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Nature Aug 2022Multiple studies have established associations between human gut bacteria and host physiology, but determining the molecular mechanisms underlying these associations has...
Multiple studies have established associations between human gut bacteria and host physiology, but determining the molecular mechanisms underlying these associations has been challenging. Akkermansia muciniphila has been robustly associated with positive systemic effects on host metabolism, favourable outcomes to checkpoint blockade in cancer immunotherapy and homeostatic immunity. Here we report the identification of a lipid from A. muciniphila's cell membrane that recapitulates the immunomodulatory activity of A. muciniphila in cell-based assays. The isolated immunogen, a diacyl phosphatidylethanolamine with two branched chains (a15:0-i15:0 PE), was characterized through both spectroscopic analysis and chemical synthesis. The immunogenic activity of a15:0-i15:0 PE has a highly restricted structure-activity relationship, and its immune signalling requires an unexpected toll-like receptor TLR2-TLR1 heterodimer. Certain features of the phospholipid's activity are worth noting: it is significantly less potent than known natural and synthetic TLR2 agonists; it preferentially induces some inflammatory cytokines but not others; and, at low doses (1% of EC) it resets activation thresholds and responses for immune signalling. Identifying both the molecule and an equipotent synthetic analogue, its non-canonical TLR2-TLR1 signalling pathway, its immunomodulatory selectivity and its low-dose immunoregulatory effects provide a molecular mechanism for a model of A. muciniphila's ability to set immunological tone and its varied roles in health and disease.
Topics: Akkermansia; Cell Membrane; Cytokines; Homeostasis; Humans; Immunity; Inflammation Mediators; Phosphatidylethanolamines; Structure-Activity Relationship; Toll-Like Receptor 1; Toll-Like Receptor 2
PubMed: 35896748
DOI: 10.1038/s41586-022-04985-7 -
Molecular Cell Oct 2022The covalent conjugation of ubiquitin family proteins is a widespread post-translational protein modification. In the ubiquitin family, the ATG8 subfamily is exceptional...
The covalent conjugation of ubiquitin family proteins is a widespread post-translational protein modification. In the ubiquitin family, the ATG8 subfamily is exceptional because it is conjugated mainly to phospholipids. However, it remains unknown whether other ubiquitin family proteins are also conjugated to phospholipids. Here, we report that ubiquitin is conjugated to phospholipids, mainly phosphatidylethanolamine (PE), in yeast and mammalian cells. Ubiquitinated PE (Ub-PE) accumulates at endosomes and the vacuole (or lysosomes), and its level increases during starvation. Ub-PE is also found in baculoviruses. In yeast, PE ubiquitination is catalyzed by the canonical ubiquitin system enzymes Uba1 (E1), Ubc4/5 (E2), and Tul1 (E3) and is reversed by Doa4. Liposomes containing Ub-PE recruit the ESCRT components Vps27-Hse1 and Vps23 in vitro. Ubiquitin-like NEDD8 and ISG15 are also conjugated to phospholipids. These findings suggest that the conjugation to membrane phospholipids is not specific to ATG8 but is a general feature of the ubiquitin family.
Topics: Animals; Endosomal Sorting Complexes Required for Transport; Liposomes; Mammals; Phosphatidylethanolamines; Phospholipids; Receptors, Cytoplasmic and Nuclear; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Ubiquitin; Ubiquitin-Conjugating Enzymes; Ubiquitination
PubMed: 36044902
DOI: 10.1016/j.molcel.2022.08.008 -
Nature Jul 2021T follicular helper (T) cells are crucial for B cell-mediated humoral immunity. Although transcription factors such as BCL6 drive the differentiation of T cells, it is...
