scholarly journals Long chain sphingomyelin depletes cholesterol from the cytoplasmic leaflet in asymmetric lipid membranes

RSC Advances ◽  
2021 ◽  
Vol 11 (37) ◽  
pp. 22677-22682
Author(s):  
Maria Lyngby Karlsen ◽  
Dennis S. Bruhn ◽  
Weria Pezeshkian ◽  
Himanshu Khandelia
Keyword(s):  
Outer Membrane ◽  
Lipid Membranes ◽  
Acyl Chain ◽  
Outer Membrane Leaflet ◽  
Long Chain

Long acyl chain sphingomyelin and saturated phospholipid tails in the outer membrane leaflet deplete cholesterol from the inner leaflet in mammalian membranes.

Biophysics (and sociology) of ceramides.

2005 ◽  
Vol 72 ◽  
pp. 177-188 ◽  
Author(s):  
Félix M. Goñi ◽  
F-Xabier Contreras ◽  
L-Ruth Montes ◽  
Jesús Sot ◽  
Alicia Alonso
Keyword(s):  
Cell Biology ◽  
Positive Curvature ◽  
Acyl Chain ◽  
Cell Signalling ◽  
Hexagonal Structure ◽  
Lipid Monolayer ◽  
Flip Flop ◽  
Long Chain ◽  
Bilayer Permeability

In the past decade, the long-neglected ceramides (N-acylsphingosines) have become one of the most attractive lipid molecules in molecular cell biology, because of their involvement in essential structures (stratum corneum) and processes (cell signalling). Most natural ceramides have a long (16-24 C atoms) N-acyl chain, but short N-acyl chain ceramides (two to six C atoms) also exist in Nature, apart from being extensively used in experimentation, because they can be dispersed easily in water. Long-chain ceramides are among the most hydrophobic molecules in Nature, they are totally insoluble in water and they hardly mix with phospholipids in membranes, giving rise to ceramide-enriched domains. In situ enzymic generation, or external addition, of long-chain ceramides in membranes has at least three important effects: (i) the lipid monolayer tendency to adopt a negative curvature, e.g. through a transition to an inverted hexagonal structure, is increased, (ii) bilayer permeability to aqueous solutes is notoriously enhanced, and (iii) transbilayer (flip-flop) lipid motion is promoted. Short-chain ceramides mix much better with phospholipids, promote a positive curvature in lipid monolayers, and their capacities to increase bilayer permeability or transbilayer motion are very low or non-existent.

scholarly journals Integrated lipidomics and proteomics reveal cardiolipin alterations, upregulation of HADHA and long chain fatty acids in pancreatic cancer stem cells

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Claudia Di Carlo ◽  
Bebiana C. Sousa ◽  
Marcello Manfredi ◽  
Jessica Brandi ◽  
Elisa Dalla Pozza ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Stem Cells ◽  
Fatty Acid ◽  
Cancer Stem Cells ◽  
Acyl Chain ◽  
Fatty Acid Elongase ◽  
Acyl Chains ◽  
A Chain ◽  
Pancreatic Cancer Stem Cells ◽  
Long Chain

AbstractPancreatic cancer stem cells (PCSCs) play a key role in the aggressiveness of pancreatic ductal adenocarcinomas (PDAC); however, little is known about their signaling and metabolic pathways. Here we show that PCSCs have specific and common proteome and lipidome modulations. PCSCs displayed downregulation of lactate dehydrogenase A chain, and upregulation of trifunctional enzyme subunit alpha. The upregulated proteins of PCSCs are mainly involved in fatty acid (FA) elongation and biosynthesis of unsaturated FAs. Accordingly, lipidomics reveals an increase in long and very long-chain unsaturated FAs, which are products of fatty acid elongase-5 predicted as a key gene. Moreover, lipidomics showed the induction in PCSCs of molecular species of cardiolipin with mixed incorporation of 16:0, 18:1, and 18:2 acyl chains. Our data indicate a crucial role of FA elongation and alteration in cardiolipin acyl chain composition in PCSCs, representing attractive therapeutic targets in PDAC.

