Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 78.597
Filtrar
1.
J Theor Biol ; 556: 111310, 2023 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-36279959

RESUMO

Midbrain dopamine (DA) neurons exhibit spiking and bursting patterns under physiological conditions. Based on the data on electrophysiological recordings, Yu et al. developed a 13-dimensional mathematical model to capture the detailed characteristics of the DA neuronal firing activities. We use the fitting method to simplify the original model into a 4-dimensional model. Then, the spiking-to-bursting transition is detected from a simple and robust mathematical condition. Physiologically, this condition is a balance of the restorative and the regenerative ion channels at resting potential. Geometrically, this condition imposes a transcritical bifurcation. Moreover, we combine singularity theory and singular perturbation methods to capture the geometry of three-timescale firing attractors in a universal unfolding of a cusp singularity. In particular, the planar description of the corresponding firing patterns can generate the corresponding firing attractors. This analysis provides a new idea for understanding the firing activities of the DA neuron and the specific mechanisms for the switching and dynamic regulation among different patterns.


Assuntos
Dopamina , Mesencéfalo , Potenciais de Ação/fisiologia , Mesencéfalo/fisiologia , Neurônios Dopaminérgicos/fisiologia , Potenciais da Membrana
2.
Artigo em Inglês | MEDLINE | ID: mdl-36306997

RESUMO

The resting membrane potential of most cells is maintained by potassium K2p channels. The pharmacological profile and distribution of various K2p channel subtypes in organisms are still being investigated. The Drosophila genome contains 11 subtypes; however, their function and expression profiles have not yet been determined. Doxapram is clinically used to enhance respiration in humans and blocks the acid-sensitive K2p TASK subtype in mammals. The resting membrane potential of larval Drosophila muscle and synaptic transmission at the neuromuscular junction are pH sensitive. The present study investigated the effects of doxapram on membrane potential and synaptic transmission using intracellular recordings of larval Drosophila muscles. Doxapram (1 mM and 10 mM) depolarizes the muscle and appears to depolarize motor neurons, causing an increase in the frequency of spontaneous quantal events and evoked excitatory junction potentials. Verapamil (1 and 10 mM) paralleled the action of doxapram. These changes were matched by an extracellular increase in KCl (50 mM) and blocked by Cd2+. It is assumed that the motor nerve depolarizes to open voltage-gated Ca2+ channels in presynaptic nerve terminals because of exposure to doxapram. These findings are significant for building models to better understand the function of pharmacological agents that affect K2p channels and how K2p channels contribute to the physiology of tissues. Drosophila offers a genetically amenable model that can alter the tissue-specific expression of K2p channel subtypes to simulate known human diseases related to this family of channels.


Assuntos
Doxapram , Drosophila , Animais , Humanos , Potenciais da Membrana , Drosophila/metabolismo , Doxapram/metabolismo , Doxapram/farmacologia , Junção Neuromuscular , Transmissão Sináptica , Canais de Potássio/metabolismo , Mamíferos/metabolismo
3.
Curr Top Membr ; 90: 123-139, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36368871

RESUMO

Vascular smooth muscle cells express several isoforms of a number of classes of K+ channels. Potassium channels play critical roles in the regulation of vascular smooth muscle contraction as well as vascular smooth muscle cell proliferation or phenotypic modulation. There is ample evidence that it is Ca2+ that enables these two seemingly disparate functions to be tightly coupled both in healthy and disease processes. Because of the central position that potassium channels have in vasocontraction, vasorelaxation, membrane potential, and smooth muscle cell proliferation, these channels continue to possess the potential to serve as novel therapeutic targets in cardiovascular disease. While there are questions that remain regarding the complete interactions between K+ channels, vascular regulation, smooth muscle cell proliferation, and phenotypic modulation in physiological and pathophysiological conditions, a broad understanding of the contributions of each class of K+ channel to contractile and proliferative states of the vasculature has been reached. This brief review will discuss the current understanding of the role of K+ channels in vascular smooth muscle cells in health and disease using the porcine vascular smooth muscle cell model with particular attention to new scientific discoveries contributed by the authors regarding the effect of endurance exercise on the function of the K+ channels.


