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Feature Papers in Membranes in Life Sciences
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Feature Papers in Membranes in Life Sciences

A topical collection in Membranes (ISSN 2077-0375).

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Editor

Prof. Dr. Shiro Suetsugu

E-Mail Website
Collection Editor
1. Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, Nara 630-0192, Japan
2. Data Science Center, Nara Institute of Science and Technology, Nara 630-0192, Japan
3. Center for Digital Green-Innovation, Nara Institute of Science and Technology, Nara 630-0192, Japan
Interests: mechanisms of cell shaping and cell fate determination
Special Issues, Collections and Topics in MDPI journals

Topical Collection Information

Dear Colleagues,

Membranes is also open to submission (research articles, short communications, and review articles) on biological membranes. We are launching a Topical Collection on "Feature Papers in Membranes in Life sciences”, which will include all the papers in the section “Membranes in Life Sciences”, including anything on biological membranes, especially:

  • Transport across the membrane;
  • Cell function related to membrane morphogenesis;
  • Membrane shaping of cells and subcellular organelles;
  • Membrane shaping of artificial liposomes;
  • Transport by membrane vesicles;
  • Membrane interaction with proteins, sugars, and other biological materials;
  • Biological membrane synthesis;
  • Application of biological membranes and their mimicry to industry and research;
  • Visualization of membranes.

Prof. Dr. Shiro Suetsugu
Collection Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the collection website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Membranes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (24 papers)

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2023

Jump to: 2022, 2021, 2020

14 pages, 23655 KiB  
Article
Interaction of Uperin Peptides with Model Membranes: Molecular Dynamics Study
by Elena A. Ermakova and Rauf Kh. Kurbanov
Membranes 2023, 13(4), 370; https://doi.org/10.3390/membranes13040370 - 23 Mar 2023
Viewed by 1320
Abstract
The interaction of antimicrobial and amyloid peptides with cell membranes is a critical step in their activities. Peptides of the uperin family obtained from the skin secretion of Australian amphibians demonstrate antimicrobial and amyloidogenic properties. All-atomic molecular dynamics and an umbrella sampling approach [...] Read more.
The interaction of antimicrobial and amyloid peptides with cell membranes is a critical step in their activities. Peptides of the uperin family obtained from the skin secretion of Australian amphibians demonstrate antimicrobial and amyloidogenic properties. All-atomic molecular dynamics and an umbrella sampling approach were used to study the interaction of uperins with model bacterial membrane. Two stable configurations of peptides were found. In the bound state, the peptides in helical form were located right under the head group region in parallel orientation with respect to the bilayer surface. Stable transmembrane configuration was observed for wild-type uperin and its alanine mutant in both alpha-helical and extended unstructured forms. The potential of mean force characterized the process of peptide binding from water to the lipid bilayer and its insertion into the membrane, and revealed that the transition of uperins from the bound state to the transmembrane position was accompanied by the rotation of peptides and passes through the energy barrier of 4–5 kcal/mol. Uperins have a weak effect on membrane properties. Full article
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23 pages, 10281 KiB  
Article
UNILIPID, a Methodology for Energetically Accurate Prediction of Protein Insertion into Implicit Membranes of Arbitrary Shape
by André Lanrezac and Marc Baaden
Membranes 2023, 13(3), 362; https://doi.org/10.3390/membranes13030362 - 21 Mar 2023
Viewed by 1522
Abstract
The insertion of proteins into membranes is crucial for understanding their function in many biological processes. In this work, we present UNILIPID, a universal implicit lipid-protein description as a methodology for dealing with implicit membranes. UNILIPID is independent of the scale of representation [...] Read more.
The insertion of proteins into membranes is crucial for understanding their function in many biological processes. In this work, we present UNILIPID, a universal implicit lipid-protein description as a methodology for dealing with implicit membranes. UNILIPID is independent of the scale of representation and can be applied at the level of all atoms, coarse-grained particles down to the level of a single bead per amino acid. We provide example implementations for these scales and demonstrate the versatility of our approach by accurately reflecting the free energy of transfer for each amino acid. In addition to single membranes, we describe the analytical implementation of double membranes and show that UNILIPID is well suited for modeling at multiple scales. We generalize to membranes of arbitrary shape. With UNILIPID, we provide a methodological framework for a simple and general parameterization tuned to reproduce a selected reference hydrophobicity scale. The software we provide along with the methodological description is optimized for specific user features such as real-time response, live visual analysis, and virtual reality experiences. Full article
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20 pages, 5261 KiB  
Article
The Unusual Aggregation and Fusion Activity of the Antimicrobial Peptide W-BP100 in Anionic Vesicles
by Ana Rita Ferreira, Mariana Ferreira, Cláudia Nunes, Salette Reis, Cátia Teixeira, Paula Gomes and Paula Gameiro
Membranes 2023, 13(2), 138; https://doi.org/10.3390/membranes13020138 - 21 Jan 2023
Cited by 2 | Viewed by 1580
Abstract
Cationic antimicrobial peptides (CAMPs) offer a promising strategy to counteract bacterial resistance, mostly due to their membrane-targeting activity. W-BP100 is a potent broad-spectrum cecropin-melittin CAMP bearing a single N-terminal Trp, which was previously found to improve its antibacterial activity. W-BP100 has high affinity [...] Read more.
Cationic antimicrobial peptides (CAMPs) offer a promising strategy to counteract bacterial resistance, mostly due to their membrane-targeting activity. W-BP100 is a potent broad-spectrum cecropin-melittin CAMP bearing a single N-terminal Trp, which was previously found to improve its antibacterial activity. W-BP100 has high affinity toward anionic membranes, inducing membrane saturation at low peptide-to-lipid (P/L) ratios and membrane permeabilization, with the unique property of promoting the aggregation of anionic vesicles only at specific P/L ratios. Herein, we aimed to investigate this unusual behavior of W-BP100 by studying its aggregation and fusion properties with negatively-charged large (LUVs) or giant (GUVs) unilamellar vesicles using biophysical tools. Circular dichroism (CD) showed that W-BP100 adopted an α-helical conformation in anionic LUVs, neutralizing its surface charge at the aggregation P/L ratio. Its fusion activity, assessed by Förster resonance energy transfer (FRET) using steady-state fluorescence spectroscopy, occurred mainly at the membrane saturation/aggregation P/L ratio. Confocal microscopy studies confirmed that W-BP100 displays aggregation and detergent-like effects at a critical P/L ratio, above which it induces the formation of new lipid aggregates. Our data suggest that W-BP100 promotes the aggregation and fusion of anionic vesicles at specific P/L ratios, being able to reshape the morphology of GUVs into new lipid structures. Full article
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2022

