共查询到20条相似文献,搜索用时 31 毫秒
1.
Xin Liang Damien S. K. Samways Kyle Wolf Elizabeth A. Bowles Jennifer P. Richards Jonathan Bruno Sébastien Dutertre Richard J. DiPaolo Terrance M. Egan 《The Journal of biological chemistry》2015,290(12):7930-7942
ATP-gated P2X7 receptors are prominently expressed in inflammatory cells and play a key role in the immune response. A major consequence of receptor activation is the regulated influx of Ca2+ through the self-contained cation non-selective channel. Although the physiological importance of the resulting rise in intracellular Ca2+ is universally acknowledged, the biophysics of the Ca2+ flux responsible for the effects are poorly understood, largely because traditional methods of measuring Ca2+ permeability are difficult to apply to P2X7 receptors. Here we use an alternative approach, called dye-overload patch-clamp photometry, to quantify the agonist-gated Ca2+ flux of recombinant P2X7 receptors of dog, guinea pig, human, monkey, mouse, rat, and zebrafish. We find that the magnitude of the Ca2+ component of the ATP-gated current depends on the species of origin, the splice variant, and the concentration of the purinergic agonist. We also measured a significant contribution of Ca2+ to the agonist-gated current of the native P2X7Rs of mouse and human immune cells. Our results provide cross-species quantitative measures of the Ca2+ current of the P2X7 receptor for the first time, and suggest that the cytoplasmic N terminus plays a meaningful role in regulating the flow of Ca2+ through the channel. 相似文献
2.
Hercules Antônio da Silva-Souza Maria Nathalia de Lira Helio Miranda Costa-Junior Cristiane Monteiro da Cruz Jorge Silvio Silva Vasconcellos Anderson Nogueira Mendes Gabriela Pimenta-Reis Cora Lilia Alvarez Lucia Helena Faccioli Carlos Henrique Serezani Julieta Schachter Pedro Muanis Persechini 《生物化学与生物物理学报:生物膜》2014
We have previously described that arachidonic acid (AA)-5-lipoxygenase (5-LO) metabolism inhibitors such as NDGA and MK886, inhibit cell death by apoptosis, but not by necrosis, induced by extracellular ATP (ATPe) binding to P2X7 receptors in macrophages. ATPe binding to P2X7 also induces large cationic and anionic organic molecules uptake in these cells, a process that involves at least two distinct transport mechanisms: one for cations and another for anions. Here we show that inhibitors of the AA-5-LO pathway do not inhibit P2X7 receptors, as judged by the maintenance of the ATPe-induced uptake of fluorescent anionic dyes. In addition, we describe two new transport phenomena induced by these inhibitors in macrophages: a cation-selective uptake of fluorescent dyes and the release of ATP. The cation uptake requires secreted ATPe, but, differently from the P2X7/ATPe-induced phenomena, it is also present in macrophages derived from mice deficient in the P2X7 gene. Inhibitors of phospholipase A2 and of the AA-cyclooxygenase pathway did not induce the cation uptake. The uptake of non-organic cations was investigated by measuring the free intracellular Ca2 + concentration ([Ca2 +]i) by Fura-2 fluorescence. NDGA, but not MK886, induced an increase in [Ca2 +]i. Chelating Ca2 + ions in the extracellular medium suppressed the intracellular Ca2 + signal without interfering in the uptake of cationic dyes. We conclude that inhibitors of the AA-5-LO pathway do not block P2X7 receptors, trigger the release of ATP, and induce an ATP-dependent uptake of organic cations by a Ca2 +- and P2X7-independent transport mechanism in macrophages. 相似文献
3.
《Cell calcium》2016,59(6):589-597
Isolated clusters of mouse parotid acinar cells in combination with live cell imaging were used to explore the crosstalk in molecular signaling between purinergic, cholinergic and adrenergic pathways that integrate to control fluid and protein secretion. This crosstalk was manifested by (1) β-adrenergic receptor activation and amplification of P2X4R evoked Ca2+ signals, (2) β-adrenergic-induced amplification of P2X7R-evoked Ca2+ signals and (3) muscarinic receptor induced activation of P2X7Rs via exocytotic activity. The findings from our study reveal that purinoceptor-mediated Ca2+ signaling is modulated by crosstalk with canonical signaling pathways in parotid acinar cells. Integration of these signals are likely important for dynamic control of saliva secretion to match physiological demand in the parotid gland. 相似文献
4.
