scholarly journals Escherichia coli response to subinhibitory concentration of Colistin: Insights from study of membrane dynamics and morphology.

2022 ◽  
Author(s):  
Ilanila Ilangumaran Ponmalar ◽  
Jitendriya Swain ◽  
Jaydeep Kumar Basu
Keyword(s):  
Bacterial Infections ◽  
Molecular Mechanisms ◽  
Lipid Membrane ◽  
Membrane Dynamics ◽  
Correlation Spectroscopy ◽  
Membrane Properties ◽  
Bacterial Response ◽  
Lipid Dynamics ◽  
The Impact ◽  
Altered Lipid

Prevalence of wide spread bacterial infections bring forth a critical need in understanding the molecular mechanisms of the antibiotics as well as the bacterial response to those antibiotics. Improper usage of antibiotics, which can be in sub-lethal concentrations is one among the multiple reasons for acquiring antibiotic resistance which makes it vital to understand the bacterial response towards sub-lethal concentrations of antibiotics. In this work, we have used colistin, a well-known membrane active antibiotic used to treat severe bacterial infections and explored the impact of its subminimum inhibitory concentration (MIC) on the lipid membrane dynamics and morphological changes of E. coli. Upon investigation of live cell membrane properties such as lipid dynamics using fluorescence correlation spectroscopy, we observed that colistin disrupts the lipid membrane at sub-MIC by altering the lipid diffusivity. Interestingly, filamentationlike cell elongation was observed upon colistin treatment which led to further exploration of surface morphology with the help of atomic force spectroscopy. The changes in the surface roughness upon colistin treatment provides additional insight on the colistin-membrane interaction corroborating with the altered lipid diffusion. Although altered lipid dynamics could be attributed to an outcome of lipid rearrangement due to direct disruption by antibiotic molecules on the membrane or an indirect consequence of disruptions in lipid biosynthetic pathways, we were able to ascertain that altered bacterial membrane dynamics is due to direct disruptions. Our results provide a broad overview on the consequence of the cyclic polypeptide, colistin on membrane specific lipid dynamics and morphology of a live Gram-negative bacterial cell.

scholarly journals Correlated protein conformational states and membrane dynamics during attack by pore-forming toxins

2019 ◽  
Vol 116 (26) ◽  
pp. 12839-12844 ◽  
Author(s):  
Ilanila I. Ponmalar ◽  
Ramesh Cheerla ◽  
K. Ganapathy Ayappa ◽  
Jaydeep K. Basu
Keyword(s):  
Conformational Changes ◽  
Pore Formation ◽  
Bacterial Infections ◽  
Cell Lysis ◽  
Membrane Dynamics ◽  
Correlation Spectroscopy ◽  
Listeriolysin O ◽  
Conformational States ◽  
Wide Range ◽  
Membrane Bound

Pore-forming toxins (PFTs) are a class of proteins implicated in a wide range of virulent bacterial infections and diseases. These toxins bind to target membranes and subsequently oligomerize to form functional pores that eventually lead to cell lysis. While the protein undergoes large conformational changes on the bilayer, the connection between intermediate oligomeric states and lipid reorganization during pore formation is largely unexplored. Cholesterol-dependent cytolysins (CDCs) are a subclass of PFTs widely implicated in food poisoning and other related infections. Using a prototypical CDC, listeriolysin O (LLO), we provide a microscopic connection between pore formation, lipid dynamics, and leakage kinetics by using a combination of Förster resonance energy transfer (FRET) and fluorescence correlation spectroscopy (FCS) measurements on single giant unilamellar vesicles (GUVs). Upon exposure to LLO, two distinct populations of GUVs with widely different leakage kinetics emerge. We attribute these differences to the existence of oligomeric intermediates, sampling various membrane-bound conformational states of the protein, and their intimate coupling to lipid rearrangement and dynamics. Molecular dynamics simulations capture the influence of various membrane-bound conformational states on the lipid and cholesterol dynamics, providing molecular interpretations to the FRET and FCS experiments. Our study establishes a microscopic connection between membrane binding and conformational changes and their influence on lipid reorganization during PFT-mediated cell lysis. Additionally, our study provides insights into membrane-mediated protein interactions widely implicated in cell signaling, fusion, folding, and other biomolecular processes.

