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1.
Methods Mol Biol ; 2543: 35-44, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36087257

RESUMO

The frequency of apoptotic cells in a given phenotypically defined population is usually calculated the apoptotic index (AI), i.e., the percentage of apoptotic cells displaying a specific linage antigen (LAg) within a population of cells that remain unfragmented and retain the expression of the LAg. However, this approach has two major limitations. Firstly, apoptotic cells fragment into apoptotic bodies that later disintegrate. Secondly, apoptotic cells frequently lose, partially or even completely, the cell surface expression of the LAg used for the identification of specific cell subsets. The present chapter will describe a flow cytometry method to calculate the apoptotic rate (AR) that takes into account both cell fragmentation and loss of lineage antigen expression on measurement of apoptosis using flow cytometry ratiometric cell enumeration that emerges as a more accurate method of measurement of the occurrence of apoptosis in normal and tumoral cell cultures.


Assuntos
Apoptose , Neoplasias , Membrana Celular , Citometria de Fluxo/métodos
2.
Microb Cell Fact ; 21(1): 192, 2022 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-36109736

RESUMO

BACKGROUND: Replacement of radioligand binding assays with antibody-antigen interaction-based approaches for quantitative analysis of G protein-coupled receptor (GPCR) levels requires the use of purified protein standards containing the antigen. GPCRs in general and cannabinoid CB1 receptor in particular show a progressive tendency to aggregate and precipitate in aqueous solution outside of their biological context due to the low solubility that the hydrophobic nature imprinted by their seven transmembrane domains. This renders full-length recombinant GPCRs useless for analytical purposes, a problem that can be overcome by engineering soluble recombinant fragments of the receptor containing the antigen. RESULTS: Here we generated highly soluble and stable recombinant protein constructs GST-CB1414-472 and GST-CB1414-442 containing much of the human CB1 receptor C-terminal tail for use as standard and negative control, respectively, in quantitative Western blot analysis of CB1 receptor expression on crude synaptosomes of the adult rat brain cortex. To this end we used three different antibodies, all raised against a peptide comprising the C-terminal residues 443-473 of the mouse CB1 receptor that corresponds to residues 442-472 in the human homolog. Estimated values of CB1 receptor density obtained by quantitative Western blot were of the same order of magnitude but slightly higher than values obtained by the radioligand saturation binding assay. CONCLUSIONS: Collectively, here we provide a suitable Western blot-based design as a simple, cost-effective and radioactivity-free alternative for the quantitative analysis of CB1 receptor expression, and potentially of any GPCR, in a variety of biological samples. The discrepancies between the results obtained by quantitative Western blot and radioligand saturation binding techniques are discussed in the context of their particular theoretical bases and methodological constraints.


Assuntos
Canabinoides , Adulto , Animais , Western Blotting , Canabinoides/química , Membrana Celular , Humanos , Camundongos , Ratos , Receptores de Canabinoides , Proteínas Recombinantes
3.
J Zhejiang Univ Sci B ; 23(9): 770-777, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36111573

RESUMO

Malignant tumors pose a serious threat to human health but during the past decade, great progress has been made in the treatment of tumors. The tumor-cell membrane is well constructed and can be used to solve problems in tumor therapy. Tumor-cell membranes exhibit not only high biocompatibility due to their homology but also enhanced therapeutic effects when combined with nanotechnology. Meanwhile, nanomaterials show high selectivity, sensitivity, and clinical transformation potential. Enhanced immunotherapy or tumor vaccines have potential clinical application because of tumor-membrane surface-specific antigens. Several studies have confirmed the feasibility and advantages of using tumor-cell membrane-incorporated nanosystems for tumor therapy. Considering all this, we focus in this review on the application of tumor-cell-membrane bionic platforms and, in the summary, provide ideas for new scientific developments.