scholarly journals Structural Insight Into Aeromonas Hydrophila AHL Synthase AhyI Driving Acyl-ACP Selective Recognition

2021 ◽  
Author(s):  
Lei Jin ◽  
Yu chen ◽  
Wenge Yang
Keyword(s):  
Aeromonas Hydrophila ◽  
Acyl Chain ◽  
Virulence Gene ◽  
Kinetic Studies ◽  
Homoserine Lactone ◽  
Selective Recognition ◽  
Acyl Donor ◽  
Virulence Gene Expression ◽  
Long Chain

Abstract Background: The gram-negative bacterium Aeromonas hydrophila as the major causative agent of the fish disease motile aeromonad septicemia, uses N-acyl-homoserine lactone quorum sensing signals to coordinate biofilm formation, motility and virulence gene expression in pathogens. Thus, AHL signaling pathway is considered as a therapeutic target against pathogenic A. hydrophila infection. AHL autoinducers biosynthesis in A. hydrophila are specifically catalyzed by an ACP-dependent AHL synthase AhyI using SAM and acyl-ACP as the precursors. Our previously reported AhyI protein heterologously expressed in E. coli strain showed the production characteristics of medium-long chain AHLs, although AhyI was only considered as a short-chain C4/C6-HSL synthase during the past two decades.Results: In this study, we carried out the in vitro biosynthetic assays of six AHL molecules and kinetic studies of recombinant AhyI with a panel of four linear acyl-ACPs. These resulting data all indicate that C4/C6-ACP are the native acyl substrates for AhyI against acyl-ACPs with longer linear chains as the non-native acyl donor. In an effort to further understand AhyI acyl-donor substrates preferences, we performed a structural comparison of three ACP-dependent LuxI homologs (TofI, BmaI1 and AhyI), and identified three key hydrophobic residues (I67, F125 and L157) as part of the acyl-chain binding pocket that confer AhyI to selectively recognize native C4/C6-ACP substrates. The predictions were further supported by computational Ala mutation assay.Conclusions: Our current studies redefined AhyI protein that is a multiple short- to long-chain AHL molecules synthase with longer acyl-ACPs (C8~C14) as the non-native substrates, and we also theorized that with knowledge of the key residues in AHL signal synthase AhyI to drive acyl-ACP selective recognition.

scholarly journals Effect of different long-chain fatty acids on cholecystokinin releasein vitroand energy intake in free-living healthy males

2012 ◽  
Vol 108 (4) ◽  
pp. 755-758 ◽  
Author(s):  
Charlotte J. Harden ◽  
Adam N. Jones ◽  
Tannia Maya-Jimenez ◽  
Margo E. Barker ◽  
Natalie J. Hepburn ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Chain Length ◽  
Energy Intake ◽  
Acyl Chain ◽  
Dependent Manner ◽  
Long Chain Fatty Acids ◽  
Long Chain ◽  
Healthy Males ◽  
Cck Release ◽  
Chain Fatty Acids

Long-chain fatty acids have been shown to suppress appetite and reduce energy intake (EI) by stimulating the release of gastrointestinal hormones such as cholecystokinin (CCK). The effect of NEFA acyl chain length on these parameters is not comprehensively understood. Anin vitroscreen tested the capacity of individual NEFA (C12 to C22) to trigger CCK release. There was a gradient in CCK release with increasing chain length. DHA (C22) stimulated significantly (P < 0·01) more CCK release than all other NEFA tested. Subsequently, we conducted a randomised, controlled, crossover intervention study using healthy males (n18). The effects of no treatment (NT) and oral doses of emulsified DHA-rich (DHA) and oleic acid (OA)-rich oils were compared using 24 h EI as the primary endpoint. Participants reported significantly (P = 0·039) lower total daily EI (29 % reduction) with DHA compared to NT. There were no differences between DHA compared to OA and OA compared to NT. There was no between-treatment difference in the time to, or EI of, the first post-intervention eating occasion. It is concluded that NEFA stimulate CCK release in a chain length-dependent manner up to C22. These effects may be extended to thein vivosetting, as a DHA-based emulsion significantly reduced short-term EI.