Assuntos
Aterosclerose , Músculo Liso Vascular , Suínos , Animais , Músculo Liso Vascular/fisiologia , Canais de Potássio/metabolismo , Potenciais da Membrana , Contração Muscular , Aterosclerose/metabolismo
4.
Commun Biol ; 5(1): 1178, 2022 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-36369329

RESUMO

Cancer cells feature a resting membrane potential (Vm) that is depolarized compared to normal cells, and express active ionic conductances, which factor directly in their pathophysiological behavior. Despite similarities to 'excitable' tissues, relatively little is known about cancer cell Vm dynamics. Here high-throughput, cellular-resolution Vm imaging reveals that Vm fluctuates dynamically in several breast cancer cell lines compared to non-cancerous MCF-10A cells. We characterize Vm fluctuations of hundreds of human triple-negative breast cancer MDA-MB-231 cells. By quantifying their Dynamic Electrical Signatures (DESs) through an unsupervised machine-learning protocol, we identify four classes ranging from "noisy" to "blinking/waving". The Vm of MDA-MB-231 cells exhibits spontaneous, transient hyperpolarizations inhibited by the voltage-gated sodium channel blocker tetrodotoxin, and by calcium-activated potassium channel inhibitors apamin and iberiotoxin. The Vm of MCF-10A cells is comparatively static, but fluctuations increase following treatment with transforming growth factor-ß1, a canonical inducer of the epithelial-to-mesenchymal transition. These data suggest that the ability to generate Vm fluctuations may be a property of hybrid epithelial-mesenchymal cells or those originated from luminal progenitors.


Assuntos
Transição Epitelial-Mesenquimal , Neoplasias de Mama Triplo Negativas , Humanos , Linhagem Celular Tumoral , Células MCF-7 , Potenciais da Membrana
5.
Nat Commun ; 13(1): 6681, 2022 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-36335122

RESUMO

Transitioning from pluripotency to differentiated cell fates is fundamental to both embryonic development and adult tissue homeostasis. Improving our understanding of this transition would facilitate our ability to manipulate pluripotent cells into tissues for therapeutic use. Here, we show that membrane voltage (Vm) regulates the exit from pluripotency and the onset of germ layer differentiation in the embryo, a process that affects both gastrulation and left-right patterning. By examining candidate genes of congenital heart disease and heterotaxy, we identify KCNH6, a member of the ether-a-go-go class of potassium channels that hyperpolarizes the Vm and thus limits the activation of voltage gated calcium channels, lowering intracellular calcium. In pluripotent embryonic cells, depletion of kcnh6 leads to membrane depolarization, elevation of intracellular calcium levels, and the maintenance of a pluripotent state at the expense of differentiation into ectodermal and myogenic lineages. Using high-resolution temporal transcriptome analysis, we identify the gene regulatory networks downstream of membrane depolarization and calcium signaling and discover that inhibition of the mTOR pathway transitions the pluripotent cell to a differentiated fate. By manipulating Vm using a suite of tools, we establish a bioelectric pathway that regulates pluripotency in vertebrates, including human embryonic stem cells.


Assuntos
Células-Tronco Pluripotentes , Animais , Humanos , Cálcio/metabolismo , Potenciais da Membrana , Diferenciação Celular/genética , Serina-Treonina Quinases TOR/genética , Serina-Treonina Quinases TOR/metabolismo , Canais de Potássio Éter-A-Go-Go/metabolismo
6.
Commun Biol ; 5(1): 1189, 2022 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-36335275

RESUMO

The type VI secretion system (T6SS) of Pseudomonas aeruginosa injects effector proteins into neighbouring competitors and host cells, providing a fitness advantage that allows this opportunistic nosocomial pathogen to persist and prevail during the onset of infections. However, despite the high clinical relevance of P. aeruginosa, the identity and mode of action of most P. aeruginosa T6SS-dependent effectors remain to be discovered. Here, we report the molecular mechanism of Tse5-CT, the toxic auto-proteolytic product of the P. aeruginosa T6SS exported effector Tse5. Our results demonstrate that Tse5-CT is a pore-forming toxin that can transport ions across the membrane, causing membrane depolarisation and bacterial death. The membrane potential regulates a wide range of essential cellular functions; therefore, membrane depolarisation is an efficient strategy to compete with other microorganisms in polymicrobial environments.


