Academic literature on the topic 'Cellule non excitable'

Secretion of vesicular contents by exocytosis is a common feature of excitable (neurones, chromaffin cells, beta cells) and non-excitable cells (platelets, neutrophils, mast cells). The simplistic view that the universal mechanism controlling secretion is elevation of [Ca2+]i--whatever the source of this second messenger may be--is no longer tenable in view of recent reports demonstrating secretion at basal or even reduced [Ca2+]i. It is nevertheless clear that in excitable cells an increase in [Ca2+]i is the triggering event that induces secretion. In non-excitable cells, secretion is presumably triggered by other second messengers, although [Ca2+]i appears to act as an important modulator of the rate of secretion. Conversely, these second messenger systems may serve a regulatory function in excitable cells. Given the relative importance of [Ca2+]i in the regulation of cellular functions in excitable and non-excitable cells, it is not surprising that several mechanisms are expressed in these cells to regulate intracellular calcium concentration. The major pathway for Ca2+ in excitable cells is by voltage-activated Ca2+ channels, but release of Ca2+ from intracellular stores, via second messengers, predominates in non-excitable cells, and may also be important in excitable cells. In addition, receptor-operated channels and second messenger-gated conductances may prove to be important. All of these pathways are subject to regulation by a variety of interactive second messenger systems, which provide necessary tuning for an appropriate control of intracellular calcium level.

SummaryIncreases in cytosolic calcium concentrations regulate many cellular processes, including aspects of early development. Calcium release from intracellular stores and calcium entry through non-voltage-gated channels account for signalling in non-excitable cells, whereas voltage-gated calcium channels (CaV) are important in excitable cells. We report the expression of multiple transcripts of CaV, identified by its homology to other species, in the early embryo of the zebrafish, Danio rerio, at stages prior to the differentiation of excitable cells. CaV mRNAs and proteins were detected as early as the 2-cell stages, which indicate that they arise from both maternal and zygotic transcription. Exposure of embryos to pharmacological blockers of CaV does not perturb early development significantly, although late effects are appreciable. These results suggest that CaV may have a role in calcium homeostasis and control of cellular process during early embryonic development.

Calcium (Ca2+) functions as a second messenger that is critical in regulating fundamental physiological functions such as cell growth/development, cell survival, neuronal development and/or the maintenance of cellular functions. The coordination among various proteins/pumps/Ca2+ channels and Ca2+ storage in various organelles is critical in maintaining cytosolic Ca2+ levels that provide the spatial resolution needed for cellular homeostasis. An important regulatory aspect of Ca2+ homeostasis is a store operated Ca2+ entry (SOCE) mechanism that is activated by the depletion of Ca2+ from internal ER stores and has gained much attention for influencing functions in both excitable and non-excitable cells. Ca2+ has been shown to regulate opposing functions such as autophagy, that promote cell survival; on the other hand, Ca2+ also regulates programmed cell death processes such as apoptosis. The functional significance of the TRP/Orai channels has been elaborately studied; however, information on how they can modulate opposing functions and modulate function in excitable and non-excitable cells is limited. Importantly, perturbations in SOCE have been implicated in a spectrum of pathological neurodegenerative conditions. The critical role of autophagy machinery in the pathogenesis of neurodegenerative diseases such as Alzheimer’s, Parkinson’s, and Huntington’s diseases, would presumably unveil avenues for plausible therapeutic interventions for these diseases. We thus review the role of SOCE-regulated Ca2+ signaling in modulating these diverse functions in stem cell, immune regulation and neuromodulation.

Two-pore domain K+channels are an emerging family of K+channels that may contribute to setting membrane potential in both electrically excitable and non-excitable cells and, as such, influence cellular function. The human uteroplacental unit contains both excitable (e.g. myometrial) and non-excitable cells, whose function depends upon the activity of K+channels. We have therefore investigated the expression of two members of this family, TWIK (two-pore domain weak inward rectifying K+channel)-related acid-sensitive K+channel (TASK) and TWIK-related K+channel (TREK) in human myometrium. Using RT-PCR the mRNA expression of TASK and TREK isoforms was examined in myometrial tissue from pregnant women. mRNAs encoding TASK1, 4 and 5 and TREK1 were detected whereas weak or no signals were observed for TASK2, TASK3 and TREK2. Western blotting for TASK1 gave two bands of approximately 44 and 65 kDa, whereas TREK1 gave bands of approximately 59 and 90 kDa in myometrium from pregnant women. TASK1 and TREK1 immunofluorescence was prominent in intracellular and plasmalemmal locations within myometrial cells. Therefore, we conclude that the human myometrium is a site of expression for the two-pore domain K+channel proteins TASK1 and TREK1.