Abstract 16607: Age-induced Endoplasmic Reticulum Stress in the Heart: Role of Increased Very Long-chain Ceramides

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Qun Chen ◽  
Anna Kovilakath ◽  
Jeremy Allegood ◽  
Lauren A Cowart ◽  
Edward J Lesnefsky
Keyword(s):  
Er Stress ◽  
Mitochondrial Dysfunction ◽  
Acyl Chain ◽  
Membrane Domains ◽  
Ceramide Synthase ◽  
Age Related ◽  
Chain Lengths ◽  
Endoplasm Reticulum ◽  
Long Chain

Introduction: Mitochondrial function is impaired in aged hearts. Increased endoplasm reticulum (ER) stress contributes to the mitochondrial dysfunction observed during aging. Ceramides (CRMD) are sphingolipid metabolites that contribute key roles in cell signaling. Increased CRMD can lead to ER stress. Ceramide synthase enzymes (CerS) generate chain length specific CRMD with the CerS isoform 2 (Cers2) forming very long chain CRMD of ≥ 20 carbon acyl chain lengths. Hypothesis: An increase in CRMD content during aging contributes to age-related ER stress. Methods: Male mice (3, 18, 24 mo.) from the NIA colony were studied. Cardiac mitochondria (MITO), mitochondrial associated membranes (MAM), and ER were isolated from mouse hearts. CRMD content was measured using LC-MS. The contents of CerS enzymes were measured by immunoblotting in myocardial homogenates. Results: ER stress increased progressively during aging with increased contents of cleaved ATF6 and CHOP, indicators of increased ER stress, evident at 18 and 24 mo. (Panel A) (all data mean±SEM; *p<0.05 vs. 3 mo., † p<0.05 vs. 18 mo.). Aging increased very long-chain CRMD (≥C20) in ER (Panel B) at 18 and 24 mo. Similar CRMD trends were observed MAM (Panel C), shared membrane domains where ER and MITO interact. The content of CerS2 was increased at 24 mo. compared to 3 mo. (Panel D, n=4 each age). In contrast, the contents of CerS isoforms 4 and 5, that generate shorter chain CRMD (<C20) were unchanged (not shown). CRMD contents in MITO were unaltered with age (not shown). Thus, increased generation of very long chain CRMD in the ER is the likely mechanism of increased ER stress in the aged heart. Conclusion: Aging increased ER CRMD content by enhancing the formation of very long chain CRMD in ER by an increase in CerS2 content, concomitant with the onset of ER stress. The increase in age-induced ER stress, in turn, leads to mitochondrial dysfunction in the aged heart.

The Epicuticle of an Arachnid, Palamneus swammerdami

1954 ◽  
Vol s3-95 (31) ◽  
pp. 371-381
Author(s):  
G. KRISHNAN
Keyword(s):  
Outer Membrane ◽  
Diffraction Pattern ◽  
Basal Layer ◽  
Thin Membrane ◽  
Basic Pattern ◽  
X Ray Diffraction ◽  
X Ray ◽  
Chemical Constitution ◽  
Long Chain

The epicuticle of Palamneus swammerdami in the unhardened condition is homogeneous. It stains uniformly red with Mallory. When hardened, it comprises an internal unstained region, giving evidence of --S--S-- bonding, and is bounded externally by a very thin membrane which stains blue with Mallory. The protein of the inner basal layer differs from its counterpart in the insect epicuticle in the absence of tyrosine, in the occurrence of cystine and cysteine, and in being resistant to the action of hot alkalis. Though apparently related to the keratin of vertebrates, it is not identical with it. The outer thin membrane is lipide in nature. X-ray diffraction studies show that the epicuticular protein is unique: it is unlike both arthropodin and the keratin of vertebrates. However, the outer membrane of the epicuticle yields a diffraction pattern indicating the presence of long-chain paraffins and is similar to the outer epicuticle of the blowfly larva. The chitin of the cuticle appears to be identical in pattern with that of insects. In spite of differences in structural and chemical constitution, the epicuticle of the scorpion shows a resemblance to the basic pattern of the insect epicuticle. The differences may be attributed to the absence of phenolic tanning and the occurrence of --S--S-- bonding. The possible role of the purines present in the cuticle of the scorpion is discussed in relation to --S--S-- bonding.

