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Macrophage reprogramming by negatively charged membrane phospholipids controls infection.

ABSTRACT: Extracellular vesicles (ECVs) are heterogeneous membrane-enclosed structures containing proteins, nucleic acids, and lipids that participate in intercellular communication by transferring their contents to recipient cells. Although most of the attention has been directed at the biologic effect of proteins and microRNA, the contribution of phospholipids present in ECVs on cellular activation has not been extensively addressed. We investigated the biologic effect of phosphatidylserine (PS) and phosphatidylcholine (PC), 2 phospholipids highly abundant in ECVs. A transcriptomic analysis revealed that ∼4700 genes were specifically modified by exposing peritoneal macrophages to PS or PC liposomes in vivo. Among them, the expression of several chemokines and cytokines was highly upregulated by PS liposome treatment, translating into a massive neutrophil infiltration of the peritoneum capable of neutralizing a septic polymicrobial insult. Both the l and d stereoisomers of PS induced the same response, suggesting that the effect was related to the negative charge of the phospholipid head. We concluded that an increase in the internal negative charge of the cell triggers a signaling cascade activating an innate immune response capable of controlling infection.-Cauvi, D. M., Hawisher, D., Dores-Silva, P. R., Lizardo, R. E., De Maio, A. Macrophage reprogramming by negatively charged membrane phospholipids controls infection.

SUBMITTER: Cauvi DM

PROVIDER: S-EPMC6338646 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Macrophage reprogramming by negatively-charged membrane phospholipids controls infection

Project description:Extracellular vesicles (ECV) are heterogeneous membrane-enclosed structures containing proteins, nucleic acids and lipids that participate in intercellular communication by transferring their content to recipient cells. Although most of the attention has been directed at the biological effect of proteins and microRNA, the contribution of phospholipids present in ECV on cellular activation has not been extensively addressed. Here we investigated the biological effect of phosphatidylserine (PS) and phosphatidylcholine (PC), two phospholipids highly abundant in ECV. A transcriptomic analysis revealed that about 4,700 genes were specifically modified by exposing peritoneal macrophages to PS or PC liposomes in vivo. Among them, the expression of several chemokines and cytokines was highly upregulated by PS liposome treatment, translating into a massive neutrophil infiltration into the peritoneum capable of neutralizing a septic polymicrobial insult. Both the L and D stereoisomers of PS induced the same response, suggesting that the effect was related to the negative charge of the phospholipid head. We concluded that an increase in the internal negative charge of the cell triggers a signaling cascade activating an innate immune response capable of controlling infection.

2018-11-02 | GSE115489 | GEO

Macrophage reprogramming by negatively-charged membrane phospholipids controls infection

Project description:Macrophage reprogramming by negatively-charged membrane phospholipids controls infection

| PRJNA475156 | ENA

Segregation of negatively charged phospholipids by the polycationic and farnesylated membrane anchor of Kras.

Project description:The Kras protein, a member of the Ras family of bio-switches that are frequently mutated in cancer and developmental disorders, becomes functional when anchored to the inner surface of the plasma membrane. It is well known that membrane attachment involves the farnesylated and poylcationic C-terminus of the protein. However, little is known about the structure of the complex and the specific protein-lipid interactions that are responsible for the binding. On the basis of data from extensive (>0.55 ?s) molecular dynamics simulations of multiple Kras anchors in bilayers of POPC/POPG lipids (4:1 ratio), we show that, as expected, Kras is tethered to the bilayer surface by specific lysine-POPG salt bridges and by nonspecific farnesyl-phospholipid van der Waals interactions. Unexpectedly, however, only the C-terminal five of the eight Kras Lys side chains were found to directly interact with the bilayer, with the N-terminal ones staying in water. Furthermore, the positively charged Kras anchors pull the negatively charged POPG lipids together, leading to the clustering of the POPG lipids around the proteins. This selective Kras-POPG interaction is directly related to the specific geometry of the backbone, which exists in two major conformational states: 1), a stable native-like ensemble of structures characterized by an extended geometry with a pseudohelical turn; and 2), less stable nonnative ensembles of conformers characterized by severely bent geometries. Finally, although the interface-bound anchor has little effect on the overall structure of the bilayer, it induces local thinning within a persistence length of ?12 Å. Our results thus go beyond documenting how Kras attaches to a mixed bilayer of charged and neutral lipids; they highlight a fascinating process of protein-induced lipid sorting coupled with the (re)shaping of a surface-bound protein by the host lipids.

| S-EPMC2998625 | biostudies-literature

A modified clot-based assay to measure negatively charged procoagulant phospholipids.