There is a dizzying array of fluorescent probes now commercially available to monitor cellular processes, and advances in molecular biology have highlighted the ease with which proteins can now be labelled with fluorophores without loss of functionality. This has led to an explosion in the popularity of fluorescence microscopy techniques. One such specialized technique, total internal reflection fluorescence microscopy (TIR-FM), is ideally suited to gaining insight into events occurring at, or close to, the plasma membrane of live cells with excellent optical resolution. In the last few years, the application of TIR-FM to membrane trafficking events in both non-excitable and excitable cells has been an area of notable expansion and fruition. This review gives a brief overview of that literature, with emphasis on the study of the regulation of exocytosis and endocytosis in excitable cells using TIR-FM. Finally, recent applications of TIR-FM to the study of cellular processes at the molecular level are discussed briefly, providing promise that the future of TIR-FM in cell biology will only get brighter.

Peroxisomes communicate with other cellular compartments by transfer of various metabolites. However, whether peroxisomes are sites for calcium handling and exchange has remained contentious. Here we generated sensors for assessment of peroxisomal calcium and applied them for single cell-based calcium imaging in HeLa cells and cardiomyocytes. We found that peroxisomes in HeLa cells take up calcium upon depletion of intracellular calcium stores and upon calcium influx across the plasma membrane. Furthermore, we show that peroxisomes of neonatal rat cardiomyocytes and human induced pluripotent stem cell–derived cardiomyocytes can take up calcium. Our results indicate that peroxisomal and cytosolic calcium signals are tightly interconnected both in HeLa cells and in cardiomyocytes. Cardiac peroxisomes take up calcium on beat-to-beat basis. Hence, peroxisomes may play an important role in shaping cellular calcium dynamics of cardiomyocytes.

Evolution of the nervous system progressed through cellular diversification and specialization of functions. Conceptually, the nervous system is composed from electrically excitable neuronal networks connected with chemical synapses and non-excitable glial cells that provide for homeostasis and defence. Astrocytes are integrated into neural networks through multipartite synapses; astroglial perisynaptic processes closely enwrap synaptic contacts and control homeostasis of the synaptic cleft, supply neurons with glutamate and GABA obligatory precursor glutamine and contribute to synaptic plasticity, learning and memory. In neuropathology, astrocytes may undergo reactive remodelling or degeneration; to a large extent, astroglial reactions define progression of the pathology and neurological outcome. This article is part of the themed issue ‘Evolution brings Ca 2+ and ATP together to control life and death’.

La voie d'entrée du calcium implique les canaux contrôlés par les réserves intracellulaires (store-operated channels, SOC). Dans les cellules de mammifères, le canal SOC le plus étudié est le canal CRAC (calcium release-activated Ca2+ channel). Dans les cellules myéloïdes dendritiques de souris, nous avons étudié le mécanisme de signalisation par le calcium par des techniques d'imagerie calcique et d'électrophysiologie. Nos résultats ont permis de montrer que ces cellules n'expriment pas plus de canaux couplés au voltage que de canaux couplés à la dihydropyridine (DHP). Au contraire, la DHP participe à la mobilisation de calcium des réserves intracellulaires ce qui induit une entrée de calcium par l'intermédiaire de CRAC. De même, la signalisation par l'ATP dans ces cellules conduit principalement à une mobilisation de calcium plutôt qu'une entrée par les canaux de la membrane plasmique. CRAC constitue la voie prédominante d'entrée du calcium après fixation de l'ATP. Nous avons montré que CRAC est activé dans des conditions physiologiques ce qui implique la maturation des cellules myéloïdes dendritiques de souris. Nous avons aussi détecté CRAC dans des lignées cellulaires de drosophiles. Les caractéristiques de son activation ainsi que ses propriétés biophysiques sont comparables à celles des cellules de mammifères, mais sans phase d'inactivation très rapide chez la drosophile. Enfin, nous avons identifié un nouveau mécanisme de modulation des SOC. Notre étude sur des cellules acinaires pancréatiques de rat AR42J et les cellules humaines embryonnaires de rein HEK 293 a permis de montrer que les phosphatases à tyrosine en particulier PTP1B sont impliquées dans l'inactivation de l'entrée de calcium après déplétion des réserves intracellulaires.