scholarly journals Physicochemical Evidence that Francisella FupA and FupB Proteins Are Porins

2020 ◽  
Vol 21 (15) ◽  
pp. 5496
Author(s):  
Claire Siebert ◽  
Corinne Mercier ◽  
Donald K. Martin ◽  
Patricia Renesto ◽  
Beatrice Schaack
Keyword(s):  
Outer Membrane ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Iron Transport ◽  
Molecular Mechanisms ◽  
Protein A ◽  
Membrane Vesicles ◽  
Disodium Salt ◽  
Outer Membrane Vesicles ◽  
Novel Therapeutic Strategies

Responsible for tularemia, Francisella tularensis bacteria are highly infectious Gram-negative, category A bioterrorism agents. The molecular mechanisms for their virulence and resistance to antibiotics remain largely unknown. FupA (Fer Utilization Protein), a protein mediating high-affinity transport of ferrous iron across the outer membrane, is associated with both. Recent studies demonstrated that fupA deletion contributed to lower F. tularensis susceptibility towards fluoroquinolones, by increasing the production of outer membrane vesicles. Although the paralogous FupB protein lacks such activity, iron transport capacity and a role in membrane stability were reported for the FupA/B chimera, a protein found in some F. tularensis strains, including the live vaccine strain (LVS). To investigate the mode of action of these proteins, we purified recombinant FupA, FupB and FupA/B proteins expressed in Escherichia coli and incorporated them into mixed lipid bilayers. We examined the porin-forming activity of the FupA/B proteoliposomes using a fluorescent 8-aminonaphthalene-1,3,6-trisulfonic acid, disodium salt (ANTS) probe. Using electrophysiology on tethered bilayer lipid membranes, we confirmed that the FupA/B fusion protein exhibits pore-forming activity with large ionic conductance, a property shared with both FupA and FupB. This demonstration opens up new avenues for identifying functional genes, and novel therapeutic strategies against F. tularensis infections.

scholarly journals Genetic Basis and Physiological Effects of Lipid A Hydroxylation in Pseudomonas aeruginosa PAO1

Pathogens ◽  
2019 ◽  
Vol 8 (4) ◽  
pp. 291 ◽  
Author(s):  
Alessandra Lo Sciuto ◽  
Matteo Cervoni ◽  
Roberta Stefanelli ◽  
Maria Concetta Spinnato ◽  
Alessandra Di Giamberardino ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Outer Membrane ◽  
Human Blood ◽  
Genetic Basis ◽  
Lipid A ◽  
Acyl Chain ◽  
Membrane Integrity ◽  
Physiological Role ◽  
Infection Model ◽  
Acyl Chains

Modifications of the lipid A moiety of lipopolysaccharide influence the physicochemical properties of the outer membrane of Gram-negative bacteria. Some bacteria produce lipid A with a single hydroxylated secondary acyl chain. This hydroxylation is catalyzed by the dioxygenase LpxO, and is important for resistance to cationic antimicrobial peptides (e.g., polymyxins), survival in human blood, and pathogenicity in animal models. The lipid A of the human pathogen Pseudomonas aeruginosa can be hydroxylated in both secondary acyl chains, but the genetic basis and physiological role of these hydroxylations are still unknown. Through the generation of single and double deletion mutants in the lpxO1 and lpxO2 homologs of P. aeruginosa PAO1 and lipid A analysis by mass spectrometry, we demonstrate that both LpxO1 and LpxO2 are responsible for lipid A hydroxylation, likely acting on different secondary acyl chains. Lipid A hydroxylation does not appear to affect in vitro growth, cell wall stability, and resistance to human blood or antibiotics in P. aeruginosa. In contrast, it is required for infectivity in the Galleria mellonella infection model, without relevantly affecting in vivo persistence. Overall, these findings suggest a role for lipid A hydroxylation in P. aeruginosa virulence that could not be directly related to outer membrane integrity.

