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Iqbal J, Jahangir Z, Al-Qarni AA. Microsomal Triglyceride Transfer Protein: From Lipid Metabolism to Metabolic Diseases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1276:37-52. [DOI: 10.1007/978-981-15-6082-8_4] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Korber M, Klein I, Daum G. Steryl ester synthesis, storage and hydrolysis: A contribution to sterol homeostasis. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1534-1545. [DOI: 10.1016/j.bbalip.2017.09.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 08/25/2017] [Accepted: 09/05/2017] [Indexed: 02/01/2023]
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Qiao LS, Zhang XB, Jiang LD, Zhang YL, Li GY. Identification of potential ACAT-2 selective inhibitors using pharmacophore, SVM and SVR from Chinese herbs. Mol Divers 2016; 20:933-944. [PMID: 27329301 DOI: 10.1007/s11030-016-9684-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2016] [Accepted: 06/06/2016] [Indexed: 12/13/2022]
Abstract
Acyl-coenzyme A cholesterol acyltransferase (ACAT) plays an important role in maintaining cellular and organismal cholesterol homeostasis. Two types of ACAT isozymes with different functions exist in mammals, named ACAT-1 and ACAT-2. Numerous studies showed that ACAT-2 selective inhibitors are effective for the treatment of hypercholesterolemia and atherosclerosis. However, as a typical endoplasmic reticulum protein, ACAT-2 protein has not been purified and revealed, so combinatorial ligand-based methods might be the optimal strategy for discovering the ACAT-2 selective inhibitors. In this study, selective pharmacophore models of ACAT-1 inhibitors and ACAT-2 inhibitors were built, respectively. The optimal pharmacophore model for each subtype was identified and utilized as queries for the Traditional Chinese Medicine Database screening. A total of 180 potential ACAT-2 selective inhibitors were obtained, which were identified using an ACAT-2 pharmacophore and not by our ACAT-1 model. Selective SVM model and bioactive SVR model were generated for further identification of the obtained ACAT-2 inhibitors. Ten compounds were finally obtained with predicted inhibitory activities toward ACAT-2. Hydrogen bond acceptor, 2D autocorrelations, GETAWAY descriptors, and BCUT descriptors were identified as key structural features for selectivity and activity of ACAT-2 inhibitors. This study provides a reasonable ligand-based approach to discover potential ACAT-2 selective inhibitors from Chinese herbs, which could help in further screening and development of ACAT-2 selective inhibitors.
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Affiliation(s)
- Lian-Sheng Qiao
- Key Laboratory of TCM Foundation and New Drug Research, School of Chinese Material Medica, Beijing University of Chinese Medicine, Beijing, 100102, China
| | - Xian-Bao Zhang
- Key Laboratory of TCM Foundation and New Drug Research, School of Chinese Material Medica, Beijing University of Chinese Medicine, Beijing, 100102, China
| | - Lu-di Jiang
- Key Laboratory of TCM Foundation and New Drug Research, School of Chinese Material Medica, Beijing University of Chinese Medicine, Beijing, 100102, China
| | - Yan-Ling Zhang
- Key Laboratory of TCM Foundation and New Drug Research, School of Chinese Material Medica, Beijing University of Chinese Medicine, Beijing, 100102, China.
| | - Gong-Yu Li
- Key Laboratory of TCM Foundation and New Drug Research, School of Chinese Material Medica, Beijing University of Chinese Medicine, Beijing, 100102, China
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Ge J, Cheng B, Qi B, Peng W, Wen H, Bai L, Liu Y, Zhai W. Cloning and functional analysis of human acyl coenzyme A: Cholesterol acyltransferase1 gene P1 promoter. Mol Med Rep 2016; 14:831-8. [PMID: 27220725 DOI: 10.3892/mmr.2016.5295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 04/13/2016] [Indexed: 11/05/2022] Open
Abstract
Acyl-coenzyme A: cholesterol acyltransferase 1 (ACAT1) catalyzes the conversion of free cholesterol (FC) to cholesterol ester. The human ACAT1 gene P1 promoter has been cloned. However, the activity and specificity of the ACAT1 gene P1 promoter in diverse cell types remains unclear. The P1 promoter fragment was digested with KpnI/XhoI from a P1 promoter cloning vector, and was subcloned into the multiple cloning site of the Firefly luciferase vector pGL3‑Enhancer to obtain the construct P1E‑1. According to the analysis of biological information, the P1E‑1 plasmid was used to generate deletions of the ACAT1 gene P1 promoter with varying 5' ends and an identical 3' end at +65 by polymerase chain reaction (PCR). All the 5'‑deletion constructs of the P1 promoter were identified by PCR, restriction enzyme digestion mapping and DNA sequencing. The transcriptional activity of each construct was detected after transient transfection into THP‑1, HepG2, HEK293 and Hela cells using DEAE‑dextran and Lipofectamine 2000 liposome transfection reagent. Results showed that the transcriptional activity of the ACAT1 gene P1 promoter and deletions of P1 promoter in THP‑1 and HepG2 cells was higher than that in HEK293 and HeLa cells. Moreover, the transcriptional activity of P1E‑9 was higher compared with those of other deletions in THP‑1, HepG2, HEK293 and HeLa cells. These findings indicate that the transcriptional activity of the P1 promoter and the effects of deletions vary with different cell lines. Thus, the P1 promoter may drive ACAT1 gene expression with cell‑type specificity. In addition, the core sequence of ACAT1 gene P1 promoter was suggested to be between -125 and +65 bp.
