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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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2
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Stone SJ. Mechanisms of intestinal triacylglycerol synthesis. Biochim Biophys Acta Mol Cell Biol Lipids 2022; 1867:159151. [PMID: 35296424 DOI: 10.1016/j.bbalip.2022.159151] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 01/13/2022] [Accepted: 02/16/2022] [Indexed: 02/07/2023]
Abstract
Triacylglycerols are a major source of stored energy that are obtained either from the diet or can be synthesized to some extent by most tissues. Alterations in pathways of triacylglycerol metabolism can result in their excessive accumulation leading to obesity, insulin resistance, cardiovascular disease and nonalcoholic fatty liver disease. Most tissues in mammals synthesize triacylglycerols via the glycerol 3-phosphate pathway. However, in the small intestine the monoacylglycerol acyltransferase pathway is the predominant pathway for triacylglycerol biosynthesis where it participates in the absorption of dietary triacylglycerol. In this review, the enzymes that are part of both the glycerol 3-phosphate and monoacylglycerol acyltransferase pathways and their contributions to intestinal triacylglycerol metabolism are reviewed. The potential of some of the enzymes involved in triacylglycerol synthesis in the small intestine as possible therapeutic targets for treating metabolic disorders associated with elevated triacylglycerol is briefly discussed.
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Affiliation(s)
- Scot J Stone
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
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3
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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] [MESH Headings] [Track Full Text] [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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Zhukovsky MA, Filograna A, Luini A, Corda D, Valente C. The Structure and Function of Acylglycerophosphate Acyltransferase 4/ Lysophosphatidic Acid Acyltransferase Delta (AGPAT4/LPAATδ). Front Cell Dev Biol 2019; 7:147. [PMID: 31428612 PMCID: PMC6688108 DOI: 10.3389/fcell.2019.00147] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 07/16/2019] [Indexed: 12/27/2022] Open
Abstract
Lipid-modifying enzymes serve crucial roles in cellular processes such as signal transduction (producing lipid-derived second messengers), intracellular membrane transport (facilitating membrane remodeling needed for membrane fusion/fission), and protein clustering (organizing lipid domains as anchoring platforms). The lipid products crucial in these processes can derive from different metabolic pathways, thus it is essential to know the localization, substrate specificity, deriving products (and their function) of all lipid-modifying enzymes. Here we discuss an emerging family of these enzymes, the lysophosphatidic acid acyltransferases (LPAATs), also known as acylglycerophosphate acyltransferases (AGPATs), that produce phosphatidic acid (PA) having as substrates lysophosphatidic acid (LPA) and acyl-CoA. Eleven LPAAT/AGPAT enzymes have been identified in mice and humans based on sequence homologies, and their localization, specific substrates and functions explored. We focus on one member of the family, LPAATδ, a protein expressed mainly in brain and in muscle (though to a lesser extent in other tissues); while at the cellular level it is localized at the trans-Golgi network membranes and at the mitochondrial outer membranes. LPAATδ is a physiologically essential enzyme since mice knocked-out for Lpaatδ show severe dysfunctions including cognitive impairment, impaired force contractility and altered white adipose tissue. The LPAATδ physiological roles are related to the formation of its product PA. PA is a multifunctional lipid involved in cell signaling as well as in membrane remodeling. In particular, the LPAATδ-catalyzed conversion of LPA (inverted-cone-shaped lipid) to PA (cone-shaped lipid) is considered a mechanism of deformation of the bilayer that favors membrane fission. Indeed, LPAATδ is an essential component of the fission-inducing machinery driven by the protein BARS. In this process, a protein-tripartite complex (BARS/14-3-3γ/phosphoinositide kinase PI4KIIIβ) is recruited at the trans-Golgi network, at the sites where membrane fission is to occur; there, LPAATδ directly interacts with BARS and is activated by BARS. The resulting formation of PA is essential for membrane fission occurring at those spots. Also in mitochondria PA formation has been related to fusion/fission events. Since PA is formed by various enzymatic pathways in different cell compartments, the BARS-LPAATδ interaction indicates the relevance of lipid-modifying enzymes acting exactly where their products are needed (i.e., PA at the Golgi membranes).