Project description:Growing evidence supports a role for extracellular vesicles (EVs) in haemostasis and thrombosis due to exposure of negatively charged procoagulant phospholipids (PPL). Current commercial PPL-dependent clotting assays use chemically phospholipid depleted plasma to measure PPL activity. The purpose of our study was to modify the PPL assay by substituting the chemically phospholipid depleted plasma with PPL depleted plasma obtained by ultracentrifugation This in order to get readily access to a sensitive and reliable assay to measure PPL activity in human plasma and cell supernatants. The performance of the assay was tested, including the influence of individual coagulation factors and postprandial lipoproteins and compared to a commercial PPL assay (STA-Procoag-PPL). The two PPL assays displayed similar sensitivity to exogenously added standardized phospholipids. The PPL activity measured by the modified assay strongly correlates with the results from the commercial assay. The intraday- and between-days coefficients of variation ranged from 2-4% depending on the PPL activity in the sample. The modified PPL assay was insensitive to postprandial lipoprotein levels in plasma, as well as to tissue factor (TF) positive EVs from stimulated whole blood. Our findings showed that the modified assay performed equal to the comparator, and was insensitive to postprandial lipoproteins and TF+ EVs.

| S-EPMC8085201 | biostudies-literature

Negatively charged phospholipids accelerate the membrane fusion activity of the plant-specific insert domain of an aspartic protease.

Project description:Various plants use antimicrobial proteins/peptides to resist phytopathogens. In the potato, Solanum tuberosum, the plant-specific insert (PSI) domain of an aspartic protease performs this role by disrupting phytopathogen plasma membranes. However, the mechanism by which PSI selects target membranes has not been elucidated. Here, we studied PSI-induced membrane fusion, focusing on the effects of lipid composition on fusion efficiency. Membrane fusion by the PSI involves an intermediate state whereby adjacent liposomes share their bilayers. We found that increasing the concentration of negatively charged phosphatidylserine (PS) phospholipids substantially accelerated PSI-mediated membrane fusion. NMR data demonstrated that PS did not affect the binding between the PSI and liposomes but had seminal effects on the dynamics of PSI interaction with liposomes. In PS-free liposomes, the PSI underwent significant motion, which was suppressed on PS-contained liposomes. Molecular dynamics simulations showed that the PSI binds to PS-containing membranes with a dominant angle ranging from -31° to 30°, with respect to the bilayer, and is closer to the membrane surfaces. In contrast, PSI is mobile and exhibits multiple topological states on the surface of PS-free membranes. Taken together, our data suggested that PS lipids limit the motion of the anchored PSI, bringing it closer to the membrane surface and efficiently bridging different liposomes to accelerate fusion. As most phytopathogens have a higher content of negatively charged lipids as compared with host cells, these results indicate that the PSI selectively targets negatively charged lipids, which likely represents a way of distinguishing the pathogen from the host.

| S-EPMC8683733 | biostudies-literature

Modulation of toxin stability by 4-phenylbutyric acid and negatively charged phospholipids.

Project description:AB toxins such as ricin and cholera toxin (CT) consist of an enzymatic A domain and a receptor-binding B domain. After endocytosis of the surface-bound toxin, both ricin and CT are transported by vesicle carriers to the endoplasmic reticulum (ER). The A subunit then dissociates from its holotoxin, unfolds, and crosses the ER membrane to reach its cytosolic target. Since protein unfolding at physiological temperature and neutral pH allows the dissociated A chain to attain a translocation-competent state for export to the cytosol, the underlying regulatory mechanisms of toxin unfolding are of paramount biological interest. Here we report a biophysical analysis of the effects of anionic phospholipid membranes and two chemical chaperones, 4-phenylbutyric acid (PBA) and glycerol, on the thermal stabilities and the toxic potencies of ricin toxin A chain (RTA) and CT A1 chain (CTA1). Phospholipid vesicles that mimic the ER membrane dramatically decreased the thermal stability of RTA but not CTA1. PBA and glycerol both inhibited the thermal disordering of RTA, but only glycerol could reverse the destabilizing effect of anionic phospholipids. In contrast, PBA was able to increase the thermal stability of CTA1 in the presence of anionic phospholipids. PBA inhibits cellular intoxication by CT but not ricin, which is explained by its ability to stabilize CTA1 and its inability to reverse the destabilizing effect of membranes on RTA. Our data highlight the toxin-specific intracellular events underlying ER-to-cytosol translocation of the toxin A chain and identify a potential means to supplement the long-term stabilization of toxin vaccines.

| S-EPMC3161752 | biostudies-literature

Regulation of DGK? Activity and Substrate Acyl Chain Specificity by Negatively Charged Phospholipids.

Project description:Diacylglycerol kinase ? (DGK?) is a membrane-bound enzyme that catalyzes the ATP-dependent phosphorylation of diacylglycerol to form phosphatidic acid (PA) in the phosphatidylinositol cycle. DGK? lacks a putative regulatory domain and has recently been reported to be regulated by highly curved membranes. To further study the effect of other membrane properties as a regulatory mechanism of DGK?, our work reports the effect of negatively charged phospholipids on DGK? activity and substrate acyl chain specificity. These studies were conducted using purified DGK? and detergent-free phospholipid aggregates, which present a more suitable model system to access the impact of membrane physical properties on membrane-active enzymes. The structural properties of the different model membranes were studied by means of differential scanning calorimetry and 31P-NMR. It is shown that the enzyme is inhibited by a variety of negatively charged phospholipids. However, PA, which is a negatively charged phospholipid and the product of DGK? catalyzed reaction, showed a varied regulatory effect on the enzyme from being an activator to an inhibitor. The type of feedback regulation of DGK? by PA depends on the particular PA molecular species as well as the physical properties of the membrane that the enzyme binds to. In the presence of highly packed PA-rich domains, the enzyme is activated. However, its acyl chain specificity is only observed in liposomes containing 1,2-dioleoyl PA in the presence of Ca2+. It is proposed that to endow the enzyme with its substrate acyl chain specificity, a highly dehydrated (hydrophobic) membrane interface is needed. The presence of an overlap of mechanisms to regulate DGK? ensures proper phosphatidylinositol cycle function regardless of the trigged stimulus and represents a sophisticated and specialized manner of membrane-enzyme regulation.

