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Science (New York, N.Y.) May 2023Cytotoxic T lymphocytes (CTLs) kill virus-infected and cancer cells through T cell receptor (TCR) recognition. How CTLs terminate signaling and disengage to allow serial...
Cytotoxic T lymphocytes (CTLs) kill virus-infected and cancer cells through T cell receptor (TCR) recognition. How CTLs terminate signaling and disengage to allow serial killing has remained a mystery. TCR activation triggers membrane specialization within the immune synapse, including the production of diacylglycerol (DAG), a lipid that can induce negative membrane curvature. We found that activated TCRs were shed into DAG-enriched ectosomes at the immune synapse rather than internalized through endocytosis, suggesting that DAG may contribute to the outward budding required for ectocytosis. Budding ectosomes were endocytosed directly by target cells, thereby terminating TCR signaling and simultaneously disengaging the CTL from the target cell to allow serial killing. Thus, ectocytosis renders TCR signaling self-limiting.
Topics: Cell Division; Cell Membrane; Receptors, Antigen, T-Cell; T-Lymphocytes, Cytotoxic; Exocytosis; Immunological Synapses; Cell-Derived Microparticles; Diglycerides
PubMed: 37228189
DOI: 10.1126/science.abp8933 -
Cell Metabolism Jan 2023sn-1,2-diacylglycerol (sn-1,2-DAG)-mediated activation of protein kinase Cε (PKCε) is a key pathway that is responsible for obesity-related lipid metabolism disorders,...
sn-1,2-diacylglycerol (sn-1,2-DAG)-mediated activation of protein kinase Cε (PKCε) is a key pathway that is responsible for obesity-related lipid metabolism disorders, which induces hepatic insulin resistance and type 2 diabetes. No small molecules have been previously reported to ameliorate these diseases through this pathway. Here, we screened and identified the phytochemical atractylenolide II (AT II) that reduces the hepatic sn-1,2-DAG levels, deactivates PKCε activity, and improves obesity-induced hyperlipidemia, hepatosteatosis, and insulin resistance. Furthermore, using the ABPP strategy, the diacylglycerol kinase family member DGKQ was identified as a direct target of AT II. AT II may act on a novel drug-binding pocket in the CRD and PH domains of DGKQ to thereby allosterically regulate its kinase activity. Moreover, AT II also increases weight loss by activating DGKQ-AMPK-PGC1α-UCP-1 signaling in adipose tissue. These findings suggest that AT II is a promising lead compound to improve obesity-induced insulin resistance.
Topics: Humans; Protein Kinase C-epsilon; Insulin Resistance; Diabetes Mellitus, Type 2; Diglycerides; Obesity
PubMed: 36525963
DOI: 10.1016/j.cmet.2022.11.012 -
Cell Metabolism Aug 2020The coronavirus disease 2019 (COVID-19) pandemic presents an unprecedented threat to global public health. Herein, we utilized a combination of targeted and untargeted...
The coronavirus disease 2019 (COVID-19) pandemic presents an unprecedented threat to global public health. Herein, we utilized a combination of targeted and untargeted tandem mass spectrometry to analyze the plasma lipidome and metabolome in mild, moderate, and severe COVID-19 patients and healthy controls. A panel of 10 plasma metabolites effectively distinguished COVID-19 patients from healthy controls (AUC = 0.975). Plasma lipidome of COVID-19 resembled that of monosialodihexosyl ganglioside (GM3)-enriched exosomes, with enhanced levels of sphingomyelins (SMs) and GM3s, and reduced diacylglycerols (DAGs). Systems evaluation of metabolic dysregulation in COVID-19 was performed using multiscale embedded differential correlation network analyses. Using exosomes isolated from the same cohort, we demonstrated that exosomes of COVID-19 patients with elevating disease severity were increasingly enriched in GM3s. Our work suggests that GM3-enriched exosomes may partake in pathological processes related to COVID-19 pathogenesis and presents the largest repository on the plasma lipidome and metabolome distinct to COVID-19.
