RESUMEN
In food industry, Listeria monocytogenes contamination can occur accidentally despite the quality control of raw materials and factory. Decontamination processes or inhibitory effects of ingredients/additives in food products are set up to ensure compliance with hygiene and microbiological criteria. These actions represent stresses for the pathogenic agent, causing fluctuations in its physiological states. Moreover, during these environmental stresses, Listeria monocytogenes can enter in a viable but nonculturable (VBNC) state which is not detected by plate counting but by flow cytometry. This technique coupled with cell staining by fluorescent dyes offers the possibility to assess different physiological states based on different cellular parameters: enzymatic activity, transmembrane integrity, membrane potential, and respiratory activity. In this chapter, we present a method to assess the viability of foodborne pathogens using a double-staining principle based on the assessment of membrane integrity and intracellular esterase activity.
Asunto(s)
Citometría de Flujo , Listeria monocytogenes , Viabilidad Microbiana , Listeria monocytogenes/crecimiento & desarrollo , Listeria monocytogenes/fisiología , Citometría de Flujo/métodos , Microbiología de Alimentos/métodos , Colorantes Fluorescentes/química , Coloración y Etiquetado/métodos , Membrana Celular/metabolismoRESUMEN
When submitted to environmental stresses, bacteria can modulate its fatty acid composition of membrane phospholipids in order to optimize membrane fluidity. Characterization of bacterial membrane fatty acid profiles is thus an interesting indicator of cellular physiological state. The methodology described here aims to improve the recovering of biofilm cells for the characterization of their fatty acid profiles. The saponification reagent is directly applied on the whole biofilm before the removal of cells from the inert surface. In this way, maximum of the cells and their fatty acids can be recovered from the deepest layers of the biofilm.
Asunto(s)
Biopelículas , Membrana Celular , Ácidos Grasos , Biopelículas/crecimiento & desarrollo , Ácidos Grasos/metabolismo , Membrana Celular/metabolismo , Bacterias/metabolismo , Fosfolípidos/metabolismo , Fluidez de la MembranaRESUMEN
Polypyrimidine tract-binding protein 1 (PTBP1) regulates numerous alternative splicing events during tumor progression and neurogenesis. Previously, PTBP1 downregulation was reported to convert astrocytes into functional neurons; however, how PTBP1 regulates astrocytic physiology remains unclear. In this study, we revealed that PTBP1 modulated glutamate uptake via ATP1a2, a member of Na+/K+-ATPases, and glutamate transporters in astrocytes. Ptbp1 knockdown altered mitochondrial function and energy metabolism, which involved PTBP1 regulating mitochondrial redox homeostasis via the succinate dehydrogenase (SDH)/Nrf2 pathway. The malfunction of glutamate transporters following Ptbp1 knockdown resulted in enhanced excitatory synaptic transmission in the cortex. Notably, we developed a biomimetic cationic triblock polypeptide system, i.e., polyethylene glycol44-polylysine30-polyleucine10 (PEG44-PLL30-PLLeu10) with astrocytic membrane coating to deliver Ptbp1 siRNA in vitro and in vivo, which approach allowed Ptbp1 siRNA to efficiently cross the blood-brain barrier and target astrocytes in the brain. Collectively, our findings suggest a framework whereby PTBP1 serves as a modulator in glutamate transport machinery, and indicate that biomimetic methodology is a promising route for in vivo siRNA delivery.