Jump to: 2023, 2021, 2020

21 pages, 2452 KiB  
Review
Host–Bacterial Interactions: Outcomes of Antimicrobial Peptide Applications
by Asma Hussain Alkatheri, Polly Soo-Xi Yap, Aisha Abushelaibi, Kok-Song Lai, Wan-Hee Cheng and Swee-Hua Erin Lim
Membranes 2022, 12(7), 715; https://doi.org/10.3390/membranes12070715 - 19 Jul 2022
Cited by 2 | Viewed by 2629
Abstract
The bacterial membrane is part of a secretion system which plays an integral role to secrete proteins responsible for cell viability and pathogenicity; pathogenic bacteria, for example, secrete virulence factors and other membrane-associated proteins to invade the host cells through various types of [...] Read more.
The bacterial membrane is part of a secretion system which plays an integral role to secrete proteins responsible for cell viability and pathogenicity; pathogenic bacteria, for example, secrete virulence factors and other membrane-associated proteins to invade the host cells through various types of secretion systems (Type I to Type IX). The bacterial membrane can also mediate microbial communities’ communication through quorum sensing (QS), by secreting auto-stimulants to coordinate gene expression. QS plays an important role in regulating various physiological processes, including bacterial biofilm formation while providing increased virulence, subsequently leading to antimicrobial resistance. Multi-drug resistant (MDR) bacteria have emerged as a threat to global health, and various strategies targeting QS and biofilm formation have been explored by researchers worldwide. Since the bacterial secretion systems play such a crucial role in host–bacterial interactions, this review intends to outline current understanding of bacterial membrane systems, which may provide new insights for designing approaches aimed at antimicrobials discovery. Various mechanisms pertaining interaction of the bacterial membrane with host cells and antimicrobial agents will be highlighted, as well as the evolution of bacterial membranes in evasion of antimicrobial agents. Finally, the use of antimicrobial peptides (AMPs) as a cellular device for bacterial secretion systems will be discussed as emerging potential candidates for the treatment of multidrug resistance infections. Full article
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12 pages, 1971 KiB  
Article
Experimental Investigations on the Conductance of Lipid Membranes under Differential Hydrostatic Pressure
by Rose Whiting, Pangaea W. Finn, Andrew Bogard, Fulton McKinney, Dallin Pankratz, Aviana R. Smith, Elen A. Gardner and Daniel Fologea
Membranes 2022, 12(5), 479; https://doi.org/10.3390/membranes12050479 - 29 Apr 2022
Cited by 1 | Viewed by 2007
Abstract
The unassisted transport of inorganic ions through lipid membranes has become increasingly relevant to an expansive range of biological phenomena. Recent simulations indicate a strong influence of a lipid membrane’s curvature on its permeability, which may be part of the overall cell sensitivity [...] Read more.
The unassisted transport of inorganic ions through lipid membranes has become increasingly relevant to an expansive range of biological phenomena. Recent simulations indicate a strong influence of a lipid membrane’s curvature on its permeability, which may be part of the overall cell sensitivity to mechanical stimulation. However, most ionic permeability experiments employ a flat, uncurved lipid membrane, which disregards the physiological relevance of curvature on such investigations. To fill this gap in our knowledge, we adapted a traditional experimental system consisting of a planar lipid membrane, which we exposed to a controlled, differential hydrostatic pressure. Our electrophysiology experiments indicate a strong correlation between the changes in membrane geometry elicited by the application of pressure, as inferred from capacitance measurements, and the resulting conductance. Our experiments also confirmed the well-established influence of cholesterol addition to lipid membranes in adjusting their mechanical properties and overall permeability. Therefore, the proposed experimental system may prove useful for a better understanding of the intricate connections between membrane mechanics and adjustments of cellular functionalities upon mechanical stimulation, as well as for confirmation of predictions made by simulations and theoretical modeling. Full article
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2021