Shayan Chen Wenli Feng Xiao Yang Wanzhu Yang Yongxin Ru Jinfeng Liao Lina Wang Yongmin Lin Qian Ren Guoguang Zheng 《Biochemical and biophysical research communications》2014
Nucleotides are important players in intercellular signaling communication network. P2X family receptors (P2XRs) are ATP-gated plasma membrane ion channels with diverse biological functions. Macrophages are important components in the microenvironment of hematopoiesis participating in both physiological and pathological processes. However, the role of P2XRs in macrophages in leukemia has not been established. Here we investigated expression pattern and functions of P2XRs in macrophages from bone marrow (BM) and spleen of Notch1-induced T-ALL mice. Real-time PCR showed that P2XRs except P2X5R were expressed in BM and spleen macrophages. Furthermore, with the development of leukemia, the expression of P2X7R increased in both BM and spleen macrophages whereas expression of P2X1R increased in spleen macrophages. Live cell imaging recoding the Ca2+ response demonstrated that P2X7R expressed in macrophages was functional. TUNEL and electron microscopy analysis found that apoptotic macrophages were frequently observed in BM and spleen at late stage of leukemia, which was partly contributed by the activation of overexpressed P2X7R. Our results suggested that the intercellular communication mediated by nucleotides might orchestrate in the pathological process of leukemia and could be a potential target for the treatment of leukemia. 相似文献
5.
Nicholas Mikolajewicz Delaney Smith Svetlana V. Komarova Anmar Khadra 《PLoS computational biology》2021,17(6)
The P2 purinergic receptor family implicated in many physiological processes, including neurotransmission, mechanical adaptation and inflammation, consists of ATP-gated non-specific cation channels P2XRs and G-protein coupled receptors P2YRs. Different cells, including bone forming osteoblasts, express multiple P2 receptors; however, how P2X and P2Y receptors interact in generating cellular responses to various doses of [ATP] remains poorly understood. Using primary bone marrow and compact bone derived osteoblasts and BMP2-expressing C2C12 osteoblastic cells, we demonstrated conserved features in the P2-mediated Ca2+ responses to ATP, including a transition of Ca2+ response signatures from transient at low [ATP] to oscillatory at moderate [ATP], and back to transient at high [ATP], and a non-monotonic changes in the response magnitudes which exhibited two troughs at 10−4 and 10−2 M [ATP]. We identified P2Y2 and P2X7 receptors as predominantly contributing to these responses and constructed a mathematical model of P2Y2R-induced inositol trisphosphate (IP3) mediated Ca2+ release coupled to a Markov model of P2X7R dynamics to study this system. Model predictions were validated using parental and CRISPR/Cas9-generated P2Y2 and P2Y7 knockouts in osteoblastic C2C12-BMP cells. Activation of P2Y2 by progressively increasing [ATP] induced a transition from transient to oscillatory to transient Ca2+ responses due to the biphasic nature of IP3Rs and the interaction of SERCA pumps with IP3Rs. At high [ATP], activation of P2X7R modulated the response magnitudes through an interplay between the biphasic nature of IP3Rs and the desensitization kinetics of P2X7Rs. Moreover, we found that P2Y2 activity may alter the kinetics of P2X7 towards favouring naïve state activation. Finally, we demonstrated the functional consequences of lacking P2Y2 or P2X7 in osteoblast mechanotransduction. This study thus provides important insights into the biophysical mechanisms underlying ATP-dependent Ca2+ response signatures, which are important in mediating bone mechanoadaptation. 相似文献
6.
