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1.
Int J Mol Sci ; 22(16)2021 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-34445139

RESUMO

Recent evidence pinpoints extracellular vesicles (EVs) as key players in intercellular communication. Given the importance of cholesterol and sphingomyelin in EV biology, and the relevance of mitochondria-associated endoplasmic reticulum membranes (MAMs) in cholesterol/sphingomyelin homeostasis, we evaluated if MAMs and sphingomyelinases (SMases) could participate in ethanol-induced EV release. EVs were isolated from the extracellular medium of BV2 microglia treated or not with ethanol (50 and 100 mM). Radioactive metabolic tracers combined with thin layer chromatography were used as quantitative methods to assay phospholipid transfer, SMase activity and cholesterol uptake/esterification. Inhibitors of SMase (desipramine and GW4869) and MAM (cyclosporin A) activities were also utilized. Our data show that ethanol increases the secretion and inflammatory molecule concentration of EVs. Ethanol also upregulates MAM activity and alters lipid metabolism by increasing cholesterol uptake, cholesterol esterification and SMase activity in microglia. Notably, the inhibition of either SMase or MAM activity prevented the ethanol-induced increase in EV secretion. Collectively, these results strongly support a lipid-driven mechanism, specifically via SMases and MAM, to explain the effect of ethanol on EV secretion in glial cells.


Assuntos
Retículo Endoplasmático/efeitos dos fármacos , Etanol/farmacologia , Vesículas Extracelulares/efeitos dos fármacos , Metabolismo dos Lipídeos/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Membranas Mitocondriais/efeitos dos fármacos , Esfingomielina Fosfodiesterase/metabolismo , Compostos de Anilina/farmacologia , Animais , Compostos de Benzilideno/farmacologia , Células Cultivadas , Colesterol/metabolismo , Ciclosporina/farmacologia , Retículo Endoplasmático/metabolismo , Vesículas Extracelulares/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microglia/efeitos dos fármacos , Microglia/metabolismo , Mitocôndrias/metabolismo , Membranas Mitocondriais/metabolismo , Fosfolipídeos/metabolismo
2.
Nat Commun ; 12(1): 4990, 2021 08 17.
Artigo em Inglês | MEDLINE | ID: mdl-34404808

RESUMO

Cells can expand their plasma membrane laterally by unfolding membrane undulations and by exocytosis. Here, we describe a third mechanism involving invaginations held shut by the membrane adapter, dynamin. Compartments open when Ca activates the lipid scramblase, TMEM16F, anionic phospholipids escape from the cytoplasmic monolayer in exchange for neutral lipids, and dynamins relax. Deletion of TMEM16F or dynamins blocks expansion, with loss of dynamin expression generating a maximally expanded basal plasma membrane state. Re-expression of dynamin2 or its GTPase-inactivated mutant, but not a lipid binding mutant, regenerates reserve compartments and rescues expansion. Dynamin2-GFP fusion proteins form punctae that rapidly dissipate from these compartments during TMEM16F activation. Newly exposed compartments extend deeply into the cytoplasm, lack numerous organellar markers, and remain closure-competent for many seconds. Without Ca, compartments open slowly when dynamins are sequestered by cytoplasmic dynamin antibodies or when scrambling is mimicked by neutralizing anionic phospholipids and supplementing neutral lipids. Activation of Ca-permeable mechanosensitive channels via cell swelling or channel agonists opens the compartments in parallel with phospholipid scrambling. Thus, dynamins and TMEM16F control large plasma membrane reserves that open in response to lateral membrane stress and Ca influx.


Assuntos
Anoctaminas/metabolismo , Membrana Celular/metabolismo , Dinaminas/metabolismo , Proteínas de Transferência de Fosfolipídeos/metabolismo , Anoctaminas/genética , Cálcio/metabolismo , Citoplasma , Técnicas de Inativação de Genes , Células HEK293 , Humanos , Membranas/metabolismo , Proteínas de Transferência de Fosfolipídeos/genética , Fosfolipídeos/metabolismo
3.
Int J Mol Sci ; 22(15)2021 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-34360941

RESUMO

Phospholipids (PLs) are amphiphilic molecules that were essential for life to become cellular. PLs have not only a key role in compartmentation as they are the main components of membrane, but they are also involved in cell signaling, cell metabolism, and even cell pathophysiology. Considered for a long time to simply be structural elements of membranes, phospholipids are increasingly being viewed as sensors of their environment and regulators of many metabolic processes. After presenting their main characteristics, we expose the increasing methods of PL detection and identification that help to understand their key role in life processes. Interest and importance of PL homeostasis is growing as pathogenic variants in genes involved in PL biosynthesis and/or remodeling are linked to human diseases. We here review diseases that involve deregulation of PL homeostasis and present a predominantly muscular phenotype.


