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Nature May 2020Diacylglycerol O-acyltransferase 1 (DGAT1) synthesizes triacylglycerides and is required for dietary fat absorption and fat storage in humans. DGAT1 belongs to the...
Diacylglycerol O-acyltransferase 1 (DGAT1) synthesizes triacylglycerides and is required for dietary fat absorption and fat storage in humans. DGAT1 belongs to the membrane-bound O-acyltransferase (MBOAT) superfamily, members of which are found in all kingdoms of life and are involved in the acylation of lipids and proteins. How human DGAT1 and other mammalian members of the MBOAT family recognize their substrates and catalyse their reactions is unknown. The absence of three-dimensional structures also hampers rational targeting of DGAT1 for therapeutic purposes. Here we present the cryo-electron microscopy structure of human DGAT1 in complex with an oleoyl-CoA substrate. Each DGAT1 protomer has nine transmembrane helices, eight of which form a conserved structural fold that we name the MBOAT fold. The MBOAT fold in DGAT1 forms a hollow chamber in the membrane that encloses highly conserved catalytic residues. The chamber has separate entrances for each of the two substrates, fatty acyl-CoA and diacylglycerol. DGAT1 can exist as either a homodimer or a homotetramer and the two forms have similar enzymatic activity. The N terminus of DGAT1 interacts with the neighbouring protomer and these interactions are required for enzymatic activity.
Topics: Acyl Coenzyme A; Binding Sites; Cryoelectron Microscopy; Diacylglycerol O-Acyltransferase; Diglycerides; Humans; Models, Molecular; Protein Multimerization; Structure-Activity Relationship; Triglycerides
PubMed: 32433610
DOI: 10.1038/s41586-020-2280-2 -
Science Signaling Jan 2017The NHERF molecular adaptors serve as gates for TRPC4 and TRPC5 regulation by diacylglycerol and recognition of CFTR by the quality control checkpoint.
The NHERF molecular adaptors serve as gates for TRPC4 and TRPC5 regulation by diacylglycerol and recognition of CFTR by the quality control checkpoint.
Topics: Diglycerides; Phosphoproteins; Sodium-Hydrogen Exchangers
PubMed: 28074011
DOI: 10.1126/scisignal.aam7242 -
FEBS Letters Aug 2016Lipids are commonly known for the structural roles they play, however, the specific contribution of different lipid classes to wide-ranging signalling pathways is... (Review)
Review
Lipids are commonly known for the structural roles they play, however, the specific contribution of different lipid classes to wide-ranging signalling pathways is progressively being unravelled. Signalling lipids and their associated effector proteins are emerging as significant contributors to a vast array of effector functions within cells, including essential processes such as membrane fusion and vesicle exocytosis. Many phospholipids have signalling capacity, however, this review will focus on phosphatidic acid (PA) and the enzymes implicated in its production from diacylglycerol (DAG) and phosphatidylcholine (PC): DGK and PLD respectively. PA is a negatively charged, cone-shaped lipid identified as a key mediator in specific membrane fusion and vesicle exocytosis events in a variety of mammalian cells, and has recently been implicated in specialised secretory organelle exocytosis in apicomplexan parasites. This review summarises the recent work implicating a role for PA regulation in exocytosis in various cell types. We will discuss how these signalling events are linked to pathogenesis in the phylum Apicomplexa.
Topics: Apicomplexa; Diglycerides; Exocytosis; Lipid Metabolism; Lipids; Phosphatidic Acids; Phosphatidylcholines; Signal Transduction
PubMed: 27403735
DOI: 10.1002/1873-3468.12296 -
Insect Biochemistry and Molecular... Jul 2015The insect fat body and the adipose tissue of vertebrates store fatty acids (FA) as triacylglycerols (TG). However, the fat body of most insects has the unique ability...