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Affiliation(s)
- Mikhail A Zhukovsky
- Institute of Biochemistry and Cell Biology and Institute of Protein Biochemistry, National Research Council, Naples, Italy
| | - Angela Filograna
- Institute of Biochemistry and Cell Biology and Institute of Protein Biochemistry, National Research Council, Naples, Italy
| | - Alberto Luini
- Institute of Biochemistry and Cell Biology and Institute of Protein Biochemistry, National Research Council, Naples, Italy
| | - Daniela Corda
- Institute of Biochemistry and Cell Biology and Institute of Protein Biochemistry, National Research Council, Naples, Italy
| | - Carmen Valente
- Institute of Biochemistry and Cell Biology and Institute of Protein Biochemistry, National Research Council, Naples, Italy
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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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McFie PJ, Banman SL, Stone SJ. Diacylglycerol acyltransferase-2 contains a c-terminal sequence that interacts with lipid droplets. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1863:1068-1081. [PMID: 29902571 DOI: 10.1016/j.bbalip.2018.06.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 06/04/2018] [Accepted: 06/09/2018] [Indexed: 11/30/2022]
Abstract
Diacylglycerol acyltranferase-2 (DGAT2) is a resident protein of the endoplasmic reticulum that catalyzes the synthesis of triacylglycerol. When lipid droplet formation is stimulated by incubating cells with fatty acids, DGAT2 becomes concentrated around the surface of cytosolic lipid droplets. Using confocal microscopy and directed mutagenesis, we have identified a 17-amino acid sequence in the C-terminal region of DGAT2 that is necessary and sufficient for targeting DGAT2 to lipid droplets. When this region was deleted, DGAT2 remained in the ER and did not target to lipid droplets. Fusing this sequence to mCherry directed the fluorescent reporter to lipid droplets. Similarly, when the corresponding region of monoacylglycerol acyltransferase-2 (MGAT2) was replaced with this sequence, MGAT2 was also targeted to lipid droplets. Lastly, we demonstrated that DGAT2 in ER membranes is continuous with lipid droplets. We propose a new model whereby DGAT2 remains in the ER during lipid droplet formation via it's transmembrane domains and interacts with nascent lipid droplets via its C-terminal lipid droplet interacting domain as they expand.
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Affiliation(s)
- Pamela J McFie
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Shanna L Banman
- Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B4, Canada
| | - Scot J Stone
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
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7
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Barbosa AD, Siniossoglou S. Function of lipid droplet-organelle interactions in lipid homeostasis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1864:1459-1468. [DOI: 10.1016/j.bbamcr.2017.04.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 03/31/2017] [Accepted: 04/02/2017] [Indexed: 12/20/2022]
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Senkal CE, Salama MF, Snider AJ, Allopenna JJ, Rana NA, Koller A, Hannun YA, Obeid LM. Ceramide Is Metabolized to Acylceramide and Stored in Lipid Droplets. Cell Metab 2017; 25:686-697. [PMID: 28273483 PMCID: PMC5472424 DOI: 10.1016/j.cmet.2017.02.010] [Citation(s) in RCA: 156] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 11/22/2016] [Accepted: 02/16/2017] [Indexed: 12/26/2022]
Abstract
In an approach aimed at defining interacting partners of ceramide synthases (CerSs), we found that fatty acyl-CoA synthase ACSL5 interacts with all CerSs. We demonstrate that ACSL5-generated FA-CoA was utilized with de novo ceramide for the generation of acylceramides, poorly studied ceramide metabolites. Functionally, inhibition of ceramide channeling to acylceramide enhanced accumulation of de novo ceramide and resulted in augmentation of ceramide-mediated apoptosis. Mechanistically, we show that acylceramide generation is catalyzed by diacylglycerol acyltransferase 2 (DGAT2) on lipid droplets. In summary, this study identifies a metabolic pathway of acylceramide generation and its sequestration in LDs in cells and in livers of mice on a high-fat diet. The study also implicates this pathway in ceramide-mediated apoptosis, and has implications in co-regulation of triglyceride and sphingolipid metabolisms.