Jump to: 2023, 2022, 2020

12 pages, 1909 KiB  
Article
The Ionic Selectivity of Lysenin Channels in Open and Sub-Conducting States
by Andrew Bogard, Pangaea W. Finn, Fulton McKinney, Ilinca M. Flacau, Aviana R. Smith, Rosey Whiting and Daniel Fologea
Membranes 2021, 11(11), 897; https://doi.org/10.3390/membranes11110897 - 19 Nov 2021
Cited by 4 | Viewed by 2102
Abstract
The electrochemical gradients established across cell membranes are paramount for the execution of biological functions. Besides ion channels, other transporters, such as exogenous pore-forming toxins, may present ionic selectivity upon reconstitution in natural and artificial lipid membranes and contribute to the electrochemical gradients. [...] Read more.
The electrochemical gradients established across cell membranes are paramount for the execution of biological functions. Besides ion channels, other transporters, such as exogenous pore-forming toxins, may present ionic selectivity upon reconstitution in natural and artificial lipid membranes and contribute to the electrochemical gradients. In this context, we utilized electrophysiology approaches to assess the ionic selectivity of the pore-forming toxin lysenin reconstituted in planar bilayer lipid membranes. The membrane voltages were determined from the reversal potentials recorded upon channel exposure to asymmetrical ionic conditions, and the permeability ratios were calculated from the fit with the Goldman–Hodgkin–Katz equation. Our work shows that lysenin channels are ion-selective and the determined permeability coefficients are cation and anion-species dependent. We also exploited the unique property of lysenin channels to transition to a stable sub-conducting state upon exposure to calcium ions and assessed their subsequent change in ionic selectivity. The observed loss of selectivity was implemented in an electrical model describing the dependency of reversal potentials on calcium concentration. In conclusion, our work demonstrates that this pore-forming toxin presents ionic selectivity but this is adjusted by the particular conduction state of the channels. Full article
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14 pages, 2447 KiB  
Article
Nanodrug Transmembrane Transport Research Based on Fluorescence Correlation Spectroscopy
by Xinwei Gao, Yanfeng Liu, Jia Zhang, Luwei Wang, Yong Guo, Yinru Zhu, Zhigang Yang, Wei Yan and Junle Qu
Membranes 2021, 11(11), 891; https://doi.org/10.3390/membranes11110891 - 19 Nov 2021
Cited by 2 | Viewed by 1727
Abstract
Although conventional fluorescence intensity imaging can be used to qualitatively study the drug toxicity of nanodrug carrier systems at the single-cell level, it has limitations for studying nanodrug transport across membranes. Fluorescence correlation spectroscopy (FCS) can provide quantitative information on nanodrug concentration and [...] Read more.
Although conventional fluorescence intensity imaging can be used to qualitatively study the drug toxicity of nanodrug carrier systems at the single-cell level, it has limitations for studying nanodrug transport across membranes. Fluorescence correlation spectroscopy (FCS) can provide quantitative information on nanodrug concentration and diffusion in a small area of the cell membrane; thus, it is an ideal tool for studying drug transport across the membrane. In this paper, the FCS method was used to measure the diffusion coefficients and concentrations of carbon dots (CDs), doxorubicin (DOX) and CDs-DOX composites in living cells (COS7 and U2OS) for the first time. The drug concentration and diffusion coefficient in living cells determined by FCS measurements indicated that the CDs-DOX composite distinctively improved the transmembrane efficiency and rate of drug molecules, in accordance with the conclusions drawn from the fluorescence imaging results. Furthermore, the effects of pH values and ATP concentrations on drug transport across the membrane were also studied. Compared with free DOX under acidic conditions, the CDs-DOX complex has higher cellular uptake and better transmembrane efficacy in U2OS cells. Additionally, high concentrations of ATP will cause negative changes in cell membrane permeability, which will hinder the transmembrane transport of CDs and DOX and delay the rapid diffusion of CDs-DOX. The results of this study show that the FCS method can be utilized as a powerful tool for studying the expansion and transport of nanodrugs in living cells, and might provide a new drug exploitation strategy for cancer treatment in vivo. Full article
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20 pages, 5468 KiB  
Article
Characterization of Extracellular Vesicles Labelled with a Lipophilic Dye Using Fluorescence Nanoparticle Tracking Analysis
by Getnet Midekessa, Kasun Godakumara, Keerthie Dissanayake, Mohammad Mehedi Hasan, Qurat Ul Ain Reshi, Toonika Rinken and Alireza Fazeli
Membranes 2021, 11(10), 779; https://doi.org/10.3390/membranes11100779 - 12 Oct 2021
Cited by 4 | Viewed by 4324
Abstract
Research on extracellular vesicles (EVs) has intensified over the past decade, including fluorescent membrane labeling of EVs. An optimal fluorescent method requires the size of EVs to be preserved after labeling. Lipophilic fluorescent dyes, such as CellMask™ Green (CMG), have been widely used [...] Read more.
Research on extracellular vesicles (EVs) has intensified over the past decade, including fluorescent membrane labeling of EVs. An optimal fluorescent method requires the size of EVs to be preserved after labeling. Lipophilic fluorescent dyes, such as CellMask™ Green (CMG), have been widely used for this purpose. Here, we investigated conditions affecting the optimum CMG labeling of EVs derived from human choriocarcinoma cells (JAr) and different biological fluids using fluorescence NTA (fl-NTA). The effect of CMG labeling on the size, concentration and zeta potential (ZP) on JAr EVs purified with different methods were measured along with biological fluid-derived EVs. With the increase of CMG dye concentration, a significant decrease in the mean size of fluorescent nanoparticles (fl-NPs) was observed. The ZP of fl-NPs originating from JAr cells with the lowest and highest dye concentrations showed a significant shift towards more and less negative ZP values, respectively. Differences in the concentration of fl-NPs were observed for JAr EVs purified using size-exclusion chromatography (SEC) alone and SEC in combination with tangential flow filtration. The proportion of CMG labeling of NPs varied across different biological sources. CMG labeling may be a reliable technique for the detection of EVs using fl-NTA. Full article