Assuntos
Músculo Estriado/metabolismo , Fosfolipídeos/metabolismo , Animais , Membrana Celular/metabolismo , Retículo Endoplasmático/metabolismo , Humanos , Mitocôndrias/metabolismo , Músculo Estriado/fisiologia , Fosfolipídeos/química
4.
J Am Chem Soc ; 143(33): 13205-13211, 2021 08 25.
Artigo em Inglês | MEDLINE | ID: mdl-34375093

RESUMO

The receptor binding and proteolysis of Spike of SARS-CoV-2 release its S2 subunit to rearrange and catalyze viral-cell fusion. This deploys the fusion peptide for insertion into the cell membranes targeted. We show that this fusion peptide transforms from intrinsic disorder in solution into a wedge-shaped structure inserted in bilayered micelles, according to chemical shifts, 15N NMR relaxation, and NOEs. The globular fold of three helices contrasts the open, extended forms of this region observed in the electron density of compact prefusion states. In the hydrophobic, narrow end of the wedge, helices 1 and 2 contact the fatty acyl chains of phospholipids, according to NOEs and proximity to a nitroxide spin label deep in the membrane mimic. The polar end of the wedge may engage and displace lipid head groups and bind Ca2+ ions for membrane fusion. Polar helix 3 protrudes from the bilayer where it might be accessible to antibodies.


Assuntos
Micelas , Peptídeos/metabolismo , SARS-CoV-2/metabolismo , Glicoproteína da Espícula de Coronavírus/química , COVID-19/patologia , COVID-19/virologia , Humanos , Interações Hidrofóbicas e Hidrofílicas , Peptídeos/química , Fosfolipídeos/química , Fosfolipídeos/metabolismo , Ligação Proteica , Conformação Proteica em alfa-Hélice , Subunidades Proteicas/química , Subunidades Proteicas/metabolismo , SARS-CoV-2/isolamento & purificação , Glicoproteína da Espícula de Coronavírus/metabolismo
5.
Int J Mol Sci ; 22(15)2021 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-34360917

RESUMO

Although once perceived as inert structures that merely serve for lipid storage, lipid droplets (LDs) have proven to be the dynamic organelles that hold many cellular functions. The LDs' basic structure of a hydrophobic core consisting of neutral lipids and enclosed in a phospholipid monolayer allows for quick lipid accessibility for intracellular energy and membrane production. Whereas formed at the peripheral and perinuclear endoplasmic reticulum, LDs are degraded either in the cytosol by lipolysis or in the vacuoles/lysosomes by autophagy. Autophagy is a regulated breakdown of dysfunctional, damaged, or surplus cellular components. The selective autophagy of LDs is called lipophagy. Here, we review LDs and their degradation by lipophagy in yeast, which proceeds via the micrometer-scale raft-like lipid domains in the vacuolar membrane. These vacuolar microdomains form during nutrient deprivation and facilitate internalization of LDs via the vacuolar membrane invagination and scission. The resultant intra-vacuolar autophagic bodies with LDs inside are broken down by vacuolar lipases and proteases. This type of lipophagy is called microlipophagy as it resembles microautophagy, the type of autophagy when substrates are sequestered right at the surface of a lytic compartment. Yeast microlipophagy via the raft-like vacuolar microdomains is a great model system to study the role of lipid domains in microautophagic pathways.


Assuntos
Autofagia/fisiologia , Gotículas Lipídicas/metabolismo , Microdomínios da Membrana/metabolismo , Saccharomyces cerevisiae/metabolismo , Vacúolos/metabolismo , Citosol/metabolismo , Retículo Endoplasmático/metabolismo , Homeostase/fisiologia , Lipólise/fisiologia , Lisossomos/metabolismo , Fosfolipídeos/metabolismo
6.
Nutrients ; 13(8)2021 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-34444713