Asunto(s)
Astrocitos , Ácido Glutámico , Ribonucleoproteínas Nucleares Heterogéneas , Homeostasis , Factor 2 Relacionado con NF-E2 , Proteína de Unión al Tracto de Polipirimidina , ARN Interferente Pequeño , Animales , Astrocitos/metabolismo , Ácido Glutámico/metabolismo , Proteína de Unión al Tracto de Polipirimidina/metabolismo , Proteína de Unión al Tracto de Polipirimidina/genética , Factor 2 Relacionado con NF-E2/metabolismo , Ribonucleoproteínas Nucleares Heterogéneas/metabolismo , Ribonucleoproteínas Nucleares Heterogéneas/genética , Ratones , Transducción de Señal , Membrana Celular/metabolismo , Ratones Endogámicos C57BL , Masculino , Humanos , Mitocondrias/metabolismoRESUMEN
Trogocytosis is the intercellular transfer of membrane and membrane-associated proteins between cells. Trogocytosis is an underappreciated phenomenon that has historically routinely been dismissed as an artefact. With a greater understanding of the process and the implications it has on biological systems, trogocytosis has the potential to become a paradigm changer. The presence on a cell of molecules they don't endogenously express can alter the biological activity of the cell and could also lead to the acquisition of new functions. To better appreciate this phenomenon, it is important to understand how these intercellular membrane exchanges influence the function and activity of the donor and the recipient cells. In this chapter, we will examine how the molecules acquired by trogocytosis influence the biology of a variety of systems including mammalian fertilization, treatment of hemolytic disease of the newborn, viral and parasitic infections, cancer immunotherapy, and immune modulation.
Asunto(s)
Membrana Celular , Humanos , Animales , Membrana Celular/metabolismoRESUMEN
Neurons establish functional connections responsible for how we perceive and react to the world around us. Communication from a neuron to its target cell occurs through a long projection called an axon. Axon distances can exceed 1 m in length in humans and require a dynamic microtubule cytoskeleton for growth during development and maintenance in adulthood. Stathmins are microtubule-associated proteins that function as relays between kinase signaling and microtubule polymerization. In this review, we describe the prolific role of Stathmins in microtubule homeostasis with an emphasis on emerging roles for Stathmin-2 (Stmn2) in axon integrity and neurodegeneration. Stmn2 levels are altered in Amyotrophic Lateral Sclerosis and loss of Stmn2 provokes motor and sensory neuropathies. There is growing potential for employing Stmn2 as a disease biomarker or even a therapeutic target. Meeting this potential requires a mechanistic understanding of emerging complexity in Stmn2 function. In particular, Stmn2 palmitoylation has a surprising contribution to axon maintenance through undefined mechanisms linking membrane association, tubulin interaction, and axon transport. Exploring these connections will reveal new insight on neuronal cell biology and novel opportunities for disease intervention.
Asunto(s)
Axones , Microtúbulos , Estatmina , Estatmina/metabolismo , Microtúbulos/metabolismo , Humanos , Axones/metabolismo , Axones/fisiología , Animales , Membrana Celular/metabolismo , Esclerosis Amiotrófica Lateral/metabolismo , Esclerosis Amiotrófica Lateral/patologíaRESUMEN
G protein-coupled receptors' conformational landscape can be affected by their local, microscopic interactions within the cell plasma membrane. We employ here a pleiotropic stimulus, namely osmotic swelling, to alter the cortical environment within intact cells and monitor the response in terms of receptor function and downstream signaling. We observe that in osmotically swollen cells the ß2-adrenergic receptor, a prototypical GPCR, favors an active conformation, resulting in cAMP transient responses to adrenergic stimulation that have increased amplitude. The results are validated in primary cell types such as adult cardiomyocytes, a model system where swelling occurs upon ischemia-reperfusion injury. Our results suggest that receptors' function is finely modulated by their biophysical context, and specifically that osmotic swelling acts as a potentiator of downstream signaling, not only for the ß2-adrenergic receptor, but also for other receptors, hinting at a more general regulatory mechanism.