Assuntos
Pseudomonas aeruginosa , Sistemas de Secreção Tipo VI , Pseudomonas aeruginosa/metabolismo , Potenciais da Membrana , Proteínas de Bactérias/metabolismo , Sistemas de Secreção Tipo VI/genética , Sistemas de Secreção Tipo VI/metabolismo
7.
Mol Brain ; 15(1): 91, 2022 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-36397158

RESUMO

Trigeminal neuralgia (TN) is a rare form of chronic neuropathic pain characterized by spontaneous or elicited paroxysms of electric shock-like or stabbing pain in a region of the face. While most cases occur in a sporadic manner and are accompanied by intracranial vascular compression of the trigeminal nerve root, alteration of ion channels has emerged as a potential exacerbating factor. Recently, whole exome sequencing analysis of familial TN patients identified 19 rare variants in the gene CACNA1H encoding for Cav3.2T-type calcium channels. An initial analysis of 4 of these variants pointed to a pathogenic role. In this study, we assessed the electrophysiological properties of 13 additional TN-associated Cav3.2 variants expressed in tsA-201 cells. Our data indicate that 6 out of the 13 variants analyzed display alteration of their gating properties as evidenced by a hyperpolarizing shift of their voltage dependence of activation and/or inactivation resulting in an enhanced window current supported by Cav3.2 channels. An additional variant enhanced the recovery from inactivation. Simulation of neuronal electrical membrane potential using a computational model of reticular thalamic neuron suggests that TN-associated Cav3.2 variants could enhance neuronal excitability. Altogether, the present study adds to the notion that ion channel polymorphisms could contribute to the etiology of some cases of TN and further support a role for Cav3.2 channels.


Assuntos
Neuralgia do Trigêmeo , Humanos , Canais de Cálcio , Potenciais da Membrana , Neurônios , Neuralgia do Trigêmeo/genética , Fenômenos Eletrofisiológicos
8.
J Chem Inf Model ; 62(20): 4963-4969, 2022 10 24.
Artigo em Inglês | MEDLINE | ID: mdl-36190907

RESUMO

Cationic antimicrobial peptide PGLa gets into close contact with the anionic bacterial cell membrane, facilitating cross-membrane transport phenomena and membrane disruption depending on the concentration. The mechanisms of action are closely associated with the tilted insertion geometry of PGLa. Therefore, we aimed to understand the interaction between the transmembrane potential (TMP) and the orientation of the membrane-bound PGLa helix. Molecular dynamics simulations were performed with TMP, and we found that the PGLa tilt angle relative to the membrane is coupled with the TMP. Elevated TMP increases the population of the tilted state. We observed positive feedback between the tilt angle and the TMP, which occurs due to the electrostatic interaction between the peptidic helix and the Na+ cations at the membrane-water interface. These TMP coupled phenomena can contribute to understanding the direct antimicrobial and adjuvant effects of PGLa in combination with regular antibiotics.


Assuntos
Anti-Infecciosos , Peptídeos Antimicrobianos , Potenciais da Membrana , Anti-Infecciosos/farmacologia , Anti-Infecciosos/química , Antibacterianos/farmacologia , Água , Bicamadas Lipídicas/química
9.
Adv Physiol Educ ; 46(4): 693-702, 2022 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-36173340

RESUMO

Since its discovery in the mid-20th century, the Hodgkin-Huxley biophysical model of the squid giant axon's (SGA's) neurophysiology has traditionally served as the basis for the teaching of action potential (AP) dynamics in the physiology classroom. This model teaches that leak conductances set membrane resting potential; that fast, inactivating, voltage-gated sodium channels effect the SGA AP upstroke; and that delayed, rectifying, noninactivating voltage-gated potassium channels carry AP repolarization and the early part of the afterhyperpolarization (AHP). This model serves well to introduce students to the fundamental ideas of resting potential establishment and maintenance, as well as basic principles of AP generation and propagation. Furthermore, the Hodgkin-Huxley SGA model represents an excellent and accessible starting point for discussion of the concept of AP threshold and the role of passive electrical properties of the neuron. Additionally, the introduction of the Hodgkin-Huxley model of the SGA AP permits the integration of physiological principles, as instructors ask students to apply previously studied principles of transporter and channel biophysics to the essential physiological phenomenon of electrical signal conduction. However, both some early observations as well as more recent evidence strongly suggest that this seminal invertebrate model of AP dynamics does not appropriately capture the full story for mammalian axons. We review recent evidence that mammalian axonal nodes of Ranvier repolarize largely (though not exclusively) through the activity of leak potassium-ion (K+) conductances carried through two-pore domain (K2P) channels. We call for changes to physiology textbooks and curricula to highlight this remarkable difference in invertebrate and mammalian AP repolarization mechanisms.NEW & NOTEWORTHY Historically, physiology courses have typically taught that action potential repolarization occurs exclusively due to the activation of delayed-rectifier voltage-gated potassium channels. Here, we review and highlight recent evidence that leak potassium channels of the two-pore domain (K2P) class may largely serve this repolarization role at mammalian nodes of Ranvier. We call for the inclusion of these ideas in physiology curricula at all levels, from high school to graduate school.