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Affiliation(s)
- Jing Ge
- Department of Geriatrics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, P.R. China
| | - Bei Cheng
- Department of Geriatrics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, P.R. China
| | - Benling Qi
- Department of Geriatrics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, P.R. China
| | - Wen Peng
- Department of Geriatrics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, P.R. China
| | - Hui Wen
- Department of Geriatrics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, P.R. China
| | - Lijuan Bai
- Department of Geriatrics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, P.R. China
| | - Yun Liu
- Department of Geriatrics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, P.R. China
| | - Wei Zhai
- Department of Thoracic Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, P.R. China
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Pramfalk C, Eriksson M, Parini P. Role of TG-interacting factor (Tgif) in lipid metabolism. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1851:9-12. [PMID: 25088698 DOI: 10.1016/j.bbalip.2014.07.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 07/17/2014] [Accepted: 07/24/2014] [Indexed: 11/18/2022]
Abstract
TG interacting factors (Tgifs) 1 and 2 are members of the TALE (three-amino-acid loop extension) superfamily of homeodomain proteins. These two proteins bind to the same DNA sequence and share a conserved C-terminal repression domain. Mutations in TGIF1 have been linked to holoprosencephaly, which is a human genetic disease that affects craniofacial development. As these proteins can interact with the ligand binding domain of retinoid X receptor α, a common heterodimeric partner of several nuclear receptors [e.g., liver X receptors (LXRs) and peroxisome proliferator-activated receptors (PPARs)], Tgif1 and Tgif2 might repress other transcriptional pathways activated by lipids. In line with this, Tgif1 interacts with LXRα and Tgif1 null mice have increased expression of the two Lxrα target genes apolipoproteins (Apo) c2 and a4. Also, we have recently identified Tgif1 to function as a transcriptional repressor of the cholesterol esterifying enzyme acyl-coenzyme A:cholesterol acyltransferase 2 (gene name SOAT2). As no studies yet have shown involvement of Tgif2 in the lipid metabolism, this review will focus on the role of Tgif1 in lipid and cholesterol metabolism. This article is part of a Special Issue entitled: Linking transcription to physiology in lipodomics.
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Affiliation(s)
- Camilla Pramfalk
- Division of Clinical Chemistry, Department of Laboratory Medicine, Centre for Nutrition and Toxicology, NOVUM, Karolinska Institutet at Karolinska University Hospital Huddinge, Sweden; Molecular Nutrition Unit, Department of Biosciences and Nutrition, Centre for Nutrition and Toxicology, NOVUM, Karolinska Institutet at Karolinska University Hospital Huddinge, Sweden
| | - Mats Eriksson
- Molecular Nutrition Unit, Department of Biosciences and Nutrition, Centre for Nutrition and Toxicology, NOVUM, Karolinska Institutet at Karolinska University Hospital Huddinge, Sweden; Metabolism Unit, Department of Endocrinology, Metabolism and Diabetes, and Department of Medicine, Karolinska Institutet at Karolinska University Hospital, Huddinge, S-141 86 Stockholm, Sweden
| | - Paolo Parini
- Division of Clinical Chemistry, Department of Laboratory Medicine, Centre for Nutrition and Toxicology, NOVUM, Karolinska Institutet at Karolinska University Hospital Huddinge, Sweden; Molecular Nutrition Unit, Department of Biosciences and Nutrition, Centre for Nutrition and Toxicology, NOVUM, Karolinska Institutet at Karolinska University Hospital Huddinge, Sweden.
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Pramfalk C, Melhuish TA, Wotton D, Jiang ZY, Eriksson M, Parini P. TG-interacting factor 1 acts as a transcriptional repressor of sterol O-acyltransferase 2. J Lipid Res 2014; 55:709-17. [PMID: 24478032 PMCID: PMC3966704 DOI: 10.1194/jlr.m045922] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Revised: 01/26/2014] [Indexed: 11/20/2022] Open
Abstract
Acat2 [gene name: sterol O-acyltransferase 2 (SOAT2)] esterifies cholesterol in enterocytes and hepatocytes. This study aims to identify repressor elements in the human SOAT2 promoter and evaluate their in vivo relevance. We identified TG-interacting factor 1 (Tgif1) to function as an important repressor of SOAT2. Tgif1 could also block the induction of the SOAT2 promoter activity by hepatocyte nuclear factor 1α and 4α. Women have ∼ 30% higher hepatic TGIF1 mRNA compared with men. Depletion of Tgif1 in mice increased the hepatic Soat2 expression and resulted in higher hepatic lipid accumulation and plasma cholesterol levels. Tgif1 is a new player in human cholesterol metabolism.
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Affiliation(s)
- Camilla Pramfalk
- Division of Clinical Chemistry, Department of Laboratory Medicine, and Centre for Nutrition and Toxicology, NOVUM, Karolinska Institutet at Karolinska University Hospital Huddinge, Stockholm, Sweden
- Molecular Nutrition Unit, Department of Biosciences and Nutrition, Centre for Nutrition and Toxicology, NOVUM, Karolinska Institutet at Karolinska University Hospital Huddinge, Stockholm, Sweden
| | - Tiffany A. Melhuish
- Department of Biochemistry and Molecular Genetics and Center for Cell Signaling, University of Virginia, Charlottesville, VA
| | - David Wotton
- Department of Biochemistry and Molecular Genetics and Center for Cell Signaling, University of Virginia, Charlottesville, VA
| | - Zhao-Yan Jiang
- Department of Surgery, Shanghai Institute of Digestive Surgery, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China; and
| | - Mats Eriksson
- Molecular Nutrition Unit, Department of Biosciences and Nutrition, Centre for Nutrition and Toxicology, NOVUM, Karolinska Institutet at Karolinska University Hospital Huddinge, Stockholm, Sweden
- Metabolism Unit, Department of Endocrinology, Metabolism and Diabetes, and Department of Medicine, Karolinska Institutet at Karolinska University Hospital Huddinge, Stockholm, Sweden
| | - Paolo Parini
- Division of Clinical Chemistry, Department of Laboratory Medicine, and Centre for Nutrition and Toxicology, NOVUM, Karolinska Institutet at Karolinska University Hospital Huddinge, Stockholm, Sweden
- Molecular Nutrition Unit, Department of Biosciences and Nutrition, Centre for Nutrition and Toxicology, NOVUM, Karolinska Institutet at Karolinska University Hospital Huddinge, Stockholm, Sweden
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Acyltransferases and transacylases that determine the fatty acid composition of glycerolipids and the metabolism of bioactive lipid mediators in mammalian cells and model organisms. Prog Lipid Res 2014; 53:18-81. [DOI: 10.1016/j.plipres.2013.10.001] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 07/20/2013] [Accepted: 10/01/2013] [Indexed: 12/21/2022]
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Lu M, Hu XH, Li Q, Xiong Y, Hu GJ, Xu JJ, Zhao XN, Wei XX, Chang CCY, Liu YK, Nan FJ, Li J, Chang TY, Song BL, Li BL. A specific cholesterol metabolic pathway is established in a subset of HCCs for tumor growth. J Mol Cell Biol 2013; 5:404-15. [PMID: 24163426 DOI: 10.1093/jmcb/mjt039] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The liver plays a central role in cholesterol homeostasis. It exclusively receives and metabolizes oxysterols, which are important metabolites of cholesterol and are more cytotoxic than free cholesterol, from all extrahepatic tissues. Hepatocellular carcinomas (HCCs) impair certain liver functions and cause pathological alterations in many processes including cholesterol metabolism. However, the link between an altered cholesterol metabolism and HCC development is unclear. Human ACAT2 is abundantly expressed in intestine and fetal liver. Our previous studies have shown that ACAT2 is induced in certain HCC tissues. Here, by investigating tissue samples from HCC patients and HCC cell lines, we report that a specific cholesterol metabolic pathway, involving induction of ACAT2 and esterification of excess oxysterols for secretion to avoid cytotoxicity, is established in a subset of HCCs for tumor growth. Inhibiting ACAT2 leads to the intracellular accumulation of unesterified oxysterols and suppresses the growth of both HCC cell lines and their xenograft tumors. Further mechanistic studies reveal that HCC-linked promoter hypomethylation is essential for the induction of ACAT2 gene expression. We postulate that specifically blocking this HCC-established cholesterol metabolic pathway may have potential therapeutic applications for HCC patients.
