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Zou Y, Zhang Y, Li M, Cao K, Song C, Zhang Z, Cai K, Geng D, Chen S, Wu Y, Zhang N, Sun G, Wang J, Zhang Y, Sun Y. Regulation of lipid metabolism by E3 ubiquitin ligases in lipid-associated metabolic diseases. Int J Biol Macromol 2024; 265:130961. [PMID: 38508558 DOI: 10.1016/j.ijbiomac.2024.130961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 03/10/2024] [Accepted: 03/15/2024] [Indexed: 03/22/2024]
Abstract
Previous studies have progressively elucidated the involvement of E3 ubiquitin (Ub) ligases in regulating lipid metabolism. Ubiquitination, facilitated by E3 Ub ligases, modifies critical enzymes in lipid metabolism, enabling them to respond to specific signals. In this review, we aim to present a comprehensive analysis of the role of E3 Ub ligases in lipid metabolism, which includes lipid synthesis and lipolysis, and their influence on cellular lipid homeostasis through the modulation of lipid uptake and efflux. Furthermore, it explores how the ubiquitination process governs the degradation or activation of pivotal enzymes, thereby regulating lipid metabolism at the transcriptional level. Perturbations in lipid metabolism have been implicated in various diseases, including hepatic lipid metabolism disorders, atherosclerosis, diabetes, and cancer. Therefore, this review focuses on the association between E3 Ub ligases and lipid metabolism in lipid-related diseases, highlighting enzymes critically involved in lipid synthesis and catabolism, transcriptional regulators, lipid uptake translocators, and transporters. Overall, this review aims to identify gaps in current knowledge, highlight areas requiring further research, offer potential targeted therapeutic approaches, and provide a comprehensive outlook on clinical conditions associated with lipid metabolic diseases.
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Affiliation(s)
- Yuanming Zou
- Department of Cardiology, the First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Ying Zhang
- Department of Cardiology, the First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China; Institute of Health Sciences, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang, 110001, Liaoning Province, People's Republic of China.
| | - Mohan Li
- Department of Cardiology, the First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Kexin Cao
- Department of Cardiology, the First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Chunyu Song
- Department of Cardiology, the First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Zhaobo Zhang
- Department of Cardiology, the First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Kexin Cai
- Department of Cardiology, the First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Danxi Geng
- Department of Cardiology, the First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Shuxian Chen
- Department of Cardiology, the First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Yanjiao Wu
- Department of Cardiology, the First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Naijin Zhang
- Department of Cardiology, the First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China; Institute of Health Sciences, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang, 110001, Liaoning Province, People's Republic of China; Key Laboratory of Reproductive and Genetic Medicine (China Medical University), National Health Commission, 77 Puhe Road, Shenbei New District, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Guozhe Sun
- Department of Cardiology, the First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China.
| | - Jing Wang
- Department of Hematology, the First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China.
| | - Yixiao Zhang
- Department of Urology Surgery, Shengjing Hospital of China Medical University, 36 Sanhao Street, Heping District, Shenyang, 110004, Liaoning Province, People's Republic of China.
| | - Yingxian Sun
- Department of Cardiology, the First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China; Institute of Health Sciences, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang, 110001, Liaoning Province, People's Republic of China; Key Laboratory of Environmental Stress and Chronic Disease Control and Prevention, Ministry of Education, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang, 110001, Liaoning Province, People's Republic of China.
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Mostofinejad Z, Cremonini E, Kang J, Oteiza PI. Effects of (-)-epicatechin on hepatic triglyceride metabolism. Food Funct 2024; 15:326-337. [PMID: 38086683 DOI: 10.1039/d3fo03666a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
(-)-Epicatechin (EC) consumption is associated with an improvement of hyperlipemia and other metabolic changes linked to obesity and western-style diets. This work investigated the effects of EC on triglyceride (TG) metabolism both in vivo, where mice were supplemented with EC (2 and 20 mg EC per kg body weight), and in vitro, when human HepG2 hepatocytes were incubated in the presence of EC and the main EC metabolites found in human plasma. Increased hepatic TG levels were only observed after 24 weeks supplementation with EC (20 mg per kg body weight), with a preserved liver structure and absence of inflammation or oxidative stress. EC caused increased expression of diacylglycerol acyltransferases (DGAT2), key enzymes in TG synthesis, and the upregulation of PPARα, which promotes free fatty acid (FFA) oxidation. On the other hand, incubation of HepG2 cells in the presence of high concentrations of EC (1-10 μM) did not affect TG deposition nor DGAT2 expression. In summary, in mouse liver, EC upregulated mechanisms that can neutralize the potential toxicity of FFA, i.e. TG synthesis and FFA β-oxidation. Results in mouse liver and HepG2 cells stress the safety of EC in terms of TG metabolism and development of hepatopathies in doses within the limits given by a rational time and dose for human consumption.
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Affiliation(s)
- Zahra Mostofinejad
- Department of Nutrition, University of California, One Shields Avenue, Davis, CA 95616, USA.
| | - Eleonora Cremonini
- Department of Nutrition, University of California, One Shields Avenue, Davis, CA 95616, USA.
| | - Jiye Kang
- Department of Nutrition, University of California, One Shields Avenue, Davis, CA 95616, USA.
| | - Patricia I Oteiza
- Department of Nutrition, University of California, One Shields Avenue, Davis, CA 95616, USA.
- Department of Environmental Toxicology, University of California, Davis, USA
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Erzurumlu Y, Muhammed MT. Triiodothyronine positively regulates endoplasmic reticulum-associated degradation (ERAD) and promotes androgenic signaling in androgen-dependent prostate cancer cells. Cell Signal 2023:110745. [PMID: 37271348 DOI: 10.1016/j.cellsig.2023.110745] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2023] [Revised: 05/29/2023] [Accepted: 05/30/2023] [Indexed: 06/06/2023]
Abstract
Thyroid hormones (THs) play crucial roles in numerous physiological processes of nearly all mammalian tissues, including differentiation and metabolism. Deterioration of TH signaling has been associated with several pathologies, including cancer. The effect of highly active triiodothyronine (T3) has been investigated in many in vivo and in vitro cancer models. However, the role of T3 on cancerous prostate tissue is controversial. Recent studies have focused on the characterization of the supportive roles of the endoplasmic reticulum-associated degradation (ERAD) and unfolded protein response (UPR) signaling in prostate cancer (PCa) and investigating new hormonal regulation patterns, including estrogen, progesterone and 1,25(OH)2D3. Additionally, androgenic signaling controlled by androgens, which are critical in PCa progression, has been shown to be regulated by other steroid hormones. While the effects of T3 on ERAD and UPR are unknown today, the impact on androgenic signaling is still not understood in PCa. Therefore, we aimed to investigate the molecular action of T3 on the ERAD mechanism and UPR signaling in PCa cells and also extensively examined the effect of T3 on androgenic signaling. Our data strongly indicated that T3 tightly regulates ERAD and UPR signaling in androgen-dependent PCa cells. We also found that T3 stimulates androgenic signaling by upregulating AR mRNA and protein levels and enhancing its nuclear translocation. Additionally, advanced computational studies supported the ligand binding effect of T3 on AR protein. Our data suggest that targeting thyroidal signaling should be considered in therapeutic approaches to be developed for prostate malignancy in addition to other steroidal regulations.
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Affiliation(s)
- Yalcin Erzurumlu
- Department of Biochemistry, Faculty of Pharmacy, Suleyman Demirel University, 32260, Turkey.
| | - Muhammed Tilahun Muhammed
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Suleyman Demirel University, 32260 Isparta, Turkey.
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Raja R, Fonseka O, Ganenthiran H, Liu W. The multifaceted roles of ER and Golgi in metabolic cardiomyopathy. Front Cardiovasc Med 2022; 9:999044. [PMID: 36119738 PMCID: PMC9479098 DOI: 10.3389/fcvm.2022.999044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Accepted: 08/15/2022] [Indexed: 01/10/2023] Open
Abstract
Metabolic cardiomyopathy is a significant global financial and health challenge; however, pathophysiological mechanisms governing this entity remain poorly understood. Among the main features of metabolic cardiomyopathy, the changes to cellular lipid metabolism have been studied and targeted for the discovery of novel treatment strategies obtaining contrasting results. The endoplasmic reticulum (ER) and Golgi apparatus (GA) carry out protein modification, sorting, and secretion activities that are more commonly studied from the perspective of protein quality control; however, they also drive the maintenance of lipid homeostasis. In response to metabolic stress, ER and GA regulate the expression of genes involved in cardiac lipid biogenesis and participate in lipid droplet formation and degradation. Due to the varied roles these organelles play, this review will focus on recapitulating the alterations and crosstalk between ER, GA, and lipid metabolism in cardiac metabolic syndrome.
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Chen G, Harwood JL, Lemieux MJ, Stone SJ, Weselake RJ. Acyl-CoA:diacylglycerol acyltransferase: Properties, physiological roles, metabolic engineering and intentional control. Prog Lipid Res 2022; 88:101181. [PMID: 35820474 DOI: 10.1016/j.plipres.2022.101181] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 05/31/2022] [Accepted: 07/04/2022] [Indexed: 12/15/2022]
Abstract
Acyl-CoA:diacylglycerol acyltransferase (DGAT, EC 2.3.1.20) catalyzes the last reaction in the acyl-CoA-dependent biosynthesis of triacylglycerol (TAG). DGAT activity resides mainly in membrane-bound DGAT1 and DGAT2 in eukaryotes and bifunctional wax ester synthase-diacylglycerol acyltransferase (WSD) in bacteria, which are all membrane-bound proteins but exhibit no sequence homology to each other. Recent studies also identified other DGAT enzymes such as the soluble DGAT3 and diacylglycerol acetyltransferase (EaDAcT), as well as enzymes with DGAT activities including defective in cuticular ridges (DCR) and steryl and phytyl ester synthases (PESs). This review comprehensively discusses research advances on DGATs in prokaryotes and eukaryotes with a focus on their biochemical properties, physiological roles, and biotechnological and therapeutic applications. The review begins with a discussion of DGAT assay methods, followed by a systematic discussion of TAG biosynthesis and the properties and physiological role of DGATs. Thereafter, the review discusses the three-dimensional structure and insights into mechanism of action of human DGAT1, and the modeled DGAT1 from Brassica napus. The review then examines metabolic engineering strategies involving manipulation of DGAT, followed by a discussion of its therapeutic applications. DGAT in relation to improvement of livestock traits is also discussed along with DGATs in various other eukaryotic organisms.