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Affiliation(s)
- Can E Senkal
- Department of Medicine, Stony Brook University, Stony Brook, NY 11794, USA; Stony Brook Cancer Center, Stony Brook University, Stony Brook, NY 11794, USA
| | - Mohamed F Salama
- Department of Medicine, Stony Brook University, Stony Brook, NY 11794, USA; Department of Biochemistry, Faculty of Veterinary Medicine, Mansoura University, Mansoura, Dakahlia Governorate 35516, Egypt
| | - Ashley J Snider
- Department of Medicine, Stony Brook University, Stony Brook, NY 11794, USA; Stony Brook Cancer Center, Stony Brook University, Stony Brook, NY 11794, USA; Northport Veterans Affairs Medical Center, Northport, NY 11768, USA
| | - Janet J Allopenna
- Department of Medicine, Stony Brook University, Stony Brook, NY 11794, USA
| | - Nadia A Rana
- Department of Medicine, Stony Brook University, Stony Brook, NY 11794, USA
| | - Antonius Koller
- Proteomics Center, Stony Brook University, Stony Brook, NY 11794, USA
| | - Yusuf A Hannun
- Department of Medicine, Stony Brook University, Stony Brook, NY 11794, USA; Stony Brook Cancer Center, Stony Brook University, Stony Brook, NY 11794, USA
| | - Lina M Obeid
- Department of Medicine, Stony Brook University, Stony Brook, NY 11794, USA; Stony Brook Cancer Center, Stony Brook University, Stony Brook, NY 11794, USA; Northport Veterans Affairs Medical Center, Northport, NY 11768, USA.
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Abstract
Lipid droplets are the universal cellular organelles for the transient or long-term storage of lipids. The number, size and composition of lipid droplets vary greatly within cells in a homogenous population as well as in different cell types. The variability of intracellular lipid-storage organelles reflects the diversification of lipid droplet composition and function. Lipid droplet diversification results, for example, in two cellular lipid droplet populations that are prone to diminish and grow, respectively. The aberrant accumulation or depletion of lipids are hallmarks or causes of various human pathologies. Thus, a better understanding of the origins of lipid droplet diversification is not only a fascinating cell biology question but also potentially serves to improve comprehension of pathologies that entail the accumulation of lipids. This Commentary covers the lipid droplet life cycle and highlights the early steps during lipid droplet biogenesis, which we propose to be the potential driving forces of lipid droplet diversification.
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Affiliation(s)
- Abdou Rachid Thiam
- Laboratoire de Physique Statistique, École Normale Supérieure, PSL Research University; Université Paris Diderot Sorbonne Paris-Cité; Sorbonne Universités UPMC Univ Paris 06; CNRS; 24 rue Lhomond, Paris 75005, France
| | - Mathias Beller
- Institute for Mathematical Modeling of Biological Systems, Heinrich Heine University, Universitätsstr. 1, Düsseldorf 40225, Germany .,Systems Biology of Lipid Metabolism, Heinrich Heine University, Universitätsstr. 1, Düsseldorf 40225, Germany
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10
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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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11
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McFie PJ, Izzard S, Vu H, Jin Y, Beauchamp E, Berthiaume LG, Stone SJ. Membrane topology of human monoacylglycerol acyltransferase-2 and identification of regions important for its localization to the endoplasmic reticulum. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:1192-1204. [PMID: 27373844 DOI: 10.1016/j.bbalip.2016.06.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 06/27/2016] [Accepted: 06/30/2016] [Indexed: 11/16/2022]
Abstract
Acyl CoA:2-monoacylglycerol acyltransferase (MGAT)-2 has an important role in dietary fat absorption in the intestine. MGAT2 resides in the endoplasmic reticulum and catalyzes the synthesis of diacylglycerol which is then utilized as a substrate for triacylglycerol synthesis. This triacylglycerol is then incorporated into chylomicrons which are released into the circulation. In this study, we determined the membrane topology of human MGAT2. Protease protection experiments showed that the C-terminus is exposed to the cytosol, while the N-terminus is partially buried in the ER membrane. MGAT2, like murine DGAT2, was found to have two transmembrane domains. We also identified a region of MGAT2 associated with the ER membrane that contains the histidine-proline-histidine-glycine sequence present in all DGAT2 family members that is thought to comprise the active site. Proteolysis experiments demonstrated that digestion of total cellular membranes from cells expressing MGAT2 with trypsin abolished MGAT activity, indicating that domains that are important for catalysis face the cytosol. We also explored the role that the five cysteines residues present in MGAT2 have in catalysis. MGAT activity was sensitive to two thiol modifiers, N-ethylmaleimide and 5,5'-dithiobis-(2-nitrobenzoic acid). Furthermore, mutation of four cysteines resulted in a reduction in MGAT activity. However, when the C-terminal cysteine (C334) was mutated, MGAT activity was actually higher than that of wild-type FL-MGAT2. Lastly, we determined that both transmembrane domains of MGAT2 are important for its ER localization, and that MGAT2 is present in mitochondrial-associated membranes.