T follicular helper (T) cells are crucial for B cell-mediated humoral immunity. Although transcription factors such as BCL6 drive the differentiation of T cells, it is unclear whether and how post-transcriptional and metabolic programs enforce T cell programming. Here we show that the cytidine diphosphate (CDP)-ethanolamine pathway co-ordinates the expression and localization of CXCR5 with the responses of T cells and humoral immunity. Using in vivo CRISPR-Cas9 screening and functional validation in mice, we identify ETNK1, PCYT2, and SELENOI-enzymes in the CDP-ethanolamine pathway for de novo synthesis of phosphatidylethanolamine (PE)-as selective post-transcriptional regulators of T cell differentiation that act by promoting the surface expression and functional effects of CXCR5. T cells exhibit unique lipid metabolic programs and PE is distributed to the outer layer of the plasma membrane, where it colocalizes with CXCR5. De novo synthesis of PE through the CDP-ethanolamine pathway co-ordinates these events to prevent the internalization and degradation of CXCR5. Genetic deletion of Pcyt2, but not of Pcyt1a (which mediates the CDP-choline pathway), in activated T cells impairs the differentiation of T cells, and this is associated with reduced humoral immune responses. Surface levels of PE and CXCR5 expression on B cells also depend on Pcyt2. Our results reveal that phospholipid metabolism orchestrates post-transcriptional mechanisms for T cell differentiation and humoral immunity, highlighting the metabolic control of context-dependent immune signalling and effector programs.
Topics: Animals; B-Lymphocytes; CRISPR-Cas Systems; Cell Differentiation; Cytidine Diphosphate; Female; Gene Expression Regulation; Humans; Immunity, Humoral; Leukocytes, Mononuclear; Lymphocyte Activation; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Phosphatidylethanolamines; Phosphotransferases (Alcohol Group Acceptor); RNA Nucleotidyltransferases; Receptors, CXCR5; Signal Transduction; T-Lymphocytes, Helper-Inducer
PubMed: 34234346
DOI: 10.1038/s41586-021-03692-z -
Cell Metabolism Mar 2024Diacylglycerol acyltransferase 2 (DGAT2) catalyzes the final step of triglyceride (TG) synthesis. DGAT2 deletion in mice lowers liver TGs, and DGAT2 inhibitors are under...
Diacylglycerol acyltransferase 2 (DGAT2) catalyzes the final step of triglyceride (TG) synthesis. DGAT2 deletion in mice lowers liver TGs, and DGAT2 inhibitors are under investigation for the treatment of fatty liver disease. Here, we show that DGAT2 inhibition also suppressed SREBP-1 cleavage, reduced fatty acid synthesis, and lowered TG accumulation and secretion from liver. DGAT2 inhibition increased phosphatidylethanolamine (PE) levels in the endoplasmic reticulum (ER) and inhibited SREBP-1 cleavage, while DGAT2 overexpression lowered ER PE concentrations and increased SREBP-1 cleavage in vivo. ER enrichment with PE blocked SREBP-1 cleavage independent of Insigs, which are ER proteins that normally retain SREBPs in the ER. Thus, inhibition of DGAT2 shunted diacylglycerol into phospholipid synthesis, increasing the PE content of the ER, resulting in reduced SREBP-1 cleavage and less hepatic steatosis. This study reveals a new mechanism that regulates SREBP-1 activation and lipogenesis that is independent of sterols and SREBP-2 in liver.
Topics: Animals; Mice; Diacylglycerol O-Acyltransferase; Endoplasmic Reticulum; Liver; Non-alcoholic Fatty Liver Disease; Phosphatidylethanolamines; Sterol Regulatory Element Binding Protein 1; Triglycerides
PubMed: 38340721
DOI: 10.1016/j.cmet.2024.01.011 -
Science Advances Feb 2023Thermogenesis by uncoupling protein 1 (UCP1) is one of the primary mechanisms by which brown adipose tissue (BAT) increases energy expenditure. UCP1 resides in the inner...
Thermogenesis by uncoupling protein 1 (UCP1) is one of the primary mechanisms by which brown adipose tissue (BAT) increases energy expenditure. UCP1 resides in the inner mitochondrial membrane (IMM), where it dissipates membrane potential independent of adenosine triphosphate (ATP) synthase. Here, we provide evidence that phosphatidylethanolamine (PE) modulates UCP1-dependent proton conductance across the IMM to modulate thermogenesis. Mitochondrial lipidomic analyses revealed PE as a signature molecule whose abundance bidirectionally responds to changes in thermogenic burden. Reduction in mitochondrial PE by deletion of phosphatidylserine decarboxylase (PSD) made mice cold intolerant and insensitive to β3 adrenergic receptor agonist-induced increase in whole-body oxygen consumption. High-resolution respirometry and fluorometry of BAT mitochondria showed that loss of mitochondrial PE specifically lowers UCP1-dependent respiration without compromising electron transfer efficiency or ATP synthesis. These findings were confirmed by a reduction in UCP1 proton current in PE-deficient mitoplasts. Thus, PE performs a previously unknown role as a temperature-responsive rheostat that regulates UCP1-dependent thermogenesis.