Assuntos
Vacinas Anticâncer , Neoplasias , Biônica , Membrana Celular , Humanos , Imunoterapia , Neoplasias/terapia
4.
Biochem J ; 479(17): 1825-1842, 2022 09 16.
Artigo em Inglês | MEDLINE | ID: mdl-36094371

RESUMO

Cell stiffness is an important characteristic of cells and their response to external stimuli. In this review, we survey methods used to measure cell stiffness, summarize stimuli that alter cell stiffness, and discuss signaling pathways and mechanisms that control cell stiffness. Several pathological states are characterized by changes in cell stiffness, suggesting this property can serve as a potential diagnostic marker or therapeutic target. Therefore, we consider the effect of cell stiffness on signaling and growth processes required for homeostasis and dysfunction in healthy and pathological states. Specifically, the composition and structure of the cell membrane and cytoskeleton are major determinants of cell stiffness, and studies have identified signaling pathways that affect cytoskeletal dynamics both directly and by altered gene expression. We present the results of studies interrogating the effects of biophysical and biochemical stimuli on the cytoskeleton and other cellular components and how these factors determine the stiffness of both individual cells and multicellular structures. Overall, these studies represent an intersection of the fields of polymer physics, protein biochemistry, and mechanics, and identify specific mechanisms involved in mediating cell stiffness that can serve as therapeutic targets.


Assuntos
Citoesqueleto , Transdução de Sinais , Membrana Celular , Citoesqueleto/metabolismo , Microtúbulos
5.
J Cell Biol ; 221(10)2022 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-36108241

RESUMO

The endoplasmic reticulum (ER), which occupies a large portion of the cytoplasm, is the cell's main site for the biosynthesis of lipids and carbohydrate conjugates, and it is essential for folding, assembly, and biosynthetic transport of secreted proteins and integral membrane proteins. The discovery of abundant membrane contact sites (MCSs) between the ER and other membrane compartments has revealed that, in addition to its biosynthetic and secretory functions, the ER plays key roles in the regulation of organelle dynamics and functions. In this review, we will discuss how the ER regulates endosomes, lysosomes, autophagosomes, mitochondria, peroxisomes, and the Golgi apparatus via MCSs. Such regulation occurs via lipid and Ca2+ transfer and also via control of in trans dephosphorylation reactions and organelle motility, positioning, fusion, and fission. The diverse controls of other organelles via MCSs manifest the ER as master regulator of organelle biology.


Assuntos
Membrana Celular , Retículo Endoplasmático , Cálcio/metabolismo , Carboidratos/biossíntese , Membrana Celular/metabolismo , Retículo Endoplasmático/metabolismo , Lipídeos/biossíntese , Proteínas de Membrana/metabolismo , Organelas
6.
Front Immunol ; 13: 973601, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36105816

RESUMO

Background: As the forefront of nanomedicine, bionic nanotechnology has been widely used for drug delivery in order to obtain better efficacy but less toxicity for cancer treatments. With the rise of immunotherapy, the combination of nanotechnology and immunotherapy will play a greater potential of anti-tumor therapy. Due to its advantage of homologous targeting and antigen library from source cells, cancer cell membrane (CCM)-wrapped nanoparticles (CCNPs) has become an emerging topic in the field of immunotherapy. Key scientific concepts of review: CCNP strategies include targeting or modulating the tumor immune microenvironment and combination therapy with immune checkpoint inhibitors and cancer vaccines. This review summarizes the current developments in CCNPs for cancer immunotherapy and provides insight into the challenges of transferring this technology from the laboratory to the clinic as well as the potential future of this technology. Conclusion: This review described CCNPs have enormous potential in cancer immunotherapy, but there are still challenges in terms of translating their effects in vitro to the clinical setting. We believe that these challenges can be addressed in the future with a focus on individualized treatment with CCNPs as well as CCNPs combined with other effective treatments.


Assuntos
Vacinas Anticâncer , Nanopartículas , Neoplasias , Vacinas Anticâncer/uso terapêutico , Membrana Celular , Humanos , Fatores Imunológicos , Imunoterapia , Microambiente Tumoral
7.
Front Endocrinol (Lausanne) ; 13: 934685, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36093106

RESUMO

G protein-coupled receptors (GPCRs) are plasma membrane proteins associated with an array of functions. Mutations in these receptors lead to a number of genetic diseases, including diseases involving the endocrine system. A particular subset of loss-of-function mutant GPCRs are misfolded receptors unable to traffic to their site of function (i.e. the cell surface plasma membrane). Endocrine disorders in humans caused by GPCR misfolding include, among others, hypo- and hyper-gonadotropic hypogonadism, morbid obesity, familial hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism, X-linked nephrogenic diabetes insipidus, congenital hypothyroidism, and familial glucocorticoid resistance. Several in vitro and in vivo experimental approaches have been employed to restore function of some misfolded GPCRs linked to endocrine disfunction. The most promising approach is by employing pharmacological chaperones or pharmacoperones, which assist abnormally and incompletely folded proteins to refold correctly and adopt a more stable configuration to pass the scrutiny of the cell's quality control system, thereby correcting misrouting. This review covers the most important aspects that regulate folding and traffic of newly synthesized proteins, as well as the experimental approaches targeted to overcome protein misfolding, with special focus on GPCRs involved in endocrine diseases.