Asunto(s)
AMP Cíclico , Miocitos Cardíacos , Receptores Adrenérgicos beta 2 , Transducción de Señal , Receptores Adrenérgicos beta 2/metabolismo , Miocitos Cardíacos/metabolismo , Humanos , Animales , Ligandos , AMP Cíclico/metabolismo , Membrana Celular/metabolismo , Células HEK293 , RatonesRESUMEN
Delivering foreign molecules and genetic material into cells is a crucial process in life sciences and biotechnology, resulting in great interest in effective cell transfection methods. Importantly, physical transfection methods allow delivery of molecules of different chemical composition and are, thus, very flexible. Here, we investigated the influence of microwave radiation on the transfection and survival of mammalian cells. We made use of an optimized microwave-poration device and analyzed its performance (frequency and electric field strength) in comparison with simulations. We, then, tested the effect of microwave irradiation on cells and found that 18 GHz had the least impact on cell survival, viability, cell division and genotoxicity while 10 GHz drastically impacted cell physiology. Using live-cell fluorescence microscopy and image analysis, we tested the uptake of small chemical substances, which was most efficient at 18 GHz and correlated with electric field strength and frequency. Finally, we were able to obtain cellular uptake of molecules of very different chemical composition and sizes up to whole immunoglobulin antibodies. In conclusion, microwave-induced poration enables the uptake of widely different substances directly into mammalian cells growing as adherent cultures and with low physiological impact.
Asunto(s)
Membrana Celular , Supervivencia Celular , Microondas , Membrana Celular/metabolismo , Animales , Humanos , Transfección , Células CHO , CricetulusRESUMEN
Intercellular protein-protein interactions (PPIs) have pivotal roles in biological functions and diseases. Membrane proteins are therefore a major class of drug targets. However, studying such intercellular PPIs is challenging because of the properties of membrane proteins. Current methods commonly use purified or modified proteins that are not physiologically relevant and hence might mischaracterize interactions occurring in vivo. Here, we describe Cell-Int: a cell interaction assay for studying plasma membrane PPIs. The interaction signal is measured through conjugate formation between two populations of cells each expressing either a ligand or a receptor. In these settings, membrane proteins are in their native environment thus being physiologically relevant. Cell-Int has been applied to the study of diverse protein partners, and enables to investigate the inhibitory potential of blocking antibodies, as well as the retargeting of fusion proteins for therapeutic development. The assay was also validated for screening applications and could serve as a platform for identifying new protein interactors.
Asunto(s)
Comunicación Celular , Membrana Celular , Proteínas de la Membrana , Unión Proteica , Mapeo de Interacción de Proteínas , Humanos , Proteínas de la Membrana/metabolismo , Mapeo de Interacción de Proteínas/métodos , Membrana Celular/metabolismo , Animales , Células HEK293 , Bioensayo/métodosRESUMEN
Singlet oxygen is considered an important cell damaging agent due to its propensity to react with organic compounds. This drives the interest in developing methods for determination of 1O2. Simplicity of application and high sensitivity makes fluorescent probes a popular choice for in vivo 1O2 detection. Despite its proclaimed cell-impermeability, the commercially available Singlet Oxygen Sensor Green (SOSG) is widely applied to support assertions of 1O2 involvement in cell and tissue damage. Our investigation, however, demonstrate that different microbial species and cancer cells become fluorescent when exposed to SOSG under conditions which exclude generation of 1O2. Cells, permeabilized with chlorhexidine or by heat exposure under anaerobic conditions, exhibited SOSG fluorescence. Permeabilized cells could be stained with SOSG even 24 h post-permeabilization. Since SOSG is cell impermeable, the main factor that led to fluorescent staining was plasma membrane damage. Spectral analyses of different batches of SOSG revealed that SOSG endoperoxide (SOSG-EP) did not increase even after prolonged storage under the recommended conditions. The commercial preparations of SOSG, however, were not SOSG-EP free, which can produce erroneous results when SOSG staining is used as a proof of singlet oxygen production in vivo.