scholarly journals Roughness of a transmembrane peptide reduces lipid membrane dynamics

2016 ◽  
Author(s):  
Marie Olšinová ◽  
Piotr Jurkiewicz ◽  
Jan Sýkora ◽  
Ján Sabó ◽  
Martin Hof ◽  
...  
Keyword(s):  
Rough Surface ◽  
Lipid Membrane ◽  
Cholesterol Content ◽  
Membrane Dynamics ◽  
Membrane Properties ◽  
Helical Structures ◽  
Transmembrane Peptides ◽  
Acyl Chains ◽  
Dynamics Simulations ◽  
And Function

Transmembrane domains integrate proteins into cellular membranes and support their function. The capacity of these prevalently a-helical structures in mammals to influence membrane properties is poorly understood. Combining experiments with molecular dynamics simulations, we provide evidence that helical transmembrane peptides with their rough surface reduce lateral mobility of membrane constituents. The molecular mechanism involves trapping of lipid acyl chains on the rough surface and segregation of cholesterol from the vicinity of peptides. The observations are supported by our toy model indicating strong effect of rough objects on membrane dynamics. Herein described effect has implications for the organization and function of biological membranes, especially the plasma membrane with high cholesterol content.

scholarly journals 1-Deoxysphingolipids Tempt Autophagy Resulting in Lysosomal Lipid Substrate Accumulation: Tracing the Impact of 1-Deoxysphingolipids on Ultra-Structural Level using a Novel Click-Chemistry Detection

2021 ◽  
Author(s):  
Christian Lamberz ◽  
Marina Hesse ◽  
Gregor Kirfel
Keyword(s):  
Energy Homeostasis ◽  
Lipid Membrane ◽  
Membrane Damage ◽  
Membrane Integrity ◽  
Membrane Dynamics ◽  
Autophagic Flux ◽  
Structural Level ◽  
Cellular Energy ◽  
The Impact ◽  
Lipid Substrate

SUMMARYSphingolipids (SLs) are pivotal components of biological membranes essentially contributing to their physiological functions. 1-deoxysphingolipids (deoxySLs), an atypical cytotoxic acting sub-class of SLs, is relevant for cellular energy homeostasis and is known to be connected to neurodegenerative disorders including diabetic neuropathy and hereditary sensory neuropathy type 1 (HSAN1). High levels of deoxySLs affect lipid membrane integrity in artificial liposomes. Accordingly, recent reports questioned the impact of deoxySLs on physiological lipid membrane and organelle functions leading to impaired cellular energy homeostasis.However, DeoxySL-related structural effects on cell membranes resulting in organelle dysfunction are still obscure. To illuminate disease-relevant sub-cellular targets of deoxySLs, we traced alkyne-containing 1-deoxysphinganine (alkyne-DOXSA) and resulting metabolites on ultra-structural level using a new labeling approach for electron microscopy (EM) termed “Golden-Click-Method” (GCM). To complement high-resolution analysis with membrane dynamics, selected intracellular compartments were traced using fluorescent live dyes.Our results conclusively linked accumulating cytotoxic deoxySLs with mitochondria and endoplasmic reticulum (ER) damage triggering Autophagy of mitochondria and membrane cisterna of the ER. The induced autophagic flux ultimately leads to accumulating deoxySL containing intra-lysosomal lipid crystals. Lysosomal lipid substrate accumulation impaired physiological lysosome functions and caused cellular starvation. Lysosomal exocytosis appeared as a mechanism for cellular clearance of cytotoxic deoxySLs. In sum, our data define new ultra-structural targets of deoxySLs and link membrane damage to autophagy and abnormal lysosomal lipid accumulation. These insights may support new conclusions about diabetes type 2 and HSNA1 related tissue damage.