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10 pages, 1266 KiB  
Article
Modulation of the Human Erythroid Plasma Membrane Calcium Pump (PMCA4b) Expression by Polymorphic Genetic Variants
by Orsolya Mózner, Boglárka Zámbó and Balázs Sarkadi
Membranes 2021, 11(8), 586; https://doi.org/10.3390/membranes11080586 - 30 Jul 2021
Cited by 2 | Viewed by 1925
Abstract
In the human ATP2B4 gene, coding for the plasma membrane calcium pump PMCA4b, a minor haplotype results in the decreased expression of this membrane protein in erythroid cells. The presence of this haplotype and the consequently reduced PMCA4b expression have been suggested to [...] Read more.
In the human ATP2B4 gene, coding for the plasma membrane calcium pump PMCA4b, a minor haplotype results in the decreased expression of this membrane protein in erythroid cells. The presence of this haplotype and the consequently reduced PMCA4b expression have been suggested to affect red blood cell hydration and malaria susceptibility. By using dual-luciferase reporter assays, we have localized the erythroid-specific regulatory region within the haplotype of the ATP2B4 gene, containing predicted GATA1 binding sites that are affected by SNPs in the minor haplotype. Our results show that, in human erythroid cells, the regulation of ATP2B4 gene expression is significantly affected by GATA1 expression, and we document the role of specific SNPs involved in predicted GATA1 binding. Our findings provide a mechanistic explanation at the molecular level for the reduced erythroid-specific PMCA4b expression in carriers of ATP2B4 gene polymorphic variants. Full article
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21 pages, 3086 KiB  
Article
The Functional Significance of Hydrophobic Residue Distribution in Bacterial Beta-Barrel Transmembrane Proteins
by Irena Roterman, Katarzyna Stapor, Piotr Fabian and Leszek Konieczny
Membranes 2021, 11(8), 580; https://doi.org/10.3390/membranes11080580 - 30 Jul 2021
Cited by 16 | Viewed by 2540
Abstract
β-barrel membrane proteins have several important biological functions, including transporting water and solutes across the membrane. They are active in the highly hydrophobic environment of the lipid membrane, as opposed to soluble proteins, which function in a more polar, aqueous environment. Globular soluble [...] Read more.
β-barrel membrane proteins have several important biological functions, including transporting water and solutes across the membrane. They are active in the highly hydrophobic environment of the lipid membrane, as opposed to soluble proteins, which function in a more polar, aqueous environment. Globular soluble proteins typically have a hydrophobic core and a polar surface that interacts favorably with water. In the fuzzy oil drop (FOD) model, this distribution is represented by the 3D Gauss function (3DG). In contrast, membrane proteins expose hydrophobic residues on the surface, and, in the case of ion channels, the polar residues face inwards towards a central pore. The distribution of hydrophobic residues in membrane proteins can be characterized by means of 1–3DG, a complementary 3D Gauss function. Such an analysis was carried out on the transmembrane proteins of bacteria, which, despite the considerable similarities of their super-secondary structure (β-barrel), have highly differentiated properties in terms of stabilization based on hydrophobic interactions. The biological activity and substrate specificity of these proteins are determined by the distribution of the polar and nonpolar amino acids. The present analysis allowed us to compare the ways in which the different proteins interact with antibiotics and helped us understand their relative importance in the development of the resistance mechanism. We showed that beta barrel membrane proteins with a hydrophobic core interact less strongly with the molecules they transport. Full article
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13 pages, 307 KiB  
Review
Advances about the Roles of Membranes in Cotton Fiber Development
by Fan Xu, Qian Chen, Li Huang and Ming Luo
Membranes 2021, 11(7), 471; https://doi.org/10.3390/membranes11070471 - 25 Jun 2021
Cited by 13 | Viewed by 2543
Abstract
Cotton fiber is an extremely elongated single cell derived from the ovule epidermis and is an ideal model for studying cell development. The plasma membrane is tremendously expanded and accompanied by the coordination of various physiological and biochemical activities on the membrane, one [...] Read more.
Cotton fiber is an extremely elongated single cell derived from the ovule epidermis and is an ideal model for studying cell development. The plasma membrane is tremendously expanded and accompanied by the coordination of various physiological and biochemical activities on the membrane, one of the three major systems of a eukaryotic cell. This review compiles the recent progress and advances for the roles of the membrane in cotton fiber development: the functions of membrane lipids, especially the fatty acids, sphingolipids, and phytosterols; membrane channels, including aquaporins, the ATP-binding cassette (ABC) transporters, vacuolar invertase, and plasmodesmata; and the regulation mechanism of membrane proteins, such as membrane binding enzymes, annexins, and receptor-like kinases. Full article
12 pages, 9321 KiB  
Article
Rapid Production and Purification of Dye-Loaded Liposomes by Electrodialysis-Driven Depletion
by Gamid Abatchev, Andrew Bogard, Zoe Hutchinson, Jason Ward and Daniel Fologea
Membranes 2021, 11(6), 417; https://doi.org/10.3390/membranes11060417 - 31 May 2021
Cited by 3 | Viewed by 4799
Abstract
Liposomes are spherical-shaped vesicles that enclose an aqueous milieu surrounded by bilayer or multilayer membranes formed by self-assembly of lipid molecules. They are intensively exploited as either model membranes for fundamental studies or as vehicles for delivery of active substances in vivo and [...] Read more.