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Affiliation(s)
- Guanqun Chen
- Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta T6H 2P5, Canada.
| | - John L Harwood
- School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK
| | - M Joanne Lemieux
- Department of Biochemistry, University of Alberta, Membrane Protein Disease Research Group, Edmonton T6G 2H7, Canada
| | - Scot J Stone
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
| | - Randall J Weselake
- Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta T6H 2P5, Canada
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Liang Q, Wan J, Liu H, Chen M, Xue T, Jia D, Chen Q, Chen H, Wei T. A plant reovirus hijacks the DNAJB12-Hsc70 chaperone complex to promote viral spread in its planthopper vector. MOLECULAR PLANT PATHOLOGY 2022; 23:805-818. [PMID: 34668642 PMCID: PMC9104260 DOI: 10.1111/mpp.13152] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 09/24/2021] [Accepted: 09/25/2021] [Indexed: 05/06/2023]
Abstract
Many viruses usurp the functions of endoplasmic reticulum (ER) for virus-encoded membrane proteins proper functional folding or assembly to promote virus spread. Southern rice black-streaked dwarf virus (SRBSDV), a plant reovirus, exploits virus-containing tubules composed of nonstructural membrane protein P7-1 to spread in its planthopper vector Sogatella furcifera. Here, we report that two factors of the ER-associated degradation (ERAD) machinery, the ER chaperone DNAJB12 and its cytosolic co-chaperone Hsc70, are activated by SRBSDV to facilitate ER-to-cytosol export of P7-1 tubules in S. furcifera. Both P7-1 of SRBSDV and Hsc70 directly bind to the J-domain of DNAJB12. DNAJB12 overexpression induces ER retention of P7-1, but Hsc70 overexpression promotes the transport of P7-1 from the ER to the cytosol to initiate tubule assembly. Thus, P7-1 is initially retained in the ER by interaction with DNAJB12 and then delivered to Hsc70. Furthermore, the inhibitors of the ATPase activity of Hsc70 reduce P7-1 tubule assembly, suggesting that the proper folding and assembly of P7-1 tubules is dependent on the ATPase activity of Hsc70. The DNAJB12-Hsc70 chaperone complex is recruited to P7-1 tubules in virus-infected midgut epithelial cells in S. furcifera. The knockdown of DNAJB12 or Hsc70 strongly inhibits P7-1 tubule assembly in vivo, finally suppressing effective viral spread in S. furcifera. Taken together, our results indicate that the DNAJB12-Hsc70 chaperone complex in the ERAD machinery facilitates the ER-to-cytosol transport of P7-1 for proper assembly of tubules, enabling viral spread in insect vectors in a manner dependent on ATPase activity of Hsc70.
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Affiliation(s)
- Qifu Liang
- Fujian Province Key Laboratory of Plant Virology, Vector‐borne Virus Research Center, State Key Laboratory of Ecological Pest Control for Fujian and Taiwan CropsFujian Agriculture and Forestry UniversityFuzhouFujianChina
| | - Jiajia Wan
- Fujian Province Key Laboratory of Plant Virology, Vector‐borne Virus Research Center, State Key Laboratory of Ecological Pest Control for Fujian and Taiwan CropsFujian Agriculture and Forestry UniversityFuzhouFujianChina
| | - Huan Liu
- Fujian Province Key Laboratory of Plant Virology, Vector‐borne Virus Research Center, State Key Laboratory of Ecological Pest Control for Fujian and Taiwan CropsFujian Agriculture and Forestry UniversityFuzhouFujianChina
| | - Manni Chen
- Fujian Province Key Laboratory of Plant Virology, Vector‐borne Virus Research Center, State Key Laboratory of Ecological Pest Control for Fujian and Taiwan CropsFujian Agriculture and Forestry UniversityFuzhouFujianChina
| | - Taoran Xue
- Fujian Province Key Laboratory of Plant Virology, Vector‐borne Virus Research Center, State Key Laboratory of Ecological Pest Control for Fujian and Taiwan CropsFujian Agriculture and Forestry UniversityFuzhouFujianChina
| | - Dongsheng Jia
- Fujian Province Key Laboratory of Plant Virology, Vector‐borne Virus Research Center, State Key Laboratory of Ecological Pest Control for Fujian and Taiwan CropsFujian Agriculture and Forestry UniversityFuzhouFujianChina
| | - Qian Chen
- Fujian Province Key Laboratory of Plant Virology, Vector‐borne Virus Research Center, State Key Laboratory of Ecological Pest Control for Fujian and Taiwan CropsFujian Agriculture and Forestry UniversityFuzhouFujianChina
| | - Hongyan Chen
- Fujian Province Key Laboratory of Plant Virology, Vector‐borne Virus Research Center, State Key Laboratory of Ecological Pest Control for Fujian and Taiwan CropsFujian Agriculture and Forestry UniversityFuzhouFujianChina
| | - Taiyun Wei
- Fujian Province Key Laboratory of Plant Virology, Vector‐borne Virus Research Center, State Key Laboratory of Ecological Pest Control for Fujian and Taiwan CropsFujian Agriculture and Forestry UniversityFuzhouFujianChina
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Liao PC, Yang EJ, Borgman T, Boldogh IR, Sing CN, Swayne TC, Pon LA. Touch and Go: Membrane Contact Sites Between Lipid Droplets and Other Organelles. Front Cell Dev Biol 2022; 10:852021. [PMID: 35281095 PMCID: PMC8908909 DOI: 10.3389/fcell.2022.852021] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Accepted: 02/03/2022] [Indexed: 12/26/2022] Open
Abstract
Lipid droplets (LDs) have emerged not just as storage sites for lipids but as central regulators of metabolism and organelle quality control. These critical functions are achieved, in part, at membrane contact sites (MCS) between LDs and other organelles. MCS are sites of transfer of cellular constituents to or from LDs for energy mobilization in response to nutrient limitations, as well as LD biogenesis, expansion and autophagy. Here, we describe recent findings on the mechanisms underlying the formation and function of MCS between LDs and mitochondria, ER and lysosomes/vacuoles and the role of the cytoskeleton in promoting LD MCS through its function in LD movement and distribution in response to environmental cues.
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Affiliation(s)
- Pin-Chao Liao
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY, United States
- Institute of Molecular Medicine, National Tsing Hua University, Hsinchu, Taiwan
| | - Emily J. Yang
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY, United States
| | - Taylor Borgman
- Institute of Human Nutrition, Columbia University Irving Medical Center, New York, NY, United States
| | - Istvan R. Boldogh
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY, United States
- Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, United States
| | - Cierra N. Sing
- Institute of Human Nutrition, Columbia University Irving Medical Center, New York, NY, United States
| | - Theresa C. Swayne
- Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, United States
| | - Liza A. Pon
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY, United States
- Institute of Human Nutrition, Columbia University Irving Medical Center, New York, NY, United States
- *Correspondence: Liza A. Pon,
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Abstract
Lipid droplets (LDs) are endoplasmic reticulum-derived organelles that consist of a core of neutral lipids encircled by a phospholipid monolayer decorated with proteins. As hubs of cellular lipid and energy metabolism, LDs are inherently involved in the etiology of prevalent metabolic diseases such as obesity and nonalcoholic fatty liver disease. The functions of LDs are regulated by a unique set of associated proteins, the LD proteome, which includes integral membrane and peripheral proteins. These proteins control key activities of LDs such as triacylglycerol synthesis and breakdown, nutrient sensing and signal integration, and interactions with other organelles. Here we review the mechanisms that regulate the composition of the LD proteome, such as pathways that mediate selective and bulk LD protein degradation and potential connections between LDs and cellular protein quality control.
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Affiliation(s)
- Melissa A Roberts
- Department of Molecular and Cell Biology and Department of Nutritional Sciences and Toxicology, University of California, Berkeley, California 94720, USA;
| | - James A Olzmann
- Department of Molecular and Cell Biology and Department of Nutritional Sciences and Toxicology, University of California, Berkeley, California 94720, USA; .,Chan Zuckerberg Biohub, San Francisco, California 94158, USA
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McFie PJ, Chumala P, Katselis GS, Stone SJ. DGAT2 stability is increased in response to DGAT1 inhibition in gene edited HepG2 cells. Biochim Biophys Acta Mol Cell Biol Lipids 2021; 1866:158991. [PMID: 34116261 DOI: 10.1016/j.bbalip.2021.158991] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 05/21/2021] [Accepted: 06/05/2021] [Indexed: 12/14/2022]
Abstract
In eukaryotic organisms, two unrelated acyl-CoA:diacylglycerol acyltransferase (DGAT) enzymes, DGAT1 and DGAT2, catalyze the final step of the triacylglycerol biosynthetic pathway. Both enzymes are highly expressed in lipogenic tissues, such as adipose tissue, small intestine and the liver. DGAT2 has a prominent role in hepatocyte lipid metabolism synthesizing triacylglycerols that are utilized for very low-density lipoprotein assembly. However, due to the lack of useful antibodies to detect endogenous DGAT2 protein, it has been difficult to determine how this enzyme functions at the cellular level. We have unsuccessfully tested many commercial antibodies as well as our own "in-house" antibodies. There is currently no evidence that DGAT2 undergoes processing such that antigenic epitopes to these antibodies are removed. As an alternative, many studies have utilized epitope tagged versions of DGAT2 overexpressed in cells. These approaches can provide valuable information about a protein, but can be subject to artifacts, such as mislocalization, misregulation, protein aggregation and abnormal protein-protein interactions. In this study, we used gene editing with CRISPR/Cas9 to add three consecutive FLAG epitopes to the C-terminus of endogenous DGAT2 in HepG2 cells. HepG2 cells, derived from a human hepatocellular carcinoma, have been routinely used as a cell model to study human hepatocyte lipid and lipoprotein metabolism. Using this system allowed us to successfully detect DGAT2 expressed from its endogenous locus in HepG2 cells by immunoblotting with anti-FLAG antibodies.