scholarly journals Effects of Curcumin on Lipid Membranes: an EPR Spin-label Study

2020 ◽  
Vol 78 (2) ◽  
pp. 139-147
Author(s):  
Mariusz Duda ◽  
Kaja Cygan ◽  
Anna Wisniewska-Becker
Keyword(s):  
Phase Transition ◽  
Lipid Membranes ◽  
Acyl Chain ◽  
Protective Role ◽  
Lipid Phase ◽  
Therapeutic Effects ◽  
Structural Effects ◽  
Spectral Parameters ◽  
Paramagnetic Resonance ◽  
Lipid Order

Abstract Curcumin is a yellow–orange dye widely used as a spice, food coloring and food preservative. It also exhibits a broad range of therapeutic effects against different disorders such as cancer, diabetes, or neurodegenerative diseases. As a compound insoluble in water curcumin accumulates in cell membranes and due to this location it may indirectly lead to the observed effects by structurally altering the membrane environment. To exert strong structural effects on membrane curcumin needs to adopt a transbilayer orientation. However, there is no agreement in literature as to curcumin’s orientation and its structural effects on membranes. Here, we investigated the effects of curcumin on lipid order, lipid phase transition, and local polarity in a model liposome membranes made of DMPC or DSPC using electron paramagnetic resonance (EPR) spin labeling technique. Curcumin affected lipid order at different depths within the membrane: it slightly increased the phospholipid polar headgroup mobility as monitored by spectral parameters of T-PC, while along the acyl chain the ordering effect was observed in terms of order parameter S. Also, rotational correlation times τ2B and τ2C of 16-PC in the membrane center were increased by curcumin. Polarity measurements performed in frozen suspensions of liposomes revealed enhancement of water penetration by curcumin in the membrane center (16-PC) and in the polar headgroup region (T-PC) while the intermediate positions along the acyl chain (5-PC and 10-PC) were not significantly affected. Curcumin at a lower concentration (5 mol%) shifted the temperature of the DMPC main phase transition to lower values and increased the transition width, and at a higher concentration (10 mol%) abolished the transition completely. The observed effects suggest that curcumin adopts a transbilayer orientation within the membrane and most probably form oligomers of two molecules, each of them spanning the opposite bilayer leaflets. The effects are also discussed in terms of curcumin’s protective activity and compared with those imposed on membranes by other natural dyes known for their protective role, namely polar carotenoids, lutein and zeaxanthin.

scholarly journals Lipid Headgroup Charge and Acyl Chain Composition Modulate Closure of Bacterial β-Barrel Channels

2019 ◽  
Vol 20 (3) ◽  
pp. 674 ◽  
Author(s):  
D. Perini ◽  
Antonio Alcaraz ◽  
María Queralt-Martín
Keyword(s):  
Membrane Permeability ◽  
Outer Membrane ◽  
Protein Interactions ◽  
Membrane Lipids ◽  
Acyl Chain ◽  
Extensive Study ◽  
Electrophysiological Recordings ◽  
Sequential Closure ◽  
Lipid Protein Interactions ◽  
Outer Membrane Permeability

The outer membrane of Gram-negative bacteria contains β-barrel proteins that form high-conducting ion channels providing a path for hydrophilic molecules, including antibiotics. Traditionally, these proteins have been considered to exist only in an open state so that regulation of outer membrane permeability was accomplished via protein expression. However, electrophysiological recordings show that β-barrel channels respond to transmembrane voltages by characteristically switching from a high-conducting, open state, to a so-called ‘closed’ state, with reduced permeability and possibly exclusion of large metabolites. Here, we use the bacterial porin OmpF from E. coli as a model system to gain insight on the control of outer membrane permeability by bacterial porins through the modulation of their open state. Using planar bilayer electrophysiology, we perform an extensive study of the role of membrane lipids in the OmpF channel closure by voltage. We pay attention not only to the effects of charges in the hydrophilic lipid heads but also to the contribution of the hydrophobic tails in the lipid-protein interactions. Our results show that gating kinetics is governed by lipid characteristics so that each stage of a sequential closure is different from the previous one, probably because of intra- or intermonomeric rearrangements.

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