Liposomes are spherical-shaped vesicles that enclose an aqueous milieu surrounded by bilayer or multilayer membranes formed by self-assembly of lipid molecules. They are intensively exploited as either model membranes for fundamental studies or as vehicles for delivery of active substances in vivo and in vitro. Irrespective of the method adopted for production of loaded liposomes, obtaining the final purified product is often achieved by employing multiple, time consuming steps. To alleviate this problem, we propose a simplified approach for concomitant production and purification of loaded liposomes by exploiting the Electrodialysis-Driven Depletion of charged molecules from solutions. Our investigations show that electrically-driven migration of charged detergent and dye molecules from solutions that include natural or synthetic lipid mixtures leads to rapid self-assembly of loaded, purified liposomes, as inferred from microscopy and fluorescence spectroscopy assessments. In addition, the same procedure was successfully applied for incorporating PEGylated lipids into the membranes for the purpose of enabling long-circulation times needed for potential in vivo applications. Dynamic Light Scattering analyses and comparison of electrically-formed liposomes with liposomes produced by sonication or extrusion suggest potential use for numerous in vitro and in vivo applications. Full article
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14 pages, 2040 KiB  
Article
Liposomes Prevent In Vitro Hemolysis Induced by Streptolysin O and Lysenin
by Marcelo Ayllon, Gamid Abatchev, Andrew Bogard, Rosey Whiting, Sarah E. Hobdey and Daniel Fologea
Membranes 2021, 11(5), 364; https://doi.org/10.3390/membranes11050364 - 18 May 2021
Cited by 2 | Viewed by 3363
Abstract
The need for alternatives to antibiotics in the fight against infectious diseases has inspired scientists to focus on antivirulence factors instead of the microorganisms themselves. In this respect, prior work indicates that tiny, enclosed bilayer lipid membranes (liposomes) have the potential to compete [...] Read more.
The need for alternatives to antibiotics in the fight against infectious diseases has inspired scientists to focus on antivirulence factors instead of the microorganisms themselves. In this respect, prior work indicates that tiny, enclosed bilayer lipid membranes (liposomes) have the potential to compete with cellular targets for toxin binding, hence preventing their biological attack and aiding with their clearance. The effectiveness of liposomes as decoy targets depends on their availability in the host and how rapidly they are cleared from the circulation. Although liposome PEGylation may improve their circulation time, little is known about how such a modification influences their interactions with antivirulence factors. To fill this gap in knowledge, we investigated regular and long-circulating liposomes for their ability to prevent in vitro red blood cell hemolysis induced by two potent lytic toxins, lysenin and streptolysin O. Our explorations indicate that both regular and long-circulating liposomes are capable of similarly preventing lysis induced by streptolysin O. In contrast, PEGylation reduced the effectiveness against lysenin-induced hemolysis and altered binding dynamics. These results suggest that toxin removal by long-circulating liposomes is feasible, yet dependent on the particular virulence factor under scrutiny. Full article
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8 pages, 1376 KiB  
Article
The Profound Influence of Lipid Composition on the Catalysis of the Drug Target NADH Type II Oxidoreductase
by Albert Godoy-Hernandez and Duncan G. G. McMillan
Membranes 2021, 11(5), 363; https://doi.org/10.3390/membranes11050363 - 17 May 2021
Cited by 2 | Viewed by 2360
Abstract
Lipids play a pivotal role in cellular respiration, providing the natural environment in which an oxidoreductase interacts with the quinone pool. To date, it is generally accepted that negatively charged lipids play a major role in the activity of quinone oxidoreductases. By changing [...] Read more.
Lipids play a pivotal role in cellular respiration, providing the natural environment in which an oxidoreductase interacts with the quinone pool. To date, it is generally accepted that negatively charged lipids play a major role in the activity of quinone oxidoreductases. By changing lipid compositions when assaying a type II NADH:quinone oxidoreductase, we demonstrate that phosphatidylethanolamine has an essential role in substrate binding and catalysis. We also reveal the importance of acyl chain composition, specifically c14:0, on membrane-bound quinone-mediated catalysis. This demonstrates that oxidoreductase lipid specificity is more diverse than originally thought and that the lipid environment plays an important role in the physiological catalysis of membrane-bound oxidoreductases. Full article
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21 pages, 3980 KiB  
Review
Peripheral Membrane Proteins: Promising Therapeutic Targets across Domains of Life
by Deborah M. Boes, Albert Godoy-Hernandez and Duncan G. G. McMillan
Membranes 2021, 11(5), 346; https://doi.org/10.3390/membranes11050346 - 08 May 2021
Cited by 26 | Viewed by 6546
Abstract
Membrane proteins can be classified into two main categories—integral and peripheral membrane proteins—depending on the nature of their membrane interaction. Peripheral membrane proteins are highly unique amphipathic proteins that interact with the membrane indirectly, using electrostatic or hydrophobic interactions, or directly, using hydrophobic [...] Read more.
Membrane proteins can be classified into two main categories—integral and peripheral membrane proteins—depending on the nature of their membrane interaction. Peripheral membrane proteins are highly unique amphipathic proteins that interact with the membrane indirectly, using electrostatic or hydrophobic interactions, or directly, using hydrophobic tails or GPI-anchors. The nature of this interaction not only influences the location of the protein in the cell, but also the function. In addition to their unique relationship with the cell membrane, peripheral membrane proteins often play a key role in the development of human diseases such as African sleeping sickness, cancer, and atherosclerosis. This review will discuss the membrane interaction and role of periplasmic nitrate reductase, CymA, cytochrome c, alkaline phosphatase, ecto-5’-nucleotidase, acetylcholinesterase, alternative oxidase, type-II NADH dehydrogenase, and dihydroorotate dehydrogenase in certain diseases. The study of these proteins will give new insights into their function and structure, and may ultimately lead to ground-breaking advances in the treatment of severe diseases. Full article
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26 pages, 1055 KiB  
Article
Characteristics of Passive Solute Transport across Primary Rat Alveolar Epithelial Cell Monolayers