Assuntos
Doenças do Sistema Endócrino , Dobramento de Proteína , Membrana Celular/metabolismo , Doenças do Sistema Endócrino/metabolismo , Doenças do Sistema Endócrino/terapia , Humanos , Recém-Nascido , Mutação , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismo
9.
Cell Rep ; 40(11): 111343, 2022 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-36103816

RESUMO

Cell-surface ancillary glycoproteins basigin or embigin form heterodimeric complexes with proton-coupled monocarboxylate transporters (MCTs), facilitating the membrane trafficking of MCTs and regulating their transport activities. Here, we determine the cryoelectron microscopy (cryo-EM) structure of the human MCT1-embigin complex and observe that embigin forms extensive interactions with MCT1 to facilitate its localization to the plasma membrane. In addition, the formation of the heterodimer effectively blocks MCT1 from forming a homodimer through a steric hindrance effect, releasing the coupling between two signature motifs and driving a significant conformation change in transmembrane helix 5 (TM5) of MCTs. Consequently, the substrate-binding pocket alternates between states of homodimeric coupling and heterodimeric decoupling states and exhibits differences in substrate-binding affinity, supporting the hypothesis that the substrate-induced motion originating in one subunit of the MCT dimer could be transmitted to the adjacent subunit to alter its substrate-binding affinity.


Assuntos
Transportadores de Ácidos Monocarboxílicos , Simportadores , Membrana Celular/metabolismo , Microscopia Crioeletrônica , Humanos , Glicoproteínas de Membrana/metabolismo , Transportadores de Ácidos Monocarboxílicos/metabolismo , Simportadores/metabolismo
10.
Sci Signal ; 15(751): eabm2449, 2022 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-36099341

RESUMO

Intestinal epithelial cells absorb nutrients through the brush border, composed of dense arrays of highly ordered microvilli at their apical membranes. A protocadherin-based intermicrovillar adhesion complex localized at microvilli tips mediates microvilli packing and organization. Here, we identified a second adhesion complex localized at the proximal base region of microvilli. This complex contained the immunoglobulin superfamily member TMIGD1, which directly interacted with the microvillar scaffolding proteins EBP50 and E3KARP. Complex formation with EBP50 required the activation of EBP50 by the actin-binding protein ezrin and was enhanced by the dephosphorylation of Ser162 in the PDZ2 domain of EBP50 by the phosphatase PP1α. Binding of the EBP50-ezrin complex to TMIGD1 enhanced the dynamic turnover of EBP50 at microvilli. Enterocyte-specific inactivation of Tmigd1 in mice resulted in microvillar blebbing, loss of intermicrovillar adhesion, and perturbed brush border formation. Thus, we identified a second adhesion complex in microvilli and propose a mechanism that promotes microvillar formation and dynamics.


Assuntos
Células Epiteliais , Intestinos , Animais , Membrana Celular/metabolismo , Células Epiteliais/metabolismo , Camundongos , Proteínas dos Microfilamentos/genética , Proteínas dos Microfilamentos/metabolismo , Microvilosidades/metabolismo
11.
Methods Appl Fluoresc ; 10(4)2022 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-36067776

RESUMO

Eisosomes are nanoscale plasma membrane domains shaped as furrow-like invaginations. InSaccharomyces cerevisiaethese relatively immobile and uniform structures are mainly composed of two cytoplasmic proteins Pil1 and Lsp1. The present work uses fluctuation of fluorescence signals and analytical methods to determine Pil1 and Lsp1 dynamics at different subcellular locations. Using scanning techniques and autocorrelation analysis we determine that the cytoplasmic pools of Pil1 and Lsp1 behave mainly by passive diffusion. Single-point FCS experiments performed at several subcellular locations reveal that Pil1 mobility is faster in daughter cells. Furthermore, pair correlation function analysis indicates a rapid dynamic of Pil1 near the plasma membrane of growing yeast buds, where the membrane is expected to be actively assembling eisosomes.