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Affiliation(s)
- Pamela J McFie
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Paulos Chumala
- Department of Medicine and the Canadian Centre for Health and Safety in Agriculture, University of Saskatchewan, Saskatoon, Saskatchewan S7N 2Z4, Canada
| | - George S Katselis
- Department of Medicine and the Canadian Centre for Health and Safety in Agriculture, University of Saskatchewan, Saskatoon, Saskatchewan S7N 2Z4, Canada
| | - Scot J Stone
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
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Duwaerts CC, Maiers JL. ER Disposal Pathways in Chronic Liver Disease: Protective, Pathogenic, and Potential Therapeutic Targets. Front Mol Biosci 2021; 8:804097. [PMID: 35174209 PMCID: PMC8841999 DOI: 10.3389/fmolb.2021.804097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 11/18/2021] [Indexed: 11/13/2022] Open
Abstract
The endoplasmic reticulum is a central player in liver pathophysiology. Chronic injury to the ER through increased lipid content, alcohol metabolism, or accumulation of misfolded proteins causes ER stress, dysregulated hepatocyte function, inflammation, and worsened disease pathogenesis. A key adaptation of the ER to resolve stress is the removal of excess or misfolded proteins. Degradation of intra-luminal or ER membrane proteins occurs through distinct mechanisms that include ER-associated Degradation (ERAD) and ER-to-lysosome-associated degradation (ERLAD), which includes macro-ER-phagy, micro-ER-phagy, and Atg8/LC-3-dependent vesicular delivery. All three of these processes are critical for removing misfolded or unfolded protein aggregates, and re-establishing ER homeostasis following expansion/stress, which is critical for liver function and adaptation to injury. Despite playing a key role in resolving ER stress, the contribution of these degradative processes to liver physiology and pathophysiology is understudied. Analysis of publicly available datasets from diseased livers revealed that numerous genes involved in ER-related degradative pathways are dysregulated; however, their roles and regulation in disease progression are not well defined. Here we discuss the dynamic regulation of ER-related protein disposal pathways in chronic liver disease and cell-type specific roles, as well as potentially targetable mechanisms for treatment of chronic liver disease.
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Affiliation(s)
- Caroline C Duwaerts
- Department of Medicine, University of California, San Francisco, San Francisco, CA, United States
| | - Jessica L Maiers
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, United States
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Lee KS, Choi M, Kwon DW, Kim D, Choi JM, Kim AK, Ham Y, Han SB, Cho S, Cheon CK. A novel de novo heterozygous DYRK1A mutation causes complete loss of DYRK1A function and developmental delay. Sci Rep 2020; 10:9849. [PMID: 32555303 PMCID: PMC7299959 DOI: 10.1038/s41598-020-66750-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 05/14/2020] [Indexed: 01/01/2023] Open
Abstract
Dual-specificity tyrosine phosphorylation-regulated kinase 1 A (DYRK1A) is essential for human development, and DYRK1A haploinsufficiency is associated with a recognizable developmental syndrome and variable clinical features. Here, we present a patient with DYRK1A haploinsufficiency syndrome, including facial dysmorphism, delayed motor development, cardiovascular system defects, and brain atrophy. Exome sequencing identified a novel de novo heterozygous mutation of the human DYRK1A gene (c.1185dup), which generated a translational termination codon and resulted in a C-terminally truncated protein (DYRK1A-E396ter). To study the molecular effect of this truncation, we generated mammalian cell and Drosophila models that recapitulated the DYRK1A protein truncation. Analysis of the structure and deformation energy of the mutant protein predicted a reduction in protein stability. Experimentally, the mutant protein was efficiently degraded by the ubiquitin-dependent proteasome pathway and was barely detectable in mammalian cells. More importantly, the mutant kinase was intrinsically inactive and had little negative impact on the wild-type protein. Similarly, the mutant protein had a minimal effect on Drosophila phenotypes, confirming its loss-of-function in vivo. Together, our results suggest that the novel heterozygous mutation of DYRK1A resulted in loss-of-function of the kinase activity of DYRK1A and may contribute to the developmental delay observed in the patient.
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Affiliation(s)
- Kyu-Sun Lee
- Bionanotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology, 125 Gwahak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
- Department of Functional Genomics, KRIBB School of Bioscience, Korea University of Science and Technology, 217 Gajeong-ro, Gajeong-dong, Yuseong-gu, Daejeon, 34113, Republic of Korea
| | - Miri Choi
- Natural Medicine Research Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanji-ro, Ochang-eup, Cheongwon-gu, Cheongju-si, Chungbuk, 28116, Republic of Korea
- College of Pharmacy, Chungbuk National University, 30-1 Yeonje-ri, Osong-eup, Heungduk-gu, Cheongju-si, Chungbuk, 28644, Republic of Korea
| | - Dae-Woo Kwon
- Bionanotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology, 125 Gwahak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
- Department of Functional Genomics, KRIBB School of Bioscience, Korea University of Science and Technology, 217 Gajeong-ro, Gajeong-dong, Yuseong-gu, Daejeon, 34113, Republic of Korea
| | - Doyoun Kim
- Innovative Target Research Center, Korea Research Institute of Chemical Technology, 141 Gajeong-ro, Jang-dong, Yuseong-gu, Daejeon, 34114, Republic of Korea
| | - Jong-Moon Choi
- Green Cross Genome, Green Cross Laboratories, 107 Ihyeon-ro 30 beon-gil, Giheung-gu, Yongin-si, Gyeonggi, 16924, Republic of Korea
| | - Ae-Kyeong Kim
- Bionanotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology, 125 Gwahak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Youngwook Ham
- Natural Medicine Research Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanji-ro, Ochang-eup, Cheongwon-gu, Cheongju-si, Chungbuk, 28116, Republic of Korea
- College of Pharmacy, Chungbuk National University, 30-1 Yeonje-ri, Osong-eup, Heungduk-gu, Cheongju-si, Chungbuk, 28644, Republic of Korea
| | - Sang-Bae Han
- College of Pharmacy, Chungbuk National University, 30-1 Yeonje-ri, Osong-eup, Heungduk-gu, Cheongju-si, Chungbuk, 28644, Republic of Korea
| | - Sungchan Cho
- Natural Medicine Research Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanji-ro, Ochang-eup, Cheongwon-gu, Cheongju-si, Chungbuk, 28116, Republic of Korea.
- Department of Biomolecular Science, KRIBB School of Bioscience, Korea University of Science and Technology, 217 Gajeong-ro, Gajeong-dong, Yuseong-gu, Daejeon, 34113, Republic of Korea.
| | - Chong Kun Cheon
- Division of Medical Genetics and Metabolism, Department of Pediatrics, Pusan National University Children's Hospital, Pusan National University School of Medicine, 20 Geumo-ro, Mulgeum-eup, Yangsan-si, Gyeongnam, 50612, Republic of Korea.
- Research Institute for Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, 20 Geumo-ro, Mulgeum-eup, Yangsan-si, Gyeongnam, 50612, Republic of Korea.
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12
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The Puzzling Conservation and Diversification of Lipid Droplets from Bacteria to Eukaryotes. Results Probl Cell Differ 2020; 69:281-334. [PMID: 33263877 DOI: 10.1007/978-3-030-51849-3_11] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Membrane compartments are amongst the most fascinating markers of cell evolution from prokaryotes to eukaryotes, some being conserved and the others having emerged via a series of primary and secondary endosymbiosis events. Membrane compartments comprise the system limiting cells (one or two membranes in bacteria, a unique plasma membrane in eukaryotes) and a variety of internal vesicular, subspherical, tubular, or reticulated organelles. In eukaryotes, the internal membranes comprise on the one hand the general endomembrane system, a dynamic network including organelles like the endoplasmic reticulum, the Golgi apparatus, the nuclear envelope, etc. and also the plasma membrane, which are linked via direct lateral connectivity (e.g. between the endoplasmic reticulum and the nuclear outer envelope membrane) or indirectly via vesicular trafficking. On the other hand, semi-autonomous organelles, i.e. mitochondria and chloroplasts, are disconnected from the endomembrane system and request vertical transmission following cell division. Membranes are organized as lipid bilayers in which proteins are embedded. The budding of some of these membranes, leading to the formation of the so-called lipid droplets (LDs) loaded with hydrophobic molecules, most notably triacylglycerol, is conserved in all clades. The evolution of eukaryotes is marked by the acquisition of mitochondria and simple plastids from Gram-positive bacteria by primary endosymbiosis events and the emergence of extremely complex plastids, collectively called secondary plastids, bounded by three to four membranes, following multiple and independent secondary endosymbiosis events. There is currently no consensus view of the evolution of LDs in the Tree of Life. Some features are conserved; others show a striking level of diversification. Here, we summarize the current knowledge on the architecture, dynamics, and multitude of functions of the lipid droplets in prokaryotes and in eukaryotes deriving from primary and secondary endosymbiosis events.