by Yong Ho Kim, Kwang-Jin Kim, David Z. D’Argenio and Edward D. Crandall
Membranes 2021, 11(5), 331; https://doi.org/10.3390/membranes11050331 - 30 Apr 2021
Cited by 4 | Viewed by 2182
Abstract
Primary rat alveolar epithelial cell monolayers (RAECM) were grown without (type I cell-like phenotype, RAECM-I) or with (type II cell-like phenotype, RAECM-II) keratinocyte growth factor to assess passive transport of 11 hydrophilic solutes. We estimated apparent permeability (Papp) in the [...] Read more.
Primary rat alveolar epithelial cell monolayers (RAECM) were grown without (type I cell-like phenotype, RAECM-I) or with (type II cell-like phenotype, RAECM-II) keratinocyte growth factor to assess passive transport of 11 hydrophilic solutes. We estimated apparent permeability (Papp) in the absence/presence of calcium chelator EGTA to determine the effects of perturbing tight junctions on “equivalent” pores. Papp across RAECM-I and -II in the absence of EGTA are similar and decrease as solute size increases. We modeled Papp of the hydrophilic solutes across RAECM-I/-II as taking place via heterogeneous populations of equivalent pores comprised of small (0.41/0.32 nm radius) and large (9.88/11.56 nm radius) pores, respectively. Total equivalent pore area is dominated by small equivalent pores (99.92–99.97%). The number of small and large equivalent pores in RAECM-I was 8.55 and 1.29 times greater, respectively, than those in RAECM-II. With EGTA, the large pore radius in RAECM-I/-II increased by 1.58/4.34 times and the small equivalent pore radius increased by 1.84/1.90 times, respectively. These results indicate that passive diffusion of hydrophilic solutes across an alveolar epithelium occurs via small and large equivalent pores, reflecting interactions of transmembrane proteins expressed in intercellular tight junctions of alveolar epithelial cells. Full article
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13 pages, 2265 KiB  
Review
A Potential Role of IL-6/IL-6R in the Development and Management of Colon Cancer
by Mimmo Turano, Francesca Cammarota, Francesca Duraturo, Paola Izzo and Marina De Rosa
Membranes 2021, 11(5), 312; https://doi.org/10.3390/membranes11050312 - 24 Apr 2021
Cited by 26 | Viewed by 3805
Abstract
Colorectal cancer (CRC) is the third most frequent cancer worldwide and the second greatest cause of cancer deaths. About 75% of all CRCs are sporadic cancers and arise following somatic mutations, while about 10% are hereditary cancers caused by germline mutations in specific [...] Read more.
Colorectal cancer (CRC) is the third most frequent cancer worldwide and the second greatest cause of cancer deaths. About 75% of all CRCs are sporadic cancers and arise following somatic mutations, while about 10% are hereditary cancers caused by germline mutations in specific genes. Several factors, such as growth factors, cytokines, and genetic or epigenetic alterations in specific oncogenes or tumor-suppressor genes, play a role during the adenoma–carcinoma sequence. Recent studies have reported an increase in interleukin-6 (IL-6) and soluble interleukin-6 receptor (sIL-6R) levels in the sera of patients affected by colon cancer that correlate with the tumor size, suggesting a potential role for IL-6 in colon cancer progression. IL-6 is a pleiotropic cytokine showing both pro- and anti-inflammatory roles. Two different types of IL-6 signaling are known. Classic IL-6 signaling involves the binding of IL-6 to its membrane receptor on the surfaces of target cells; alternatively, IL-6 binds to sIL-6R in a process called IL-6 trans-signaling. The activation of IL-6 trans-signaling by metalloproteinases has been described during colon cancer progression and metastasis, involving a shift from membrane-bound interleukin-6 receptor (IL-6R) expression on the tumor cell surface toward the release of soluble IL-6R. In this review, we aim to shed light on the role of IL-6 signaling pathway alterations in sporadic colorectal cancer and the development of familial polyposis syndrome. Furthermore, we evaluate the possible roles of IL-6 and IL-6R as biomarkers useful in disease follow-up and as potential targets for therapy, such as monoclonal antibodies against IL-6 or IL-6R, or a food-based approach against IL-6. Full article
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12 pages, 4619 KiB  
Article
Trastuzumab Modulates the Protein Cargo of Extracellular Vesicles Released by ERBB2+ Breast Cancer Cells
by Silvia Marconi, Sara Santamaria, Martina Bartolucci, Sara Stigliani, Cinzia Aiello, Maria Cristina Gagliani, Grazia Bellese, Andrea Petretto, Katia Cortese and Patrizio Castagnola
Membranes 2021, 11(3), 199; https://doi.org/10.3390/membranes11030199 - 12 Mar 2021
Cited by 7 | Viewed by 2565
Abstract
Cancers overexpressing the ERBB2 oncogene are aggressive and associated with a poor prognosis. Trastuzumab is an ERBB2 specific recombinant antibody employed for the treatment of these diseases since it blocks ERBB2 signaling causing growth arrest and survival inhibition. While the effects of Trastuzumab [...] Read more.
Cancers overexpressing the ERBB2 oncogene are aggressive and associated with a poor prognosis. Trastuzumab is an ERBB2 specific recombinant antibody employed for the treatment of these diseases since it blocks ERBB2 signaling causing growth arrest and survival inhibition. While the effects of Trastuzumab on ERBB2 cancer cells are well known, those on the extracellular vesicles (EVs) released from these cells are scarce. This study focused on ERBB2+ breast cancer cells and aimed to establish what type of EVs they release and whether Trastuzumab affects their morphology and molecular composition. To these aims, we performed immunoelectron microscopy, immunoblot, and high-resolution mass spectrometry analyses on EVs purified by differential centrifugation of culture supernatant. Here, we show that EVs released from ERBB2+ breast cancer cells are polymorphic in size and appearance and that ERBB2 is preferentially associated with large (120 nm) EVs. Moreover, we report that Trastuzumab (Tz) induces the expression of a specific glycosylated 50 kDa isoform of the CD63 tetraspanin and modulates the expression of 51 EVs proteins, including TOP1. Because these proteins are functionally associated with organelle organization, cytokinesis, and response to lipids, we suggest that Tz may influence these cellular processes in target cells at distant sites via modified EVs. Full article
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2020