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Affiliation(s)
- Ming Lu
- State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
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Burst of succinate dehydrogenase and α-ketoglutarate dehydrogenase activity in concert with the expression of genes coding for respiratory chain proteins underlies short-term beneficial physiological stress in mitochondria. Int J Biochem Cell Biol 2012; 45:190-200. [PMID: 22814171 DOI: 10.1016/j.biocel.2012.07.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2012] [Revised: 06/28/2012] [Accepted: 07/01/2012] [Indexed: 11/20/2022]
Abstract
Conditions for the realization in rats of moderate physiological stress (PHS) (30-120 min) were selected, which preferentially increase adaptive restorative processes without adverse responses typical of harmful stress (HST). The succinate dehydrogenase (SDH) and α-ketoglutarate dehydrogenase (KDH) activity and the formation of reactive oxygen species (ROS) in mitochondria were measured in lymphocytes by the cytobiochemical method, which detects the regulation of mitochondria in the organism with high sensitivity. These mitochondrial markers undergo an initial 10-20-fold burst of activity followed by a decrease to a level exceeding the quiescent state 2-3-fold by 120 min of PHS. By 30-60 min, the rise in SDH activity was greater than in KDH activity, while the activity of KDH prevailed over that of SDH by 120 min. The attenuation of SDH hyperactivity during PHS occurs by a mechanism other than oxaloacetate inhibition developed under HST. The dynamics of SDH and KDH activity corresponds to the known physiological replacement of adrenergic regulation by cholinergic during PHS, which is confirmed here by mitochondrial markers because their activity reflects these two types of nerve regulation, respectively. The domination of cholinergic regulation provides the overrestoration of expenditures for activity. In essence, this phenomenon corresponds to the training of the organism. It was first revealed in mitochondria after a single short-time stress episode. The burst of ROS formation was congruous with changes in SDH and KDH activity, as well as in ucp2 and cox3 expression, while the activity of SDH was inversely dependent on the expression of the gene of its catalytic subunit in the spleen. As the SDH activity enhanced, the expression of the succinate receptor decreased with subsequent dramatic rise when the activity was becoming lower. This article is part of a Directed Issue entitled: Bioenergetic dysfunction, adaption and therapy.
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Hussain MM, Rava P, Walsh M, Rana M, Iqbal J. Multiple functions of microsomal triglyceride transfer protein. Nutr Metab (Lond) 2012; 9:14. [PMID: 22353470 PMCID: PMC3337244 DOI: 10.1186/1743-7075-9-14] [Citation(s) in RCA: 175] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 02/21/2012] [Indexed: 02/08/2023] Open
Abstract
Microsomal triglyceride transfer protein (MTP) was first identified as a major cellular protein capable of transferring neutral lipids between membrane vesicles. Its role as an essential chaperone for the biosynthesis of apolipoprotein B (apoB)-containing triglyceride-rich lipoproteins was established after the realization that abetalipoproteinemia patients carry mutations in the MTTP gene resulting in the loss of its lipid transfer activity. Now it is known that it also plays a role in the biosynthesis of CD1, glycolipid presenting molecules, as well as in the regulation of cholesterol ester biosynthesis. In this review, we will provide a historical perspective about the identification, purification and characterization of MTP, describe methods used to measure its lipid transfer activity, and discuss tissue expression and function. Finally, we will review the role MTP plays in the assembly of apoB-lipoprotein, the regulation of cholesterol ester synthesis, biosynthesis of CD1 proteins and propagation of hepatitis C virus. We will also provide a brief overview about the clinical potentials of MTP inhibition.
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Affiliation(s)
- M Mahmood Hussain
- Department of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Paul Rava
- Department of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Meghan Walsh
- Department of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Muhammad Rana
- Department of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Jahangir Iqbal
- Department of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
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García-Bilbao A, Armañanzas R, Ispizua Z, Calvo B, Alonso-Varona A, Inza I, Larrañaga P, López-Vivanco G, Suárez-Merino B, Betanzos M. Identification of a biomarker panel for colorectal cancer diagnosis. BMC Cancer 2012; 12:43. [PMID: 22280244 PMCID: PMC3323359 DOI: 10.1186/1471-2407-12-43] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Accepted: 01/26/2012] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Malignancies arising in the large bowel cause the second largest number of deaths from cancer in the Western World. Despite progresses made during the last decades, colorectal cancer remains one of the most frequent and deadly neoplasias in the western countries. METHODS A genomic study of human colorectal cancer has been carried out on a total of 31 tumoral samples, corresponding to different stages of the disease, and 33 non-tumoral samples. The study was carried out by hybridisation of the tumour samples against a reference pool of non-tumoral samples using Agilent Human 1A 60-mer oligo microarrays. The results obtained were validated by qRT-PCR. In the subsequent bioinformatics analysis, gene networks by means of Bayesian classifiers, variable selection and bootstrap resampling were built. The consensus among all the induced models produced a hierarchy of dependences and, thus, of variables. RESULTS After an exhaustive process of pre-processing to ensure data quality--lost values imputation, probes quality, data smoothing and intraclass variability filtering--the final dataset comprised a total of 8, 104 probes. Next, a supervised classification approach and data analysis was carried out to obtain the most relevant genes. Two of them are directly involved in cancer progression and in particular in colorectal cancer. Finally, a supervised classifier was induced to classify new unseen samples. CONCLUSIONS We have developed a tentative model for the diagnosis of colorectal cancer based on a biomarker panel. Our results indicate that the gene profile described herein can discriminate between non-cancerous and cancerous samples with 94.45% accuracy using different supervised classifiers (AUC values in the range of 0.997 and 0.955).