P.A.F. Pacheco R.M.S. Galvão A.F.M. Faria N.l. Von Ranke M.S. Rangel T.M. Ribeiro M.l. Bello C.R. Rodrigues V.F. Ferreira D.R. da Rocha R.X. Faria 《Bioorganic & medicinal chemistry》2019,27(8):1449-1455
Extracellular adenosine 5′-triphosphate (ATP) triggers the P2X7 receptor (P2X7R) ionic channel to stimulate the release of the interleukin-IL-1β cytokine into macrophages. The current study explored the reaction of six structurally diverse triazole derivatives on P2X7-mediated dye uptake into murine peritoneal macrophages. P2X7R activity determined by ATP-evoked fluorescent dye uptake. Triazole derivatives toxicity measured using dextran rhodamine exclusion based colorimetric assay. A740004 and BBG, both P2X7R antagonist, inhibited ATP-induced dye uptake. In contrast, the derivatives 5a, 5b, 5e, and 5f did not diminish P2X7R activity in concentrations until 100?µM. 5c and 5d analogs caused a potent inhibitory activity on P2X7-induced dye uptake. Dextran Rhodamine exclusion measurements after 24?h of continuous treatment with triazole derivatives indicated a moderated toxicity for all molecules. In conclusion, this study showed that a series of new hybrid 1,2,3-triazolic naphthoquinones reduces P2X7R-induced dye uptake into murine macrophages. In silico analysis indicates a good pharmacokinetic profile and molecular docking results of these analogs indicate the potential to bind into an allosteric site located into the P2X7R pore and juxtaposed with the ATP binding pocket. In this manner, the compounds 5c and 5d may be used as a scaffold for new P2X7R inhibitors with reduced toxicity, and good anti-inflammatory activity. 相似文献
7.
Measuring intracellular ca levels in plant cells using the fluorescent probes, indo-1 and fura-2 : progress and prospects
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Recent advances in the development of methods for measuring cytoplasmic Ca2+ levels in higher plant cells are discussed. Emphasis is placed on the new generation of Ca2+-sensitive fluorescent dyes particularly fura-2 and indo-1. These dyes offer many advantages for the measurement of cytosolic Ca2+ levels. They can be introduced into cells in a nonintrusive manner, their Kd for Ca2+ matches plant cell cytoplasmic Ca2+ levels, and shifts in their emission (indo-1) or excitation (fura-2) spectra following Ca2+ binding permit accurate quantitation of Ca2+ activities. Examples of cytoplasmic Ca2+ levels measured in plants with fura-2 and indo-1 are presented, and the prospects for applying more advanced technologies to fluorescent dye measurement are discussed. 相似文献
8.
Wolfgang Fischer Nicole Urban Kerstin Immig Heike Franke Michael Schaefer 《Purinergic signalling》2014,10(2):313-326
The adenosine 5′-triphosphate (ATP)-gated P2X7 receptor is a membrane-bound, non-selective cation channel, expressed in a variety of cell types. The P2X7 senses high extracellular ATP concentrations and seems to be implicated in a wide range of cellular functions as well as pathophysiological processes, including immune responses and inflammation, release of gliotransmitters and cytokines, cancer cell growth or development of neurodegenerative diseases. In the present study, we identified natural compounds and analogues that can block or sensitize the ATP (1 mM)-induced Ca2+ response using a HEK293 cell line stably expressing human P2X7 and fluorometric imaging plate reader technology. For instance, teniposide potently blocked the human P2X7 at sub-miromolar concentrations, but not human P2X4 or rat P2X2. A marked block of ATP-induced Ca2+ entry and Yo-Pro-1 uptake was also observed in human A375 melanoma cells and mouse microglial cells, both expressing P2X7. On the other hand, agelasine (AGL) and garcinolic acid (GA) facilitated the P2X7 response to ATP in all three cell populations. GA also enhanced the YO-PRO-1 uptake, whereas AGL did not affect the ATP-stimulated intracellular accumulation of this dye. According to the pathophysiological role of P2X7 in various diseases, selective modulators may have potential for further development, e.g. as neuroprotective or antineoplastic drugs. 相似文献
9.