The insect fat body and the adipose tissue of vertebrates store fatty acids (FA) as triacylglycerols (TG). However, the fat body of most insects has the unique ability to rapidly produce and secrete large amounts of diacylglycerol (DG). Monoacylglycerol acyltransferase (MGAT), which catalyzes the synthesis of DG from MG, and a diacylglycerol acyltransferase (DGAT), which catalyzes the synthesis of TG from DG, are key enzymes in the metabolism of neutral glycerides. However, very little is known about these acyltransferases in insects. In the present study we have cloned two predicted MGATs and a DGAT from Manduca sexta and compared their sequences with predicted MGAT and DGAT homologs from a number of insect species. The comparison suggested that insects may only have a single DGAT gene, DGAT1. The apparent absence of a DGAT2 gene in insects would represent a major difference with vertebrates, which contain DGAT1 and DGAT2 genes. Insects seem to have a single MGAT gene which is similar to the MGAT2 of vertebrates. A number of conserved phosphorylation sites of potential physiological significance were identified among insect proteins and among insect and vertebrate proteins. DGAT1 and MGAT are expressed in fat body, midgut and ovaries. The relative rates of utilization of FAs for the synthesis of DG and TG correlated with the relative expression levels of MGAT and DGAT suggesting that regulation of the expression levels of these acyltransferases could be determining whether the fat body secretes DG or stores fatty acids as TG. The expression patterns of the acyltransferases suggest a role of the monoacylglycerol pathway in the production and mobilization of DG in M. sexta fat body.
Topics: Acyltransferases; Animals; Diacylglycerol O-Acyltransferase; Diglycerides; Fat Body; Female; Gastrointestinal Tract; Gene Expression Regulation; Male; Manduca; Monoglycerides; Ovary; Triglycerides
PubMed: 25263765
DOI: 10.1016/j.ibmb.2014.09.007 -
Biochimica Et Biophysica Acta.... Oct 2019Lipins are phosphatidic acid phosphatase enzymes whose cellular function in regulating lipid metabolism has been known for decades, particularly in metabolically active... (Review)
Review
Lipins are phosphatidic acid phosphatase enzymes whose cellular function in regulating lipid metabolism has been known for decades, particularly in metabolically active tissues such as adipose tissue or liver. In recent years evidence is accumulating for key regulatory roles of the lipin family in innate immune cells. Lipins may help regulate signaling through relevant immune receptors such as Toll-like receptors, and are also integral part of the cellular machinery for lipid storage in these cells, thereby modulating certain inflammatory processes. Mutations in genes that encode for members of this family produce autoinflammatory hereditary diseases or diseases with an important inflammatory component in humans. In this review we summarize recent findings on the role of lipins in cells of the innate immune system and in the onset and progress of inflammatory processes.
Topics: Animals; Diglycerides; Humans; Immunity, Innate; Inflammation; Macrophages; Phosphatidate Phosphatase; Phosphatidic Acids
PubMed: 31220616
DOI: 10.1016/j.bbalip.2019.06.003 -
Cell Calcium Aug 2015Phospholipase C (PLC), a major membrane phospholipid hydrolyzing enzyme generates signaling messengers such as diacylglycerol (DAG) and inositol 1,4,5-trisphosphate... (Review)
Review
Phospholipase C (PLC), a major membrane phospholipid hydrolyzing enzyme generates signaling messengers such as diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (IP3) in animals, and their phosphorylated forms such as phosphatidic acid (PA) and inositol hexakisphosphate (IP6) are thought to regulate various cellular processes in plants. Based on substrate specificity, plant PLC family is sub-divided into phosphatidylinositol-PLC (PI-PLC) and phosphatidylcholine-PLC (PC-PLC) groups. The activity of plant PLCs is regulated by various factors and the major ones include, Ca(2+) concentration, phospholipid substrate, post-translational modifications and interacting proteins. Most of the PLC members have been localized at the plasma membrane, suited for their function of membrane lipid hydrolysis. Several PLC members have been implicated in various cellular processes and signaling networks, triggered in response to a number of environmental cues and developmental events in different plant species, which makes them potential candidates for genetically engineering the crop plants for stress tolerance and enhancing the crop productivity. In this review article, we are focusing mainly on the plant PLC signaling and regulation, potential cellular and physiological role in different abiotic and biotic stresses, nutrient deficiency, growth and development.