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Affiliation(s)
- Amaia García-Bilbao
- GAIKER Technology Centre, Parque Tecnológico, Edificio 202, 48170 Zamudio, (Bizkaia), Spain
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Xie SM, Fang WY, Liu TF, Yao KT, Zhong XY. Association of ABCC2 and CDDP-Resistance in Two Sublines Resistant to CDDP Derived from a Human Nasopharyngeal Carcinoma Cell Line. JOURNAL OF ONCOLOGY 2010; 2010:915046. [PMID: 20628484 PMCID: PMC2902222 DOI: 10.1155/2010/915046] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Accepted: 04/08/2010] [Indexed: 11/18/2022]
Abstract
Cisplatin (CDDP) is one of the most active drugs to treat nasopharyngeal carcinoma (NPC) patients. To further understand the mechanisms of CDDP-resistance in NPC, two CDDP-resistant sublines (CNE2-CDDP and CNE2-CDDP-5Fu) derived from parental NPC cell line CNE2 were established. It was found that at the IC50 level, the resistance of CNE2-CDDP and CNE2-CDDP-5Fu against CDDP was 2.63-fold and 5.35-fold stronger than that of parental CNE2, respectively. Of the four ABC transporters (ABCB1, ABCC1, ABCC2 and ABCG2) related to MDR, only ABCC2 was found to be elevated both in CDDP-resistant sublines, with ABCC2 located in nucleus of CNE2-CDDP-5Fu but not in CNE2-CDDP and parental CNE2. Further research showed that compared to untreated CNE2, the intracellular levels of CDDP were decreased by 2.03-fold in CNE2-CDDP and 2.78-fold in CNE2-CDDP-5Fu. After treatment with PSC833, a modulator of MDR associated transporters including ABCC2, the intracellular level of CDDP was increased in CDDP-resistant sublines, and the resistance to CDDP was partially reversed from 2.63-fold to 1.62-fold in CNE2-CDDP and from 5.35-fold to 4.62-fold in CNE2-CDDP-5Fu. These data indicate that ABCC2 may play an important role in NPC resistant to CDDP.
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Affiliation(s)
- Si Ming Xie
- Cancer Research Institute, Southern Medical University, Guangzhou City, Guangdong Province 510515, China
- Postdoctoral Station of Clinical Medicine, Medical College, Jinan University, Guangzhou City, Guangdong Province 510632, China
| | - Wei Yi Fang
- Cancer Research Institute, Southern Medical University, Guangzhou City, Guangdong Province 510515, China
| | - Teng Fei Liu
- Cancer Research Institute, Southern Medical University, Guangzhou City, Guangdong Province 510515, China
| | - Kai Tai Yao
- Cancer Research Institute, Southern Medical University, Guangzhou City, Guangdong Province 510515, China
| | - Xue Yun Zhong
- Pathology Department, Medical College, Jinan University, Guangzhou City, Guangdong Province 510632, China
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Abstract
The enzymes acyl-coenzyme A (CoA):cholesterol acyltransferases (ACATs) are membrane-bound proteins that utilize long-chain fatty acyl-CoA and cholesterol as substrates to form cholesteryl esters. In mammals, two isoenzymes, ACAT1 and ACAT2, encoded by two different genes, exist. ACATs play important roles in cellular cholesterol homeostasis in various tissues. This chapter summarizes the current knowledge on ACAT-related research in two areas: 1) ACAT genes and proteins and 2) ACAT enzymes as drug targets for atherosclerosis and for Alzheimer's disease.
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Affiliation(s)
- Ta-Yuan Chang
- Department of Biochemistry, Dartmouth Medical School, 1 Rope Ferry Rd., Hanover, NH 03755-1404, USA.
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Mehtiev AR, Kozlova NI, Skripnik VV, Misharin AY. The effects of (22S,23S)- and (22R,23R)-3β-hydroxy-22,23-oxido-5α-ergost-8(14)-en-15-ones on biosynthesis of cholesteryl esters and activity of acyl-CoA:Cholesterol acyl transferase in Hep G2 cells. BIOCHEMISTRY MOSCOW-SUPPLEMENT SERIES B-BIOMEDICAL CHEMISTRY 2008. [DOI: 10.1134/s1990750808040112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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He P, Cheng B, Wang Y, Wang H. Effect of tumor necrosis factor-alpha on acyl coenzyme A: cholesteryl acyltransferase activity and ACAT1 gene expression in THP-1 macrophages. ACTA ACUST UNITED AC 2008; 27:170-2. [PMID: 17497288 DOI: 10.1007/s11596-007-0216-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2006] [Indexed: 11/24/2022]
Abstract
In order to explore the effect and mechanisms of tumor necrosis factor-alpha (TNF-alpha) on the activity of the acyl coenzyme A: cholesteryl acyltransferase (ACAT), THP-1 monocytes were cultured and induced to differentiate into macrophages with phorbol ester. TNF-alpha (60 ng/mL) was added at different time points into the macrophage-containing medium and the ACAT enzyme activity was measured by quantifying the incorporation of [1-(14)C] oleoyl CoA into cholesteryl esters. The expression of ACAT-1 protein and mRNA was respectively detected by Western blotting and RT-PCR in THP-1 macrophages 24 h after treatment with TNF-alpha (60 ng/mL). The results indicated that ACAT activity in THP-1 macrophages treated with TNF-alpha was increased in a time-dependent manner. The expression levels of ACAT-1 protein and mRNA were significantly increased in THP-1 macrophages after treatment with TNF-alpha (P<0.05). It was suggested that TNF-alpha could increase the activity of ACAT in THP-1 macrophages by up-regulating the expression of ACAT-1 gene.