Mina Yamamoto Yosuke KamatsukaAkihiro Ohishi Kentaro NishidaKazuki Nagasawa 《Biochemical and biophysical research communications》2013
We previously demonstrated that P2X7 receptors (P2X7Rs) expressed by cultured mouse astrocytes were activated without any exogenous stimuli, but its roles in non-stimulated resting astrocytes remained unknown. It has been reported that astrocytes exhibit engulfing activity, and that the basal activity of P2X7Rs regulates the phagocytic activity of macrophages. In this study, therefore, we investigated whether P2X7Rs regulate the engulfing activity of mouse astrocytes. Uptake of non-opsonized beads by resting astrocytes derived from ddY-mouse cortex time-dependently increased, and the uptaken beads were detected in the intracellular space. The bead uptake was inhibited by cytochalasin D (CytD), an F-actin polymerization inhibitor, and agonists and antagonists of P2X7Rs apparently decreased the uptake. Spontaneous YO-PRO-1 uptake by ddY-mouse astrocytes was reduced by the agonists and antagonists of P2X7Rs, but not by CytD. Down-regulation of P2X7Rs using siRNA decreased the bead uptake by ddY-mouse astrocytes. In addition, compared to in the case of ddY-mouse astrocytes, SJL-mouse astrocytes exhibited higher YO-PRO-1 uptake activity, and their bead uptake was significantly greater. These findings suggest that resting astrocytes exhibit engulfing activity and that the activity is regulated, at least in part, by their P2X7Rs. 相似文献
10.
To study changes in the cytoplasmic Ca2+ concentration ([Ca2+]i) and the total amount of calcium in cells, we used, respectively, the fluorescent dye fura 2/AM and the metallochrome dye
arsenazo III. The total amount of calcium in acinar cells after their incubation in calcium-free ATP-containing extracellular
solution decreased. The action of ATP induced a dose-dependent increase in the [Ca2+]i; the EC50 was, on average, 130 ± ± 36 μM. Calcium transients induced by ATP demonstrated no desensitization. Against the background
of a blocker of ionotropic P2X receptors, pyridoxal phosphate-6-azophenyl-2′,4′-disulfonic acid, we observed a decrease in
the ATP-induced calcium transients by 72%. In addition, these transients were reduced by 65% in the calcium-free milieu, while
after thapsigargin-induced exhaustion of the endoplasmic reticulum store they disappeared. This is indicative of the involvement
of metabotropic P2Y receptors in the formation of the above calcium transients. Therefore, P2X and P2Y receptors participate
in ATP-induced calcium signalling in acinar cells of the submandibular salivary gland; activation of these channels results
in a rise in the [Ca2+]i. The P2X receptors to a higher extent contribute to the formation of calcium signals; the P2Y-determined increase in the
[Ca2+]i is smaller (equal to about 35%). Therefore, the functionally active ligand-operated ionotropic P2Y receptors and metabotropic
G protein-related P2Y receptors do exist in acinar cells of the submandibular salivary gland and play an important role in
the control of functioning of this gland.
Neirofiziologiya/Neurophysiology, Vol. 37, Nos. 5/6, pp. 395–402, September–December, 2005. 相似文献
11.
Peritoneal macrophages were isolated from wild type (WT) mice and from mice invalidated for the P2X7 receptor (KO) which had been pretreated with thioglycolate. In cells from WT mice, 1 mM ATP increased the intracellular concentration of calcium ([Ca2+]i), the uptake of ethidium bromide, the production of reactive oxygen species (ROS), the secretion of IL-1β, the release of oleic acid and of lactate dehydrogenase; it decreased the intracellular concentration of potassium ([K+]i). In KO mice, ATP transiently increased the [Ca2+]i confirming that the P2X7 receptor is a major receptor of peritoneal macrophages. WKYMVm, an agonist of receptors for formylated peptides (FPR) also increased the [Ca2+]i in murine macrophages. The slight increase of the [Ca2+]i was strongly potentiated by ivermectin confirming the expression of functional P2X4 receptors by murine peritoneal macrophages. CRAMP, the unique antimicrobial peptide derived from cathelin in mouse inhibited all the responses coupled to P2X7 receptors in macrophages from WT mice. Agonists for FPR had no effect on the increase of the [Ca2+]i in response to ATP. CRAMP had no effect on the increase of the [Ca2+]i evoked by a combination of ATP and ivermectin in macrophages from P2X7-KO mice.In summary CRAMP inhibits the responses secondary to the activation of the murine P2X7 receptors expressed by peritoneal macrophages. This inhibition is not mediated by FPR receptors and is specific since CRAMP has no effect on the response coupled to P2X4 receptors. It can thus be concluded that the interaction between P2X7 receptors and cathelin-derived antimicrobial peptides is species-specific, in some cases (man) positive in others (mouse) negative. 相似文献
12.