RESUMO

Herein, we investigate whether: (1) the administration of glucose or a lipid emulsion is useful in liver transplantation (LT) using steatotic (induced genetically or nutritionally) or non-steatotic livers from donors after brain death (DBDs); and (2) any such benefits are due to reductions in intestinal damage and consequently to gut microbiota preservation. In recipients from DBDs, we show increased hepatic damage and failure in the maintenance of ATP, glycogen, phospholipid and growth factor (HGF, IGF1 and VEGFA) levels, compared to recipients from non-DBDs. In recipients of non-steatotic grafts from DBDs, the administration of glucose or lipids did not protect against hepatic damage. This was associated with unchanged ATP, glycogen, phospholipid and growth factor levels. However, the administration of lipids in steatotic grafts from DBDs protected against damage and ATP and glycogen drop and increased phospholipid levels. This was associated with increases in growth factors. In all recipients from DBDs, intestinal inflammation and damage (evaluated by LPS, vascular permeability, mucosal damage, TLR4, TNF, IL1, IL-10, MPO, MDA and edema formation) was not shown. In such cases, potential changes in gut microbiota would not be relevant since neither inflammation nor damage was evidenced in the intestine following LT in any of the groups evaluated. In conclusion, lipid treatment is the preferable nutritional support to protect against hepatic damage in steatotic LT from DBDs; the benefits were independent of alterations in the recipient intestine.


Assuntos
Morte Encefálica , Fígado Gorduroso , Glucose/administração & dosagem , Transplante de Fígado , Fígado/metabolismo , Fosfolipídeos/administração & dosagem , Óleo de Soja/administração & dosagem , Trifosfato de Adenosina/metabolismo , Animais , Modelos Animais de Doenças , Emulsões/administração & dosagem , Fígado Gorduroso/metabolismo , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Intestinos/patologia , Intestinos/fisiopatologia , Fígado/patologia , Glicogênio Hepático/metabolismo , Masculino , Obesidade , Fosfolipídeos/metabolismo , Ratos , Ratos Zucker , Doadores de Tecidos
7.
Molecules ; 26(14)2021 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-34299592

RESUMO

Beta (ß)-amyloid (Aß) is a causative protein of Alzheimer's disease (AD). In the pathogenesis of AD, the apolipoprotein (apo) A-I and high-density lipoprotein (HDL) metabolism is essential for the clearance of Aß. In this study, recombinant Aß42 was expressed and purified via the pET-30a expression vector and E.coli production system to elucidate the physiological effects of Aß on HDL metabolism. The recombinant human Aß protein (51 aa) was purified to at least 95% purity and characterized in either the lipid-free and lipid-bound states with apoA-I. Aß was incorporated into the reconstituted HDL (rHDL) (molar ratio 95:5:1, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC):cholesterol:apoA-I) with various apoA-I:Aß ratios from 1:0 to 1:0.5, 1:1 and 1:2. With an increasing molar ratio of Aß, the α-helicity of apoA-I was decreased from 62% to 36% with a red shift of the Trp wavelength maximum fluorescence from 337 to 340 nm in apoA-I. The glycation reaction of apoA-I was accelerated further by the addition of Aß. The treatment of fructose and Aß caused more multimerization of apoA-I in the lipid-free state and in HDL. The phospholipid-binding ability of apoA-I was impaired severely by the addition of Aß in a dose-dependent manner. The phagocytosis of LDL into macrophages was accelerated more by the presence of Aß with the production of more oxidized species. Aß severely impaired tissue regeneration, and a microinjection of Aß enhanced embryotoxicity. In conclusion, the beneficial functions of apoA-I and HDL were severely impaired by the addition of Aß via its detrimental effect on secondary structure. The impairment of HDL functionality occurred more synergistically by means of the co-addition of fructose and Aß.


Assuntos
Peptídeos beta-Amiloides/química , Apolipoproteína A-I/química , Lipoproteínas HDL/química , Fragmentos de Peptídeos/química , Fosfolipídeos/química , Peptídeos beta-Amiloides/farmacologia , Animais , Apolipoproteína A-I/farmacologia , Humanos , Lipoproteínas HDL/farmacocinética , Fragmentos de Peptídeos/farmacologia , Fosfolipídeos/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/farmacologia , Células THP-1 , Peixe-Zebra
8.
Biochim Biophys Acta Biomembr ; 1863(11): 183697, 2021 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-34274319