Topics: Calcium; Diglycerides; Inositol 1,4,5-Trisphosphate; Lipid Metabolism; Plant Proteins; Plants; Protein Processing, Post-Translational; Signal Transduction; Type C Phospholipases
PubMed: 25933832
DOI: 10.1016/j.ceca.2015.04.003 -
Advances in Biological Regulation Jan 2018Diacylglycerol kinase (DGK) phosphorylates diacylglycerol (DG) to produce phosphatidic acid (PA). Mammalian DGK comprises ten isozymes (α-κ) and regulates a wide... (Review)
Review
Where do substrates of diacylglycerol kinases come from? Diacylglycerol kinases utilize diacylglycerol species supplied from phosphatidylinositol turnover-independent pathways.
Diacylglycerol kinase (DGK) phosphorylates diacylglycerol (DG) to produce phosphatidic acid (PA). Mammalian DGK comprises ten isozymes (α-κ) and regulates a wide variety of physiological and pathological events, such as cancer, type II diabetes, neuronal disorders and immune responses. DG and PA consist of various molecular species that have different acyl chains at the sn-1 and sn-2 positions, and consequently, mammalian cells contain at least 50 structurally distinct DG/PA species. Because DGK is one of the components of phosphatidylinositol (PI) turnover, the generally accepted dogma is that all DGK isozymes utilize 18:0/20:4-DG derived from PI turnover. We recently established a specific liquid chromatography-mass spectrometry method to analyze which PA species were generated by DGK isozymes in a cell stimulation-dependent manner. Interestingly, we determined that DGKδ, which is closely related to the pathogenesis of type II diabetes, preferentially utilized 14:0/16:0-, 14:0/16:1-, 16:0/16:0-, 16:0/16:1-, 16:0/18:0- and 16:0/18:1-DG species (X:Y = the total number of carbon atoms: the total number of double bonds) supplied from the phosphatidylcholine-specific phospholipase C pathway, but not 18:0/20:4-DG, in high glucose-stimulated C2C12 myoblasts. Moreover, DGKα mainly consumed 14:0/16:0-, 16:0/18:1-, 18:0/18:1- and 18:1/18:1-DG species during cell proliferation in AKI melanoma cells. Furthermore, we found that 16:0/16:0-PA was specifically produced by DGKζ in Neuro-2a cells during retinoic acid- and serum starvation-induced neuronal differentiation. These results indicate that DGK isozymes utilize a variety of DG molecular species derived from PI turnover-independent pathways as substrates in different stimuli and cells. DGK isozymes phosphorylate various DG species to generate various PA species. It was revealed that the modes of activation of conventional and novel protein kinase isoforms by DG molecular species varied considerably. However, PA species-selective binding proteins have not been found to date. Therefore, we next attempted to identify PA species-selective binding proteins from the mouse brain and identified α-synuclein, which has causal links to Parkinson's disease. Intriguingly, we determined that among phospholipids, including several PA species (16:0/16:0-PA, 16:0/18:1-PA, 18:1/18:1-PA, 18:0/18:0-PA and 18:0/20:4-PA); 18:1/18:1-PA was the most strongly bound PA to α-synuclein. Moreover, 18:1/18:1-PA strongly enhanced secondary structural changes from the random coil form to the α-helix form and generated a multimeric and proteinase K-resistant α-synuclein protein. In contrast with the dogma described above, our recent studies strongly suggest that PI turnover-derived DG species and also various DG species derived from PI turnover-independent pathways are utilized by DGK isozymes. DG species supplied from distinct pathways may be utilized by DGK isozymes based on different stimuli present in different types of cells, and individual PA molecular species would have specific targets and exert their own physiological functions.