Asunto(s)
Colorantes Fluorescentes , Oxígeno Singlete , Oxígeno Singlete/metabolismo , Humanos , Colorantes Fluorescentes/química , Coloración y Etiquetado/métodos , Membrana Celular/metabolismoRESUMEN
Striking morphological transformations characterize the invasion of a red blood cell by the malaria parasite. Shortly after the infection, parasite-induced membranes appear in the cytosol of the affected host erythrocyte. One intensely investigated membrane type, commonly called Maurer's clefts, has a slit-like morphology and can be arranged in the form of extended three-dimensional membrane stacks or networks. Here we report the three-dimensional reconstruction of a second membrane type, giant or extended membrane rings/loops, that have only occasionally been described on single ultrathin sections, however that have never been systematically examined so far. Serial ultrathin sectioning of P. falciparum-infected red blood cells, subsequent three-dimensional reconstructions, and in addition examination of Giemsa-stained blood films revealed that intraerythrocytic membrane rings/loops are not isolated structures but are locally in contact with the parasite. They consist either of the parasitophorous vacuolar membrane alone or contain the parasitophorous vacuolar membrane including the plasma membrane of the parasite and small amounts of parasite cytoplasm. We demonstrate that membrane rings/loops represent surface extensions of the parasite that maybe involved in ring stage parasite formation and Maurer's cleft generation at least in a subset of infected red blood cells.
Asunto(s)
Citosol , Eritrocitos , Plasmodium falciparum , Eritrocitos/parasitología , Plasmodium falciparum/fisiología , Citosol/parasitología , Citosol/química , Humanos , Membrana Eritrocítica/parasitología , Membrana Eritrocítica/ultraestructura , Malaria Falciparum/parasitología , Imagenología Tridimensional , Membrana Celular/parasitologíaRESUMEN
Microtubule-based vesicle trafficking usually relies upon kinesin and dynein motors and few reports describe microtubule polymerisation driving directional vesicle trafficking. Here we show that Arabidopsis END BINDING1b (EB1b), a microtubule plus-end binding protein, directly interacts with SYP121, a SNARE protein that mediates the trafficking of the K+ channel KAT1 and its distribution to the plasma membrane (PM) in Arabidopsis guard cells. Knockout of AtEB1b and its homologous proteins results in a modest but significant change in the distribution of KAT1 and SYP121 in guard cells and consequently delays light-induced stomatal opening. Live-cell imaging reveals that a portion of SYP121-associated endomembrane compartments co-localise with AtEB1b at the growing ends of microtubules, trafficking along with the growth of microtubules for targeting to the PM. Our study reveals a mechanism of vesicle trafficking driven by microtubule growth, which is involved in the redistribution of PM proteins to modulate guard cell movement.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Membrana Celular , Proteínas Asociadas a Microtúbulos , Microtúbulos , Estomas de Plantas , Arabidopsis/metabolismo , Arabidopsis/genética , Arabidopsis/fisiología , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Microtúbulos/metabolismo , Estomas de Plantas/metabolismo , Estomas de Plantas/fisiología , Membrana Celular/metabolismo , Proteínas Asociadas a Microtúbulos/metabolismo , Proteínas Asociadas a Microtúbulos/genética , Transporte de Proteínas , Katanina/metabolismo , Katanina/genética , Movimiento Celular , Proteínas de Ciclo CelularRESUMEN
Purpose: Ischemic stroke is a refractory disease wherein the reperfusion injury caused by sudden restoration of blood supply is the main cause of increased mortality and disability. However, current therapeutic strategies for the inflammatory response induced by cerebral ischemia-reperfusion (I/R) injury are unsatisfactory. This study aimed to develop a functional nanoparticle (MM/ANPs) comprising apelin-13 (APNs) encapsulated in macrophage membranes (MM) modified with distearoyl phosphatidylethanolamine-polyethylene glycol-RVG29 (DSPE-PEG-RVG29) to achieve targeted therapy against ischemic stroke. Methods: MM were extracted from RAW264.7. PLGA was dissolved in dichloromethane, while Apelin-13 was dissolved in water, and CY5.5 was dissolved in dichloromethane. The precipitate was washed twice with ultrapure water and then resuspended in 10 mL to obtain an aqueous solution of PLGA nanoparticles. Subsequently, the cell membrane was evenly dispersed homogeneously and mixed with PLGA-COOH at a mass ratio of 1:1 for the hybrid ultrasound. DSPE-PEG-RVG29 was added and incubated for 1 h to obtain MM/ANPs. Results: In this study, we developed a functional nanoparticle delivery system (MM/ANPs) that utilizes macrophage membranes coated with DSPE-PEG-RVG29 peptide to efficiently deliver Apelin-13 to inflammatory areas using ischemic stroke therapy. MM/ANPs effectively cross the blood-brain barrier and selectively accumulate in ischemic and inflamed areas. In a mouse I/R injury model, these nanoparticles significantly improved neurological scores and reduced infarct volume. Apelin-13 is gradually released from the MM/ANPs, inhibiting NLRP3 inflammasome assembly by enhancing sirtuin 3 (SIRT3) activity, which suppresses the inflammatory response and pyroptosis. The positive regulation of SIRT3 further inhibits the NLRP3-mediated inflammation, showing the clinical potential of these nanoparticles for ischemic stroke treatment. The biocompatibility and safety of MM/ANPs were confirmed through in vitro cytotoxicity tests, blood-brain barrier permeability tests, biosafety evaluations, and blood compatibility studies. Conclusion: MM/ANPs offer a highly promising approach to achieve ischemic stroke-targeted therapy inhibiting NLRP3 inflammasome-mediated pyroptosis.