RESUMO

Fusion peptides (FP) are prominent hydrophobic segments of viral fusion proteins that play critical roles in viral entry. FPs interact with and insert into the host lipid membranes, triggering conformational changes in the viral protein that leads to the viral-cell fusion. Multiple membrane-active domains from the severe acute respiratory syndrome (SARS) coronavirus (CoV) spike protein have been reported to act as the functional fusion peptide such as the peptide sequence located between the S1/S2 and S2' cleavage sites (FP1), the S2'-adjacent fusion peptide domain (FP2), and the internal FP sequence (cIFP). Using a combined biophysical approach, we demonstrated that the α-helical coiled-coil-forming internal cIFP displayed the highest membrane fusion and permeabilizing activities along with membrane ordering effect in phosphatidylcholine (PC)/phosphatidylglycerol (PG) unilamellar vesicles compared to the other two N-proximal fusion peptide counterparts. While the FP1 sequence displayed intermediate membranotropic activities, the well-conserved FP2 peptide was substantially less effective in promoting fusion, leakage, and membrane ordering in PC/PG model membranes. Furthermore, Ca2+ did not enhance the FP2-induced lipid mixing activity in PC/phosphatidylserine/cholesterol lipid membranes, despite its strong erythrocyte membrane perturbation. Nonetheless, we found that the three putative SARS-CoV membrane-active fusion peptide sequences here studied altered the physical properties of model and erythrocyte membranes to different extents. The importance of the distinct membranotropic and biological activities of all SARS-CoV fusion peptide domains and the pronounced effect of the internal fusion peptide sequence to the whole spike-mediated membrane fusion process are discussed.


Assuntos
Membrana Eritrocítica/metabolismo , Fosfolipídeos/metabolismo , Glicoproteína da Espícula de Coronavírus/química , Cálcio/química , Cálcio/metabolismo , Membrana Eritrocítica/química , Humanos , Fosfolipídeos/química , Ligação Proteica , Conformação Proteica em alfa-Hélice , Domínios Proteicos , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Glicoproteína da Espícula de Coronavírus/metabolismo , Lipossomas Unilamelares/química , Lipossomas Unilamelares/metabolismo
9.
Science ; 373(6554): 541-547, 2021 07 30.
Artigo em Inglês | MEDLINE | ID: mdl-34326236

RESUMO

Repurposing drugs as treatments for COVID-19, the disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has drawn much attention. Beginning with sigma receptor ligands and expanding to other drugs from screening in the field, we became concerned that phospholipidosis was a shared mechanism underlying the antiviral activity of many repurposed drugs. For all of the 23 cationic amphiphilic drugs we tested, including hydroxychloroquine, azithromycin, amiodarone, and four others already in clinical trials, phospholipidosis was monotonically correlated with antiviral efficacy. Conversely, drugs active against the same targets that did not induce phospholipidosis were not antiviral. Phospholipidosis depends on the physicochemical properties of drugs and does not reflect specific target-based activities-rather, it may be considered a toxic confound in early drug discovery. Early detection of phospholipidosis could eliminate these artifacts, enabling a focus on molecules with therapeutic potential.


Assuntos
Antivirais/farmacologia , COVID-19/tratamento farmacológico , Reposicionamento de Medicamentos , Lipidoses/induzido quimicamente , Fosfolipídeos/metabolismo , SARS-CoV-2/efeitos dos fármacos , Células A549 , Animais , Antivirais/química , Antivirais/uso terapêutico , Antivirais/toxicidade , COVID-19/virologia , Cátions , Chlorocebus aethiops , Relação Dose-Resposta a Droga , Feminino , Humanos , Camundongos , Testes de Sensibilidade Microbiana , SARS-CoV-2/fisiologia , Tensoativos/química , Tensoativos/farmacologia , Tensoativos/toxicidade , Células Vero , Replicação Viral/efeitos dos fármacos
10.
Nat Rev Drug Discov ; 20(9): 710-722, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34257432

RESUMO

Many drug targets are embedded within the phospholipid bilayer of cellular membranes, including G protein-coupled receptors, ion channels, transporters and membrane-bound enzymes. Increasing evidence from biophysical and structural studies suggests that many small-molecule drugs commonly associate with these targets at binding sites at the protein-phospholipid interface. Without a direct path from bulk solvent to a binding site, a drug must first partition in the phospholipid membrane before interacting with the protein target. This membrane access mechanism necessarily affects the interpretation of potency data, structure-activity relationships, pharmacokinetics and physicochemical properties for drugs that target these sites. With an increasing number of small-molecule intramembrane binding sites revealed through X-ray crystallography and cryogenic electron microscopy, we suggest that ligand-lipid interactions likely play a larger role in small-molecule drug action than commonly appreciated. This Perspective introduces key concepts and drug design considerations to aid discovery teams operating within this target space, and discusses challenges and future opportunities in the field.