Assuntos
Canais de Potássio de Domínios Poros em Tandem , Canais de Potássio de Abertura Dependente da Tensão da Membrana , Animais , Humanos , Potenciais de Ação/fisiologia , Potenciais da Membrana/fisiologia , Axônios/fisiologia , Potássio , Mamíferos
10.
J Alzheimers Dis ; 90(1): 119-137, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36093691

RESUMO

BACKGROUND: Alzheimer's disease (AD) is a neurological disease that has both a genetic and non-genetic origin. Mitochondrial dysfunction is a critical component in the pathogenesis of AD as deficits in oxidative capacity and energy production have been reported. OBJECTIVE: Nuclear-encoded mitochondrial genes were studied in order to understand the effects of mitochondrial expression changes on mitochondrial function in AD brains. These expression data were to be incorporated into a testable mathematical model for AD used to further assess the genes of interest as therapeutic targets for AD. METHODS: RT2-PCR arrays were used to assess expression of 84 genes involved in mitochondrial biogenesis in AD brains. A subset of mitochondrial genes of interest was identified after extensive Ingenuity Pathway Analysis (IPA) (Qiagen). Further filtering of this subset of genes of interest was achieved by individual qPCR analyses. Expression values from this group of genes were included in a mathematical model being developed to identify potential therapeutic targets. RESULTS: Nine genes involved in trafficking proteins to mitochondria, morphology of mitochondria, maintenance of mitochondrial transmembrane potential, fragmentation of mitochondria and mitochondrial dysfunction, amyloidosis, and neuronal cell death were identified as significant to the changes seen. These genes include TP53, SOD2, CDKN2A, MFN2, DNM1L, OPA1, FIS1, BNIP3, and GAPDH. CONCLUSION: Altered mitochondrial gene expression indicates that a subset of nuclear-encoded mitochondrial genes compromise multiple aspects of mitochondrial function in AD brains. A new mathematical modeling system may provide further insights into potential therapeutic targets.


Assuntos
Doença de Alzheimer , Amiloidose , Humanos , Doença de Alzheimer/patologia , Genes Mitocondriais , Dinaminas/metabolismo , Potenciais da Membrana , Mitocôndrias/metabolismo , Encéfalo/patologia , Morte Celular/genética , Amiloidose/metabolismo
11.
Annu Int Conf IEEE Eng Med Biol Soc ; 2022: 3682-3685, 2022 07.
Artigo em Inglês | MEDLINE | ID: mdl-36085904

RESUMO

In the uterus, the characteristics of smooth muscle contraction and the electrical activity that drives this contraction depends on hormonal cycles, and pregnancy status. Smooth muscle contraction is initiated by a change in membrane electrical potential, due to the flux of ions in and out of the intracellular space. Chains of action potentials throughout a section of muscle can result in coordinated contraction events. In this study, flexible printed circuit electrode arrays were applied to measure the bioelectric signals on the surface of a rat uterus in vivo. Variations in the electrical activity were quantified, including intermittent periods of activity and inactivity, which contain both slow-wave type activity (0.039 Hz ±0.017 Hz) and faster, spike-like activity (3.26 Hz ±0.27 Hz). The spike activity initiated at the ovarian end of the uterine horn, spreading towards the cervical end with a propagation velocity of 5.34 ± 2.32 mm [Formula: see text]. In conclusion, this pilot study outlines a new method of in vivo measurement of uterine electrical activity in rats. Clinical Relevance- Measurement of bioelectrical data using in vivo techniques provides insight into the electromechanical function of uterine smooth muscle, which could provide insights into what drives coordinated contraction in the uterus.