Topics: Adult; Aged; Betacoronavirus; CD4-Positive T-Lymphocytes; COVID-19; Coronavirus Infections; Diglycerides; Exosomes; Female; G(M3) Ganglioside; Gangliosides; Humans; Male; Metabolome; Metabolomics; Middle Aged; Pandemics; Pneumonia, Viral; SARS-CoV-2; Sphingomyelins; Tandem Mass Spectrometry; Young Adult
PubMed: 32610096
DOI: 10.1016/j.cmet.2020.06.016 -
Autophagy Oct 2022The endolysosomal system not only is an integral part of the cellular catabolic machinery that processes and recycles nutrients for synthesis of biomaterials, but also...
The endolysosomal system not only is an integral part of the cellular catabolic machinery that processes and recycles nutrients for synthesis of biomaterials, but also acts as signaling hub to sense and coordinate the energy state of cells with growth and differentiation. Lysosomal dysfunction adversely influences vesicular transport-dependent macromolecular degradation and thus causes serious problems for human health. In mammalian cells, loss of the lysosome associated membrane proteins LAMP1 and LAMP2 strongly affects autophagy and cholesterol trafficking. Here we show that the previously uncharacterized Lamp1 is a ortholog of vertebrate LAMP1 and LAMP2. Surprisingly and in contrast to double-mutant mice, Lamp1 is not required for viability or autophagy, suggesting that fly and vertebrate LAMP proteins acquired distinct functions, or that autophagy defects in mutants may have indirect causes. However, Lamp1 deficiency results in an increase in the number of acidic organelles in flies. Furthermore, we find that mutant larvae have defects in lipid metabolism as they show elevated levels of sterols and diacylglycerols (DAGs). Because DAGs are the main lipid species used for transport through the hemolymph (blood) in insects, our results indicate broader functions of Lamp1 in lipid transport. Our findings make an ideal model to study the role of LAMP proteins in lipid assimilation without the confounding effects of their storage and without interfering with autophagic processes.: aa: amino acid; AL: autolysosome; AP: autophagosome; APGL: autophagolysosome; AV: autophagic vacuole (i.e. AP and APGL/AL); AVi: early/initial autophagic vacuoles; AVd: late/degradative autophagic vacuoles; : autophagy-related; CMA: chaperone-mediated autophagy; Cnx99A: Calnexin 99A; DAG: diacylglycerol; eMI: endosomal microautophagy; ESCRT: endosomal sorting complexes required for transport; FB: fat body; HDL: high-density lipoprotein; Hrs: Hepatocyte growth factor regulated tyrosine kinase substrate; LAMP: lysosomal associated membrane protein; LD: lipid droplet; LDL: low-density lipoprotein; Lpp: lipophorin; LTP: Lipid transfer particle; LTR: LysoTracker Red; MA: macroautophagy; MCC: Manders colocalization coefficient; MEF: mouse embryonic fibroblast MTORC: mechanistic target of rapamycin kinase complex; PV: parasitophorous vacuole; SNARE: soluble N-ethylmaleimide sensitive factor attachment protein receptor; Snap: Synaptosomal-associated protein; st: starved; TAG: triacylglycerol; TEM: transmission electron microscopy; TFEB/Mitf: transcription factor EB; TM: transmembrane domain; tub: tubulin; UTR: untranslated region.
Topics: Amino Acids; Animals; Autophagy; Biocompatible Materials; Calnexin; Diglycerides; Drosophila; Drosophila Proteins; Endosomal Sorting Complexes Required for Transport; Ethylmaleimide; Fibroblasts; Hepatocyte Growth Factor; Humans; Lipoproteins, HDL; Lipoproteins, LDL; Lysosomal Membrane Proteins; Lysosomes; Mammals; Mice; Protein-Tyrosine Kinases; SNARE Proteins; Sirolimus; Sterols; Triglycerides; Tubulin; Untranslated Regions
PubMed: 35266854
DOI: 10.1080/15548627.2022.2038999 -
BMJ (Clinical Research Ed.) Sep 2023To assess the associations between exposure to food additive emulsifiers and risk of cardiovascular disease (CVD).