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Affiliation(s)
- Pamela J McFie
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Sabrina Izzard
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Huyen Vu
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Youzhi Jin
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Erwan Beauchamp
- Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Luc G Berthiaume
- Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Scot J Stone
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
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12
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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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13
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D’Aquila T, Sirohi D, Grabowski JM, Hedrick VE, Paul LN, Greenberg AS, Kuhn RJ, Buhman KK. Characterization of the proteome of cytoplasmic lipid droplets in mouse enterocytes after a dietary fat challenge. PLoS One 2015; 10:e0126823. [PMID: 25992653 PMCID: PMC4436333 DOI: 10.1371/journal.pone.0126823] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 04/08/2015] [Indexed: 01/23/2023] Open
Abstract
Dietary fat absorption by the small intestine is a multistep process that regulates the uptake and delivery of essential nutrients and energy. One step of this process is the temporary storage of dietary fat in cytoplasmic lipid droplets (CLDs). The storage and mobilization of dietary fat is thought to be regulated by proteins that associate with the CLD; however, mechanistic details of this process are currently unknown. In this study we analyzed the proteome of CLDs isolated from enterocytes harvested from the small intestine of mice following a dietary fat challenge. In this analysis we identified 181 proteins associated with the CLD fraction, of which 37 are associated with known lipid related metabolic pathways. We confirmed the localization of several of these proteins on or around the CLD through confocal and electron microscopy, including perilipin 3, apolipoprotein A-IV, and acyl-CoA synthetase long-chain family member 5. The identification of the enterocyte CLD proteome provides new insight into potential regulators of CLD metabolism and the process of dietary fat absorption.
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Affiliation(s)
- Theresa D’Aquila
- Department of Nutrition Science, Purdue University, West Lafayette, Indiana, United States of America
| | - Devika Sirohi
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
- Bindley Bioscience Center, Purdue University, West Lafayette, Indiana, United States of America
| | - Jeffrey M. Grabowski
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
- Department of Entomology, Purdue University, West Lafayette, Indiana, United States of America
| | - Victoria E. Hedrick
- Bindley Bioscience Center, Purdue University, West Lafayette, Indiana, United States of America
| | - Lake N. Paul
- Bindley Bioscience Center, Purdue University, West Lafayette, Indiana, United States of America
| | - Andrew S. Greenberg
- Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, United States of America
| | - Richard J. Kuhn
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
- Bindley Bioscience Center, Purdue University, West Lafayette, Indiana, United States of America
| | - Kimberly K. Buhman
- Department of Nutrition Science, Purdue University, West Lafayette, Indiana, United States of America
- * E-mail:
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14
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Barbosa AD, Savage DB, Siniossoglou S. Lipid droplet-organelle interactions: emerging roles in lipid metabolism. Curr Opin Cell Biol 2015; 35:91-7. [PMID: 25988547 DOI: 10.1016/j.ceb.2015.04.017] [Citation(s) in RCA: 107] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 04/27/2015] [Accepted: 04/28/2015] [Indexed: 01/02/2023]
Abstract
Cellular homeostasis depends on the precisely coordinated use of lipids as fuels for energy production, building blocks for membrane biogenesis or chemical signals for intra-cellular and inter-cellular communication. Lipid droplets (LDs) are universally conserved dynamic organelles that can store and mobilize fatty acids and other lipid species for their multiple cellular roles. Increasing evidence suggests that contact zones between LDs and other organelles play important roles in the trafficking of lipids and in the regulation of lipid metabolism. Here we review recent advances regarding the nature and functional relevance of interactions between LDs and other organelles-particularly the endoplasmic reticulum (ER), LDs, mitochondria and vacuoles-that highlight their importance for lipid metabolism.
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Affiliation(s)
- Antonio Daniel Barbosa
- Cambridge Institute for Medical Research, University of Cambridge, CB2 0XY Cambridge, United Kingdom
| | - David B Savage
- University of Cambridge Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, Cambridge CB2 0QQ, United Kingdom
| | - Symeon Siniossoglou
- Cambridge Institute for Medical Research, University of Cambridge, CB2 0XY Cambridge, United Kingdom.
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