Assuntos
Proteínas de Saccharomyces cerevisiae , Membrana Celular/metabolismo , Feminino , Humanos , Mães , Fosfoproteínas/química , Fosfoproteínas/metabolismo , Saccharomyces cerevisiae , Proteínas de Saccharomyces cerevisiae/química , Proteínas de Saccharomyces cerevisiae/metabolismo
12.
Int J Mol Sci ; 23(17)2022 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-36077010

RESUMO

Cystic fibrosis (CF) is caused by mutations in the gene encoding of the cystic fibrosis transmembrane conductance regulator (CFTR), an anion-selective plasma membrane channel that mainly regulates chloride transport in a variety of epithelia. More than 2000 mutations, most of which presumed to be disease-relevant, have been identified in the CFTR gene. The single CFTR mutation F508del (deletion of phenylalanine in position 508) is present in about 90% of global CF patients in at least one allele. F508del is responsible for the defective folding and processing of CFTR, failing to traffic to the plasma membrane and undergoing premature degradation via the ubiquitin-proteasome system. CFTR is subjected to different post-translational modifications (PTMs), and the possibility to modulate these PTMs has been suggested as a potential therapeutic strategy for the functional recovery of the disease-associated mutants. Recently, the PTM mapping of CFTR has identified some lysine residues that may undergo methylation or ubiquitination, suggesting a competition between these two PTMs. Our work hypothesis moves from the idea that favors methylation over ubiquitination, e.g., inhibiting demethylation could be a successful strategy for preventing the premature degradation of unstable CFTR mutants. Here, by using a siRNA library against all the human demethylases, we identified the enzymes whose downregulation increases F508del-CFTR stability and channel function. Our results show that KDM2A and KDM3B downregulation increases the stability of F508del-CFTR and boosts the functional rescue of the channel induced by CFTR correctors.


Assuntos
Fibrose Cística , Proteínas F-Box , Membrana Celular/metabolismo , Fibrose Cística/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Proteínas F-Box/genética , Humanos , Transporte de Íons , Histona Desmetilases com o Domínio Jumonji/metabolismo , Mutação
13.
Int J Mol Sci ; 23(17)2022 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-36077373

RESUMO

Opportunistic pathogen Candida albicans causes systemic infections named candidiasis. Due to the increasing number of multi-drug resistant clinical isolates of Candida sp., currently employed antifungals (e.g., azoles) are insufficient for combating fungal infection. One of the resistance mechanisms toward azoles is increased expression of plasma membrane (PM) transporters (e.g., Cdr1p), and such an effect was observed in C. albicans clinical isolates. At the same time, it has been proven that a decrease in PMs sphingolipids (SLs) content correlates with altered sensitivity to azoles and diminished Cdr1p levels. This indicates an important role for SL in maintaining the properties of PM and gaining resistance to antifungal agents. Here, we prove using a novel spot variation fluorescence correlation spectroscopy (svFCS) technique that CaCdr1p localizes in detergent resistant microdomains (DRMs). Immunoblot analysis confirmed the localization of CaCdr1p in DRMs fraction in both the C. albicans WT and erg11Δ/Δ strains after 14 and 24 h of culture. We also show that the C. albicanserg11Δ/Δ strain is more sensitive to the inhibitor of SLs synthesis; aureobasidin A (AbA). AbA treatment leads to a diminished amount of SLs in C. albicans WT and erg11Δ/Δ PM, while, for C. albicanserg11Δ/Δ, the general levels of mannose-inositol-P-ceramide and inositol-P-ceramide are significantly lower than for the C. albicans WT strain. Simultaneously, the level of ergosterol in the C. albicans WT strain after adding of AbA remains unchanged, compared to the control conditions. Analysis of PM permeabilization revealed that treatment with AbA correlates with the disruption of PM integrity in C. albicanserg11Δ/Δ but not in the C. albicans WT strain. Additionally, in the C. albicans WT strain, we observed lower activity of H+-ATPase, correlated with the delocalization of both CaCdr1p and CaPma1p.