Assuntos
Desenho de Fármacos , Terapia de Alvo Molecular , Fosfolipídeos/metabolismo , Animais , Sítios de Ligação , Humanos , Ligantes , Ligação Proteica , Relação Estrutura-Atividade
11.
Int J Mol Sci ; 22(13)2021 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-34206240

RESUMO

The development of colon cancer, one of the most common malignancies, is accompanied with numerous lipid alterations. However, analyses of whole tumor samples may not always provide an accurate description of specific changes occurring directly in tumor epithelial cells. Here, we analyzed in detail the phospholipid (PL), lysophospholipid (lysoPL), and fatty acid (FA) profiles of purified EpCAM+ cells, isolated from tumor and adjacent non-tumor tissues of colon cancer patients. We found that a number of FAs increased significantly in isolated tumor cells, which also included a number of long polyunsaturated FAs. Higher levels of FAs were associated with increased expression of FA synthesis genes, as well as with altered expression of enzymes involved in FA elongation and desaturation, including particularly fatty acid synthase, stearoyl-CoA desaturase, fatty acid desaturase 2 and ELOVL5 fatty acid elongase 5 We identified significant changes in ratios of specific lysoPLs and corresponding PLs. A number of lysophosphatidylcholine and lysophosphatidylethanolamine species, containing long-chain and very-long chain FAs, often with high numbers of double bonds, were significantly upregulated in tumor cells. Increased de novo synthesis of very long-chain FAs, or, altered uptake or incorporation of these FAs into specific lysoPLs in tumor cells, may thus contribute to reprogramming of cellular phospholipidome and membrane alterations observed in colon cancer.


Assuntos
Adenocarcinoma/metabolismo , Neoplasias do Colo/metabolismo , Ácidos Graxos/metabolismo , Regulação Neoplásica da Expressão Gênica , Metabolismo dos Lipídeos , Fosfolipídeos/metabolismo , Adenocarcinoma/enzimologia , Adenocarcinoma/genética , Idoso , Neoplasias do Colo/enzimologia , Neoplasias do Colo/genética , Células Epiteliais/enzimologia , Células Epiteliais/metabolismo , Ácidos Graxos Dessaturases/genética , Ácidos Graxos Dessaturases/metabolismo , Elongases de Ácidos Graxos/genética , Elongases de Ácidos Graxos/metabolismo , Ácido Graxo Sintases/genética , Ácido Graxo Sintases/metabolismo , Feminino , Humanos , Lipidômica , Lipogênese , Masculino , Estearoil-CoA Dessaturase/genética , Estearoil-CoA Dessaturase/metabolismo
12.
Nat Commun ; 12(1): 3416, 2021 06 07.
Artigo em Inglês | MEDLINE | ID: mdl-34099706

RESUMO

APOE and Trem2 are major genetic risk factors for Alzheimer's disease (AD), but how they affect microglia response to Aß remains unclear. Here we report an APOE isoform-specific phospholipid signature with correlation between human APOEε3/3 and APOEε4/4 AD brain and lipoproteins from astrocyte conditioned media of APOE3 and APOE4 mice. Using preclinical AD mouse models, we show that APOE3 lipoproteins, unlike APOE4, induce faster microglial migration towards injected Aß, facilitate Aß uptake, and ameliorate Aß effects on cognition. Bulk and single-cell RNA-seq demonstrate that, compared to APOE4, cortical infusion of APOE3 lipoproteins upregulates a higher proportion of genes linked to an activated microglia response, and this trend is augmented by TREM2 deficiency. In vitro, lack of TREM2 decreases Aß uptake by APOE4-treated microglia only, suggesting TREM2-APOE interaction. Our study elucidates phenotypic and transcriptional differences in microglial response to Aß mediated by APOE3 or APOE4 lipoproteins in preclinical models of AD.


Assuntos
Doença de Alzheimer/patologia , Apolipoproteína E3/metabolismo , Apolipoproteína E4/metabolismo , Encéfalo/patologia , Microglia/patologia , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/genética , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Animais , Apolipoproteína E3/administração & dosagem , Apolipoproteína E3/genética , Apolipoproteína E4/administração & dosagem , Apolipoproteína E4/genética , Encéfalo/citologia , Modelos Animais de Doenças , Feminino , Humanos , Masculino , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Camundongos , Camundongos Transgênicos , Mutação , Fosfolipídeos/metabolismo , Presenilina-1/genética , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , RNA-Seq , Receptores Imunológicos/genética , Receptores Imunológicos/metabolismo
13.
Commun Biol ; 4(1): 797, 2021 06 25.
Artigo em Inglês | MEDLINE | ID: mdl-34172821