scholarly journals Influenza A virus hemagglutinin prevents extensive membrane damage upon dehydration

2021 ◽  
Author(s):  
Maiara A. Iriarte-Alonso ◽  
Salvatore Chiantia ◽  
Alexander M. Bittner
Keyword(s):  
Relative Humidity ◽  
Influenza A ◽  
Molecular Mechanisms ◽  
Membrane Damage ◽  
Correlation Spectroscopy ◽  
Viral Envelope ◽  
Image Correlation ◽  
Membrane Properties ◽  
Virus Infectivity ◽  
Influenza A H1n1

While the molecular mechanisms of virus infectivity are rather well known, the detailed consequences of environmental factors on virus biophysical properties are poorly understood. 20 Seasonal influenza outbreaks are usually connected to the low winter temperature, but also to the low relative air humidity. Indeed, transmission rates increase in cold regions during winter. While low temperature must slow degradation processes, the role of low humidity is not clear. We studied the effect of relative humidity on a model of influenza A H1N1 virus envelope, a supported lipid bilayer containing the surface glycoprotein hemagglutinin (HA), which is 25 present in the viral envelope in very high density. For complete cycles of hydration, dehydration and rehydration, we evaluate the membrane properties in terms of structure and dynamics, which we assess by combining confocal fluorescence microscopy, raster image correlation spectroscopy, line-scan fluorescence correlation spectroscopy and atomic force microscopy. Our findings indicate that the presence of HA prevents macroscopic membrane 30 damage after dehydration. Without HA, fast membrane disruption is followed by irreversible loss of lipid and protein mobility. Although our model is principally limited by the membrane composition, the macroscopic effects of HA under dehydration stress reveal new insights on the stability of the virus at low relative humidity.

scholarly journals Complementary studies of lipid membrane dynamics using iSCAT and super-resolved fluorescence correlation spectroscopy

2018 ◽  
Vol 51 (23) ◽  
pp. 235401 ◽  
Author(s):  
Francesco Reina ◽  
Silvia Galiani ◽  
Dilip Shrestha ◽  
Erdinc Sezgin ◽  
Gabrielle de Wit ◽  
...  
Keyword(s):  
Fluorescence Correlation Spectroscopy ◽  
Lipid Membrane ◽  
Membrane Dynamics ◽  
Correlation Spectroscopy ◽  
Fluorescence Correlation

scholarly journals Visualizing the Role of Lipid Dynamics during Infrared Neural Stimulation with Hyperspectral Stimulated Raman Scattering Microscopy

2021 ◽  
Author(s):  
Wilson R Adams ◽  
Rekha Gautam ◽  
Andrea K Locke ◽  
Ana I Borrachero-Conejo ◽  
Bryan R Dollinger ◽  
...  
Keyword(s):  
Raman Scattering ◽  
High Speed ◽  
Lipid Membrane ◽  
Stimulated Raman Scattering ◽  
Membrane Dynamics ◽  
Neural Stimulation ◽  
Lipid Dynamics ◽  
Infrared Neural Stimulation ◽  
Stimulated Raman

Infrared neural stimulation, or INS, is a method of using pulsed infrared light to yield label-free neuronal stimulation with broad experimental and translational utility. Despite its robust demonstration, the mechanistic and biophysical underpinnings of INS have been the subject of debate for more than a decade. The role of lipid membrane thermodynamics appears to play an important role in how fast IR-mediated heating nonspecifically drives action potential generation. Direct observation of lipid membrane dynamics during INS remains to be shown in a live neural model system. To directly test the involvement of lipid dynamics in INS, we used hyperspectral stimulated Raman scattering (hsSRS) microscopy to study biochemical signatures of high speed vibrational dynamics underlying INS in a live neural cell culture model. Findings suggest that lipid bilayer structural changes are occurring during INS in vitro in NG108-15 neuroglioma cells. Lipid-specific signatures of cell SRS spectra were found to vary with stimulation energy and radiant exposure. Spectroscopic observations were verified against high-speed ratiometric fluorescence imaging of a conventional lipophilic membrane structure reporter, di-4-ANNEPS. Overall, the presented data supports the hypothesis that INS causes changes in the lipid membrane of neural cells by changing lipid membrane packing order - which coincides with likelihood of cell stimulation. Furthermore, this work highlights the potential of hsSRS as a method to study biophysical and biochemical dynamics safely in live cells.