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Affiliation(s)
- Ping He
- Department of Gerontology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
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Jacolot S, Férec C, Mura C. Iron responses in hepatic, intestinal and macrophage/monocyte cell lines under different culture conditions. Blood Cells Mol Dis 2008; 41:100-8. [DOI: 10.1016/j.bcmd.2008.01.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Revised: 01/21/2008] [Accepted: 01/25/2008] [Indexed: 01/24/2023]
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Iqbal J, Rudel LL, Hussain MM. Microsomal triglyceride transfer protein enhances cellular cholesteryl esterification by relieving product inhibition. J Biol Chem 2008; 283:19967-80. [PMID: 18502767 DOI: 10.1074/jbc.m800398200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cholesteryl ester synthesis by the acyl-CoA:cholesterol acyltransferase enzymes ACAT1 and ACAT2 is, in part, a cellular homeostatic mechanism to avoid toxicity associated with high free cholesterol levels. In hepatocytes and enterocytes, cholesteryl esters are secreted as part of apoB lipoproteins, the assembly of which is critically dependent on microsomal triglyceride transfer protein (MTP). Conditional genetic ablation of MTP reduces cholesteryl esters and enhances free cholesterol in the liver and intestine without diminishing ACAT1 and ACAT2 mRNA levels. As expected, increases in hepatic free cholesterol are associated with decreases in 3-hydroxy-3-methylglutaryl-CoA reductase and increases in ATP-binding cassette transporter 1 mRNA levels. Chemical inhibition of MTP also decreases esterification of cholesterol in Caco-2 and HepG2 cells. Conversely, coexpression of MTP and apoB in AC29 cells stably transfected with ACAT1 and ACAT2 increases cholesteryl ester synthesis. Liver and enterocyte microsomes from MTP-deficient animals synthesize lesser amounts of cholesteryl esters in vitro, but addition of purified MTP and low density lipoprotein corrects this deficiency. Enrichment of microsomes with cholesteryl esters also inhibits cholesterol ester synthesis. Thus, MTP enhances cellular cholesterol esterification by removing cholesteryl esters from their site of synthesis and depositing them into nascent apoB lipoproteins. Therefore, MTP plays a novel role in regulating cholesteryl ester biosynthesis in cells that produce lipoproteins. We speculate that non-lipoprotein-producing cells may use different mechanisms to alleviate product inhibition and modulate cholesteryl ester biosynthesis.
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Affiliation(s)
- Jahangir Iqbal
- Department of Anatomy and Cell Biology and Pediatrics, State University of New York Downstate Medical Center, Brooklyn, NY 11203, USA
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19
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Zamorano-León JJ, Fernández-Sánchez R, López Farré AJ, Lapuente-Tiana L, Alonso-Orgaz S, Sacristán D, Junquera D, Delhon A, Conesa A, Mateos-Cáceres PJ, Macaya C. Direct Effect of F12511, A Systemic Inhibitor of Acyl-CoA Cholesterol Acyltransferase on Bovine Aortic Endothelial Cells. J Cardiovasc Pharmacol 2006; 48:128-34. [PMID: 17031267 DOI: 10.1097/01.fjc.0000246263.67515.6a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
F12511(S)-2',3',5'-trimethyl-4'-hydroxy-alpha-dodecylthio-alpha-phenylacetanilide (F12511) is a new Acyl-CoA cholesterol acyltransferase (ACAT) inhibitor that not only reduces the plasma cholesterol levels but also has anti-atherosclerotic actions in animals models. The study's aim was to analyze if F12511 may directly modify the ability of tumor necrosis factor--alpha (TNF-alpha)-incubated bovine aortic endothelial cells (BAEC) to express endothelial nitric oxide synthase (eNOS) protein and inflammatory-related proteins such as platelet endothelial cell adhesion molecule (PECAM) and CD40 ligand (CD40L). The addition of increasing concentrations of F12511 (10 to 10 mol/L) failed to modify the level of eNOS protein expressed in control BAEC. TNF-alpha (10 ng/mL) reduced the expression of eNOS protein. In TNF-alpha--incubated BAEC, F12511 protected eNOS expression in a concentration-dependent manner. TNF-alpha stimulated the expression of both CD40L and PECAM in cultured BAEC. F12511 (10 mol/L) failed to modify the expression of CD40L and PECAM in control and TNF-alpha-incubated BAEC. Reverse transcriptase polymerase chain reaction showed a marked expression of the ACAT-2 isoform and absent of expression of the ACAT-1 isoform in BAEC. The presence of ACAT-2 isoform in BAEC was further confirmed by Western blot. F12511 failed to modify the expression of the proinflammatory associated proteins PECAM and CD40L in the endothelium but protected eNOS expression in the endothelial cells exposed to inflammatory conditions.
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Affiliation(s)
- José J Zamorano-León
- Cardiovascular Research Unit, Cardiovascular Institute, Hospital Clínico San Carlos, Madrid, Spain
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20
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Meuwese MC, Franssen R, Stroes ESG, Kastelein JJP. And then there were acyl coenzyme A:cholesterol acyl transferase inhibitors. Curr Opin Lipidol 2006; 17:426-30. [PMID: 16832167 DOI: 10.1097/01.mol.0000236369.50378.6e] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW The reputation of acyl coenzyme A:cholesterol acyltransferase (ACAT) inhibitors has changed profoundly from promising new drugs for cardiovascular prevention to drugs without clinical benefits or possibly even with adverse effects. RECENT FINDINGS ACAT inhibitors decrease the intracellular conversion of free cholesterol into cholesteryl ester in a number of tissues, including intestine, liver and macrophages. In contrast to promising results in experimental animal models, all subsequent clinical studies in humans with ACAT inhibitors failed to show lipid profile changes as well as reductions in surrogate markers for coronary artery disease. In fact, there was even a tendency towards an increase in atheroma burden in the most recent and well executed clinical trials. In addition, the inhibition of this pivotal enzyme in cholesterol esterification may interfere with reverse cholesterol transport. SUMMARY In our opinion, the consistent negative findings in recent clinical trials have virtually eliminated the chances for this class of drugs to be introduced for cardiovascular prevention. Possible strategies focused on selective ACAT 2 inhibition or the combination of ACAT inhibitors with compounds that stimulate reverse cholesterol transport may prove to have clinical benefit. This will have to await further clinical research in humans, however, as, obviously, rodent models cannot provide reliable data as to the efficacy of this class of drugs in humans.