Assuntos
Músculo Liso , Útero , Potenciais de Ação , Animais , Feminino , Potenciais da Membrana , Projetos Piloto , Gravidez , Ratos
12.
Biosystems ; 222: 104780, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36179938

RESUMO

We present a comparison of the intrinsic saturation of firing frequency in four simple neural models: leaky integrate-and-fire model, leaky integrate-and-fire model with reversal potentials, two-point leaky integrate-and-fire model, and a two-point leaky integrate-and-fire model with reversal potentials. "Two-point" means that the equivalent circuit has two nodes (dendritic and somatic) instead of one (somatic only). The results suggest that the reversal potential increases the slope of the "firing rate vs input" curve due to a smaller effective membrane time constant, but does not necessarily induce saturation of the firing rate. The two-point model without the reversal potential does not limit the voltage or the firing rate. In contrast to the previous models, the two-point model with the reversal potential limits the asymptotic voltage and the firing rate, which is the main result of this paper. The case of excitatory inputs is considered first and followed by the case of both excitatory and inhibitory inputs.


Assuntos
Modelos Neurológicos , Neurônios , Neurônios/fisiologia , Potenciais da Membrana/fisiologia , Fenômenos Físicos , Potenciais de Ação/fisiologia
13.
Sci Rep ; 12(1): 15005, 2022 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-36056086

RESUMO

Electrical aspects of cell function manifest in many ways. The most widely studied is the cell membrane potential, Vm, but others include the conductance and capacitance of the membrane, the conductance of the enclosed cytoplasm, as well as the charge at the cell surface (an electrical double layer) producing an extracellular electrical potential, the ζ-potential. Empirical relationships have been identified between many of these, but not the mechanisms that link them all. Here we examine relationships between Vm and the electrical conductivities of both the cytoplasm and extracellular media, using data from a suspensions of red blood cells. We have identified linear relationships between extracellular medium conductivity, cytoplasm conductivity and Vm. This is in contrast to the standard model of a resting membrane potential which describes a logarithmic relationship between Vm and the concentration of permeable ions in the extracellular medium. The model here suggests that Vm is partially electrostatic in origin, arising from a charge imbalance at an inner electrical double-layer, acting across the membrane and double-layer capacitances to produce a voltage. This model describes an origin for coupling between Vm and ζ, by which cells can alter their electrostatic relationship with their environment, with implications for modulation of membrane ion transport, adhesion of proteins such as antibodies and wider cell-cell interactions.


Assuntos
Eritrócitos , Ânions , Cátions , Citoplasma , Condutividade Elétrica , Potenciais da Membrana/fisiologia
14.
BMC Microbiol ; 22(1): 215, 2022 09 12.
Artigo em Inglês | MEDLINE | ID: mdl-36089583

RESUMO

BACKGROUND: Acinetobacter baumannii (A. baumannii) is an opportunistic pathogen and has emerged as one of the most troublesome pathogens. Drug resistance in A. baumannii has been reported on a global scale. Minocycline was found to be active against multi-drug resistant A. baumannii and was approved by the FDA for the infections caused by sensitive strains of A. baumannii. However, the emergence of minocycline resistance and its toxic effects still need to be addressed. Therefore, this study aimed to evaluate the synergistic effects of metformin combined with minocycline on minocycline-resistant A. baumannii. RESULTS: The effect of metformin on the antibacterial activity of minocycline was determined by checkerboard and time-killing assay. Further, it was observed by biofilm formation assay that metformin combination with minocycline can inhibit the formation of biofilm. Outer membrane integrity, membrane permeability, membrane potential and reactive oxygen species (ROS) were monitored to explore the underlying synergistic mechanisms of metformin on minocycline. And the results shown that metformin can destroy the outer membrane of A. baumannii, enhance its membrane potential, but does not affect the membrane permeability and ROS. CONCLUSION: These findings suggested that the combination of metformin and minocycline has the potential for rejuvenating the activity of minocycline against minocycline-resistant A. baumannii.