The Impact of Ultraviolet Radiation on Barrier Function in Human Skin: Molecular Mechanisms and Topical Therapeutics

2019 ◽  
Vol 25 (40) ◽  
pp. 5503-5511 ◽  
Author(s):  
Abdulaziz Alhasaniah ◽  
Michael J. Sherratt ◽  
Catherine A. O'Neill
Keyword(s):  
Ultraviolet Radiation ◽  
Barrier Function ◽  
Molecular Mechanisms ◽  
Transepidermal Water Loss ◽  
Protective Effects ◽  
Barrier Dysfunction ◽  
Epidermal Barrier ◽  
Positive Effects ◽  
Terrestrial Mammals ◽  
The Impact

A competent epidermal barrier is crucial for terrestrial mammals. This barrier must keep in water and prevent entry of noxious stimuli. Most importantly, the epidermis must also be a barrier to ultraviolet radiation (UVR) from the sunlight. Currently, the effects of ultraviolet radiation on epidermal barrier function are poorly understood. However, studies in mice and more limited work in humans suggest that the epidermal barrier becomes more permeable, as measured by increased transepidermal water loss, in response UVR, at doses sufficiently high to induce erythema. The mechanisms may include disturbance in the organisation of lipids in the stratum corneum (the outermost layer of the epidermis) and reduction in tight junction function in the granular layer (the first living layer of the skin). By contrast, suberythemal doses of UVR appear to have positive effects on epidermal barrier function. Topical sunscreens have direct and indirect protective effects on the barrier through their ability to block UV and also due to their moisturising or occlusive effects, which trap water in the skin, respectively. Some topical agents such as specific botanical extracts have been shown to prevent the loss of water associated with high doses of UVR. In this review, we discuss the current literature and suggest that the biology of UVR-induced barrier dysfunction, and the use of topical products to protect the barrier, are areas worthy of further investigation.

The Role of Vascular Aging in Atherosclerotic Plaque Development and Vulnerability

2019 ◽  
Vol 25 (29) ◽  
pp. 3098-3111 ◽  
Author(s):  
Luca Liberale ◽  
Giovanni G. Camici
Keyword(s):  
Atherosclerotic Plaque ◽  
Molecular Mechanisms ◽  
Driving Forces ◽  
Plaque Burden ◽  
Vascular Aging ◽  
Age Related ◽  
Plaque Development ◽  
Increased Risk ◽  
The Impact ◽  
Over Time

Background: The ongoing demographical shift is leading to an unprecedented aging of the population. As a consequence, the prevalence of age-related diseases, such as atherosclerosis and its thrombotic complications is set to increase in the near future. Endothelial dysfunction and vascular stiffening characterize arterial aging and set the stage for the development of cardiovascular diseases. Atherosclerotic plaques evolve over time, the extent to which these changes might affect their stability and predispose to sudden complications remains to be determined. Recent advances in imaging technology will allow for longitudinal prospective studies following the progression of plaque burden aimed at better characterizing changes over time associated with plaque stability or rupture. Oxidative stress and inflammation, firmly established driving forces of age-related CV dysfunction, also play an important role in atherosclerotic plaque destabilization and rupture. Several genes involved in lifespan determination are known regulator of redox cellular balance and pre-clinical evidence underlines their pathophysiological roles in age-related cardiovascular dysfunction and atherosclerosis. Objective: The aim of this narrative review is to examine the impact of aging on arterial function and atherosclerotic plaque development. Furthermore, we report how molecular mechanisms of vascular aging might regulate age-related plaque modifications and how this may help to identify novel therapeutic targets to attenuate the increased risk of CV disease in elderly people.