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Affiliation(s)
- Marijn C Meuwese
- Department of Vascular Medicine, Academic Medical Center, Amsterdam, The Netherlands
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21
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Ruan XZ, Moorhead JF, Tao JL, Ma KL, Wheeler DC, Powis SH, Varghese Z. Mechanisms of dysregulation of low-density lipoprotein receptor expression in vascular smooth muscle cells by inflammatory cytokines. Arterioscler Thromb Vasc Biol 2006; 26:1150-5. [PMID: 16543490 DOI: 10.1161/01.atv.0000217957.93135.c2] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Although inflammation is a recognized feature of atherosclerosis, the impact of inflammation on cellular cholesterol homeostasis is unclear. This study focuses on the molecular mechanisms by which inflammatory cytokines disrupt low-density lipoprotein (LDL) receptor regulation. METHODS AND RESULTS IL-1beta enhanced transformation of vascular smooth muscle cells into foam cells by increasing uptake of unmodified LDL via LDL receptors and by enhancing cholesterol esterification as demonstrated by Oil Red O staining and direct assay of intracellular cholesterol concentrations. In the absence of IL-1beta, a high concentration of LDL decreased LDL receptor promoter activity, mRNA synthesis and protein expression. However, IL-1beta enhanced LDL receptor expression, overriding the suppression usually induced by a high concentration of LDL and inappropriately increasing LDL uptake. Exposure to IL-1beta also caused overexpression of the sterol regulatory element binding protein (SREBP) cleavage-activating protein (SCAP), and enhanced its translocation from the endoplasmic reticulum to the Golgi, where it is known to cleave SREBP, thereby enhancing LDL receptor gene expression. CONCLUSIONS These observations demonstrate that IL-1beta disrupts cholesterol-mediated LDL receptor feedback regulation, permitting intracellular accumulation of unmodified LDL and causing foam cell formation. The implication of these findings is that inflammatory cytokines may contribute to intracellular LDL accumulation without previous modification of the lipoprotein.
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Affiliation(s)
- Xiong Z Ruan
- Centre for Nephrology, Royal Free and University College Medical School, Royal Free Campus, London NW3 2PF, UK.
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22
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Song BL, Wang CH, Yao XM, Yang L, Zhang WJ, Wang ZZ, Zhao XN, Yang JB, Qi W, Yang XY, Inoue K, Lin ZX, Zhang HZ, Kodama T, Chang C, Liu YK, Chang TY, Li BL. Human acyl-CoA:cholesterol acyltransferase 2 gene expression in intestinal Caco-2 cells and in hepatocellular carcinoma. Biochem J 2006; 394:617-26. [PMID: 16274362 PMCID: PMC1383711 DOI: 10.1042/bj20051417] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2005] [Revised: 11/02/2005] [Accepted: 11/08/2005] [Indexed: 11/17/2022]
Abstract
Humans express two ACAT (acyl-CoA:cholesterol acyltransferase) genes, ACAT1 and ACAT2. ACAT1 is ubiquitously expressed, whereas ACAT2 is primarily expressed in intestinal mucosa and plays an important role in intestinal cholesterol absorption. To investigate the molecular mechanism(s) responsible for the tissue-specific expression of ACAT2, we identified five cis-elements within the human ACAT2 promoter, four for the intestinal-specific transcription factor CDX2 (caudal type homeobox transcription factor 2), and one for the transcription factor HNF1alpha (hepatocyte nuclear factor 1alpha). Results of luciferase reporter and electrophoretic mobility shift assays show that CDX2 and HNF1alpha exert a synergistic effect, enhancing the ACAT2 promoter activity through binding to these cis-elements. In undifferentiated Caco-2 cells, the ACAT2 expression is increased when exogenous CDX2 and/or HNF1alpha are expressed by co-transfection. In differentiated Caco-2 cells, the ACAT2 expression significantly decreases when the endogenous CDX2 or HNF1alpha expression is suppressed by using RNAi (RNA interference) technology. The expression levels of CDX2, HNF1alpha, and ACAT2 are all greatly increased when the Caco-2 cells differentiate to become intestinal-like cells. These results provide a molecular mechanism for the tissue-specific expression of ACAT2 in intestine. In normal adult human liver, CDX2 expression is not detectable and the ACAT2 expression is very low. In the hepatoma cell line HepG2 the CDX2 expression is elevated, accounting for its elevated ACAT2 expression. A high percentage (seven of fourteen) of liver samples from patients affected with hepatocellular carcinoma exhibited elevated ACAT2 expression. Thus, the elevated ACAT2 expression may serve as a new biomarker for certain form(s) of hepatocellular carcinoma.
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Key Words
- acyl-coa:cholesterol acyltransferase (acat2)
- caudal type homeobox transcription factor 2 (cdx2)
- hepatocyte nuclear factor 1α (hnf1α)
- intestine
- hepatocellular carcinoma (hcc)
- acat, acyl-coa:cholesterol acyltransferase
- afp, α-fetalprotein
- cdx2, caudal type homeobox transcription factor 2
- cldn2, claudin 2 gene
- dmem, dulbecco's modified eagle's medium
- emsa, electrophoretic mobility shift assay
- fbs, fetal bovine serum
- gapdh, glyceraldehyde-3-phosphate dehydrogenase
- hcc, hepatocellular carcinoma
- hnf1α, hepatocyte nuclear factor 1α
- lph, lactase-phlorizin hydrolase gene
- luc, luciferase reporter
- rnai, rna interference
- rt, reverse transcriptase
- ugt1a8–10, udp glucuronosyltransferase 1 family polypeptides a8–10 gene
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Affiliation(s)
- Bao-Liang Song
- *State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Can-Hua Wang
- *State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
- †Department of Biochemistry and Technology, Jiao Tong University, Shanghai 200030, China
| | - Xiao-Min Yao
- *State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
- †Department of Biochemistry and Technology, Jiao Tong University, Shanghai 200030, China
| | - Li Yang
- *State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Wen-Jing Zhang
- *State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
- ‡Department of Biochemistry and Technology, East China University of Science and Technology, Shanghai 200237, China
| | - Zhen-Zhen Wang
- *State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Xiao-Nan Zhao
- *State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Jin-Bo Yang
- *State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Wei Qi
- *State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Xin-Ying Yang
- *State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Kenji Inoue
- §Laboratory for Systems Biology and Medicine, Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | - Zhi-Xin Lin
- †Department of Biochemistry and Technology, Jiao Tong University, Shanghai 200030, China
| | - Hui-Zhan Zhang
- ‡Department of Biochemistry and Technology, East China University of Science and Technology, Shanghai 200237, China
| | - Tatsuhiko Kodama
- §Laboratory for Systems Biology and Medicine, Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | | | - Yin-Kun Liu
- ¶Liver Cancer Institute of Zhong San Hospital, Fudan University, Shanghai 200031, China
| | - Ta-Yuan Chang
- ∥Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755, U.S.A
| | - Bo-Liang Li
- *State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
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Chang C, Dong R, Miyazaki A, Sakashita N, Zhang Y, Liu J, Guo M, Li BL, Chang TY. Human acyl-CoA:cholesterol acyltransferase (ACAT) and its potential as a target for pharmaceutical intervention against atherosclerosis. Acta Biochim Biophys Sin (Shanghai) 2006; 38:151-6. [PMID: 16518538 DOI: 10.1111/j.1745-7270.2006.00154.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Acyl-CoA:cholesterol acyltransferase (ACAT) catalyzes the formation of cholesteryl esters from cholesterol and long-chain fatty-acyl-coenzyme A. At the single-cell level, ACAT serves as a regulator of intracellular cholesterol homeostasis. In addition, ACAT supplies cholesteryl esters for lipoprotein assembly in the liver and small intestine. Under pathological conditions, the accumulation of cholesteryl esters produced by ACAT in macrophages contributes to foam cell formation, a hallmark of the early stage of atherosclerosis. Several reviews addressing various aspects of ACAT and ACAT inhibitors are available. This review briefly outlines the current knowledge on the biochemical properties of human ACATs, and then focuses on discussing the merit of ACAT as a drug target for pharmaceutical interventions against atherosclerosis.