Assuntos
Candida albicans , Ergosterol , Adenosina Trifosfatases/metabolismo , Antifúngicos/metabolismo , Antifúngicos/farmacologia , Azóis/farmacologia , Membrana Celular/metabolismo , Ceramidas/metabolismo , Farmacorresistência Fúngica , Ergosterol/metabolismo , Proteínas Fúngicas/metabolismo , Inositol/farmacologia , Proteínas de Membrana Transportadoras/metabolismo , Testes de Sensibilidade Microbiana , Esfingolipídeos/metabolismo
14.
J Nanobiotechnology ; 20(1): 401, 2022 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-36064356

RESUMO

BACKGROUND: Cancer cell membrane-camouflaged nanotechnology for metal complex can enhance its biocompatibility and extend the effective circulation time in body. The ruthenium polypyridyl complex (RuPOP) has extensive antitumor activity, but it still has disadvantages such as poor biocompatibility, lack of targeting, and being easily metabolized by the organism. Cancer cell membranes retain a large number of surface antigens and tumor adhesion molecules CD47, which can be used to camouflage the metal complex and give it tumor homing ability and high biocompatibility. RESULTS: Therefore, this study provides an electrostatic adsorption method, which uses the electrostatic interaction of positive and negative charges between RuPOP and cell membranes to construct a cancer cell membrane-camouflaged nano-platform (RuPOP@CM). Interestingly, RuPOP@CM maintains the expression of surface antigens and tumor adhesion molecules, which can inhibit the phagocytosis of macrophage, reduce the clearance rate of RuPOP, and increase effective circulation time, thus enhancing the accumulation in tumor sites. Besides, RuPOP@CM can enhance the activity of cellular immune response and promote the production of inflammatory cytokines including TNF-α, IL-12 and IL-6, which is of great significance in treatment of tumor. On the other hand, RuPOP@MCM can produce intracellular ROS overproduction, thereby accelerating the apoptosis and cell cycle arrest of tumor cells to play an excellent antitumor effect in vitro and in vivo. CONCLUSION: In brief, engineering cancer cell membrane-camouflaged metal complex is a potential strategy to improve its biocompatibility, biological safety and antitumor effects.


Assuntos
Neoplasias da Mama , Rutênio , Antígenos de Superfície/metabolismo , Apoptose , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/metabolismo , Membrana Celular/metabolismo , Feminino , Humanos
15.
Annu Int Conf IEEE Eng Med Biol Soc ; 2022: 4723-4726, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-36086609

RESUMO

This study is based on the quantification of the influence of the presence of gold nanoparticles (Au NPs), of their geometry and their distance from cell membrane during time-varying electromagnetic fields cell membrane permeabilization on the pores opening dynamics. Results showed that the combined use of Au NPs and time-varying magnetic field can improve significantly the permeabilization of cell membrane. The presence of Au NPs allowed to reach transmembrane potential values enabling the cell membrane permeabilization only when placed at very short distance, equal to 20 nm. Both geometry and variability of the positioning in proximity of the cell membrane showed a strong influence on the probability of enabling pores opening. Clinical Relevance- This study provides a better comprehension about the mechanisms, still not completely understood, underlying cell membrane permeabilization by combining Au NPs and time-varying magnetic fields.


Assuntos
Ouro , Nanopartículas Metálicas , Membrana Celular , Campos Eletromagnéticos
16.
Phys Rev Lett ; 129(8): 088101, 2022 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-36053696

RESUMO

Self-organized patterns in the actin cytoskeleton are essential for eukaryotic cellular life. They are the building blocks of many functional structures that often operate simultaneously to facilitate, for example, nutrient uptake and movement of cells. However, identifying how qualitatively distinct actin patterns can coexist remains a challenge. Using bifurcation theory of a mass conserved activator-inhibitor system, we uncover a generic mechanism of how different actin waves-traveling waves and excitable pulses-organize and simultaneously emerge. Live-cell imaging experiments indeed reveal that narrow, planar, and fast-moving excitable pulses may coexist with ring-shaped macropinocytic actin waves in the cortex of motile amoeboid cells.


Assuntos
Actinas , Dictyostelium , Citoesqueleto de Actina , Membrana Celular , Movimento
17.
Methods Cell Biol ; 172: 37-50, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36064225

RESUMO

Lipid peroxidation occurs under conditions where reactive oxygen species (ROS) readily react with vulnerable lipids on cell membranes. Polyunsaturated fatty acids (PUFAs) are highly susceptible to lipid peroxidation because of their unstable double bonds. Because the cell membrane is particularly rich in PUFAs, it is often the site at which many lipid peroxidation chain reactions occur. Lipid peroxidation is considered the ultimate trigger of ferroptosis, an iron-dependent form of non-apoptotic cell death. Radiotherapy is a common cancer treatment that uses high-energy ionizing radiation to kill cancer cells, and radiation-induced cell death is partially attributed to lipid peroxidation-driven ferroptosis. Here, we describe methods to assess lipid peroxidation in irradiated cells. The same techniques can be applied to a variety of lipid peroxidation measurements under different treatment conditions.