RESUMO

Phosphorus (P) is an essential nutrient for marine phytoplankton. Maintaining intracellular P homeostasis against environmental P variability is critical for phytoplankton, but how they achieve this is poorly understood. Here we identify a SPX gene and investigate its role in Phaeodactylum tricornutum. SPX knockout led to significant increases in the expression of phosphate transporters, alkaline phosphatases (the P acquisition machinery) and phospholipid hydrolases (a mechanism to reduce P demand). These demonstrate that SPX is a negative regulator of both P uptake and P-stress responses. Furthermore, we show that SPX regulation of P uptake and metabolism involves a phosphate starvation response regulator (PHR) as an intermediate. Additionally, we find the SPX related genes exist and operate across the phytoplankton phylogenetic spectrum and in the global oceans, indicating its universal importance in marine phytoplankton. This study lays a foundation for better understanding phytoplankton adaptation to P variability in the future changing oceans.


Assuntos
Homeostase , Fósforo/metabolismo , Fitoplâncton/metabolismo , Fosfatase Alcalina/metabolismo , Fosfolipídeos/metabolismo , Fotossíntese , Fitoplâncton/genética , Fitoplâncton/crescimento & desenvolvimento , Domínios Proteicos , Transcrição Genética
14.
Commun Biol ; 4(1): 720, 2021 06 11.
Artigo em Inglês | MEDLINE | ID: mdl-34117357

RESUMO

Cholesterol is an essential component of cellular membranes regulating the structural integrity and fluidity of biological bilayers and cellular processes such as signal transduction and membrane trafficking. However, tools to investigate the role and dynamics of cholesterol in live cells are still scarce and often show limited applicability. To address this, we previously developed a class of imidazolium-based cholesterol analogs, CHIMs. Here we confirm that CHIM membrane integration characteristics largely mimic those of cholesterol. Computational studies in simulated phospholipid bilayers and biophysical analyses of model membranes reveal that in biologically relevant systems CHIMs behave similarly to natural cholesterol. Importantly, the analogs can functionally replace cholesterol in membranes, can be readily labeled by click chemistry and follow trafficking pathways of cholesterol in live cells. Thus, CHIMs represent chemically versatile cholesterol analogs that can serve as a flexible toolbox to study cholesterol behavior and function in live cells and organisms.


Assuntos
Membrana Celular/metabolismo , Colesterol/análogos & derivados , Colesterol/metabolismo , Imidazóis/metabolismo , Bicamadas Lipídicas/metabolismo , Mimetismo Molecular , Células HeLa/metabolismo , Humanos , Microscopia de Fluorescência , Fosfolipídeos/metabolismo
15.
Nat Commun ; 12(1): 3443, 2021 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-34103527

RESUMO

Polyunsaturated free fatty acids (FFAs) such as arachidonic acid, released by phospholipase activity on membrane phospholipids, have long been considered beneficial for learning and memory and are known modulators of neurotransmission and synaptic plasticity. However, the precise nature of other FFA and phospholipid changes in specific areas of the brain during learning is unknown. Here, using a targeted lipidomics approach to characterise FFAs and phospholipids across the rat brain, we demonstrated that the highest concentrations of these analytes were found in areas of the brain classically involved in fear learning and memory, such as the amygdala. Auditory fear conditioning led to an increase in saturated (particularly myristic and palmitic acids) and to a lesser extent unsaturated FFAs (predominantly arachidonic acid) in the amygdala and prefrontal cortex. Both fear conditioning and changes in FFA required activation of NMDA receptors. These results suggest a role for saturated FFAs in memory acquisition.


Assuntos
Ácidos Graxos não Esterificados/metabolismo , Memória/fisiologia , Estimulação Acústica , Animais , Comportamento Animal , Encéfalo/metabolismo , Análise por Conglomerados , Condicionamento Clássico , Medo , Masculino , Fosfolipídeos/metabolismo , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/metabolismo
16.
Nat Commun ; 12(1): 3853, 2021 06 22.
Artigo em Inglês | MEDLINE | ID: mdl-34158497

RESUMO

Human ATP-binding cassette (ABC) subfamily A (ABCA) transporters mediate the transport of various lipid compounds across the membrane. Mutations in human ABCA transporters have been described to cause severe hereditary disorders associated with impaired lipid transport. However, little is known about the mechanistic details of substrate recognition and translocation by ABCA transporters. Here, we present three cryo-EM structures of human ABCA4, a retina-specific ABCA transporter, in distinct functional states at resolutions of 3.3-3.4 Å. In the nucleotide-free state, the two transmembrane domains (TMDs) exhibit a lateral-opening conformation, allowing the lateral entry of substrate from the lipid bilayer. The N-retinylidene-phosphatidylethanolamine (NRPE), the physiological lipid substrate of ABCA4, is sandwiched between the two TMDs in the luminal leaflet and is further stabilized by an extended loop from extracellular domain 1. In the ATP-bound state, the two TMDs display a closed conformation, which precludes the substrate binding. Our study provides a molecular basis to understand the mechanism of ABCA4-mediated NRPE recognition and translocation, and suggests a common 'lateral access and extrusion' mechanism for ABCA-mediated lipid transport.