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Affiliation(s)
- Catherine Chang
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
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24
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Li BL, Chang TY, Chen J, Chang CCY, Zhao XN. Human ACAT1 gene expression and its involvement in the development of atherosclerosis. Future Cardiol 2006; 2:93-9. [DOI: 10.2217/14796678.2.1.93] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Atherosclerosis is caused by a series of pathologic changes at the cellular level, with formation of macrophage-derived foam cells occurring at an early stage. Most of the cholesteryl esters in macrophage foam cells are produced by the enzyme acyl-coenzyme A:cholesterol acyltransferase (ACAT). Two ACAT genes, Acat1 and Acat2, exist in mammals. In the monocyte–macrophages, ACAT1 is the major isoenzyme and is a drug target for atherosclerosis treatment. Various proatherogenic stimuli, including interferon-γ and dexamethasone, cause upregulation of human Acat1 expression in macrophages. Thus, it should be possible to find antagonist(s) to downregulate human Acat1 expression. A greater understanding of human Acat1 expression may provide scientists with opportunities for novel therapeutic approaches to combat atherosclerosis.
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Affiliation(s)
- Bo-Liang Li
- State Key Laboratory of Molecular Biology, 320 Yue-Yang Road, Shanghai 200031, China
| | - Ta-Yuan Chang
- Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755 USA
| | - Jia Chen
- State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Catherine CY Chang
- Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755, USA
| | - Xiao-Nan Zhao
- State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
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25
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Kushwaha RS, Rosillo A, Rodriguez R, McGill HC. Expression levels of ACAT1 and ACAT2 genes in the liver and intestine of baboons with high and low lipemic responses to dietary lipids. J Nutr Biochem 2005; 16:714-21. [PMID: 16081263 DOI: 10.1016/j.jnutbio.2005.03.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2004] [Revised: 02/28/2005] [Accepted: 03/15/2005] [Indexed: 01/26/2023]
Abstract
Acyl-coenzyme A:cholesterol acyltransferase (ACAT) 1 and ACAT2 play an important role in cellular cholesterol esterification and thus modulate intestinal cholesterol absorption and hepatic lipoprotein secretion. The relative expression levels of ACAT1 and ACAT2 in human tissues differ from those in other animals, including nonhuman primates. The present study compared the relative expression levels of ACAT1 and ACAT2 in baboons with high and low lipemic responses to dietary lipids. We isolated RNA and prepared cDNA from frozen liver and small intestine from high- and low-responding pedigreed baboons necropsied after consuming a high-cholesterol and high-fat diet for 18 months. The expression of ACAT1 and ACAT2 was measured by TaqMan real-time quantitative PCR normalized to 18s ribosomal RNA. The expression of ACAT1 was higher than that of ACAT2 in the liver, whereas the expression of ACAT2 was higher than that of ACAT1 in the duodenum and jejunum. There was no difference in the expression of ACAT1 or ACAT2 in the liver and intestine between high- and low-responding baboons except that the expression of ACAT1 was higher in the duodenum of high responders than in that of low responders. Western blot analysis also showed a higher level of ACAT1 protein in the duodenum of high responders than in that of low responders. There was a significant correlation between duodenal ACAT expression levels and total plasma cholesterol concentration in baboons. These results suggest that differences in ACAT1 expression may affect plasma cholesterol concentration and partly affect diet-induced hyperlipidemia.
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Affiliation(s)
- Rampratap S Kushwaha
- Department of Physiology and Medicine, Southwest Foundation for Biomedical Research, San Antonio, TX 78245-0549, USA.
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26
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Liu J, Chang C, Westover E, Covey D, Chang TY. Investigating the allosterism of acyl-CoA:cholesterol acyltransferase (ACAT) by using various sterols: in vitro and intact cell studies. Biochem J 2005; 391:389-97. [PMID: 15992359 PMCID: PMC1276938 DOI: 10.1042/bj20050428] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2005] [Revised: 06/30/2005] [Accepted: 07/04/2005] [Indexed: 11/17/2022]
Abstract
ACAT1 (acyl-CoA:cholesterol acyltransferase 1) is thought to have two distinct sterol-binding sites: a substrate-binding site and an allosteric-activator site. In the present work, we investigated the structural features of various sterols as substrates and/or activators in vitro. The results show that without cholesterol, the plant sterol sitosterol is a poor substrate for ACAT. In the presence of cholesterol, ACAT1-mediated esterification of sitosterol is highly activated while ACAT2-mediated esterification of sitosterol is only moderately activated. For ACAT1, we show that the stereochemistry of the 3-hydroxy group at steroid ring A is a critical structural feature for a sterol to serve as a substrate, but less critical for activation. Additionally, enantiomeric cholesterol, which has the same biophysical properties as cholesterol in membranes, fails to activate ACAT1. Thus ACAT1 activation by cholesterol is the result of stereo-specific interactions between cholesterol and ACAT1, and is not related to the biophysical properties of phospholipid membranes. To demonstrate the relevance of the ACAT1 allosteric model in intact cells, we showed that sitosterol esterification in human macrophages is activated upon cholesterol loading. We further show that the activation is not due to an increase in ACAT1 protein content, but is partly due to an increase in the cholesterol content in the endoplasmic reticulum where ACAT1 resides. Together, our results support the existence of a distinct sterol-activator site in addition to the sterol-substrate site of ACAT1 and demonstrate the applicability of the ACAT1 allosteric model in intact cells.