| S-EPMC7036746 | biostudies-literature

SARS-CoV-2 Protein S Fusion Peptide Is Capable of Wrapping Negatively-Charged Phospholipids.

Project description:COVID-19, caused by SARS-CoV-2, which is a positive-sense, single-stranded RNA enveloped virus, emerged in late 2019 and was declared a worldwide pandemic in early 2020 causing more than 600 million infections so far and more than 6 million deaths in the world. Although new vaccines have been implemented, the pandemic continues to impact world health dramatically. Membrane fusion, critical for the viral entry into the host cell, is one of the main targets for the development of novel antiviral therapies to combat COVID-19. The S2 subunit of the viral S protein, a class I membrane fusion protein, contains the fusion domain which is directly implicated in the fusion mechanism. The knowledge of the membrane fusion mechanism at the molecular level will undoubtedly result in the development of effective antiviral strategies. We have used all-atom molecular dynamics to analyse the binding of the SARS-CoV-2 fusion peptide to specific phospholipids in model membranes composed of only one phospholipid plus cholesterol in the presence of either Na+ or Ca2+. Our results show that the fusion peptide is capable of binding to the membrane, that its secondary structure does not change significantly upon binding, that it tends to preferentially bind electronegatively charged phospholipids, and that it does not bind cholesterol at all. Understanding the intricacies of the membrane fusion mechanism and the molecular interactions involved will lead us to the development of antiviral molecules that will allow a more efficient battle against these viruses.

| S-EPMC10057416 | biostudies-literature

Role of arginine residues in the stimulation of the smooth-muscle plasma-membrane Ca2+ pump by negatively charged phospholipids.

Project description:Negatively charged phospholipids strongly stimulate the purified plasma membrane Ca2+ pump of erythrocytes [Enyedi, Flura, Sarkadi, Gardos & Carafoli (1987) J. Biol. Chem. 262, 6425-6430] and of smooth muscle [Missiaen, Raeymaekers, Wuytack, Vrolix, De Smedt & Casteels, (1989) Biochem. J. 263, 687-694]. We have investigated the role of arginine residues in the interaction of these acidic phospholipids with the smooth-muscle Ca2+ transport ATPase. The arginine-modifying reagent phenylglyoxal inhiibited the ATPase activity in a time-dependent fashion by decreasing the Vmax. of the Ca2(+)-activation curve. Low concentrations of PtdIns, PtdIns4P, PtdIns(4,5) P2, phosphatidylserine and phosphatidic acid partially prevented this inactivation. This protective effect was however not apparent at higher concentrations of PtdIns4P, PtdIns(4,5) P2 and phosphatidic acid, which may be related to the previously observed inhibition of the enzyme at higher concentrations of these phospholipids. These findings indicate that the functionally important interaction of the acidic lipids with the protein occurs at least partially via arginine residue(s).

| S-EPMC1133623 | biostudies-other

Performance Evaluation and Clinical Associations of Immunoassays That Detect Antibodies to Negatively Charged Phospholipids Other Than Cardiolipin.

Project description:Objectives:We evaluate the performance characteristics of antiphosphatidylserine (anti-PS), antiphosphatidylinositol (anti-PI), and antiphospholipid mixture (APhL) enzyme-linked immunosorbent assays (ELISAs) compared with anticardiolipin (aCL) and anti-?2 glycoprotein I (anti-?2GPI) in a large group of patients with antiphospholipid (aPL)-related diseases. Methods:Serum samples from 548 patients from the Hopkins and Jamaican systemic lupus erythematosus cohorts, the PROMISSE cohort, and the Antiphospholipid Standardization Laboratory were examined for immunoglobulin G (IgG)/immunoglobulin M (IgM) positivity in aCL, anti-?2GPI, anti-PS, anti-PI, and APhL ELISA assays. Results:All IgG assays were associated with one or more thrombotic and/or obstetric manifestations, with an increased risk associated with higher antibody titers. Analytical performance was similar among assays, but IgG assays performed better than IgM counterparts. Conclusions:Increasing titers of APhL, anti-PS, and anti-PI antibodies could indicate an increased risk of thrombotic and/or obstetric aPL-related manifestations. These assays may be promising biomarkers for particular APS manifestations.

| S-EPMC5889035 | biostudies-literature

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