Asunto(s)
Inflamasomas , Accidente Cerebrovascular Isquémico , Macrófagos , Proteína con Dominio Pirina 3 de la Familia NLR , Nanopartículas , Piroptosis , Animales , Ratones , Accidente Cerebrovascular Isquémico/tratamiento farmacológico , Células RAW 264.7 , Piroptosis/efectos de los fármacos , Nanopartículas/química , Proteína con Dominio Pirina 3 de la Familia NLR/metabolismo , Macrófagos/efectos de los fármacos , Macrófagos/metabolismo , Inflamasomas/metabolismo , Inflamasomas/efectos de los fármacos , Masculino , Péptidos y Proteínas de Señalización Intercelular/farmacología , Péptidos y Proteínas de Señalización Intercelular/química , Polietilenglicoles/química , Ratones Endogámicos C57BL , Daño por Reperfusión/tratamiento farmacológico , Fosfatidiletanolaminas/química , Membrana Celular/efectos de los fármacos , Membrana Celular/metabolismoRESUMEN
Rationale: An impairment of plasma membrane repair has been implicated in various diseases such as muscular dystrophy and ischemia/reperfusion injury. MOTS-c, a short peptide encoded by mitochondria, has been shown to pass through the plasma membrane into the bloodstream. This study determined whether this biological behavior was involved in membrane repair and its underlying mechanism. Methods and Results: In human participants, the level of MOTS-c was positively correlated with the abundance of mitochondria, and the membrane repair molecule TRIM72. In contrast to high-intensity eccentric exercise, moderate-intensity exercise improved sarcolemma integrity and physical performance, accompanied by an increase of mitochondria beneath the damaged sarcolemma and secretion of MOTS-c. Furthermore, moderate-intensity exercise increased the interaction between MOTS-c and TRIM72, and MOTS-c facilitated the trafficking of TRIM72 to the sarcolemma. In vitro studies demonstrated that MOTS-c attenuated membrane damage induced by hypotonic solution, which could be blocked by siRNA-TRIM72, but not AMPK inhibitor. Co-immunoprecipitation study showed that MOTS-c interacted with TRIM72 C-terminus, but not N-terminus. The dynamic membrane repair assay revealed that MOTS-c boosted the trafficking of TRIM72 to the injured membrane. However, MOTS-c itself had negligible effects on membrane repair, which was recapitulated in TRIM72-/- mice. Unexpectedly, MOTS-c still increased the fusion of vesicles with the membrane in TRIM72-/- mice, and dot blot analysis revealed an interaction between MOTS-c and phosphatidylinositol (4,5) bisphosphate [PtdIns (4,5) P2]. Finally, MOTS-c blunted ischemia/reperfusion-induced membrane disruption, and preserved heart function. Conclusions: MOTS-c/TRIM72-mediated membrane integrity improvement participates in mitochondria-triggered membrane repair. An interaction between MOTS-c and plasma lipid contributes to the fusion of vesicles with membrane. Our data provide a novel therapeutic strategy for rescuing organ function by facilitating membrane repair with MOTS-c.