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13
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Dgat2 reduces hepatocellular carcinoma malignancy via downregulation of cell cycle-related gene expression. Biomed Pharmacother 2019; 115:108950. [PMID: 31078041 DOI: 10.1016/j.biopha.2019.108950] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 04/22/2019] [Accepted: 05/02/2019] [Indexed: 02/06/2023] Open
Abstract
Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide, mainly due to the absence of effective diagnostic biomarkers and therapeutic targets. Therefore, novel molecular targets are urgently needed, in order to formulate novel therapeutic approaches for this devastating disease. In the present study, we demonstrated that diacylglycerol acyltransferase 2 (Dgat2) was downregulated in human HCC tissues compared with in matched normal tissues. Furthermore, its high expression was significantly associated with longer survival. In addition, Dgat2 overexpression significantly suppressed HCC cell proliferation. in vivo studies, we revealed that the weight and volume of the tumors derived from Balb/c nude mice was markedly decreased when using HCC cells overexpressing Dgat2. Mechanism analysis demonstrated that cell cycle-related gene expressions were significantly downregulated in HCC cells overexpressing Dgat2. Taken together, these data suggest that Dgat2 is an important regulator of HCC cell proliferation, and could represent a potential anticancer target and diagnostic biomarker for HCC.
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14
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Wang X, Wang QC, Sun Z, Li T, Yang K, An C, Guo C, Tang TS. ER stress mediated degradation of diacylglycerol acyltransferase impairs mitochondrial functions in TMCO1 deficient cells. Biochem Biophys Res Commun 2019; 512:914-920. [DOI: 10.1016/j.bbrc.2019.03.115] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 03/18/2019] [Indexed: 12/17/2022]
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15
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Lee J, Ridgway ND. Substrate channeling in the glycerol-3-phosphate pathway regulates the synthesis, storage and secretion of glycerolipids. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1865:158438. [PMID: 30959116 DOI: 10.1016/j.bbalip.2019.03.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 03/26/2019] [Accepted: 03/27/2019] [Indexed: 01/16/2023]
Abstract
The successive acylation of glycerol-3-phosphate (G3P) by glycerol-3-phosphate acyltransferases and acylglycerol-3-phosphate acyltransferases produces phosphatidic acid (PA), a precursor for CDP-diacylglycerol-dependent phospholipid synthesis. PA is further dephosphorylated by LIPINs to produce diacylglycerol (DG), a substrate for the synthesis of triglyceride (TG) by DG acyltransferases and a precursor for phospholipid synthesis via the CDP-choline and CDP-ethanolamine (Kennedy) pathways. The channeling of fatty acids into TG for storage in lipid droplets and secretion in lipoproteins or phospholipids for membrane biogenesis is dependent on isoform expression, activity and localization of G3P pathway enzymes, as well as dietary and hormonal and tissue-specific factors. Here, we review the mechanisms that control partitioning of substrates into lipid products of the G3P pathway.
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Affiliation(s)
- Jonghwa Lee
- Atlantic Research Center, Depts. of Pediatrics and Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, Canada
| | - Neale D Ridgway
- Atlantic Research Center, Depts. of Pediatrics and Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, Canada.
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16
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Brandt C, McFie PJ, Vu H, Chumala P, Katselis GS, Stone SJ. Identification of calnexin as a diacylglycerol acyltransferase-2 interacting protein. PLoS One 2019; 14:e0210396. [PMID: 30615684 PMCID: PMC6322727 DOI: 10.1371/journal.pone.0210396] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Accepted: 12/21/2018] [Indexed: 11/26/2022] Open
Abstract
Triacylglycerol synthesis is catalyzed by acyl CoA:diacylglycerol acyltransferase-2 (DGAT2). DGAT2 is an integral membrane protein that is localized to the endoplasmic reticulum and interacts with lipid droplets. Using BioId, a method to detect proximal and interacting proteins, we identified calnexin as a DGAT2-interacting protein. Co-immunoprecipitation and proximity ligation assays confirmed this finding. We found that calnexin-deficient mouse embryonic fibroblasts had reduced intracellular triacylglycerol levels and fewer large lipid droplets (>1.0 μm2 area). Despite the alterations in triacylglycerol metabolism, in vitro DGAT2 activity, localization and protein stability were not affected by the absence of calnexin.
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Affiliation(s)
- Curtis Brandt
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Pamela J. McFie
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Huyen Vu
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Paulos Chumala
- Department of Medicine and the Canadian Centre for Health and Safety in Agriculture, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - George S. Katselis
- Department of Medicine and the Canadian Centre for Health and Safety in Agriculture, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Scot J. Stone
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
- * E-mail:
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17
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Bhutada G, Kavšček M, Hofer F, Gogg-Fassolter G, Schweiger M, Darnhofer B, Kordiš D, Birner-Gruenberger R, Natter K. Characterization of a lipid droplet protein from Yarrowia lipolytica that is required for its oleaginous phenotype. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1863:1193-1205. [DOI: 10.1016/j.bbalip.2018.07.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 06/26/2018] [Accepted: 07/21/2018] [Indexed: 10/28/2022]
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18
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Xu Y, Caldo KMP, Pal-Nath D, Ozga J, Lemieux MJ, Weselake RJ, Chen G. Properties and Biotechnological Applications of Acyl-CoA:diacylglycerol Acyltransferase and Phospholipid:diacylglycerol Acyltransferase from Terrestrial Plants and Microalgae. Lipids 2018; 53:663-688. [PMID: 30252128 DOI: 10.1002/lipd.12081] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2018] [Revised: 07/23/2018] [Accepted: 07/24/2018] [Indexed: 12/14/2022]
Abstract
Triacylglycerol (TAG) is the major storage lipid in most terrestrial plants and microalgae, and has great nutritional and industrial value. Since the demand for vegetable oil is consistently increasing, numerous studies have been focused on improving the TAG content and modifying the fatty-acid compositions of plant seed oils. In addition, there is a strong research interest in establishing plant vegetative tissues and microalgae as platforms for lipid production. In higher plants and microalgae, TAG biosynthesis occurs via acyl-CoA-dependent or acyl-CoA-independent pathways. Diacylglycerol acyltransferase (DGAT) catalyzes the last and committed step in the acyl-CoA-dependent biosynthesis of TAG, which appears to represent a bottleneck in oil accumulation in some oilseed species. Membrane-bound and soluble forms of DGAT have been identified with very different amino-acid sequences and biochemical properties. Alternatively, TAG can be formed through acyl-CoA-independent pathways via the catalytic action of membrane-bound phospholipid:diacylglycerol acyltransferase (PDAT). As the enzymes catalyzing the terminal steps of TAG formation, DGAT and PDAT play crucial roles in determining the flux of carbon into seed TAG and thus have been considered as the key targets for engineering oil production. Here, we summarize the most recent knowledge on DGAT and PDAT in higher plants and microalgae, with the emphasis on their physiological roles, structural features, and regulation. The development of various metabolic engineering strategies to enhance the TAG content and alter the fatty-acid composition of TAG is also discussed.
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Affiliation(s)
- Yang Xu
- Department of Agricultural, Food and Nutritional Science, University of Alberta, 116 Street and 85 Avenue, Edmonton, Alberta, T6G 2P5, Canada
| | - Kristian Mark P Caldo
- Department of Agricultural, Food and Nutritional Science, University of Alberta, 116 Street and 85 Avenue, Edmonton, Alberta, T6G 2P5, Canada
- Department of Biochemistry, University of Alberta, 116 Street and 85 Avenue, Edmonton, Alberta, T6G 2H7, Canada
| | - Dipasmita Pal-Nath
- French Associates Institute for Agriculture and Biotechnology of Drylands, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, 8499000, Israel
| | - Jocelyn Ozga
- Department of Agricultural, Food and Nutritional Science, University of Alberta, 116 Street and 85 Avenue, Edmonton, Alberta, T6G 2P5, Canada
| | - M Joanne Lemieux
- Department of Biochemistry, University of Alberta, 116 Street and 85 Avenue, Edmonton, Alberta, T6G 2H7, Canada
| | - Randall J Weselake
- Department of Agricultural, Food and Nutritional Science, University of Alberta, 116 Street and 85 Avenue, Edmonton, Alberta, T6G 2P5, Canada
| | - Guanqun Chen
- Department of Agricultural, Food and Nutritional Science, University of Alberta, 116 Street and 85 Avenue, Edmonton, Alberta, T6G 2P5, Canada
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19
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Joshi V, Upadhyay A, Chhangani D, Amanullah A, Sharan RN, Mishra A. Gp78 involvement in cellular proliferation: Can act as a promising modulator for cell cycle regulatory proteins? J Cell Physiol 2018; 233:6352-6368. [PMID: 29741771 DOI: 10.1002/jcp.26618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 03/28/2018] [Indexed: 11/07/2022]
Abstract
In cells, protein synthesis and degradation are normal processes, which are tightly regulated by various cellular metabolic pathways. Cellular protein quality control (PQC) mechanisms always present a continuous and rigorous check over all intracellular proteins before they can participate in various cellular physiological processes with the help of PQC pathways like autophagy and ubiquitin proteasome system (UPS). The UPS employs few selective E3 ubiquitin ligases for the intracellular degradation of cyclin-dependent kinase inhibitor 1B (p27Kip1 ) that tightly controls cell cycle progression. But, the complex mechanistic interactions and the interplay between E3 ubiquitin ligases involved in the functional regulation as well as expression of p27 are not well known. Here, we demonstrate that cell surface glycoprotein Gp78, a putative E3 ubiquitin ligase, is involved in the stabilization of intracellular steady-state levels of p27. Transient overexpression of Gp78 increases the accumulation of p27 in cells in the form of massive inclusions like structures, which could be due to its cumulative increased stability in cells. We have also monitored how under stress condition, E3 ubiquitin ligase Gp78 regulates endogenous levels of p27 in cells. ER stress treatment generates a marginal increase in Gp78 endogenous levels, and this elevation effect was prominent for intracellular accumulation of p27 in cells. Taken together, our current findings suggest a valuable multifactorial regulatory mechanism and linkage of p27 with UPS pathway.