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Affiliation(s)
- Jay Liu
- *Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755, U.S.A
| | | | - Emily J. Westover
- †Department of Molecular Biology and Pharmacology, Washington University Medical School, St. Louis, MO 63110, U.S.A
| | - Douglas F. Covey
- †Department of Molecular Biology and Pharmacology, Washington University Medical School, St. Louis, MO 63110, U.S.A
| | - Ta-Yuan Chang
- *Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755, U.S.A
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27
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Leon C, Hill JS, Wasan KM. Potential role of acyl-coenzyme A:cholesterol transferase (ACAT) Inhibitors as hypolipidemic and antiatherosclerosis drugs. Pharm Res 2005; 22:1578-88. [PMID: 16180116 DOI: 10.1007/s11095-005-6306-0] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2005] [Accepted: 06/03/2005] [Indexed: 11/29/2022]
Abstract
Acyl-coenzyme A:cholesterol transferase (ACAT) is an integral membrane protein localized in the endoplasmic reticulum. ACAT catalyzes the formation of cholesteryl esters from cholesterol and fatty acyl coenzyme A. The cholesteryl esters are stored as cytoplasmic lipid droplets inside the cell. This process is very important to the organism as high cholesterol levels have been associated with cardiovascular disease. In mammals, two ACAT genes have been identified, ACAT1 and ACAT2. ACAT1 is ubiquitous and is responsible for cholesteryl ester formation in brain, adrenal glands, macrophages, and kidneys. ACAT2 is expressed in the liver and intestine. The inhibition of ACAT activity has been associated with decreased plasma cholesterol levels by suppressing cholesterol absorption and by diminishing the assembly and secretion of apolipoprotein B-containing lipoproteins such as very low density lipoprotein (VLDL). ACAT inhibition also prevents the conversion of macrophages into foam cells in the arterial walls, a critical event in the development of atherosclerosis. This review paper will focus on the role of ACAT in cholesterol metabolism, in particular as a target to develop novel therapeutic agents to control hypercholesterolemia, atherosclerosis, and Alzheimer's disease.
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Affiliation(s)
- Carlos Leon
- Division of Pharmaceutics and Biopharmaceutics, Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
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28
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Li CM, Presley JB, Zhang X, Dashti N, Chung BH, Medeiros NE, Guidry C, Curcio CA. Retina expresses microsomal triglyceride transfer protein: implications for age-related maculopathy. J Lipid Res 2005; 46:628-40. [PMID: 15654125 DOI: 10.1194/jlr.m400428-jlr200] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The principal extracellular lesions of age-related maculopathy (ARM), the leading cause of vision loss in the elderly, involve Bruch's membrane (BrM), a thin vascular intima between the retinal pigment epithelium (RPE) and its blood supply. With age, 80-100 nm solid particles containing esterified cholesterol (EC) accumulate in normal BrM, and apolipoprotein B (apoB) immunoreactivity is detectable in BrM- and ARM-associated lesions. Yet little evidence indicates that increased plasma cholesterol is a risk factor for ARM. To determine if RPE is capable of assembling its own apoB-containing lipoprotein, we examined RPE for the expression of microsomal triglyceride transfer protein (MTP), which is required for this process. Consistent with previous evidence for apoB expression, MTP is expressed in RPE, the ARPE-19 cell line, and, unexpectedly, retinal ganglion cells, which are neurons of the central nervous system. De novo synthesis and secretion of neutral lipid by ARPE-19 was supported by high levels of radiolabeled EC and triglyceride in medium after supplementation with oleate. Lipoprotein assembly and secretion is implicated as a constitutive retinal function and a plausible candidate mechanism involved in forming extracellular cholesterol-containing lesions in ARM. The pigmentary retinopathy and neuropathy of abetalipoproteinemia (Mendelian Inheritance of Man 200100; Bassen-Kornzwieg disease), which is caused by mutations in the MTP gene, may involve loss of function at the retina.
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Affiliation(s)
- Chuan-Ming Li
- Department of Ophthalmology, University of Alabama School of Medicine, Birmingham, AL, USA
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Narce M, Poisson JP. Lipid metabolism: is liver X receptor (LXR) a regulator of adipocyte differentiation? Consequences of stearoyl-CoA desaturase activation by LXR. Curr Opin Lipidol 2004; 15:703-6. [PMID: 15529031 DOI: 10.1097/00041433-200412000-00012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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30
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Parini P, Davis M, Lada AT, Erickson SK, Wright TL, Gustafsson U, Sahlin S, Einarsson C, Eriksson M, Angelin B, Tomoda H, Omura S, Willingham MC, Rudel LL. ACAT2 is localized to hepatocytes and is the major cholesterol-esterifying enzyme in human liver. Circulation 2004; 110:2017-23. [PMID: 15451793 DOI: 10.1161/01.cir.0000143163.76212.0b] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Two acyl-coenzyme A:cholesterol acyltransferase (ACAT) genes, ACAT1 and ACAT2, have been identified that encode 2 proteins responsible for intracellular cholesterol esterification. METHODS AND RESULTS In this study, immunohistology was used to establish their cellular localization in human liver biopsies. ACAT2 protein expression was confined to hepatocytes, whereas ACAT1 protein was found in Kupffer cells only. Studies with a highly specific ACAT2 inhibitor, pyripyropene A, in microsomal activity assays demonstrated that ACAT2 activity was highly variable among individual human liver samples, whereas ACAT1 activity was more similar in all specimens. ACAT2 provided the major cholesterol-esterifying activity in 3 of 4 human liver samples examined. CONCLUSIONS The data suggest that in diseases in which dysregulation of cholesterol metabolism occurs, such as hypercholesterolemia and atherosclerosis, ACAT2 should be considered a target for prevention and treatment.
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Affiliation(s)
- Paolo Parini
- Metabolism Unit, Center for Metabolism and Endocrinology, Department of Medicine, Novum, Karolinska Institute at Huddinge University Hospital, Huddinge, Sweden
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