Topics: Mice; Animals; Uncoupling Protein 1; Phosphatidylethanolamines; Protons; Mitochondria; Thermogenesis; Obesity; Adenosine Triphosphate; Mice, Knockout
PubMed: 36827367
DOI: 10.1126/sciadv.ade7864 -
The Journal of Biological Chemistry Mar 2020An early exposure to lipid biochemistry in the laboratory of Konrad Bloch resulted in a fascination with the biosynthesis, structures, and functions of bacterial lipids....
An early exposure to lipid biochemistry in the laboratory of Konrad Bloch resulted in a fascination with the biosynthesis, structures, and functions of bacterial lipids. The discovery of plasmalogens (1-alk-1'-enyl, 2-acyl phospholipids) in anaerobic Gram-positive bacteria led to studies on the physical chemistry of these lipids and the cellular regulation of membrane lipid polymorphism in bacteria. Later studies in several laboratories showed that the formation of the alk-1-enyl ether bond involves an aerobic process in animal cells and thus is fundamentally different from that in anaerobic organisms. Our work provides evidence for an anaerobic process in which plasmalogens are formed from their corresponding diacyl lipids. Studies on the roles of phospholipases in revealed distinctions between its phospholipases and those previously discovered in other bacteria and showed how the enzymes are uniquely fitted to the intracellular lifestyle of this significant human pathogen.
Topics: Anaerobiosis; Bacteria, Anaerobic; Fatty Acids; Gram-Positive Bacteria; Lipids; Phosphatidylethanolamines; Plasmalogens
PubMed: 32221031
DOI: 10.1074/jbc.X120.013022 -
Molecular Pharmaceutics Jan 2023Phospholipids are lipids that constitute the basic structure of cell membranes. In-depth research has shown that in addition to supporting cell structures, phospholipids... (Review)
Review
Phospholipids are lipids that constitute the basic structure of cell membranes. In-depth research has shown that in addition to supporting cell structures, phospholipids participate in multiple cellular processes, including promoting cell signal transduction, guiding protein translocation, activating enzymatic activity, and eliminating dysfunctional/redundant organelles/cells. Diabetes is a chronic metabolic disease with a complicated etiology and pathology. Studies have shown that the level of certain phospholipids, for example, the ratio of phosphatidylcholine (PC) to phosphatidylethanolamine (PE) in liver tissue, is negatively associated with insulin sensitivity. In addition, PS is a phospholipid exhibiting extensive cellular functions in diabetes. For this review, we analyzed many PS studies focusing on diabetes and insulin sensitivity in recent years and found that PS participates in controlling insulin secretion, regulating insulin signaling transduction, and participating in the progression of diabetic complications by mediating coagulation disorders in the microvasculature or targeting mitochondria. Moreover, PS supplements in food and PS-containing liposomes have been shown to protect against type 1 and type 2 diabetes (T1D and T2D, respectively) in animal studies. Therefore, by summarizing the regulatory roles played by PS in diabetes and the potential of successfully using PS or PS-containing liposomes for diabetic therapy, we hope to provide new ideas for further research into the mechanisms of diabetes and for drug development for treating diabetes and its complications.
Topics: Animals; Liposomes; Phosphatidylserines; Diabetes Mellitus, Type 2; Insulin Resistance; Phospholipids; Phosphatidylethanolamines
PubMed: 36480277
DOI: 10.1021/acs.molpharmaceut.2c00707 -
Proceedings of the National Academy of... Nov 2020The recently identified ferroptotic cell death is characterized by excessive accumulation of hydroperoxy-arachidonoyl (C20:4)- or adrenoyl (C22:4)-...