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Affiliation(s)
- Vibhuti Joshi
- Cellular and Molecular Neurobiology Unit, Indian Institute of Technology Jodhpur, Rajasthan, India
| | - Arun Upadhyay
- Cellular and Molecular Neurobiology Unit, Indian Institute of Technology Jodhpur, Rajasthan, India
| | - Deepak Chhangani
- Cellular and Molecular Neurobiology Unit, Indian Institute of Technology Jodhpur, Rajasthan, India
| | - Ayeman Amanullah
- Cellular and Molecular Neurobiology Unit, Indian Institute of Technology Jodhpur, Rajasthan, India
| | - Rajesh N Sharan
- Radiation and Molecular Biology Unit, Department of Biochemistry, North-Eastern Hill University, Shillong, Meghalaya, India
| | - Amit Mishra
- Cellular and Molecular Neurobiology Unit, Indian Institute of Technology Jodhpur, Rajasthan, India
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20
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Bersuker K, Peterson CWH, To M, Sahl SJ, Savikhin V, Grossman EA, Nomura DK, Olzmann JA. A Proximity Labeling Strategy Provides Insights into the Composition and Dynamics of Lipid Droplet Proteomes. Dev Cell 2017; 44:97-112.e7. [PMID: 29275994 DOI: 10.1016/j.devcel.2017.11.020] [Citation(s) in RCA: 207] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 10/18/2017] [Accepted: 11/27/2017] [Indexed: 01/06/2023]
Abstract
Lipid droplet (LD) functions are regulated by a complement of integral and peripheral proteins that associate with the bounding LD phospholipid monolayer. Defining the composition of the LD proteome has remained a challenge due to the presence of contaminating proteins in LD-enriched buoyant fractions. To overcome this limitation, we developed a proximity labeling strategy that exploits LD-targeted APEX2 to biotinylate LD proteins in living cells. Application of this approach to two different cell types identified the vast majority of previously validated LD proteins, excluded common contaminating proteins, and revealed new LD proteins. Moreover, quantitative analysis of LD proteome dynamics uncovered a role for endoplasmic reticulum-associated degradation in controlling the composition of the LD proteome. These data provide an important resource for future LD studies and demonstrate the utility of proximity labeling to study the regulation of LD proteomes.
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Affiliation(s)
- Kirill Bersuker
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Clark W H Peterson
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Milton To
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Steffen J Sahl
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Victoria Savikhin
- SLAC National Accelerator Center, SSRL, Menlo Park, CA 94025, USA; Stanford Electrical Engineering Department, Stanford University, Stanford, CA 94305, USA
| | - Elizabeth A Grossman
- Departments of Chemistry and Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Daniel K Nomura
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720, USA; Departments of Chemistry and Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - James A Olzmann
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA 94720, USA.
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21
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Wang H, Airola MV, Reue K. How lipid droplets "TAG" along: Glycerolipid synthetic enzymes and lipid storage. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1131-1145. [PMID: 28642195 PMCID: PMC5688854 DOI: 10.1016/j.bbalip.2017.06.010] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 06/15/2017] [Accepted: 06/15/2017] [Indexed: 02/06/2023]
Abstract
Triacylglycerols (TAG) serve as the predominant form of energy storage in mammalian cells, and TAG synthesis influences conditions such as obesity, fatty liver, and insulin resistance. In most tissues, the glycerol 3-phosphate pathway enzymes are responsible for TAG synthesis, and the regulation and function of these enzymes is therefore important for metabolic homeostasis. Here we review the sites and regulation of glycerol-3-phosphate acyltransferase (GPAT), acylglycerol-3-phosphate acyltransferase (AGPAT), lipin phosphatidic acid phosphatase (PAP), and diacylglycerol acyltransferase (DGAT) enzyme action. We highlight the critical roles that these enzymes play in human health by reviewing Mendelian disorders that result from mutation in the corresponding genes. We also summarize the valuable insights that genetically engineered mouse models have provided into the cellular and physiological roles of GPATs, AGPATs, lipins and DGATs. Finally, we comment on the status and feasibility of therapeutic approaches to metabolic disease that target enzymes of the glycerol 3-phosphate pathway. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.
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Affiliation(s)
- Huan Wang
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States
| | - Michael V Airola
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, United States
| | - Karen Reue
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States; Molecular Biology Institute, University of California, Los Angeles, CA, United States.
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22
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Joshi V, Upadhyay A, Kumar A, Mishra A. Gp78 E3 Ubiquitin Ligase: Essential Functions and Contributions in Proteostasis. Front Cell Neurosci 2017; 11:259. [PMID: 28890687 PMCID: PMC5575403 DOI: 10.3389/fncel.2017.00259] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 08/09/2017] [Indexed: 11/26/2022] Open
Abstract
As per the requirement of metabolism and fitness, normal cellular functions are controlled by several proteins, and their interactive molecular and signaling events at multiple levels. Protein quality control (PQC) mechanisms ensure the correct folding and proper utilization of these proteins to avoid their misfolding and aggregation. To maintain the optimum environment of complex proteome PQC system employs various E3 ubiquitin ligases for the selective degradation of aberrant proteins. Glycoprotein 78 (Gp78) is an E3 ubiquitin ligase that prevents multifactorial deleterious accumulation of different misfolded proteins via endoplasmic reticulum-associated degradation (ERAD). However, the precise role of Gp78 under stress conditions to avoid bulk misfolded aggregation is unclear, which can act as a crucial resource to establish the dynamic nature of the proteome. Present article systematically explains the detailed molecular characterization of Gp78 and also addresses its various cellular physiological functions, which could be crucial to achieving protein homeostasis. Here, we comprehensively represent the current findings of Gp78, which shows its PQC roles in different physiological functions and diseases; and thereby propose novel opportunities to better understand the unsolved questions for therapeutic interventions linked with different protein misfolding disorders.
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Affiliation(s)
- Vibhuti Joshi
- Cellular and Molecular Neurobiology Unit, Indian Institute of Technology JodhpurJodhpur, India
| | - Arun Upadhyay
- Cellular and Molecular Neurobiology Unit, Indian Institute of Technology JodhpurJodhpur, India
| | - Amit Kumar
- Centre for Biosciences and Biomedical Engineering, Indian Institute of Technology IndoreIndore, India
| | - Amit Mishra
- Cellular and Molecular Neurobiology Unit, Indian Institute of Technology JodhpurJodhpur, India
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23
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Printsev I, Curiel D, Carraway KL. Membrane Protein Quantity Control at the Endoplasmic Reticulum. J Membr Biol 2017; 250:379-392. [PMID: 27743014 PMCID: PMC5392169 DOI: 10.1007/s00232-016-9931-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2016] [Accepted: 09/28/2016] [Indexed: 02/07/2023]
Abstract
The canonical function of the endoplasmic reticulum-associated degradation (ERAD) system is to enforce quality control among membrane-associated proteins by targeting misfolded secreted, intra-organellar, and intramembrane proteins for degradation. However, increasing evidence suggests that ERAD additionally functions in maintaining appropriate levels of a subset of membrane-associated proteins. In this 'quantity control' capacity, ERAD responds to environmental cues to regulate the proteasomal degradation of specific ERAD substrates according to cellular need. In this review, we discuss in detail seven proteins that are targeted by the ERAD quantity control system. Not surprisingly, ERAD-mediated protein degradation is a key regulatory feature of a variety of ER-resident proteins, including HMG-CoA reductase, cytochrome P450 3A4, IP3 receptor, and type II iodothyronine deiodinase. In addition, the ERAD quantity control system plays roles in maintaining the proper stoichiometry of multi-protein complexes by mediating the degradation of components that are produced in excess of the limiting subunit. Perhaps somewhat unexpectedly, recent evidence suggests that the ERAD quantity control system also contributes to the regulation of plasma membrane-localized signaling receptors, including the ErbB3 receptor tyrosine kinase and the GABA neurotransmitter receptors. For these substrates, a proportion of the newly synthesized yet properly folded receptors are diverted for degradation at the ER, and are unable to traffic to the plasma membrane. Given that receptor abundance or concentration within the plasma membrane plays key roles in determining signaling efficiency, these observations may point to a novel mechanism for modulating receptor-mediated cellular signaling.
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Affiliation(s)
- Ignat Printsev
- Department of Biochemistry and Molecular Medicine, and UC Davis Comprehensive Cancer Center, UC Davis School of Medicine, Research Building III, Room 1100B, 4645 2nd Avenue, Sacramento, CA, 95817, USA
| | - Daniel Curiel
- Department of Biochemistry and Molecular Medicine, and UC Davis Comprehensive Cancer Center, UC Davis School of Medicine, Research Building III, Room 1100B, 4645 2nd Avenue, Sacramento, CA, 95817, USA
| | - Kermit L Carraway
- Department of Biochemistry and Molecular Medicine, and UC Davis Comprehensive Cancer Center, UC Davis School of Medicine, Research Building III, Room 1100B, 4645 2nd Avenue, Sacramento, CA, 95817, USA.