Assuntos
Infecções por Acinetobacter , Acinetobacter baumannii , Metformina , Infecções por Acinetobacter/tratamento farmacológico , Infecções por Acinetobacter/microbiologia , Humanos , Potenciais da Membrana , Metformina/farmacologia , Minociclina/farmacologia , Espécies Reativas de Oxigênio/farmacologia
15.
Biosystems ; 221: 104772, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36113739

RESUMO

Presently a detailed biophysical model describing reversible and irreversible swelling dynamics of Müller cells (MC) is reported. The model includes a biophysical block of ionic and neutral species transport via MC membrane, water transport induced by osmotic pressure and pressure generated by membrane deformations, MC membrane potential and membrane mechanical properties. The model describes reversible and irreversible MC swelling (MCS) using the same set of parameters. The model was used in fitting available experimental data, and produced numerical values of previously unknown model parameters, including those describing mechanical properties of Müller cell membrane (MCM) with respect to bending and stretching. Numerical experiments simulating MC swelling showed complex oscillation dynamics of the relevant parameters in physiological initial conditions. In particular, MC membrane potential (ΔΨMC) demonstrated complex oscillation dynamics, which may be described by a superposition of several oscillations with their periods in the milliseconds, 100-ms and seconds time ranges. Dynamics of reversible and irreversible MCS, and the transition criteria from reversible to irreversible MCS modes were determined in model simulations.


Assuntos
Células Ependimogliais , Neuroglia , Potenciais da Membrana , Neuroglia/metabolismo , Pressão Osmótica , Água/metabolismo
16.
Sci Adv ; 8(38): eabq8489, 2022 09 23.
Artigo em Inglês | MEDLINE | ID: mdl-36149965

RESUMO

We present the first structure of the human Kir2.1 channel containing both transmembrane domain (TMD) and cytoplasmic domain (CTD). Kir2.1 channels are strongly inward-rectifying potassium channels that play a key role in maintaining resting membrane potential. Their gating is modulated by phosphatidylinositol 4,5-bisphosphate (PIP2). Genetically inherited defects in Kir2.1 channels are responsible for several rare human diseases, including Andersen's syndrome. The structural analysis (cryo-electron microscopy), surface plasmon resonance, and electrophysiological experiments revealed a well-connected network of interactions between the PIP2-binding site and the G-loop through residues R312 and H221. In addition, molecular dynamics simulations and normal mode analysis showed the intrinsic tendency of the CTD to tether to the TMD and a movement of the secondary anionic binding site to the membrane even without PIP2. Our results revealed structural features unique to human Kir2.1 and provided insights into the connection between G-loop and gating and the pathological mechanisms associated with this channel.


Assuntos
Simulação de Dinâmica Molecular , Fosfatidilinositóis , Canais de Potássio Corretores do Fluxo de Internalização , Microscopia Crioeletrônica , Humanos , Potenciais da Membrana , Canais de Potássio Corretores do Fluxo de Internalização/química
17.
Microbiology (Reading) ; 168(9)2022 09.
Artigo em Inglês | MEDLINE | ID: mdl-36165741

RESUMO

Transmembrane potential is one of the main bioenergetic parameters of bacterial cells, and is directly involved in energizing key cellular processes such as transport, ATP synthesis and motility. The most common approach to measure membrane potential levels is through use of voltage-sensitive fluorescent dyes. Such dyes either accumulate or are excluded from the cell in a voltage-dependent manner, which can be followed by means of fluorescence microscopy, flow cytometry, or fluorometry. Since the cell's ability to maintain transmembrane potential relies upon low and selective membrane ion conductivity, voltage-sensitive dyes are also highly sensitive reporters for the activity of membrane-targeting antibacterials. However, the presence of an additional membrane layer in Gram-negative (diderm) bacteria complicates their use significantly. In this paper, we provide guidance on how membrane potential and its changes can be monitored reliably in Gram-negatives using the voltage-sensitive dye 3,3'-dipropylthiadicarbocyanine iodide [DiSC3(5)]. We also discuss the confounding effects caused by the presence of the outer membrane, or by measurements performed in buffers rather than growth medium. We hope that the discussed methods and protocols provide an easily accessible basis for the use of voltage-sensitive dyes in Gram-negative organisms, and raise awareness of potential experimental pitfalls associated with their use.