Assuntos
Ferro , Morte Celular/fisiologia , Membrana Celular/metabolismo , Ferro/metabolismo , Peroxidação de Lipídeos/fisiologia , Espécies Reativas de Oxigênio/metabolismo
18.
Anal Chim Acta ; 1226: 340263, 2022 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-36068062

RESUMO

The upregulation of glucose transporter (GLUT) is a typical pathological marker in numerous cancer types and a potential target for anti-cancer drug therapy. We developed a cell membrane-based glucose sensor for real-time monitoring of GLUT transport kinetics. By combining hydrogel layers and liposomes, a planar cell membrane was constructed over the electrode, preventing pore leakage and allowing for highly sensitive and selective measurements. Based on this continuous monitoring technique, we investigated the effect of GLUT1-specific inhibitors such as Cytorelaxation B and BAY-876. We also measured the affinity of different hexoses to GLUT1 using a normalized response time comparison based on the cell membrane sensor. Experimental results were consistent with the molecular docking simulation, indicating that the sensor can be adapted to measure the glucose transport kinetics in different pharmacological conditions. This work demonstrated that cell membrane transport channels could maintain their transmembrane function in-vitro, and it has potential application in evaluating drug-receptor interaction.


Assuntos
Proteínas Facilitadoras de Transporte de Glucose , Proteínas de Transporte de Monossacarídeos , Transporte Biológico , Membrana Celular/metabolismo , Glucose/metabolismo , Proteínas Facilitadoras de Transporte de Glucose/metabolismo , Transportador de Glucose Tipo 1/metabolismo , Cinética , Simulação de Acoplamento Molecular
19.
Eur Phys J E Soft Matter ; 45(9): 79, 2022 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-36125628

RESUMO

Experiments show that elastic constants of lipid bilayers vary greatly during the liquid-to-gel phase transition. This fact forms the cornerstone of the Heimburg-Jackson model of soliton propagation along membranes of axons, in which the action potential is accompanied by a traveling phase transition. However, the dispersion term, which is crucial for the existence of solitons, is added to the Heimburg-Jackson model ad hoc and set to fit experimental observations. In the present paper, we aim to consolidate this view with continuous membrane mechanics. Using literature data, we show that the compression modulus of a DPPC membrane is smaller by approximately an order of magnitude during phase transition. With a series expansion of the compression modulus, we write the action of a membrane and solve the corresponding wave equation analytically using an Exp-function method. We confirm that membrane solitons with speeds around 200 m/s are possible with amplitudes inversely proportional to their speed. We conclude that dispersion necessary for existence of solitons is directly related to a membrane's bending properties, offering a possible explanation for h. Our findings are in general agreement with existing literature and give insight into a general mechanism of wave propagation in membranes close to transition.


Assuntos
Bicamadas Lipídicas , Membrana Celular , Pressão
20.
Methods Mol Biol ; 2522: 435-448, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36125769

RESUMO

Membrane vesicles (MVs), also described as extracellular vesicles (EVs), exosomes, or outer membrane vesicles (OMVs), are nano-sized (10-300 nm) spherical, membrane-bound structures deriving from the cell envelope. MVs have been studied extensively in both eukaryotic and prokaryotic systems, revealing a plethora of unique functions including cell-to-cell communication and protection of the cell. They are able to encapsulate specific cargos from nucleic acids to proteins, thereby concentrating cargo and providing protection from the extracellular environment. While MV production has been identified for all domains of life, with extensive investigation particularly for Bacteria and Eukaryota, it has only been studied in a few members of the archaeal domain, leaving a void of information concerning the role of MVs for the majority of Archaea. In addition, several discrepancies exist in the process of MV preparation and analysis between studies of MV production in different archaeal organisms. To further encourage the investigation of MVs in Archaea among the scientific community, we present a standardized method for the isolation, purification, and characterization of MVs based on the archaeal model organism, Haloferax volcanii. However, the described protocol can be applied to other Archaea with the appropriate modifications that are highlighted in Subheading 4.


Assuntos
Haloferax volcanii , Ácidos Nucleicos , Bactérias , Membrana Celular/metabolismo , Eucariotos , Ácidos Nucleicos/metabolismo
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