There are long-standing hypotheses that endogenous ion currents act to control cell dynamics in development, wound healing and regeneration. However, the mechanisms employed by cells to detect the electric field (EF) and translate it into a discernable message to drive specific cell behaviors, such as migration, proliferation and differentiation, are not well understood. A better understanding of how cells are able to sense EFs and react to them is vital to understanding physiological mechanisms are involved in regeneration. Ion channel signaling provides a reasonable suspect for mediating these effects based on their documented involvement in proliferation, migration and differentiation. To investigate mechanisms underlying ionic regulation of critical cellular processes in non-excitable cells, a novel, in vivo assay was developed to screen multiple pharmacological inhibitors of ion channels during larval A. mexicanum tail regeneration. This assay was used to identify individual channels that were then targeted for further analysis regarding their involvement in the regenerative process. Chapter 2 presents data from a study that indicates that a wound-like response can be generated in an invertebrate model by application of exogenous, low-amplitude sine-wave electrical stimulation. This was characterized by recruitment of hemocytes at the stimulation site which was dependent on voltage-gated potassium channels. Chapter 3 presents data from a comprehensive and systematic screen of pharmacological compounds against larval salamander tail regeneration that indicates 8 specific target ion channels. This chapter also describes results indicating specific mechanisms by which these channels may be perturbing regeneration. Chapter 4 presents data that indicate that the Anoctamin 1 channel identified in the aforementioned screen is a regulator of cellular proliferation. This is shown to be accomplished via amplification of intracellular calcium surges and a subsequent increase in the activity of the p44/42 MAPK signaling cascade.

L'utilisation de champs électriques pulsés (PEF) dans les secteurs de la médecine et de la biotechnologie est devenue de plus en plus courante au cours des dernières décennies. La recherche a montré qu'en ajustant la durée du PEF, nous pouvons prédire quels effets seront observés. Alors que les PEF dans la gamme micro - milliseconde ont été utilisés pour perméabiliser la membrane cellulaire et améliorer l'absorption de médicament ou de protéine, le PEF nanoseconde (nsPEF) a démontré des effets uniques sur les organites intracellulaires. Les deux PEF et nsPEF ont démontré un potentiel thérapeutique pour une variété de pathologies humaines, y compris le traitement du cancer. Utilisant l'imagerie des cellules vivantes, cette thèse a étudié in vitro les effets de champs pulsés d'une durée de 10 ns à 10 ms sur des lignées cancéreuses (U87 glioblastome multiforme) et non cancéreuses (neurones hippocampes de souris (HT22) et cellules ovariennes du hamster chinois (CHO)). Des résultats publiés antérieurement ont démontré que les cellules cancéreuses sont plus sensibles aux champs électriques que les cellules saines. Nos résultats sont en accord avec ces résultats, dans la mesure où les cellules U87 ont subi une dépolarisation significativement plus importante de leur potentiel transmembranaire après une seule impulsion électrique à toutes les durées. Dans un ensemble d'expériences parallèles, malgré des seuils de champ électrique similaires pour la perméabilisation membranaire, les cellules U87 ont démontré une absorption significativement améliorée de YO-PRO par rapport aux autres lignées cellulaires. Bien que les cellules U87 aient subi le plus grand changement dans la dépolarisation membranaire et la perméabilisation membranaire, elles ont également montré la constante de rescellement de la membrane la plus rapide, qui était environ 30 secondes plus rapide que les autres lignées cellulaires. Pour élucider certains des mécanismes sous-jacents par lesquels les cellules U87 répondent aux champs électriques, une série d'expériences a examiné le rôle des canaux ioniques transmembranaires. Plusieurs études récentes ont rapporté que les PEF peuvent agir directement sur les canaux ioniques voltage-dépendants. En utilisant divers modulateurs de canaux ioniques pharmacologiques spécifiques et à action large, nous avons démontré que nous pouvions presque entièrement inhiber la dépolarisation membranaire induite par le champ électrique dans les cellules U87 en bloquant certains canaux cationiques. Ces résultats étaient assez spécifiques, tels que le canal de potassium de grande conductance (BK), les canaux calciques de type L et T, et le canal cationique non spécifique, TRPM8, étaient capables d'inhiber la dépolarisation tandis que le blocage d'autres canaux ioniques ne produisait aucun changement significatif. . Les travaux de cette thèse ont montré que la lignée cellulaire maligne U87 présentait une plus grande sensibilité aux champs électriques allant de 10 ns à 10 ms par rapport aux lignées cellulaires non cancéreuses étudiées. Des améliorations potentielles aux protocoles de traitement actuels ont été proposées sur la base des résultats présentés ici
The use of pulsed electric fields (PEF) in medical and biotechnology sectors has become increasingly prevalent over the last few decades. Research has shown that by adjusting the duration of the PEF we can predict what effects will be observed. Whereas PEF in the micro-to-millisecond range have been used to permeabilize the cell membrane and enhance drug or protein uptake, nanosecond PEF (nsPEF) have demonstrated unique effects on intracellular organelles. Both PEF and nsPEF have demonstrated therapeutic potential for a variety of human pathologies, including the treatment of cancer. Using live-cell imaging, this thesis investigated, in vitro, the effects of pulsed fields ranging in duration from 10 ns to 10 ms on cancerous (U87 glioblastoma multiforme) and non-cancerous cell lines (mouse hippocampal neurons (HT22) and Chinese hamster ovary (CHO) cells). Previously published results have demonstrated that cancerous cells have a greater sensitivity to applied electric fields than healthy cells do. Our results are in agreement with these findings, insofar as the U87 cells underwent a significantly greater depolarization of their transmembrane potential following a single electric pulse at all durations. In a parallel set of experiments, despite having similar electric field thresholds for membrane permeabilization, the U87 cells demonstrated significantly enhanced YO-PRO uptake compared to the other cells lines. Although U87 cells underwent the greatest change in both membrane depolarization and membrane permeabilization, they also showed the fastest membrane resealing constant, which was approximately 30 seconds faster than other cell lines. To elucidate some of the underlying mechanisms by which U87 cells respond to electric fields, a series of experiments looked at the role of transmembrane ion channels. Several recent studies have reported that PEFs can act directly on voltage-gated ion channels. Using a variety of specific and broad acting pharmacological ion channel modulators, we demonstrated that we could almost entirely inhibit the electric field-induced membrane depolarization in U87 cells by blocking certain cationic channels. These results were quite specific, such that the big conductance potassium (BK) channel, L- and T-type calcium channels, and the non-specific cationic channel, TRPM8, were able to inhibit depolarization while blocking other ion channels produced no significant change. The work in this thesis showed that the malignant U87 cell line showed a greater sensitivity to electric fields from ranging from 10 ns – 10 ms when compared to the non-cancerous cell lines that were investigated. Potential improvements to current treatment protocols have been proposed based on the findings presented herein