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16 pages, 2458 KiB  
Article
Size of Cells and Physicochemical Properties of Membranes are Related to Flavor Production during Sake Brewing in the Yeast Saccharomyces cerevisiae
by Tsuyoshi Yoda and Tomoaki Saito
Membranes 2020, 10(12), 440; https://doi.org/10.3390/membranes10120440 - 18 Dec 2020
Cited by 12 | Viewed by 3238
Abstract
Ethyl caproate (EC) and isoamyl acetate (IA) are key flavor components of sake. Recently, attempts have been made to increase the content of good flavor components, such as EC and IA, in sake brewing. However, the functions of EC and IA in yeast [...] Read more.
Ethyl caproate (EC) and isoamyl acetate (IA) are key flavor components of sake. Recently, attempts have been made to increase the content of good flavor components, such as EC and IA, in sake brewing. However, the functions of EC and IA in yeast cells remain poorly understood. Therefore, we investigated the effects of EC and IA using cell-sized lipid vesicles. We also investigated lipid vesicles containing EC and/or caproic acid (CA) as well as IA and/or isoamyl alcohol (IAA). CA and IAA are precursors of EC and IA, respectively, and are important flavors in sake brewing. The size of a vesicle is influenced by flavor compounds and their precursors in a concentration-dependent manner. We aimed to establish the conditions in which the vesicles contained more flavors simultaneously and with different ratios. Interestingly, vesicles were largest in a mixture of 50% of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) with 25% EC and 25% CA or a mixture of 50% DOPC with 25% IA and 25% IAA. The impact of flavor additives on membrane fluidity was also studied using Laurdan generalized polarization. During the production process, flavors may regulate the fluidity of lipid membranes. Full article
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13 pages, 1969 KiB  
Communication
Palmitoylated mNeonGreen Protein as a Tool for Visualization and Uptake Studies of Extracellular Vesicles
by Magda Wąchalska, Michał Rychłowski, Kinga Grabowska, Kinga Kowal, Magdalena Narajczyk, Krystyna Bieńkowska-Szewczyk and Andrea D. Lipińska
Membranes 2020, 10(12), 373; https://doi.org/10.3390/membranes10120373 - 27 Nov 2020
Cited by 5 | Viewed by 3169
Abstract
Extracellular vesicles (EVs) are membranous nanoparticles released by cells as vital mediators of intercellular communication. As such, EVs have become an attractive target for pathogens and cancer cells, which can take control over their cargo composition, as well as their trafficking, shaping the [...] Read more.
Extracellular vesicles (EVs) are membranous nanoparticles released by cells as vital mediators of intercellular communication. As such, EVs have become an attractive target for pathogens and cancer cells, which can take control over their cargo composition, as well as their trafficking, shaping the pathogenesis. Despite almost four decades of research on EVs, the number of specific and efficient EV labeling methods is limited, and there is still no universal method for the visualization of their transport in living cells. Lipophilic dyes that non-specifically intercalate into the EVs membranes may diffuse to other membranes, leading to the misinterpretation of the results. Here, we propose a palmitoylated fluorescent mNeonGreen (palmNG) protein as an alternative to chemical dyes for EVs visualization. The Branchiostoma lanceolatum-derived mNeonGreen is a brighter, more stable, and less sensitive to laser-induced bleaching alternative to green fluorescent protein (GFP), which makes it a more potent tag in a variety of fluorescence-based techniques. A palmNG-expressing stable human melanoma cell line was generated using retrovirus gene transfer and cell sorting. This protein partially localizes to cellular membranes, and can be detected inside size-exclusion (SEC)-purified EVs. With the use of flow cytometry and fluorescent confocal microscopy, we performed qualitative and quantitative analyses of palmNG-EVs uptake in recipient human hepatoma cells, in comparison to PKH67-labeled vesicles. Our findings confirm that membrane-embedded mNeonGreen can be successfully applied as a tool in EVs transfer and uptake studies. Full article
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12 pages, 21554 KiB  
Article
Electrophysiology Measurements of Metal Transport by MntH2 from Enterococcus faecalis
by Matthias Gantner, Theodoros Laftsoglou, Honglin Rong, Vincent L. G. Postis and Lars J. C. Jeuken
Membranes 2020, 10(10), 255; https://doi.org/10.3390/membranes10100255 - 24 Sep 2020
Cited by 1 | Viewed by 2439
Abstract
Transition metals are essential trace elements and their high-affinity uptake is required for many organisms. Metal transporters are often characterised using metal-sensitive fluorescent dyes, limiting the metals and experimental conditions that can be studied. Here, we have tested whether metal transport by Enterococcus [...] Read more.
Transition metals are essential trace elements and their high-affinity uptake is required for many organisms. Metal transporters are often characterised using metal-sensitive fluorescent dyes, limiting the metals and experimental conditions that can be studied. Here, we have tested whether metal transport by Enterococcus faecalis MntH2 can be measured with an electrophysiology method that is based on the solid-supported membrane technology. E. faecalis MntH2 belongs to the Natural Resistance-Associated Macrophage Protein (Nramp) family of proton-coupled transporters, which transport divalent transition metals and do not transport the earth metals. Electrophysiology confirms transport of Mn(II), Co(II), Zn(II) and Cd(II) by MntH2. However, no uptake responses for Cu(II), Fe(II) and Ni(II) were observed, while the presence of these metals abolishes the uptake signals for Mn(II). Fluorescence assays confirm that Ni(II) is transported. The data are discussed with respect to properties and structures of Nramp-type family members and the ability of electrophysiology to measure charge transport and not directly substrate transport. Full article
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8 pages, 1381 KiB  
Brief Report
Implications for SARS-CoV-2 Vaccine Design: Fusion of Spike Glycoprotein Transmembrane Domain to Receptor-Binding Domain Induces Trimerization