Assuntos
Transportadores de Cassetes de Ligação de ATP/química , Transportadores de Cassetes de Ligação de ATP/metabolismo , Fosfatidiletanolaminas/metabolismo , Domínios Proteicos , Retinoides/metabolismo , Transportadores de Cassetes de Ligação de ATP/ultraestrutura , Trifosfato de Adenosina/metabolismo , Transporte Biológico , Membrana Celular/metabolismo , Microscopia Crioeletrônica , Humanos , Modelos Moleculares , Fosfolipídeos/metabolismo , Ligação Proteica
17.
Int J Mol Sci ; 22(10)2021 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-34067535

RESUMO

We recently discovered an anti-ferroptotic mechanism inherent to M1 macrophages whereby high levels of NO● suppressed ferroptosis via inhibition of hydroperoxy-eicosatetraenoyl-phosphatidylethanolamine (HpETE-PE) production by 15-lipoxygenase (15LOX) complexed with PE-binding protein 1 (PEBP1). However, the mechanism of NO● interference with 15LOX/PEBP1 activity remained unclear. Here, we use a biochemical model of recombinant 15LOX-2 complexed with PEBP1, LC-MS redox lipidomics, and structure-based modeling and simulations to uncover the mechanism through which NO● suppresses ETE-PE oxidation. Our study reveals that O2 and NO● use the same entry pores and channels connecting to 15LOX-2 catalytic site, resulting in a competition for the catalytic site. We identified residues that direct O2 and NO● to the catalytic site, as well as those stabilizing the esterified ETE-PE phospholipid tail. The functional significance of these residues is supported by in silico saturation mutagenesis. We detected nitrosylated PE species in a biochemical system consisting of 15LOX-2/PEBP1 and NO● donor and in RAW264.7 M2 macrophages treated with ferroptosis-inducer RSL3 in the presence of NO●, in further support of the ability of NO● to diffuse to, and react at, the 15LOX-2 catalytic site. The results provide first insights into the molecular mechanism of repression of the ferroptotic Hp-ETE-PE production by NO●.


Assuntos
Ferroptose/fisiologia , Óxido Nítrico/metabolismo , Proteína de Ligação a Fosfatidiletanolamina/metabolismo , Araquidonato 15-Lipoxigenase/metabolismo , Morte Celular/fisiologia , Humanos , Lipidômica , Macrófagos/metabolismo , Simulação de Dinâmica Molecular , Oxirredução , Fosfatidiletanolaminas , Fosfolipídeos/metabolismo
18.
Int J Mol Sci ; 22(9)2021 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-34066314

RESUMO

HDL particles can be structurally modified in atherosclerotic disorders associated with low HDL cholesterol level (HDL-C). We studied whether the lipidome of the main phosphatidylcholine (PC), lysophosphatidylcholine (LPC) and sphingomyelin (SM) species of HDL2 and HDL3 subfractions is associated with premature coronary heart disease (CHD) or metabolic syndrome (MetS) in families where common low HDL-C predisposes to premature CHD. The lipidome was analyzed by LC-MS. Lysophosphatidylcholines were depleted of linoleic acid relative to more saturated and shorter-chained acids containing species in MetS compared with non-affected subjects: the ratio of palmitic to linoleic acid was elevated by more than 30%. A minor PC (16:0/16:1) was elevated (28-40%) in MetS. The contents of oleic acid containing PCs were elevated relative to linoleic acid containing PCs in MetS; the ratio of PC (16:0/18:1) to PC (16:0/18:2) was elevated by 11-16%. Certain PC and SM ratios, e.g., PC (18:0/20:3) to PC (16:0/18:2) and a minor SM 36:2 to an abundant SM 34:1, were higher (11-36%) in MetS and CHD. The fatty acid composition of certain LPCs and PCs displayed a characteristic pattern in MetS, enriched with palmitic, palmitoleic or oleic acids relative to linoleic acid. Certain PC and SM ratios related consistently to CHD and MetS.