Asunto(s)
Membrana Celular , Mitocondrias , Sarcolema , Animales , Humanos , Ratones , Membrana Celular/metabolismo , Masculino , Mitocondrias/metabolismo , Sarcolema/metabolismo , Transporte de Proteínas , Proteínas Mitocondriales/metabolismo , Proteínas de Motivos Tripartitos/metabolismo , Proteínas de Motivos Tripartitos/genética , Ratones Endogámicos C57BL , Músculo Esquelético/metabolismo , Adulto , Ejercicio Físico/fisiología , Ratones Noqueados , Femenino , Proteínas Portadoras/metabolismo , Proteínas de la MembranaRESUMEN
Helicobacter pylori is a bacterial pathogen that colonizes the human stomach, where it can cause a variety of diseases. H. pylori uses a cluster of sheathed flagella for motility, which is required for host colonization in animal models. The flagellar sheath is continuous with the outer membrane and is found in most Helicobacter species identified to date. HP0018 is a predicted lipoprotein of unknown function that is conserved in Helicobacter species that have flagellar sheaths but is absent in Helicobacter species that have sheath-less flagella. Deletion of hp0018 in H. pylori B128 resulted in the formation of long chains of outer membrane vesicles, which were most evident in an aflagellated variant of the Δhp0018 mutant that had a frameshift mutation in fliP. Flagellated cells of the Δhp0018 mutant possessed what appeared to be a normal flagellar sheath, suggesting that HP0018 is not required for sheath formation. Cells of the Δhp0018 mutant were also less helical in shape compared to wild-type cells. A HP0018-superfolder green fluorescent fusion protein expressed in the H. pylori Δhp0018 mutant formed fluorescent foci at the cell poles and lateral sites. Co-immunoprecipitation assays with HP0018 identified two enzymes involved in the modification of the cell wall peptidoglycan, AmiA and MltD, as potential HP0018 interaction partners. HP0018 may modulate the activity of AmiA or MltD, and in the absence of HP0018, the unregulated activity of these enzymes may alter the peptidoglycan layer in a manner that results in an altered cell shape and hypervesiculation.
Asunto(s)
Flagelos , Helicobacter pylori , Helicobacter pylori/genética , Helicobacter pylori/metabolismo , Helicobacter pylori/fisiología , Flagelos/metabolismo , Membrana Celular/metabolismo , Proteínas Bacterianas/metabolismo , Proteínas Bacterianas/genética , Humanos , Lipoproteínas/metabolismo , Lipoproteínas/genéticaRESUMEN
Rap2b, a proto-oncogene upregulated in colorectal cancer (CRC), undergoes protein S-palmitoylation at specific C-terminus sites (C176/C177). These palmitoylation sites are crucial for Rap2b localization on the plasma membrane (PM), as mutation of C176 or C177 results in cytosolic relocation of Rap2b. Our study demonstrates that Rap2b influences cell migration and invasion in CRC cells, independent of proliferation, and this activity relies on its palmitoylation. We identify ABHD17a as the depalmitoylating enzyme for Rap2b, altering PM localization and inhibiting cell migration and invasion. EGFR/PI3K signaling regulates Rap2b palmitoylation, with PI3K phosphorylating ABHD17a to modulate its activity. These findings highlight the potential of targeting Rap2b palmitoylation as an intervention strategy. Blocking the C176/C177 sites using an interacting peptide attenuates Rap2b palmitoylation, disrupting PM localization, and suppressing CRC metastasis. This study offers insights into therapeutic approaches targeting Rap2b palmitoylation for the treatment of metastatic CRC, presenting opportunities to improve patient outcomes.