OBJECTIVE
To assess the associations between exposure to food additive emulsifiers and risk of cardiovascular disease (CVD).
DESIGN
Prospective cohort study.
SETTING
French NutriNet-Santé study, 2009-21.
PARTICIPANTS
95 442 adults (>18 years) without prevalent CVD who completed at least three 24 hour dietary records during the first two years of follow-up.
MAIN OUTCOME MEASURES
Associations between intake of food additive emulsifiers (continuous (mg/day)) and risk of CVD, coronary heart disease, and cerebrovascular disease characterised using multivariable proportional hazard Cox models to compute hazard ratios for each additional standard deviation (SD) of emulsifier intake, along with 95% confidence intervals.
RESULTS
Mean age was 43.1 (SD 14.5) years, and 79.0% (n=75 390) of participants were women. During follow-up (median 7.4 years), 1995 incident CVD, 1044 coronary heart disease, and 974 cerebrovascular disease events were diagnosed. Higher intake of celluloses (E460-E468) was found to be positively associated with higher risks of CVD (hazard ratio for an increase of 1 standard deviation 1.05, 95% confidence interval 1.02 to 1.09, P=0.003) and coronary heart disease (1.07, 1.02 to 1.12, P=0.004). Specifically, higher cellulose E460 intake was linked to higher risks of CVD (1.05, 1.01 to 1.09, P=0.007) and coronary heart disease (1.07, 1.02 to 1.12, P=0.005), and higher intake of carboxymethylcellulose (E466) was associated with higher risks of CVD (1.03, 1.01 to 1.05, P=0.004) and coronary heart disease (1.04, 1.02 to 1.06, P=0.001). Additionally, higher intakes of monoglycerides and diglycerides of fatty acids (E471 and E472) were associated with higher risks of all outcomes. Among these emulsifiers, lactic ester of monoglycerides and diglycerides of fatty acids (E472b) was associated with higher risks of CVD (1.06, 1.02 to 1.10, P=0.002) and cerebrovascular disease (1.11, 1.06 to 1.16, P<0.001), and citric acid ester of monoglycerides and diglycerides of fatty acids (E472c) was associated with higher risks of CVD (1.04, 1.02 to 1.07, P=0.004) and coronary heart disease (1.06, 1.03 to 1.09, P<0.001). High intake of trisodium phosphate (E339) was associated with an increased risk of coronary heart disease (1.06, 1.00 to 1.12, P=0.03). Sensitivity analyses showed consistent associations.
CONCLUSION
This study found positive associations between risk of CVD and intake of five individual and two groups of food additive emulsifiers widely used in industrial foods.
TRIAL REGISTRATION
ClinicalTrials.gov NCT03335644.
Topics: Adult; Humans; Female; Male; Cardiovascular Diseases; Food Additives; Diglycerides; Monoglycerides; Prospective Studies; Cellulose; Esters; Fatty Acids
PubMed: 37673430
DOI: 10.1136/bmj-2023-076058 -
Nature Jun 2022Branched fatty acid (FA) esters of hydroxy FAs (HFAs; FAHFAs) are recently discovered lipids that are conserved from yeast to mammals. A subfamily, palmitic acid esters...