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24
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Chitraju C, Mejhert N, Haas JT, Diaz-Ramirez LG, Grueter CA, Imbriglio JE, Pinto S, Koliwad SK, Walther TC, Farese RV. Triglyceride Synthesis by DGAT1 Protects Adipocytes from Lipid-Induced ER Stress during Lipolysis. Cell Metab 2017; 26:407-418.e3. [PMID: 28768178 PMCID: PMC6195226 DOI: 10.1016/j.cmet.2017.07.012] [Citation(s) in RCA: 213] [Impact Index Per Article: 30.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 04/10/2017] [Accepted: 07/17/2017] [Indexed: 12/29/2022]
Abstract
Triglyceride (TG) storage in adipose tissue provides the major reservoir for metabolic energy in mammals. During lipolysis, fatty acids (FAs) are hydrolyzed from adipocyte TG stores and transported to other tissues for fuel. For unclear reasons, a large portion of hydrolyzed FAs in adipocytes is re-esterified to TGs in a "futile," ATP-consuming, energy dissipating cycle. Here we show that FA re-esterification during adipocyte lipolysis is mediated by DGAT1, an ER-localized DGAT enzyme. Surprisingly, this re-esterification cycle does not preserve TG mass but instead functions to protect the ER from lipotoxic stress and related consequences, such as adipose tissue inflammation. Our data reveal an important role for DGAT activity and TG synthesis generally in averting ER stress and lipotoxicity, with specifically DGAT1 performing this function during stimulated lipolysis in adipocytes.
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Affiliation(s)
- Chandramohan Chitraju
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Niklas Mejhert
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Joel T Haas
- Gladstone Institute of Cardiovascular Disease, San Francisco, CA 94158, USA
| | | | - Carrie A Grueter
- Gladstone Institute of Cardiovascular Disease, San Francisco, CA 94158, USA
| | | | | | - Suneil K Koliwad
- Gladstone Institute of Cardiovascular Disease, San Francisco, CA 94158, USA; Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Tobias C Walther
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA; Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Boston, MA 02115, USA.
| | - Robert V Farese
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA; Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA.
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25
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Jung S, Choi M, Choi K, Kwon EB, Kang M, Kim DE, Jeong H, Kim J, Kim JH, Kim MO, Han SB, Cho S. Inactivation of human DGAT2 by oxidative stress on cysteine residues. PLoS One 2017; 12:e0181076. [PMID: 28700690 PMCID: PMC5507451 DOI: 10.1371/journal.pone.0181076] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 06/26/2017] [Indexed: 12/15/2022] Open
Abstract
Diacylglycerol acyltransferases (DGATs) have a crucial role in the biosynthesis of triacylglycerol (TG), the major storage form of metabolic energy in eukaryotic organisms. Even though DGAT2, one of two distinct DGATs, has a vital role in TG biosynthesis, little is known about the regulation of DGAT2 activity. In this study, we examined the role of cysteine and its oxidation in the enzymatic activity of human DGAT2 in vitro. Human DGAT2 activity was considerably inhibited not only by thiol-modifying reagents (NEM and IA) but also by ROS-related chemicals (H2O2 and β-lapachone), while human DGAT1 and GPAT1 were little affected. Particularly, ROS-related chemicals concomitantly induced intermolecular disulfide crosslinking of human DGAT2. Both the oxidative inactivation and disulfide crosslinking were almost completely reversed by the treatment with DTT, a disulfide-reducing agent. These results clearly demonstrated the significant role of ROS-induced intermolecular crosslinking in the inactivation of human DGAT2 and also suggested DGAT2 as a redox-sensitive regulator in TG biosynthesis.
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Affiliation(s)
- Sunhee Jung
- Anticancer Agent Research Center, Korea Research Institute of Bioscience & Biotechnology, 30 Yeongudanji-ro, Ochang-eup, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do, South Korea
- College of Pharmacy, Chungbuk National University, 1 Chungdae-ro Seowon-gu, Cheongju-si, Chungcheongbuk-do, South Korea
| | - Miri Choi
- Anticancer Agent Research Center, Korea Research Institute of Bioscience & Biotechnology, 30 Yeongudanji-ro, Ochang-eup, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do, South Korea
- College of Pharmacy, Chungbuk National University, 1 Chungdae-ro Seowon-gu, Cheongju-si, Chungcheongbuk-do, South Korea
| | - Kwangman Choi
- Anticancer Agent Research Center, Korea Research Institute of Bioscience & Biotechnology, 30 Yeongudanji-ro, Ochang-eup, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do, South Korea
| | - Eun Bin Kwon
- College of Pharmacy, Chungbuk National University, 1 Chungdae-ro Seowon-gu, Cheongju-si, Chungcheongbuk-do, South Korea
- Natural Medicine Research Center, Korea Research Institute of Bioscience & Biotechnology, 30 Yeongudanji-ro, Ochang-eup, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do, South Korea
| | - Mingu Kang
- Anticancer Agent Research Center, Korea Research Institute of Bioscience & Biotechnology, 30 Yeongudanji-ro, Ochang-eup, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do, South Korea
- College of Pharmacy, Chungbuk National University, 1 Chungdae-ro Seowon-gu, Cheongju-si, Chungcheongbuk-do, South Korea
| | - Dong-eun Kim
- Anticancer Agent Research Center, Korea Research Institute of Bioscience & Biotechnology, 30 Yeongudanji-ro, Ochang-eup, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do, South Korea
- College of Pharmacy, Chungbuk National University, 1 Chungdae-ro Seowon-gu, Cheongju-si, Chungcheongbuk-do, South Korea
| | - Hyejeong Jeong
- Anticancer Agent Research Center, Korea Research Institute of Bioscience & Biotechnology, 30 Yeongudanji-ro, Ochang-eup, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do, South Korea
- College of Pharmacy, Chungbuk National University, 1 Chungdae-ro Seowon-gu, Cheongju-si, Chungcheongbuk-do, South Korea
| | - Janghwan Kim
- Stem Cell Research Center, Korea Research Institute of Bioscience & Biotechnology, 125 Gwahak-ro, Yuseong-gu, Daejeon, South Korea
| | - Jong Heon Kim
- Cancer Cell and Molecular Biology Branch, Research Institute, National Cancer Center, Ilsan-ro, Ilsandong-gu, Goyang-si, Gyeonggi-do, South Korea
| | - Mun Ock Kim
- Natural Medicine Research Center, Korea Research Institute of Bioscience & Biotechnology, 30 Yeongudanji-ro, Ochang-eup, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do, South Korea
| | - Sang-Bae Han
- College of Pharmacy, Chungbuk National University, 1 Chungdae-ro Seowon-gu, Cheongju-si, Chungcheongbuk-do, South Korea
| | - Sungchan Cho
- Anticancer Agent Research Center, Korea Research Institute of Bioscience & Biotechnology, 30 Yeongudanji-ro, Ochang-eup, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do, South Korea
- Department of Biomolecular Science, Korea University of Science and Technology, 217 Gajeong-ro, Daejeon, South Korea
- * E-mail:
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Bersuker K, Olzmann JA. Establishing the lipid droplet proteome: Mechanisms of lipid droplet protein targeting and degradation. Biochim Biophys Acta Mol Cell Biol Lipids 2017. [PMID: 28627435 DOI: 10.1016/j.bbalip.2017.06.006] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Lipid droplets (LDs) are ubiquitous, endoplasmic reticulum (ER)-derived organelles that mediate the sequestration of neutral lipids (e.g. triacylglycerol and sterol esters), providing a dynamic cellular storage depot for rapid lipid mobilization in response to increased cellular demands. LDs have a unique ultrastructure, consisting of a core of neutral lipids encircled by a phospholipid monolayer that is decorated with integral and peripheral proteins. The LD proteome contains numerous lipid metabolic enzymes, regulatory scaffold proteins, proteins involved in LD clustering and fusion, and other proteins of unknown functions. The cellular role of LDs is inherently determined by the composition of its proteome and alteration of the LD protein coat provides a powerful mechanism to adapt LDs to fluctuating metabolic states. Here, we review the current understanding of the molecular mechanisms that govern LD protein targeting and degradation. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.
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Affiliation(s)
- Kirill Bersuker
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, CA 94720, USA
| | - James A Olzmann
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, CA 94720, USA.
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Abstract
Hepatic steatosis, the first step in the progression of nonalcoholic fatty liver disease, is characterized by triglyceride accumulation in hepatocytes and is highly prevalent in people with obesity. Although initially asymptomatic, hepatic steatosis is an important risk factor for the development of hepatic insulin resistance and type 2 diabetes mellitus and can also progress to more severe pathologies such as nonalcoholic steatohepatitis, liver fibrosis and cirrhosis; hepatic steatosis has, therefore, received considerable research interest in the past 20 years. The lipid accumulation that defines hepatic steatosis disturbs the function of the endoplasmic reticulum (ER) in hepatocytes, thereby generating chronic ER stress that interferes with normal cellular function. Although ubiquitous stress response mechanisms (namely, ER-associated degradation, unfolded protein response and autophagy) are the main processes for restoring cellular proteostasis, these mechanisms are unable to alleviate ER stress in the context of the fatty liver. Furthermore, ER stress and ER stress responses can promote lipid accumulation in hepatocytes in a counter-productive manner and could, therefore, be the origin of a vicious pathological cycle.