Asunto(s)
Membrana Celular , Movimiento Celular , Neoplasias Colorrectales , Lipoilación , Proto-Oncogenes Mas , Proteínas de Unión al GTP rap , Humanos , Neoplasias Colorrectales/patología , Neoplasias Colorrectales/metabolismo , Neoplasias Colorrectales/genética , Proteínas de Unión al GTP rap/metabolismo , Proteínas de Unión al GTP rap/genética , Membrana Celular/metabolismo , Animales , Línea Celular Tumoral , Metástasis de la Neoplasia , Transducción de Señal , Ratones , Ratones Desnudos , Fosfatidilinositol 3-Quinasas/metabolismo , Receptores ErbB/metabolismo , Proliferación CelularRESUMEN
Intracellular delivery of large molecule cargo via cell penetrating peptides (CPPs) is an inefficient process and despite intense efforts in past decades, improvements in efficiency have been marginal. Utilizing a standardized and comparative analysis of the delivery efficiency of previously described cationic, anionic, and amphiphilic CPPs, we demonstrate that the delivery ceiling is accompanied by irreparable plasma membrane damage that is part of the uptake mechanism. As a consequence, intracellular delivery correlates with cell toxicity and is more efficient for smaller peptides than for large molecule cargo. The delivery of pharmaceutically relevant cargo quantities with acceptable toxicity thus seems hard to achieve with the CPPs tested in our study. Our results suggest that any engineered intracellular delivery system based on conventional cationic or amphiphilic CPPs, or the design principles underlying them, needs to accept low delivery yields due to toxicity limiting efficient cytoplasmic uptake. Novel peptide designs based on detailed study of uptake mechanisms are required to overcome these limitations.
Asunto(s)
Membrana Celular , Péptidos de Penetración Celular , Citoplasma , Péptidos de Penetración Celular/química , Péptidos de Penetración Celular/metabolismo , Membrana Celular/metabolismo , Humanos , Citoplasma/metabolismo , Sistemas de Liberación de Medicamentos , Células HeLa , AnimalesRESUMEN
-Action potential (AP) of excitable plant cells is an important signaling event that can differentially alter physicochemical and physiological processes in various parts of the same cell. In giant cells of characean algae, the AP propagation has minor effect on photosynthetic electron transport in areas with high activity of plasmalemmal H+-pump but inhibits linear electron flow in regions featuring high passive H+/OH- conductance of the plasma membrane (PM). Uneven spatial distributions of local periplasmic and cytoplasmic pH facilitate the operation of distinct (CO2-dependent and O2-mediated) pathways of photoinduced electron flow, which presumably accounts for differential influence of AP on photosynthesis. The excitation of Chara australis cell in the presence of methyl viologen (MV), a redox mediator with the prooxidant action, provides a convenient model system to clarify the influence of voltage-dependent ion fluxes across PM on photosynthetic activity of chloroplasts. This study shows that permeation of MV to their target sites in chloroplasts is restricted by PM in resting cells, but MV easily passes through ionic channels opened during the PM depolarization. This gated permeation of MV gives rise to strong non-photochemical quenching, decrease in the effective quantum yield of linear electron flow, apparent O2 uptake, and, finally, the enhanced ROS production, as detected by the fluorescent probe dichlorofluorescein. Taken together, the results indicate that the AP generation in the presence of MV acts as trigger for instant redirection of photosynthetic linear electron flow from CO2-dependent route to the path of O2 reduction with the eventual formation of H2O2 as a dominant and most stable ROS form.
Asunto(s)
Membrana Celular , Chara , Oxígeno , Paraquat , Fotosíntesis , Fotosíntesis/efectos de los fármacos , Transporte de Electrón/efectos de los fármacos , Paraquat/farmacología , Membrana Celular/metabolismo , Oxígeno/metabolismo , Chara/metabolismo , Chara/efectos de los fármacos , Oxidación-Reducción , Cloroplastos/metabolismoRESUMEN
An important functionality of lifelike "synthetic cells" is to mimic cell division. Currently, specialized proteins that induce membrane fission in living cells are the primary candidates for dividing synthetic cells. However, interactions between lipid membranes and proteins that are not found in living cells may also be suitable. Here, we discuss the potential of short membrane-anchored peptides to induce cell division. Specifically, we used the coarse-grained MARTINI model to investigate the interaction between short membrane-anchored peptides and a lipid bilayer patch. The simulation revealed that the anchored peptide induces significant spontaneous curvature and suggests that the lipid-peptide complex can be considered as a conically shaped "bulky headgroup" lipid. By systematically increasing the electrostatic charge of the peptide, we find that membrane-anchored peptides may generate sufficiently large constriction forces even at dilute coverages. Finally, we show that when the peptide has an opposite charge to the membrane, the peptide may induce division by binding the inner membrane leaflet of a synthetic cell, that is, cell division from within.