Marques-da-Silva C Chaves MM Rodrigues JC Corte-Real S Coutinho-Silva R Persechini PM 《PloS one》2011,6(9):e25356
Leishmania and other parasites display several mechanisms to subvert host immune cell function in order to achieve successful infection. The ATP receptor P2X7, an agonist-gated cation channel widely expressed in macrophages and other cells of the immune system, is also coupled to inflammasome activation, IL-1 beta secretion, production of reactive oxygen species, cell death and the induction of the permeabilization of the plasma membrane to molecules of up to 900 Da. P2X7 receptors can function as an effective microbicidal triggering receptor in macrophages infected with several microorganisms including Mycobacteria tuberculosis, Chlamydia and Leishmania. We have previously shown that its expression is up-regulated in macrophages infected with L. amazonensis and that infected cells also display an increase in P2X7-induced apoptosis and membrane permeabilization to some anionic fluorescent dyes. In an independent study we recently showed that the phenomenon of macrophage membrane permeabilization can involve at least two distinct pathways for cations and anions respectively. Here, we re-addressed the effects of ATP-induced P2X7-associated phenomena in macrophages infected with L. amazonensis and demonstrated that the P2X7-associated dye uptake mechanisms are differentially modulated. While the membrane permeabilization for anionic dyes is up-modulated, as previously described, the uptake of cationic dyes is strongly down-modulated. These results unveil new characteristics of two distinct permeabilization mechanisms associated with P2X7 receptors in macrophages and provide the first evidence indicating that these pathways can be differentially modulated in an immunologically relevant situation. The possible importance of these results to the L. amazonensis escape mechanism is discussed. 相似文献
13.
Rabbit alveolar macrophages exposed to the ionophore A23187 in the presence of extracellular Ca2+ take up about 12 nmoles of Ca2+/1 × 106 cells. This uptake induces a slight, but significant, extracellular release of granule enzymes, β-glucuronidase and lysozyme, but not of the cytoplasmic marker, lactate dehydrogenase. If either EGTA is added to the medium or Mg2+ replaces Ca2+ no stimulation of secretion is observed. If the energy supply is decreased by treating the macrophages with mitochondrial inhibitors such as oligomycin, cyanide, or rotenone and antimycin, Ca2+-dependent secretion is potentiated several fold. Selective release of granule enzymes from macrophages exposed to A23187 and Ca2+ is also stimulated by cytochalasin B (CB). 相似文献
14.
Daniel Bloch Hansen Zu-Cheng Ye Kirstine Calloe Thomas Hartig Braunstein Johannes Pauli Hofgaard Bruce R. Ransom Morten Schak Nielsen Nanna MacAulay 《The Journal of biological chemistry》2014,289(38):26058-26073
Astrocytes and neurons express several large pore (hemi)channels that may open in response to various stimuli, allowing fluorescent dyes, ions, and cytoplasmic molecules such as ATP and glutamate to permeate. Several of these large pore (hemi)channels have similar characteristics with regard to activation, permeability, and inhibitor sensitivity. Consequently, their behaviors and roles in astrocytic and neuronal (patho)physiology remain undefined. We took advantage of the Xenopus laevis expression system to determine the individual characteristics of several large pore channels in isolation. Expression of connexins Cx26, Cx30, Cx36, or Cx43, the pannexins Px1 or Px2, or the purinergic receptor P2X7 yielded functional (hemi)channels with isoform-specific characteristics. Connexin hemichannels had distinct sensitivity to alterations of extracellular Ca2+ and their permeability to dyes and small atomic ions (conductance) were not proportional. Px1 and Px2 exhibited conductance at positive membrane potentials, but only Px1 displayed detectable fluorescent dye uptake. P2X7, in the absence of Px1, was permeable to fluorescent dyes in an agonist-dependent manner. The large pore channels displayed overlapping sensitivity to the inhibitors Brilliant Blue, gadolinium, and carbenoxolone. These results demonstrated isoform-specific characteristics among the large pore membrane channels; an open (hemi)channel is not a nonselective channel. With these isoform-specific properties in mind, we characterized the divalent cation-sensitive permeation pathway in primary cultured astrocytes. We observed no activation of membrane conductance or Cx43-mediated dye uptake in astrocytes nor in Cx43-expressing C6 cells. Our data underscore that although Cx43-mediated transport is observed in overexpressing cell systems, such transport may not be detectable in native cells under comparable experimental conditions. 相似文献
15.