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Affiliation(s)
- Andrei Baiceanu
- Institut National de la Santé et de la Recherche Médicale, UMRS 1138, Centre de Recherche des Cordeliers, F-75006, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, UMRS 1138, Centre de Recherche des Cordeliers, F-75006, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, UMRS 1138, Centre de Recherche des Cordeliers, 15 rue de l'école de médecine, F-75006, Paris, France
- University of Medicine and Pharmacy Iuliu Hat¸ieganu, Faculty of Pharmacy, 8 Victor Babes Street, 400012 Cluj-Napoca, Romania
| | - Pierre Mesdom
- Institut National de la Santé et de la Recherche Médicale, UMRS 1138, Centre de Recherche des Cordeliers, F-75006, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, UMRS 1138, Centre de Recherche des Cordeliers, F-75006, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, UMRS 1138, Centre de Recherche des Cordeliers, 15 rue de l'école de médecine, F-75006, Paris, France
| | - Marie Lagouge
- Institut National de la Santé et de la Recherche Médicale, UMRS 1138, Centre de Recherche des Cordeliers, F-75006, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, UMRS 1138, Centre de Recherche des Cordeliers, F-75006, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, UMRS 1138, Centre de Recherche des Cordeliers, 15 rue de l'école de médecine, F-75006, Paris, France
| | - Fabienne Foufelle
- Institut National de la Santé et de la Recherche Médicale, UMRS 1138, Centre de Recherche des Cordeliers, F-75006, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, UMRS 1138, Centre de Recherche des Cordeliers, F-75006, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, UMRS 1138, Centre de Recherche des Cordeliers, 15 rue de l'école de médecine, F-75006, Paris, France
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Bayraktar O, Oral O, Kocaturk NM, Akkoc Y, Eberhart K, Kosar A, Gozuacik D. IBMPFD Disease-Causing Mutant VCP/p97 Proteins Are Targets of Autophagic-Lysosomal Degradation. PLoS One 2016; 11:e0164864. [PMID: 27768726 PMCID: PMC5074563 DOI: 10.1371/journal.pone.0164864] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 10/03/2016] [Indexed: 01/07/2023] Open
Abstract
The ubiquitin-proteasome system (UPS) degrades soluble proteins and small aggregates, whereas macroautophagy (autophagy herein) eliminates larger protein aggregates, tangles and even whole organelles in a lysosome-dependent manner. VCP/p97 was implicated in both pathways. VCP/p97 mutations cause a rare multisystem disease called IBMPFD (Inclusion Body Myopathy with Paget's Disease and Frontotemporal Dementia). Here, we studied the role IBMPFD-related mutants of VCP/p97 in autophagy. In contrast with the wild-type VCP/p97 protein or R155C or R191Q mutants, the P137L mutant was aggregate-prone. We showed that, unlike commonly studied R155C or R191Q mutants, the P137L mutant protein stimulated both autophagosome and autolysosome formation. Moreover, P137L mutant protein itself was a substrate of autophagy. Starvation- and mTOR inhibition-induced autophagy led to the degradation of the P137L mutant protein, while preserving the wild-type and functional VCP/p97. Strikingly, similar to the P137L mutant, other IBMPFD-related VCP/p97 mutants, namely R93C and G157R mutants induced autophagosome and autolysosome formation; and G157R mutant formed aggregates that could be cleared by autophagy. Therefore, cellular phenotypes caused by P137L mutant expression were not isolated observations, and some other IBMPFD disease-related VCP/p97 mutations could lead to similar outcomes. Our results indicate that cellular mechanisms leading to IBMPFD disease may be various, and underline the importance of studying different disease-associated mutations in order to better understand human pathologies and tailor mutation-specific treatment strategies.
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Affiliation(s)
- Oznur Bayraktar
- Sabanci University, Faculty of Engineering and Natural Sciences, Molecular Biology, Genetics and Bioengineering Program, Istanbul, 34956, Turkey
| | - Ozlem Oral
- Sabanci University, Nanotechnology Research and Application Center, Istanbul, 34956, Turkey
| | - Nur Mehpare Kocaturk
- Sabanci University, Faculty of Engineering and Natural Sciences, Molecular Biology, Genetics and Bioengineering Program, Istanbul, 34956, Turkey
| | - Yunus Akkoc
- Sabanci University, Faculty of Engineering and Natural Sciences, Molecular Biology, Genetics and Bioengineering Program, Istanbul, 34956, Turkey
| | - Karin Eberhart
- Sabanci University, Faculty of Engineering and Natural Sciences, Molecular Biology, Genetics and Bioengineering Program, Istanbul, 34956, Turkey
| | - Ali Kosar
- Sabanci University, Faculty of Engineering and Natural Sciences, Mechatronics Engineering Program, Istanbul, 34956, Turkey
- Sabanci University, Center of Excellence for Functional Surfaces and Interfaces for Nano Diagnostics (EFSUN), Istanbul, 34956, Turkey
| | - Devrim Gozuacik
- Sabanci University, Faculty of Engineering and Natural Sciences, Molecular Biology, Genetics and Bioengineering Program, Istanbul, 34956, Turkey
- Sabanci University, Center of Excellence for Functional Surfaces and Interfaces for Nano Diagnostics (EFSUN), Istanbul, 34956, Turkey
- * E-mail:
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Diacylglycerol acyltransferase-2 and monoacylglycerol acyltransferase-2 are ubiquitinated proteins that are degraded by the 26S proteasome. Biochem J 2016; 473:3621-3637. [DOI: 10.1042/bcj20160418] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 08/16/2016] [Indexed: 01/20/2023]
Abstract
Acyl-CoA:1,2-diacylglycerol acyltransferase (DGAT)-2 is one of the two DGAT enzymes that catalyzes the synthesis of triacylglycerol, which is an important form of stored energy for eukaryotic organisms. There is currently limited information available regarding how DGAT2 and triacylglycerol synthesis are regulated. Recent studies have indicated that DGAT2 can be regulated by changes in gene expression. How DGAT2 is regulated post-transcriptionally remains less clear. In this study, we demonstrated that DGAT2 is a very unstable protein and is rapidly degraded in an ubiquitin-dependent manner via the proteasome. Many of the 25 lysines present in DGAT2 appeared to be involved in promoting its degradation. However, the six C-terminal lysines were the most important in regulating stability. We also demonstrated that acyl-CoA:monoacylglycerol acyltransferase (MGAT)-2, an enzyme with extensive sequence homology to DGAT2 that catalyzes the synthesis of diacylglycerol, was also ubiquitinated. However, MGAT2 was found to be much more stable than DGAT2. Interestingly, when co-expressed, MGAT2 appeared to stabilize DGAT2. Finally, we found that both DGAT2 and MGAT2 are substrates of the endoplasmic reticulum-associated degradation pathway.
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30
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Frabutt DA, Zheng YH. Arms Race between Enveloped Viruses and the Host ERAD Machinery. Viruses 2016; 8:v8090255. [PMID: 27657106 PMCID: PMC5035969 DOI: 10.3390/v8090255] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 09/12/2016] [Accepted: 09/12/2016] [Indexed: 12/12/2022] Open
Abstract
Enveloped viruses represent a significant category of pathogens that cause serious diseases in animals. These viruses express envelope glycoproteins that are singularly important during the infection of host cells by mediating fusion between the viral envelope and host cell membranes. Despite low homology at protein levels, three classes of viral fusion proteins have, as of yet, been identified based on structural similarities. Their incorporation into viral particles is dependent upon their proper sub-cellular localization after being expressed and folded properly in the endoplasmic reticulum (ER). However, viral protein expression can cause stress in the ER, and host cells respond to alleviate the ER stress in the form of the unfolded protein response (UPR); the effects of which have been observed to potentiate or inhibit viral infection. One important arm of UPR is to elevate the capacity of the ER-associated protein degradation (ERAD) pathway, which is comprised of host quality control machinery that ensures proper protein folding. In this review, we provide relevant details regarding viral envelope glycoproteins, UPR, ERAD, and their interactions in host cells.
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Affiliation(s)
- Dylan A Frabutt
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.
| | - Yong-Hui Zheng
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.
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31
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Kim H, Lee KS, Kim AK, Choi M, Choi K, Kang M, Chi SW, Lee MS, Lee JS, Lee SY, Song WJ, Yu K, Cho S. A chemical with proven clinical safety rescues Down-syndrome-related phenotypes in through DYRK1A inhibition. Dis Model Mech 2016; 9:839-48. [PMID: 27483355 PMCID: PMC5007978 DOI: 10.1242/dmm.025668] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 06/16/2016] [Indexed: 02/01/2023] Open
Abstract
DYRK1A is important in neuronal development and function, and its excessive activity is considered a significant pathogenic factor in Down syndrome and Alzheimer's disease. Thus, inhibition of DYRK1A has been suggested to be a new strategy to modify the disease. Very few compounds, however, have been reported to act as inhibitors, and their potential clinical uses require further evaluation. Here, we newly identify CX-4945, the safety of which has been already proven in the clinical setting, as a potent inhibitor of DYRK1A that acts in an ATP-competitive manner. The inhibitory potency of CX-4945 on DYRK1A (IC50=6.8 nM) in vitro was higher than that of harmine, INDY or proINDY, which are well-known potent inhibitors of DYRK1A. CX-4945 effectively reverses the aberrant phosphorylation of Tau, amyloid precursor protein (APP) and presenilin 1 (PS1) in mammalian cells. To our surprise, feeding with CX-4945 significantly restored the neurological and phenotypic defects induced by the overexpression of minibrain, an ortholog of human DYRK1A, in the Drosophila model. Moreover, oral administration of CX-4945 acutely suppressed Tau hyperphosphorylation in the hippocampus of DYRK1A-overexpressing mice. Our research results demonstrate that CX-4945 is a potent DYRK1A inhibitor and also suggest that it has therapeutic potential for DYRK1A-associated diseases. Editors' choice:In vivo validation of a potent DYRK1A inhibitor, with proven clinical safety, using Down-syndrome- and Alzheimer's-disease-like models.
