acyl-CoA/CoA coupled by carnitine reflects intracellular metabolism. This mass action effect underlies the use of carnitine as a therapeutic agent. In summary, these new observations help to further our understanding of the molecular aspects of carnitine in medicine.
Mol Aspects Med
PMID:Carnitine: a nutritional, biosynthetic, and functional perspective. 1536 36

To investigate the response to fenofibrate in pregnant rats, 0 mg, 100 mg or 200 mg of fenofibrate per kilogram body weight oral doses were given twice a day from day 16 of gestation and studied at day 20. Virgin rats were studied in parallel. Whereas in pregnant rats plasma triglycerides significantly increased, in virgin rats, fenofibrate decreased plasma triglycerides which accumulated in liver. Fenofibrate faithfully modulated the hepatic expression of PPARalpha responsive genes. Fenofibrate increased mRNA contents corresponding to both acyl-CoA oxidase, carnitine palmitoyltransferase (CPT), and peroxisome proliferator-activated receptor alpha (PPAR), and lowered mRNA amounts of apolipoproteins B and C-III, both in virgin and pregnant rats. However, genes related to hepatic lipogenesis, such as PPARy and stearoyl-CoA desaturase (SCD), showed an augmented expression by fenofibrate in virgin rats, but not in pregnant animals. We propose that the opposite effects of fenofibrate treatment in virgin and pregnant rats are a consequence of the enhanced capability for VLDL-triglyceride production in the latter, further promoted by the elevated amount of free fatty acids (FFA), which reach the liver in treated pregnant rats and were not sufficiently oxidized and/or stored, and therefore would have to be canalized as triglycerides to the plasma. Thus, the present study shows how fenofibrate, in spite of efficiently exerting its expected molecular effects in the liver (i.e., to induce fatty acid and lipoprotein catabolism, and to reduce TG-rich lipoprotein secretion), was unable to reverse the typical hypertriglyceridaemia of gestation.
Mol Cell Biochem 2005 May
PMID:Triglyceridemia and peroxisome proliferator-activated receptor-alpha expression are not connected in fenofibrate-treated pregnant rats. 1601 44

Nonalcoholic fatty liver disease (NAFLD) is one of the most frequent causes of abnormal liver dysfunction, and its prevalence has markedly increased; however, the mechanisms involved in the pathogenesis of NAFLD have not been thoroughly investigated in humans. In this study, we evaluated the expression of fatty acid metabolism-related genes in NAFLD. Real-time RT-PCR was performed using liver biopsy samples from 12 NAFLD patients. The target genes studied were: acetyl-CoA carboxylase (ACC) 1, ACC2, and fatty acid synthase (FAS) for the evaluation of de novo fatty acid synthesis; carnitine palmitoyltransferase 1a (CPT1a), long-chain acyl-CoA dehydrogenase (LCAD), and long-chain L-3-hydroxyacyl-coenzyme A dehydrogenase alpha (HADHalpha) for beta-oxidation in the mitochondria; peroxisome proliferator-activated receptor- (PPAR-) alpha and cytochrome P450 2E1 (CYP2E1) for oxidation in peroxisomes and microsomes (endoplasmic reticulum) respectively; and diacylglycerol O-acyltransferase 1 (DGAT1), PPAR-gamma, and hormone sensitive lipase (HSL) for triglyceride synthesis and catalysis. In NAFLD, expression of ACC1 and ACC2, but not FAS was increased, indicating that de novo fatty acid synthesis is enhanced in NAFLD. In contrast, expression of CTP1a, a rate-limiting enzyme, was remarkably decreased, indicating that beta-oxidation in the mitochondria was decreased, although the expression of LCAD and HADHalpha was increased. Expression of PPAR-alpha was increased, whereas that of CYP2E1 was reduced. The expression of DGAT1, PPAR-gamma, and HSL was enhanced. These data suggest that in NAFLD, increased de novo synthesis and decreased beta-oxidation in the mitochondria lead to accumulation of fatty acids in hepatocytes, although the extent of oxidation in peroxisomes and microsomes remains unclear.
Int J Mol Med 2005 Oct
PMID:Evaluation of fatty acid metabolism-related gene expression in nonalcoholic fatty liver disease. 1614 97


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