Branched fatty acid (FA) esters of hydroxy FAs (HFAs; FAHFAs) are recently discovered lipids that are conserved from yeast to mammals. A subfamily, palmitic acid esters of hydroxy stearic acids (PAHSAs), are anti-inflammatory and anti-diabetic. Humans and mice with insulin resistance have lower PAHSA levels in subcutaneous adipose tissue and serum. PAHSA administration improves glucose tolerance and insulin sensitivity and reduces inflammation in obesity, diabetes and immune-mediated diseases. The enzyme(s) responsible for FAHFA biosynthesis in vivo remains unknown. Here we identified adipose triglyceride lipase (ATGL, also known as patatin-like phospholipase domain containing 2 (PNPLA2)) as a candidate biosynthetic enzyme for FAHFAs using chemical biology and proteomics. We discovered that recombinant ATGL uses a transacylation reaction that esterifies an HFA with a FA from triglyceride (TG) or diglyceride to produce FAHFAs. Overexpression of wild-type, but not catalytically dead, ATGL increases FAHFA biosynthesis. Chemical inhibition of ATGL or genetic deletion of Atgl inhibits FAHFA biosynthesis and reduces the levels of FAHFA and FAHFA-TG. Levels of endogenous and nascent FAHFAs and FAHFA-TGs are 80-90 per cent lower in adipose tissue of mice in which Atgl is knocked out specifically in the adipose tissue. Increasing TG levels by upregulating diacylglycerol acyltransferase (DGAT) activity promotes FAHFA biosynthesis, and decreasing DGAT activity inhibits it, reinforcing TGs as FAHFA precursors. ATGL biosynthetic transacylase activity is present in human adipose tissue underscoring its potential clinical relevance. In summary, we discovered the first, to our knowledge, biosynthetic enzyme that catalyses the formation of the FAHFA ester bond in mammals. Whereas ATGL lipase activity is well known, our data establish a paradigm shift demonstrating that ATGL transacylase activity is biologically important.
Topics: Acyltransferases; Adipose Tissue; Animals; Diglycerides; Esterification; Esters; Fatty Acids; Humans; Hydroxy Acids; Insulin Resistance; Mice; Triglycerides
PubMed: 35676490
DOI: 10.1038/s41586-022-04787-x -
Advances in Biological Regulation Jan 2017Lipids play a vital role in the health and functioning of neurons and interest in the physiological role of neuronal lipids is certainly increasing. One neuronal... (Review)
Review
Lipids play a vital role in the health and functioning of neurons and interest in the physiological role of neuronal lipids is certainly increasing. One neuronal function in which neuronal lipids appears to play key roles in neurotransmission. Our understanding of the role of lipids in the synaptic vesicle cycle and neurotransmitter release is becoming increasingly more important. Much of the initial research in this area has highlighted the major roles played by the phosphoinositides (PtdIns), diacylglycerol (DAG), and phosphatidic acid (PtdOH). Of these, PtdOH has not received as much attention as the other lipids although its role and metabolism appears to be extremely important. This lipid has been shown to play a role in modulating both exocytosis and endocytosis although its precise role in either process is not well defined. The currently evidence suggest this lipid likely participates in key processes by altering membrane architecture necessary for membrane fusion, mediating the penetration of membrane proteins, serving as a precursor for other important SV cycling lipids, or activating essential enzymes. In this review, we address the sources of PtdOH, the enzymes involved in its production, the regulation of these enzymes, and its potential roles in neurotransmission in the central nervous system.