VDAC1 Mediated Anticancer Activity of Gallic Acid in Human Lung Adenocarcinoma A549 Cells

2018 ◽  
Vol 18 (2) ◽  
pp. 255-262 ◽  
Author(s):  
Aikebaier Maimaiti ◽  
Amier Aili ◽  
Hureshitanmu Kuerban ◽  
Xuejun Li
Keyword(s):  
Western Blot ◽  
Cell Viability ◽  
Gallic Acid ◽  
Molecular Mechanisms ◽  
A549 Cells ◽  
Dependent Manner ◽  
Lung Carcinoma Cells ◽  
Induced Apoptosis ◽  
The Impact

Aims: Gallic acid (GA) is generally distributed in a variety of plants and foods, and possesses cell growth-inhibiting activities in cancer cell lines. In the present study, the impact of GA on cell viability, apoptosis induction and possible molecular mechanisms in cultured A549 lung carcinoma cells was investigated. Methods: In vitro experiments showed that treating A549 cells with various concentrations of GA inhibited cell viability and induced apoptosis in a dose-dependent manner. In order to understand the mechanism by which GA inhibits cell viability, comparative proteomic analysis was applied. The changed proteins were identified by Western blot and siRNA methods. Results: Two-dimensional electrophoresis revealed changes that occurred to the cells when treated with or without GA. Four up-regulated protein spots were clearly identified as malate dehydrogenase (MDH), voltagedependent, anion-selective channel protein 1(VDAC1), calreticulin (CRT) and brain acid soluble protein 1(BASP1). VDAC1 in A549 cells was reconfirmed by western blot. Transfection with VDAC1 siRNA significantly increased cell viability after the treatment of GA. Further investigation showed that GA down regulated PI3K/Akt signaling pathways. These data strongly suggest that up-regulation of VDAC1 by GA may play an important role in GA-induced, inhibitory effects on A549 cell viability.

scholarly journals SARS-CoV-2 and the Nervous System: From Clinical Features to Molecular Mechanisms

2020 ◽  
Vol 21 (15) ◽  
pp. 5475 ◽  
Author(s):  
Manuela Pennisi ◽  
Giuseppe Lanza ◽  
Luca Falzone ◽  
Francesco Fisicaro ◽  
Raffaele Ferri ◽  
...  
Keyword(s):  
Nervous System ◽  
Molecular Mechanisms ◽  
Neuronal Damage ◽  
Neurological Complications ◽  
Neurological Manifestations ◽  
Wide Range ◽  
Inflammatory State ◽  
Acute Polyneuropathy ◽  
The Central Nervous System ◽  
The Impact

Increasing evidence suggests that Severe Acute Respiratory Syndrome-coronavirus-2 (SARS-CoV-2) can also invade the central nervous system (CNS). However, findings available on its neurological manifestations and their pathogenic mechanisms have not yet been systematically addressed. A literature search on neurological complications reported in patients with COVID-19 until June 2020 produced a total of 23 studies. Overall, these papers report that patients may exhibit a wide range of neurological manifestations, including encephalopathy, encephalitis, seizures, cerebrovascular events, acute polyneuropathy, headache, hypogeusia, and hyposmia, as well as some non-specific symptoms. Whether these features can be an indirect and unspecific consequence of the pulmonary disease or a generalized inflammatory state on the CNS remains to be determined; also, they may rather reflect direct SARS-CoV-2-related neuronal damage. Hematogenous versus transsynaptic propagation, the role of the angiotensin II converting enzyme receptor-2, the spread across the blood-brain barrier, the impact of the hyperimmune response (the so-called “cytokine storm”), and the possibility of virus persistence within some CNS resident cells are still debated. The different levels and severity of neurotropism and neurovirulence in patients with COVID-19 might be explained by a combination of viral and host factors and by their interaction.

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