Assuntos
Doença da Artéria Coronariana/metabolismo , Ácidos Graxos/metabolismo , Lipoproteínas HDL/metabolismo , Síndrome Metabólica/metabolismo , Fosfolipídeos/metabolismo , Adulto , Família , Feminino , Humanos , Lipidômica , Masculino , Pessoa de Meia-Idade , Fatores de Risco
19.
J Biol Chem ; 296: 100729, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33933446

RESUMO

Membrane contact sites (MCSs) formed between the endoplasmic reticulum (ER) and the plasma membrane (PM) provide a platform for nonvesicular lipid exchange. The ER-anchored tricalbins (Tcb1, Tcb2, and Tcb3) are critical tethering factors at ER-PM MCSs in yeast. Tricalbins possess a synaptotagmin-like mitochondrial-lipid-binding protein (SMP) domain and multiple Ca2+-binding C2 domains. Although tricalbins have been suggested to be involved in lipid exchange at the ER-PM MCSs, it remains unclear whether they directly mediate lipid transport. Here, using in vitro lipid transfer assays, we discovered that tricalbins are capable of transferring phospholipids between membranes. Unexpectedly, while its lipid transfer activity was markedly elevated by Ca2+, Tcb3 constitutively transferred lipids even in the absence of Ca2+. The stimulatory activity of Ca2+ on Tcb3 required intact Ca2+-binding sites on both the C2C and C2D domains of Tcb3, while Ca2+-independent lipid transport was mediated by the SMP domain that transferred lipids via direct interactions with phosphatidylserine and other negatively charged lipid molecules. These findings establish tricalbins as lipid transfer proteins, and reveal Ca2+-dependent and -independent lipid transfer activities mediated by these tricalbins, providing new insights into their mechanism in maintaining PM integrity at ER-PM MCSs.


Assuntos
Proteínas de Ligação ao Cálcio/metabolismo , Cálcio/metabolismo , Fosfolipídeos/metabolismo , Saccharomyces cerevisiae/metabolismo , Transporte Biológico , Membrana Celular/metabolismo , Saccharomyces cerevisiae/citologia
20.
J Biol Chem ; 297(1): 100830, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34048714

RESUMO

Dietary lipid composition has been shown to impact brain morphology, brain development, and neurologic function. However, how diet uniquely regulates brain lipid homeostasis compared with lipid homeostasis in peripheral tissues remains largely uncharacterized. To evaluate the lipid response to dietary changes in the brain, we assessed actively translating mRNAs in astrocytes and neurons across multiple diets. From this data, ethanolamine phosphate phospholyase (Etnppl) was identified as an astrocyte-specific fasting-induced gene. Etnppl catabolizes phosphoethanolamine (PEtN), a prominent headgroup precursor in phosphatidylethanolamine (PE) also found in other classes of neurologically relevant lipid species. Altered Etnppl expression has also previously been associated with humans with mood disorders. We evaluated the relevance of Etnppl in maintaining brain lipid homeostasis by characterizing Etnppl across development and in coregulation with PEtN-relevant genes, as well as determining the impact to the brain lipidome after Etnppl loss. We found that Etnppl expression dramatically increased during a critical window of early brain development in mice and was also induced by glucocorticoids. Using a constitutive knockout of Etnppl (EtnpplKO), we did not observe robust changes in expression of PEtN-related genes. However, loss of Etnppl altered the phospholipid profile in the brain, resulting in increased total abundance of PE and in polyunsaturated fatty acids within PE and phosphatidylcholine species in the brain. Together, these data suggest that brain phospholipids are regulated by the phospholyase action of the enzyme Etnppl, which is induced by dietary fasting in astrocytes.


Assuntos
Astrócitos/metabolismo , Etanolaminas/metabolismo , Homeostase , Metabolismo dos Lipídeos , Fósforo-Oxigênio Liases/metabolismo , Animais , Astrócitos/efeitos dos fármacos , Sistema Nervoso Central/citologia , Dieta , Jejum , Ácidos Graxos/metabolismo , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Glucocorticoides/farmacologia , Homeostase/efeitos dos fármacos , Metabolismo dos Lipídeos/efeitos dos fármacos , Lipídeos de Membrana/metabolismo , Camundongos , Oxirredução , Consumo de Oxigênio/efeitos dos fármacos , Fosfolipídeos/metabolismo , Receptores de Glucocorticoides/metabolismo , Ribossomos/efeitos dos fármacos , Ribossomos/metabolismo , Especificidade por Substrato/efeitos dos fármacos
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