Assuntos
Corantes Fluorescentes , Iodetos , Trifosfato de Adenosina/metabolismo , Corantes Fluorescentes/metabolismo , Bactérias Gram-Negativas/metabolismo , Iodetos/metabolismo , Potenciais da Membrana
18.
ACS Appl Mater Interfaces ; 14(37): 42308-42316, 2022 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-36069456

RESUMO

Neurons are vital components of the brain. When stimulated by neurotransmitters at the dendrites, neurons deliver signals as changes in the membrane potential by ion movement. The signal transmission of a nervous system exhibits a high energy efficiency. These characteristics of neurons are being exploited to develop efficient neuromorphic computing systems. In this study, we develop chemical synapses for neuromorphic devices and emulate the signaling processes in a nervous system using a polymer membrane, in which the ionic permeability can be controlled. The polymer membrane comprises poly(diallyl-dimethylammonium chloride) and poly(3-sulfopropyl acrylate potassium salt), which have positive and negative charges, respectively. The ionic permeability of the polymer membrane is controlled by the injection of a neurotransmitter solution. This device emulates the signal transmission behavior of biological neurons depending on the concentration of the injected neurotransmitter solution. The proposed artificial neuronal signaling device can facilitate the development of bio-realistic neuromorphic devices.


Assuntos
Polímeros , Sinapses , Encéfalo/fisiologia , Potenciais da Membrana , Neurônios/fisiologia , Sinapses/fisiologia
19.
Sci Rep ; 12(1): 14645, 2022 08 27.
Artigo em Inglês | MEDLINE | ID: mdl-36030326

RESUMO

Heme, an iron-protoporphyrin IX complex, is a cofactor bound to various hemoproteins and supports a broad range of functions, such as electron transfer, oxygen transport, signal transduction, and drug metabolism. In recent years, there has been a growing recognition of heme as a non-genomic modulator of ion channel functions. Here, we show that intracellular free heme and hemin modulate human ether à go-go (hEAG1, Kv10.1) voltage-gated potassium channels. Application of hemin to the intracellular side potently inhibits Kv10.1 channels with an IC50 of about 4 nM under ambient and 63 nM under reducing conditions in a weakly voltage-dependent manner, favoring inhibition at resting potential. Functional studies on channel mutants and biochemical analysis of synthetic and recombinant channel fragments identified a heme-binding motif CxHx8H in the C-linker region of the Kv10.1 C terminus, with cysteine 541 and histidines 543 and 552 being important for hemin binding. Binding of hemin to the C linker may induce a conformational constraint that interferes with channel gating. Our results demonstrate that heme and hemin are endogenous modulators of Kv10.1 channels and could be exploited to modulate Kv10.1-mediated cellular functions.


Assuntos
Canais de Potássio Éter-A-Go-Go , Hemina , Humanos , Potenciais da Membrana
20.
Bioessays ; 44(10): e2100210, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-35986436

RESUMO

The osmotic activity produced by internal, non-permeable, anionic nucleic acids and metabolites causes a persistent and life-threatening cell swelling, or cellular edema, produced by the Gibbs-Donnan effect. This evolutionary-critical osmotic challenge must have been resolved by LUCA or its ancestors, but we lack a cell-physiology look into the biophysical constraints to the solutions. Like mycoplasma, early cells conceivably preserved their volume with Cl- , Na+ , and K+ -channels, Na+ /H+ -exchangers, and a light-dependent bacteriorhodopsin-like H+ -pump. Here, I simulated protocells having these ionic-permeabilities and inhabiting an oceanic pond before the Great-Oxygenation-Event. Protocells showed better volume control and stable resting potentials at lower external pH and higher temperatures, favoring a certain type of extremophile life. Prevention of Na+ -influx at night, with low bacteriorhodopsin activity, required deep shutdown of highly voltage-sensitive Na+ -channels and extremely selective K+ -channels, two conserved features essential for modern neuronal encoding. The Gibbs-Donnan effect universality implies that extraterrestrial cells, if they exist, may reveal similar volume-controlling mechanisms.


Assuntos
Bacteriorodopsinas , Ácidos Nucleicos , Fenômenos Fisiológicos Celulares , Potenciais da Membrana/fisiologia , Sódio/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...