The recently identified ferroptotic cell death is characterized by excessive accumulation of hydroperoxy-arachidonoyl (C20:4)- or adrenoyl (C22:4)- phosphatidylethanolamine (Hp-PE). The selenium-dependent glutathione peroxidase 4 (GPX4) inhibits ferroptosis, converting unstable ferroptotic lipid hydroperoxides to nontoxic lipid alcohols in a tissue-specific manner. While placental oxidative stress and lipotoxicity are hallmarks of placental dysfunction, the possible role of ferroptosis in placental dysfunction is largely unknown. We found that spontaneous preterm birth is associated with ferroptosis and that inhibition of GPX4 causes ferroptotic injury in primary human trophoblasts and during mouse pregnancy. Importantly, we uncovered a role for the phospholipase PLA2G6 (PNPLA9, iPLA2beta), known to metabolize Hp-PE to lyso-PE and oxidized fatty acid, in mitigating ferroptosis induced by GPX4 inhibition in vitro or by hypoxia/reoxygenation injury in vivo. Together, we identified ferroptosis signaling in the human and mouse placenta, established a role for PLA2G6 in attenuating trophoblastic ferroptosis, and provided mechanistic insights into the ill-defined placental lipotoxicity that may inspire PLA2G6-targeted therapeutic strategies.
Topics: Animals; Female; Ferroptosis; Glutathione Peroxidase; Group VI Phospholipases A2; Humans; Iron; Lipid Peroxides; Mice; Mice, Knockout; Phosphatidylethanolamines; Phospholipid Hydroperoxide Glutathione Peroxidase; Placenta; Pregnancy; Premature Birth; Signal Transduction; Trophoblasts
PubMed: 33087576
DOI: 10.1073/pnas.2009201117 -
Proceedings of the National Academy of... Oct 2022The lysosome is central to the degradation of proteins, carbohydrates, and lipids and their salvage back to the cytosol for reutilization. Lysosomal transporters for...
The lysosome is central to the degradation of proteins, carbohydrates, and lipids and their salvage back to the cytosol for reutilization. Lysosomal transporters for amino acids, sugars, and cholesterol have been identified, and the metabolic fates of these molecules in the cytoplasm have been elucidated. Remarkably, it is not known whether lysosomal salvage exists for glycerophospholipids, the major constituents of cellular membranes. By using a transport assay screen against orphan lysosomal transporters, we identified the major facilitator superfamily protein Spns1 that is ubiquitously expressed in all tissues as a proton-dependent lysophosphatidylcholine (LPC) and lysophosphatidylethanolamine (LPE) transporter, with LPC and LPE being the lysosomal breakdown products of the most abundant eukaryotic phospholipids, phosphatidylcholine and phosphatidylethanolamine, respectively. Spns1 deficiency in cells, zebrafish embryos, and mouse liver resulted in lysosomal accumulation of LPC and LPE species with pathological consequences on lysosomal function. Flux analysis using stable isotope-labeled phospholipid apolipoprotein E nanodiscs targeted to lysosomes showed that LPC was transported out of lysosomes in an Spns1-dependent manner and re-esterified back into the cytoplasmic pools of phosphatidylcholine. Our findings identify a phospholipid salvage pathway from lysosomes to the cytosol that is dependent on Spns1 and critical for maintaining normal lysosomal function.
Topics: Animals; Lysophosphatidylcholines; Lysophospholipids; Lysosomes; Membrane Proteins; Membrane Transport Proteins; Mice; Phosphatidylcholines; Phosphatidylethanolamines; Protons; Zebrafish; Zebrafish Proteins
PubMed: 36161949
DOI: 10.1073/pnas.2210353119 -
The Journal of Cell Biology Aug 2020Mitochondria, so much more than just being energy factories, also have the capacity to synthesize macromolecules including phospholipids, particularly cardiolipin (CL)... (Review)
Review
Mitochondria, so much more than just being energy factories, also have the capacity to synthesize macromolecules including phospholipids, particularly cardiolipin (CL) and phosphatidylethanolamine (PE). Phospholipids are vital constituents of mitochondrial membranes, impacting the plethora of functions performed by this organelle. Hence, the orchestrated movement of phospholipids to and from the mitochondrion is essential for cellular integrity. In this review, we capture recent advances in the field of mitochondrial phospholipid biosynthesis and trafficking, highlighting the significance of interorganellar communication, intramitochondrial contact sites, and lipid transfer proteins in maintaining membrane homeostasis. We then discuss the physiological functions of CL and PE, specifically how they associate with protein complexes in mitochondrial membranes to support bioenergetics and maintain mitochondrial architecture.
Topics: Animals; Biological Transport; Cardiolipins; Energy Metabolism; Humans; Mitochondria; Mitochondrial Membranes; Mitochondrial Proteins; Phosphatidylethanolamines; Phospholipids; Signal Transduction
PubMed: 32614384
DOI: 10.1083/jcb.202003131