The nervous system consists of neurons, glial cells, blood vessels, and extracellular matrix. Neurons are electrically excitable cells and are primarily responsible for initiation, processing, and transmission of information. However, their function is affected by their reciprocal interactions with glial cells, which contribute to development, survival, and plasticity of synaptic connections and shape the activity of neuronal ensembles and systems critical for cognition and behavior. Advances in molecular, cellular, and electrophysiological approaches have provided major insight not only in normal function of neurons and glial cells but also in the pathophysiology of neurologic diseases at the molecular, synaptic, cellular network, and system levels.

In chapter 5 we focused on the informational interface between cells and synthetic components of systems. This interface is concerned with facilitating and manipulating information transport and processing between and within the synthetic and whole-cell components of these hybrid systems. However, there is also a structural interface between these components that is concerned with the physical placement, entrapment, and maintenance of the cells in a manner that enables the informational interface to operate. In this chapter we focus on this structural interface. Successful integration of whole-cell matrices into microscale and nanoscale elements requires a unique environment that fosters continued cell viability while promoting, or at least not blocking, the information transport and communication pathways described in earlier chapters. A century of cell culture has provided a wealth of insight and specific protocols to maintain the viability and (typically) proliferation of virtually every type of organism that can be propagated. More recently, the demands for more efficient bioreactors, more compatible biomedical implants, and the promise of engineered tissues has driven advances in surface-modification sciences, cellular immobilization, and scaffolding that provide structure and control over cell growth, in addition to their basic metabolic requirements. In turn, hybrid biological and electronic systems have emerged, capable of transducing the often highly sensitive and specific responses of cellular matrices for biosensing in environmental, medical, and industrial applications. The demands of these systems have driven advances in cellular immobilization and encapsulation techniques, enabling improved interaction of the biological matrix with its environment while providing nutrient and respiratory requirements for prolonged viability of the living matrices. Predominantly, such devices feature a single interface between the bulk biomatrix and transducer. However, advances in lithography, micromachining, and micro-/nanoscale synthesis provide broader opportunities for interfacing whole-cell matrices with synthetic elements. Advances in engineered, patterned, or directed cell growth are now providing spatial and temporal control over cellular integration within microscale and nanoscale systems. Perhaps the best defined integration of cellular matrices with electronically active substrates has been accomplished with neuronal patterning. Topographical and physicochemical patterning of surfaces promotes the attachment and directed growth of neurites over electrically active substrates that are used to both stimulate and observe excitable cellular activity.

Store-operated Ca2+ entry (SOCE) channels mediate Ca2+ influx from the extracellular milieu into the cytosol to regulate a myriad of cellular functions. The Ca2+-release activated Ca2+ current has been well characterized in non-excitable cells such as immune cells. However, the role of SOCE proteins in cardiomyocytes and cardiac function has only been recently investigated. The localized endoplasmic reticulum protein, stromal interaction molecule (STIM) and plasma membrane Ca2+ channels, ORAI form the minimal functional unit of SOCE. The documentation of STIM and Orai expression in cardiomyocytes has raised questions regarding their role in cardiac function. Recent evidence supports the central role of STIM and Orai in gene transcription and, subsequent phenotypic changes associated with cardiac remodeling and hypertrophy. The purpose of this chapter is to provide an overview of our current understanding of SOCE proteins and, to explore their contributions to cardiovascular function and role in cardiac disorders.