Topics: Animals; Diabetes Mellitus, Type 2; Diacylglycerol Kinase; Diglycerides; Humans; Phosphatidic Acids; Phosphatidylinositols; Phosphorylation; Type C Phospholipases
PubMed: 28918129
DOI: 10.1016/j.jbior.2017.09.003 -
Lipids in Health and Disease May 2020Protein kinase C (PKC) and Protein kinase D (PKD) isoforms can sense diacylglycerol (DAG) generated in the different cellular compartments in various physiological... (Review)
Review
Protein kinase C (PKC) and Protein kinase D (PKD) isoforms can sense diacylglycerol (DAG) generated in the different cellular compartments in various physiological processes. DAG accumulates in multiple organs of the obese subjects, which leads to the disruption of metabolic homeostasis and the development of diabetes as well as associated diseases. Multiple studies proved that aberrant activation of PKCs and PKDs contributes to the development of metabolic diseases. DAG-sensing PKC and PKD isoforms play a crucial role in the regulation of metabolic homeostasis and therefore might serve as targets for the treatment of metabolic disorders such as obesity and diabetes.
Topics: Animals; Diabetes Mellitus; Diglycerides; Glucose; Humans; Insulin; Lipid Metabolism; Obesity; Protein Kinase C; Signal Transduction
PubMed: 32466765
DOI: 10.1186/s12944-020-01286-8 -
Protein and Peptide Letters 2021Protein kinase C (PKC) is a family of protein kinase enzymes that can phosphorylate other proteins and influence their functions, such as signal transduction, cell... (Review)
Review
Protein kinase C (PKC) is a family of protein kinase enzymes that can phosphorylate other proteins and influence their functions, such as signal transduction, cell survival, and death. Increased diacylglycerol (DAG) concentrations, which are typically observed raised in hyperglycemic situations such as diabetes mellitus, can also activate PKC enzymes (DM). On the other hand, PKC isomers have been shown to play an essential role in diabetes and many hyperglycemic complications, most importantly atherosclerosis and diabetic cardiomyopathy (DCM). As a result, blocking PKC activation via DAG can prevent hyperglycemia and related consequences, such as DCM. Wogonin is a herbal medicine which has anti-inflammatory properties, and investigations show that it scavenge oxidative radicals, attenuate nuclear factor-kappa B (NF-κB) activity, inhibit several essential cell cycle regulatory genes, block nitric oxide (NO) and suppress cyclooxygenase- 2 (COX-2). Furthermore, several investigations show that wogonin also attenuates diacylglycerol DAG levels in diabetic mice. Since the DAG-PKC pathway is linked with hyperglycemia and its complications, Wogonin-mediated DAG-PKC attenuation can help treat hyperglycemia and its complications.
Topics: Animals; Atherosclerosis; Diabetic Cardiomyopathies; Diglycerides; Flavanones; Humans; Hyperglycemia; Protein Kinase C
PubMed: 34711151
DOI: 10.2174/0929866528666211027113349 -
BioMed Research International 2015Numerous studies conducted on obese humans and various rodent models of obesity have identified a correlation between hepatic lipid content and the development of... (Review)
Review
Numerous studies conducted on obese humans and various rodent models of obesity have identified a correlation between hepatic lipid content and the development of insulin resistance in liver and other tissues. Despite a large body of the literature on this topic, the cause and effect relationship between hepatic steatosis and insulin resistance remains controversial. If, as many believe, lipid aggregation in liver drives insulin resistance and other metabolic abnormalities, there are significant unanswered questions as to which lipid mediators are causative in this cascade. Several published papers have now correlated levels of diacylglycerol (DAG), the penultimate intermediate in triglyceride synthesis, with development of insulin resistance and have postulated that this occurs via activation of protein kinase C signaling. Although many studies have confirmed this relationship, many others have reported a disconnect between DAG content and insulin resistance. It has been postulated that differences in methods for DAG measurement, DAG compartmentalization within the cell, or fatty acid composition of the DAG may explain these discrepancies. The purpose of this review is to compare and contrast some of the relevant findings in this area and to discuss a number of unanswered questions regarding the relationship between DAG and insulin resistance.
Topics: Animals; Diglycerides; Fatty Liver; Humans; Insulin; Insulin Resistance; Liver; Models, Biological; Signal Transduction; Up-Regulation
PubMed: 26273583
DOI: 10.1155/2015/104132