N. Chaïb E. Kabré M. Métioui E. Alzola C. Dantinne A. Wow J.P. Dehaye 《Cell calcium》1998,23(6):395-404
The intracellular concentration of calcium ([Ca2+]i) of rat submandibular ductal cells was measured with the intracellular fluorescent dye Fura-2. Carbachol (100 μM) and ATP (1 mM) both increased the [Ca2+]j. The late response to ATP was blocked by 0.5 mM Ni2+. This concentration of Ni2+ also blocked the increase of the [Ca2+]i and the uptake of manganese and calcium in response to 2′- and 3′-O-(4-benzoylbenzoyl) adenosine 5′-triphosphate (BzATP, 100 μM), a specific agonist of P2X receptors from salivary glands. The increase of the [Ca2+]i in response to 2-methylthioadenosine 5′-triphosphate (2-McSATP, 100 μM) a specific P2Y agonist in salivary glands or to a muscarinic agonist (carbachol) was not affected by 0.5 mM Ni2+. Only higher concentrations of Ni2+ (in the millimolar range) inhibited the uptake of extracellular calcium in response to carbachol. SK&F 96365, a blocker of store-operated calcium channels, inhibited the uptake of extracellular calcium in response to carbachol without affecting the response to BzATP. It is concluded that at low concentrations (below 0.5 mM), Ni2+ inhibits the non-specific cation channel coupled to P2X receptors. The uptake of extracellular calcium by store-operated calcium channels is inhibited by higher concentrations of Ni2+ and by SK&F96365. 相似文献
16.
Yaping Lin-Moshier Peter J. Sebastian LeeAnn Higgins Natalie D. Sampson Jane E. Hewitt Jonathan S. Marchant 《The Journal of biological chemistry》2013,288(1):355-367
Changes in cytoplasmic Ca2+ concentration, resulting from activation of intracellular Ca2+ channels within the endoplasmic reticulum, regulate several aspects of cellular growth and differentiation. Ca2+ homeostasis endoplasmic reticulum protein (CHERP) is a ubiquitously expressed protein that has been proposed as a regulator of both major families of endoplasmic reticulum Ca2+ channels, inositol 1,4,5-trisphosphate receptors (IP3Rs) and ryanodine receptors (RyRs), with resulting effects on mitotic cycling. However, the manner by which CHERP regulates intracellular Ca2+ channels to impact cellular growth is unknown. Here, we challenge previous findings that CHERP acts as a direct cytoplasmic regulator of IP3Rs and RyRs and propose that CHERP acts in the nucleus to impact cellular proliferation by regulating the function of the U2 snRNA spliceosomal complex. The previously reported effects of CHERP on cellular growth therefore are likely indirect effects of altered spliceosomal function, consistent with prior data showing that loss of function of U2 snRNP components can interfere with cell growth and induce cell cycle arrest. 相似文献
17.
Different patterns of Ca2+ signals are induced by low compared to high concentrations of P2Y agonists in microglia 总被引:1,自引:1,他引:0
Brain-resident macrophages (microglia) are key cellular elements in the preservation of tissue integrity. On the other hand, they can also contribute to the development of pathological events by causing an extensive and inappropriate inflammatory response. A growing number of reports indicate the involvement of nucleotides in the control of microglial functions. With this study on P2Y receptors in rat microglia, we want to contribute to the definition of their expression profile and to the characterisation of their signalling mechanisms leading to Ca2+ movements. Endogenous nucleotides, when applied at a concentration of 100 μM, elicited robust Ca2+ transients, thanks to a panel of metabotropic receptors comprising mainly P2Y2, P2Y6 and P2Y12 subtypes. The involvement of P2Y12 receptors in Ca2+ responses induced by adenine nucleotides was confirmed by the pharmacological and pertussis toxin sensitivity of the response induced by adenosine diphosphate (ADP). Beside the G protein involved, Gi and Gq respectively, adenine and uracil nucleotides differed also for induction by the latter of a capacitative Ca2+ plateau. Moreover, when applied at low (sub-micromolar) concentrations with a long-lasting challenge, uracil nucleotides elicited oscillatory Ca2+ changes with low frequency of occurrence (≤1 min−1), sometimes superimposed to an extracellular Ca2+-dependent sustained Ca2+ rise. We conclude that different patterns of Ca2+ transients are induced by low (i.e., oscillatory Ca2+ activity) compared to high (i.e., fast release followed by sustained raise) concentrations of nucleotides, which can suggest different roles played by receptor stimulation depending not only on the type but also on the concentration of nucleotides. 相似文献
18.