by Taha Azad, Ragunath Singaravelu, Mathieu J.F. Crupi, Taylor Jamieson, Jaahnavi Dave, Emily E.F. Brown, Reza Rezaei, Zaid Taha, Stephen Boulton, Nikolas T. Martin, Abera Surendran, Joanna Poutou, Mina Ghahremani, Kazem Nouri, Jack T. Whelan, Jessie Duong, Sarah Tucker, Jean-Simon Diallo, John C. Bell and Carolina S. Ilkow
Membranes 2020, 10(9), 215; https://doi.org/10.3390/membranes10090215 - 30 Aug 2020
Cited by 16 | Viewed by 5303
Abstract
The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic presents an urgent need for an effective vaccine. Molecular characterization of SARS-CoV-2 is critical to the development of effective vaccine and therapeutic strategies. In the present study, we show that the fusion of [...] Read more.
The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic presents an urgent need for an effective vaccine. Molecular characterization of SARS-CoV-2 is critical to the development of effective vaccine and therapeutic strategies. In the present study, we show that the fusion of the SARS-CoV-2 spike protein receptor-binding domain to its transmembrane domain is sufficient to mediate trimerization. Our findings may have implications for vaccine development and therapeutic drug design strategies targeting spike trimerization. As global efforts for developing SARS-CoV-2 vaccines are rapidly underway, we believe this observation is an important consideration for identifying crucial epitopes of SARS-CoV-2. Full article
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12 pages, 1735 KiB  
Article
Antifungal Properties of Nerolidol-Containing Liposomes in Association with Fluconazole
by Camila Fonseca Bezerra, José Geraldo de Alencar Júnior, Rosilaine de Lima Honorato, Antonia Thassya Lucas dos Santos, Josefa Carolaine Pereira da Silva, Taís Gusmão da Silva, Antonio Linkoln Alves Borges Leal, Thiago Sampaio de Freitas, Thiago Adler Tavares Vieira, Janaína Esmeraldo Rocha, Débora Lima Sales, José Maria Barbosa Filho, Gabriela Ribeiro de Sousa, Allyson Pontes Pinheiro, Jaime Ribeiro-Filho, Henrique Douglas Melo Coutinho, Maria Flaviana Bezerra Morais-Braga and Teresinha Gonçalves da Silva
Membranes 2020, 10(9), 194; https://doi.org/10.3390/membranes10090194 - 20 Aug 2020
Cited by 7 | Viewed by 2462
Abstract
(1) Background: Infections by Candida species represent a serious threat to the health of immunocompromised individuals. Evidence has indicated that nerolidol has significant antifungal properties. Nonetheless, its use is restricted due to a low water solubility and high photosensitivity. The incorporation into liposomes [...] Read more.
(1) Background: Infections by Candida species represent a serious threat to the health of immunocompromised individuals. Evidence has indicated that nerolidol has significant antifungal properties. Nonetheless, its use is restricted due to a low water solubility and high photosensitivity. The incorporation into liposomes may represent an efficient alternative to improve the physicochemical and biopharmaceutical properties of this compound. The present study aimed to characterize the antifungal properties of liposomal nerolidol, alone or in combination with fluconazole. Of note, this is the first study reporting the antifungal activity of liposomal nerolidol and its potentiating effect in association with fluconazole. (2) Methods: The Inhibitory Concentration 50%-IC50 and minimum fungicide concentrations (MFC) of the substances against Candida albicans (CA), Candida tropicalis (CT), and Candida krusei (CK) were established by subculture in a solid medium. To evaluate the antifungal-enhancing effect, the MFC of fluconazole was determined in the presence or absence of subinhibitory concentrations of nerolidol (free or liposomal). The analysis of fungal dimorphism was performed through optical microscopy and the characterization of liposomes was carried out considering the vesicular size, polydispersion index, and zeta medium potential, in addition to a scanning electron microscopy analysis. (3) Results: The physicochemical characterization revealed that liposomes were obtained as homogenous populations of spherical vesicles. The data obtained in the present study indicate that nerolidol acts as an antifungal agent against Candida albicans and Candida tropicalis, in addition to potentiating (only in the liposomal form) the effect of fluconazole. However, the compound had little inhibitory effect on fungal dimorphism. (4) Conclusions: The incorporation of nerolidol into liposomes improved its antifungal-modulating properties. Full article
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9 pages, 940 KiB  
Communication
Cholera Toxin Subunit B for Sensitive and Rapid Determination of Exosomes by Gel Filtration
by Karolina Sapoń, Dominika Maziarz, Teresa Janas, Aleksander F. Sikorski and Tadeusz Janas
Membranes 2020, 10(8), 172; https://doi.org/10.3390/membranes10080172 - 31 Jul 2020
Cited by 7 | Viewed by 2826
Abstract
We developed a sensitive fluorescence-based assay for determination of exosome concentration. In our assay, Cholera toxin subunit B (CTB) conjugated to a fluorescence probe and a gel filtration technique (size-exclusion chromatography) are used. Exosomal membranes are particularly enriched in raft-forming lipids (cholesterol, sphingolipids, [...] Read more.
We developed a sensitive fluorescence-based assay for determination of exosome concentration. In our assay, Cholera toxin subunit B (CTB) conjugated to a fluorescence probe and a gel filtration technique (size-exclusion chromatography) are used. Exosomal membranes are particularly enriched in raft-forming lipids (cholesterol, sphingolipids, and saturated phospholipids) and in GM1 ganglioside. CTB binds specifically and with high affinity to exosomal GM1 ganglioside residing in rafts only, and it has long been the probe of choice for membrane rafts. The CTB-gel filtration assay allows for detection of as little as 3 × 108 isolated exosomes/mL in a standard fluorometer, which has a sensitivity comparable to other methods using advanced instrumentation. The linear quantitation range for CTB-gel filtration assay extends over one order of magnitude in exosome concentration. Using 80 nM fluorescence-labeled CTB, we quantitated 3 × 108 to 6 × 109 exosomes/mL. The assay ranges exhibited linear fluorescence increases versus exosome concentration (r2 = 0.987). The assay was verified for exosomal liposomes. The assay is easy to use, rapid, and does not require any expensive or sophisticated instrumentation. Full article
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