Asunto(s)
Membrana Dobles de Lípidos , Simulación de Dinámica Molecular , Péptidos , Membrana Dobles de Lípidos/química , Membrana Dobles de Lípidos/metabolismo , Péptidos/química , Péptidos/metabolismo , División Celular/efectos de los fármacos , Membrana Celular/química , Membrana Celular/metabolismo , Electricidad EstáticaRESUMEN
Natural products containing the carboxy-2H-azirine moiety are an exciting target for investigation due to their broad-spectrum antimicrobial activity and new chemical space they afford for novel therapeutic development. The carboxy-2H-azirine moiety, including those appended to well-characterized chemical scaffolds, is understudied, which creates a challenge for understanding potential modes of inhibition. In particular, some known natural product carboxy-2H-azirines have long hydrophobic tails, which could implicate them in membrane-associated processes. In this study, we examined a small set of carboxy-2H-azirine natural products with varied structural features that could alter membrane partitioning. We compared the predicted membrane partitioning and alignment of these compounds to those of established membrane embedders with similar chemical scaffolds. To accomplish this, we developed parameters within the framework of the CHARMM36 force field for the 2H-azirine functional group and performed metadynamics simulations of the partitioning into a model bacterial membrane from aqueous solution. We determined that the carboxy-2H-azirine functional group is strongly hydrophilic, imbuing the long-chain natural products with amphipathicity similar to the known membrane-embedding molecules to which they were compared. For the long-chain analogs, the carboxy-2H-azirine head group stays within 1 nm of the phosphate layer, while the hydrophobic tail sits within the membrane. The carboxy-2H-azirine lacking the long alkyl chain instead partitions completely into aqueous solution.
Asunto(s)
Azirinas , Productos Biológicos , Simulación de Dinámica Molecular , Productos Biológicos/química , Productos Biológicos/farmacología , Azirinas/química , Interacciones Hidrofóbicas e Hidrofílicas , Membrana Celular/química , Termodinámica , Estructura MolecularRESUMEN
Accurate and rapid imaging of tumor cells is of vital importance for early cancer diagnosis and intervention. Aptamer-based fluorescence sensors have become a potent instrument for bioimaging, while false positives and on-target off-tumors linked to single-biomarker aptasensors compromise the specificity and sensitivity of cancer imaging. In this paper, we describe a sequential response aptasensor for precise cancer cell identification that is based on a DNA "AND" logic gate. Specifically, the sensor consists of three single-stranded DNA, including the P-strand that can sensitively respond to an acid environment, the L-strand containing the ATP aptamer sequence, and the R-strand for target cell anchoring. These DNA strands hybridize with one another to create a Y-shaped structure (named Y-ALGN). The aptamer in the R-strand is utilized to anchor the sensor to the target cell membrane primarily. Responding to the extracellular acidic environment of the tumor (input 1), the I-motif sequence forms a tetramer structure so that the P-strand is released from the Y-shaped structure and exposes the ATP binding sites in the L-strand. Extracellular ATP, as input 2, continuously operates the DNA aptasensor to complete the logic computation. Upon the sequential response of both protons and ATP molecules, the aptasensor is activated with restored fluorescence on a particular cancer cell membrane. Benefiting from the precise computation capacity of the "AND" logic gate, the Y-ALGN aptasensor can distinguish between MCF-7 cells and normal cells with high accuracy. As a simple and dual-stimuli-responsive strategy, this nanodevice would offer a fresh approach for accurately diagnosing tumor cells.