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Affiliation(s)
- Hyeongki Kim
- Anticancer Agent Research Center, Korea Research Institute of Bioscience and Biotechnology, Cheongju, Chungbuk 28115, Republic of Korea Department of Biomolecular Science, University of Science and Technology, Daejeon 34113, Republic of Korea
| | - Kyu-Sun Lee
- Neurophysiology Research Group, Hazard Monitoring BioNano Research Center, Korea Research Institute of Bioscience and Biotechnology, Deajeon 34141, Republic of Korea Department of Functional Genomics, University of Science and Technology, Daejeon 34113, Republic of Korea
| | - Ae-Kyeong Kim
- Neurophysiology Research Group, Hazard Monitoring BioNano Research Center, Korea Research Institute of Bioscience and Biotechnology, Deajeon 34141, Republic of Korea
| | - Miri Choi
- Anticancer Agent Research Center, Korea Research Institute of Bioscience and Biotechnology, Cheongju, Chungbuk 28115, Republic of Korea
| | - Kwangman Choi
- Anticancer Agent Research Center, Korea Research Institute of Bioscience and Biotechnology, Cheongju, Chungbuk 28115, Republic of Korea
| | - Mingu Kang
- Anticancer Agent Research Center, Korea Research Institute of Bioscience and Biotechnology, Cheongju, Chungbuk 28115, Republic of Korea
| | - Seung-Wook Chi
- Disease Target Structure Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, Republic of Korea
| | - Min-Sung Lee
- Disease Target Structure Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, Republic of Korea
| | - Jeong-Soo Lee
- Neurophysiology Research Group, Hazard Monitoring BioNano Research Center, Korea Research Institute of Bioscience and Biotechnology, Deajeon 34141, Republic of Korea Department of Functional Genomics, University of Science and Technology, Daejeon 34113, Republic of Korea
| | - So-Young Lee
- International Cooperation Office, Ministry of Food & Drug Safety, Cheongju, Chungbuk 28159, Republic of Korea
| | - Woo-Joo Song
- Department of Biochemistry and Molecular Biology, Neurodegeneration Control Research Center, School of Medicine, Kyung Hee University, Seoul 02447, Republic of Korea
| | - Kweon Yu
- Neurophysiology Research Group, Hazard Monitoring BioNano Research Center, Korea Research Institute of Bioscience and Biotechnology, Deajeon 34141, Republic of Korea Department of Functional Genomics, University of Science and Technology, Daejeon 34113, Republic of Korea
| | - Sungchan Cho
- Anticancer Agent Research Center, Korea Research Institute of Bioscience and Biotechnology, Cheongju, Chungbuk 28115, Republic of Korea Department of Biomolecular Science, University of Science and Technology, Daejeon 34113, Republic of Korea
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32
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Ruggiano A, Mora G, Buxó L, Carvalho P. Spatial control of lipid droplet proteins by the ERAD ubiquitin ligase Doa10. EMBO J 2016; 35:1644-55. [PMID: 27357570 PMCID: PMC4969576 DOI: 10.15252/embj.201593106] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 06/02/2016] [Indexed: 01/20/2023] Open
Abstract
The endoplasmic reticulum (ER) plays a central role in the biogenesis of most membrane proteins. Among these are proteins localized to the surface of lipid droplets (LDs), fat storage organelles delimited by a phospholipid monolayer. The LD monolayer is often continuous with the membrane of the ER allowing certain membrane proteins to diffuse between the two organelles. In these connected organelles, how some proteins concentrate specifically at the surface of LDs is not known. Here, we show that the ERAD ubiquitin ligase Doa10 controls the levels of some LD proteins. Their degradation is dependent on the localization to the ER and appears independent of the folding state. Moreover, we show that by degrading the ER pool of these LD proteins, ERAD contributes to restrict their localization to LDs. The signals for LD targeting and Doa10‐mediated degradation overlap, indicating that these are competing events. This spatial control of protein localization is a novel function of ERAD that might contribute to generate functional diversity in a continuous membrane system.
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Affiliation(s)
- Annamaria Ruggiano
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Barcelona, Spain Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Gabriel Mora
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Barcelona, Spain Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Laura Buxó
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Barcelona, Spain Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Pedro Carvalho
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Barcelona, Spain Universitat Pompeu Fabra (UPF), Barcelona, Spain
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Abstract
The endoplasmic reticulum is the port of entry for proteins into the secretory pathway and the site of synthesis for several important lipids, including cholesterol, triacylglycerol, and phospholipids. Protein production within the endoplasmic reticulum is tightly regulated by a cohort of resident machinery that coordinates the folding, modification, and deployment of secreted and integral membrane proteins. Proteins failing to attain their native conformation are degraded through the endoplasmic reticulum-associated degradation (ERAD) pathway via a series of tightly coupled steps: substrate recognition, dislocation, and ubiquitin-dependent proteasomal destruction. The same ERAD machinery also controls the flux through various metabolic pathways by coupling the turnover of metabolic enzymes to the levels of key metabolites. We review the current understanding and biological significance of ERAD-mediated regulation of lipid metabolism in mammalian cells.
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Affiliation(s)
- Julian Stevenson
- Program in Metabolic Biology, Department of Nutritional Sciences and Toxicology, University of California, Berkeley, California 94720;
| | - Edmond Y Huang
- Program in Metabolic Biology, Department of Nutritional Sciences and Toxicology, University of California, Berkeley, California 94720;
| | - James A Olzmann
- Program in Metabolic Biology, Department of Nutritional Sciences and Toxicology, University of California, Berkeley, California 94720;
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Biochemical characterization of human acyl coenzyme A: 2-monoacylglycerol acyltransferase-3 (MGAT3). Biochem Biophys Res Commun 2016; 475:264-70. [PMID: 27184406 DOI: 10.1016/j.bbrc.2016.05.071] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 05/12/2016] [Indexed: 01/31/2023]
Abstract
BACKGROUND MGAT3 catalyzes the synthesis of 1,2-diacylglycerol from 2-monoacylglycerol in an acyl CoA-dependent reaction. Although initially identified as an MGAT enzyme, MGAT3 is more closely related to DGAT2 than to MGAT1 and MGAT2. Furthermore, MGAT3 possesses both DGAT and MGAT activities, in vitro. MGAT3 is almost exclusively expressed in the small intestine in humans, suggesting that it has a role in dietary fat absorption. Although identified many years ago, little information is available regarding the contribution of MGAT3 to triacylglycerol biosynthesis. RESULTS This study confirmed the initial observations that MGAT3 possessed both MGAT and DGAT activities. When expressed in cells in culture, MGAT3 stimulated lipid droplet growth, but unlike DGAT2, does not become concentrated around the lipid droplet surface. We also characterized the MGAT activity of an MGAT3 mutant in which a conserved cysteine was changed to a tyrosine residue. Lastly, although they share significant sequence identity, MGAT3 is a much more stable protein than DGAT2, yet they are both polyubiquitinated and degraded through ER-associated degradation by the proteasome. CONCLUSION Our findings provide additional evidence that MGAT3 likely functions as a TG synthase in cells.
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35
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Mansbach CM, Siddiqi S. Control of chylomicron export from the intestine. Am J Physiol Gastrointest Liver Physiol 2016; 310:G659-68. [PMID: 26950854 DOI: 10.1152/ajpgi.00228.2015] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 02/22/2016] [Indexed: 01/31/2023]
Abstract
The control of chylomicron output by the intestine is a complex process whose outlines have only recently come into focus. In this review we will cover aspects of chylomicron formation and prechylomicron vesicle generation that elucidate potential control points. Substrate (dietary fatty acids and monoacylglycerols) availability is directly related to the output rate of chylomicrons. These substrates must be converted to triacylglycerol before packaging in prechylomicrons by a series of endoplasmic reticulum (ER)-localized acylating enzymes that rapidly convert fatty acids and monoacylglycerols to triacylglycerol. The packaging of the prechylomicron with triacylglycerol is controlled by the microsomal triglyceride transport protein, another potential limiting step. The prechylomicrons, once loaded with triacylglycerol, are ready to be incorporated into the prechylomicron transport vesicle that transports the prechylomicron from the ER to the Golgi. Control of this exit step from the ER, the rate-limiting step in the transcellular movement of the triacylglycerol, is a multistep process involving the activation of PKCζ, the phosphorylation of Sar1b, releasing the liver fatty acid binding protein from a heteroquatromeric complex, which enables it to bind to the ER and organize the prechylomicron transport vesicle budding complex. We propose that control of PKCζ activation is the major physiological regulator of chylomicron output.
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Affiliation(s)
- Charles M Mansbach
- Department of Medicine, Division of Gastroenterology, University of Tennessee Health Science Center, Memphis, Tennessee; and Department of Medicine, Veterans Affairs Medical Center, Memphis, Tennessee
| | - Shahzad Siddiqi
- Department of Medicine, Division of Gastroenterology, University of Tennessee Health Science Center, Memphis, Tennessee; and Department of Medicine, Veterans Affairs Medical Center, Memphis, Tennessee
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36
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Yin J, Park G, Lee JE, Choi EY, Park JY, Kim TH, Park N, Jin X, Jung JE, Shin D, Hong JH, Kim H, Yoo H, Lee SH, Kim YJ, Park JB, Kim JH. DEAD-box RNA helicase DDX23 modulates glioma malignancy via elevating miR-21 biogenesis. Brain 2015; 138:2553-70. [DOI: 10.1093/brain/awv167] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Accepted: 04/17/2015] [Indexed: 01/01/2023] Open
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37
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CPEB1 modulates differentiation of glioma stem cells via downregulation of HES1 and SIRT1 expression. Oncotarget 2015; 5:6756-69. [PMID: 25216517 PMCID: PMC4196161 DOI: 10.18632/oncotarget.2250] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Glioma stemness has been recognized as the most important reason for glioma relapse and drug resistance. Differentiation of glioma stem cells (GSCs) has been implicated as a novel approach to target recurrent glioma. However, the detailed molecular mechanism involved in the differentiation of GSCs has not yet been elucidated. This study identified CPEB1 as the key modulator that induces the differentiation of GSCs at the post-transcriptional level. Gain and loss of function experiments showed that CPEB1 expression reduced sphere formation ability and the expression of stemness markers such as Nestin and Notch. To elucidate the detailed molecular mechanism underlying the action of CPEB1, we investigated the interacting ribonome of the CPEB1 complex using a Ribonomics approach. CPEB1 specifically suppressed the translation of HES1 and SIRT1 by interacting with a cytoplasmic polyadenylation element. The expression profile of CPEB1 negatively correlated with overall survival in glioma patients. Overexpression of CPEB1 decreased the number of GSCs in an orthotopically implanted glioma animal model. These results suggest that CPEB1-mediated translational control is essential for the differentiation of GSCs and provides novel therapeutic concepts for differentiation therapy.
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