《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》2019,1866(7):1092-1100
Inositol 1,4,5-trisphosphate receptors (IP3R) are the most widely expressed intracellular Ca2+ release channels. Their activation by IP3 and Ca2+ allows Ca2+ to pass rapidly from the ER lumen to the cytosol. The resulting increase in cytosolic [Ca2+] may directly regulate cytosolic effectors or fuel Ca2+ uptake by other organelles, while the decrease in ER luminal [Ca2+] stimulates store-operated Ca2+ entry (SOCE). We are close to understanding the structural basis of both IP3R activation, and the interactions between the ER Ca2+-sensor, STIM, and the plasma membrane Ca2+ channel, Orai, that lead to SOCE. IP3Rs are the usual means through which extracellular stimuli, through ER Ca2+ release, stimulate SOCE. Here, we review evidence that the IP3Rs most likely to respond to IP3 are optimally placed to allow regulation of SOCE. We also consider evidence that IP3Rs may regulate SOCE downstream of their ability to deplete ER Ca2+ stores. Finally, we review evidence that IP3Rs in the plasma membrane can also directly mediate Ca2+ entry in some cells. 相似文献
19.
Major histocompatibility complex class I (MHC I) on antigen presenting cells (APCs) is a potent molecule to activate CD8+ T cells and initiate immunity. P2X7 receptors (P2X7Rs) are present on the plasma membrane of APCs to sense the extracellular danger signal adenosine-5′-triphosphate (ATP). P2X7R activates the inflammasome and the release of IL-1β in macrophages and other immune cells to initiate the inflammatory response. Here we show that P2X7R stimulation by ATP in APCs decreased the amount of MHC I at the plasma membrane. Specific antagonism or genetic ablation of P2X7R inhibited the effects of ATP on levels of cellular MHC I. Furthermore, P2X7R stimulation was able to inhibit activation of CD8+ T cells via specific MHC I-oligopeptide complexes. Our study suggests that P2X7R activation on APCs is a novel inhibitor of adaptive CD8+ T cell immunity. 相似文献
20.
Xin Zhou Li-Min Ma Yan Xiong Hao Huang Jin-Xian Yuan Ruo-Han Li Jia-Ni Li Yang-Mei Chen 《Neurochemical research》2016,41(6):1263-1273
Purinergic P2X3 receptors (P2X3Rs) play extensive roles in nerve cells in the central nervous system, particularly in hyperexcitability and calcium (Ca2+) influx. However, the role of P2X3Rs in epilepsy has not been previously investigated. To determine the relationship between P2X3Rs and epilepsy, the expression and cellular location of P2X3Rs in patients with intractable temporal lobe epilepsy (TLE) and in a lithium chloride-pilocarpine-induced chronic rat model of epilepsy were assessed. Furthermore, the function of P2X3Rs was assessed in vitro. Real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis were used to evaluate the expression levels of P2X3Rs in brain tissues from TLE patients and an epileptic rat model, whereas immunofluorescence labeling was applied to determine the distribution of target proteins. Whole-cell recording was subsequently performed to identify the influence of P2X3Rs on seizure-like discharges. P2X3Rs were located at the cell bodies and dendrites of neurons with significantly increased expression in the TLE patients and epileptic rat model. In vitro, P2X3R activation accelerated sustained repetitive firing, whereas P2X3R inhibition led to relatively low-frequency discharges. To the best of our knowledge, this is the first study provide evidence that upregulated P2X3R expression exists in both epileptic humans and rats and may aggravate the epileptic state in vitro. Thus, P2X3Rs may represent a novel therapeutic target for antiepileptic drugs. 相似文献