Topics: Animals; Biological Transport; Cell Membrane; Central Nervous System; Diglycerides; Endocytosis; Exocytosis; Humans; Lipid Metabolism; Neurons; Phosphatidic Acids; Phosphatidylinositol 4,5-Diphosphate; Synaptic Transmission; Synaptic Vesicles
PubMed: 27671966
DOI: 10.1016/j.jbior.2016.09.004 -
International Journal of Molecular... Feb 2020Ca is a universal intracellular signal. The modulation of cytoplasmic Ca concentration regulates a plethora of cellular processes, such as: synaptic plasticity, neuronal... (Review)
Review
Ca is a universal intracellular signal. The modulation of cytoplasmic Ca concentration regulates a plethora of cellular processes, such as: synaptic plasticity, neuronal survival, chemotaxis of immune cells, platelet aggregation, vasodilation, and cardiac excitation-contraction coupling. Rap1 GTPases are ubiquitously expressed binary switches that alternate between active and inactive states and are regulated by diverse families of guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). Active Rap1 couples extracellular stimulation with intracellular signaling through secondary messengers-cyclic adenosine monophosphate (cAMP), Ca, and diacylglycerol (DAG). Much evidence indicates that Rap1 signaling intersects with Ca signaling pathways to control the important cellular functions of platelet activation or neuronal plasticity. Rap1 acts as an effector of Ca signaling when activated by mechanisms involving Ca and DAG-activated (CalDAG-) GEFs. Conversely, activated by other GEFs, such as cAMP-dependent GEF Epac, Rap1 controls cytoplasmic Ca levels. It does so by regulating the activity of Ca signaling proteins such as sarcoendoplasmic reticulum Ca-ATPase (SERCA). In this review, we focus on the physiological significance of the links between Rap1 and Ca signaling and emphasize the molecular interactions that may offer new targets for the therapy of Alzheimer's disease, hypertension, and atherosclerosis, among other diseases.
Topics: Animals; Ca(2+) Mg(2+)-ATPase; Calcium; Calcium Signaling; Cardiomegaly; Cyclic AMP; Diglycerides; Endothelium; Humans; Integrins; Muscle, Smooth, Vascular; Neurodegenerative Diseases; Toll-Like Receptors; Vasodilation; rap1 GTP-Binding Proteins
PubMed: 32120817
DOI: 10.3390/ijms21051616 -
Biochimica Et Biophysica Acta Aug 2016Glycerophospholipids are the principal fabric of cellular membranes. The pathways by which these lipids are synthesized were elucidated mainly through the work of... (Review)
Review
Glycerophospholipids are the principal fabric of cellular membranes. The pathways by which these lipids are synthesized were elucidated mainly through the work of Kennedy and colleagues in the late 1950s and early 1960s. Subsequently, attention turned to cell biological aspects of lipids: Where in the cell are lipids synthesized? How are lipids integrated into membranes to form a bilayer? How are they sorted and transported from their site of synthesis to other cellular destinations? These topics, collectively termed 'lipid topogenesis', were the subject of a review article in 1981 by Bell, Ballas and Coleman. We now assess what has been learned about early events of lipid topogenesis, i.e. "lipid synthesis, the integration of lipids into membranes, and lipid translocation across membranes", in the 35 years since the publication of this important review. We highlight the recent elucidation of the X-ray structures of key membrane enzymes of glycerophospholipid synthesis, progress on identifying lipid scramblase proteins needed to equilibrate lipids across membranes, and new complexities in the subcellular location and membrane topology of phosphatidylinositol synthesis revealed through a comparison of two unicellular model eukaryotes. This article is part of a Special Issue entitled: The cellular lipid landscape edited by Tim P. Levine and Anant K. Menon.
Topics: Animals; CDP-Diacylglycerol-Inositol 3-Phosphatidyltransferase; Cell Membrane; Cytidine Diphosphate Diglycerides; Glycerophospholipids; Humans; Lipid Bilayers; Metabolic Networks and Pathways; Mitochondria
PubMed: 26946259
DOI: 10.1016/j.bbalip.2016.02.025 -
International Journal of Molecular... Jul 2022In recent years, the significant research efforts put into the clarification of the PI3K/AKT/mTOR pathway resulted in the approval of the first targeted therapies based...
In recent years, the significant research efforts put into the clarification of the PI3K/AKT/mTOR pathway resulted in the approval of the first targeted therapies based on lipid kinase inhibitors [...].
Topics: Diacylglycerol Kinase; Diglycerides; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Signal Transduction
PubMed: 35955558
DOI: 10.3390/ijms23158423