Inhibition of inositol trisphosphate-induced calcium release by caffeine is prevented by ATP.
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ABSTRACT:
SUBMITTER: Missiaen L
PROVIDER: S-EPMC1138126 | biostudies-other | 1994 May
REPOSITORIES: biostudies-other
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Project description:Calcium signaling is important in many signaling processes in cancer cell proliferation and motility including in deadly glioblastomas of the brain that aggressively invade neighboring tissue. We hypothesized that disturbing Ca(2+) signaling pathways might decrease the invasive behavior of giloblastoma, extending survival. Evaluating a panel of small-molecule modulators of Ca(2+) signaling, we identified caffeine as an inhibitor of glioblastoma cell motility. Caffeine, which is known to activate ryanodine receptors, paradoxically inhibits Ca(2+) increase by inositol 1,4,5-trisphospate receptor subtype 3 (IP(3)R3), the expression of which is increased in glioblastoma cells. Consequently, by inhibiting IP(3)R3-mediated Ca(2+) release, caffeine inhibited migration of glioblastoma cells in various in vitro assays. Consistent with these effects, caffeine greatly increased mean survival in a mouse xenograft model of glioblastoma. These findings suggest IP(3)R3 as a novel therapeutic target and identify caffeine as a possible adjunct therapy to slow invasive growth of glioblastoma.
| S-EPMC3273964 | biostudies-literature
Project description:ObjectiveCaffeine reduces toxic Ca2+ signals in pancreatic acinar cells via inhibition of inositol 1,4,5-trisphosphate receptor (IP3R)-mediated signalling, but effects of other xanthines have not been evaluated, nor effects of xanthines on experimental acute pancreatitis (AP). We have determined effects of caffeine and its xanthine metabolites on pancreatic acinar IP3R-mediated Ca2+ signalling and experimental AP.DesignIsolated pancreatic acinar cells were exposed to secretagogues, uncaged IP3 or toxins that induce AP and effects of xanthines, non-xanthine phosphodiesterase (PDE) inhibitors and cyclic adenosine monophosphate and cyclic guanosine monophosphate (cAMP/cGMP) determined. The intracellular cytosolic calcium concentration ([Ca2+]C), mitochondrial depolarisation and necrosis were assessed by confocal microscopy. Effects of xanthines were evaluated in caerulein-induced AP (CER-AP), taurolithocholic acid 3-sulfate-induced AP (TLCS-AP) or palmitoleic acid plus ethanol-induced AP (fatty acid ethyl ester AP (FAEE-AP)). Serum xanthines were measured by liquid chromatography-mass spectrometry.ResultsCaffeine, dimethylxanthines and non-xanthine PDE inhibitors blocked IP3-mediated Ca2+ oscillations, while monomethylxanthines had little effect. Caffeine and dimethylxanthines inhibited uncaged IP3-induced Ca2+ rises, toxin-induced Ca2+ release, mitochondrial depolarisation and necrotic cell death pathway activation; cAMP/cGMP did not inhibit toxin-induced Ca2+ rises. Caffeine significantly ameliorated CER-AP with most effect at 25?mg/kg (seven injections hourly); paraxanthine or theophylline did not. Caffeine at 25?mg/kg significantly ameliorated TLCS-AP and FAEE-AP. Mean total serum levels of dimethylxanthines and trimethylxanthines peaked at >2?mM with 25?mg/kg caffeine but at <100?µM with 25?mg/kg paraxanthine or theophylline.ConclusionsCaffeine and its dimethylxanthine metabolites reduced pathological IP3R-mediated pancreatic acinar Ca2+ signals but only caffeine ameliorated experimental AP. Caffeine is a suitable starting point for medicinal chemistry.
| S-EPMC5284483 | biostudies-literature
Project description:Endothelial cells are reported to be glycolytic and to minimally rely on mitochondria for ATP generation. Rather than providing energy, mitochondria in endothelial cells may act as signaling organelles that control cytosolic Ca2+ signaling or modify reactive oxygen species (ROS). To control Ca2+ signaling, these organelles are often observed close to influx and release sites and may be tethered near Ca2+ transporters. In this study, we used high-resolution, wide-field fluorescence imaging to investigate the regulation of Ca2+ signaling by mitochondria in large numbers of endothelial cells (?50 per field) in intact arteries from rats. We observed that mitochondria were mostly spherical or short-rod structures and were distributed widely throughout the cytoplasm. The density of these organelles did not increase near contact sites with smooth muscle cells. However, local inositol trisphosphate (IP3)-mediated Ca2+ signaling predominated near these contact sites and required polarized mitochondria. Of note, mitochondrial control of Ca2+ signals occurred even when mitochondria were far from Ca2+ release sites. Indeed, the endothelial mitochondria were mobile and moved throughout the cytoplasm. Mitochondrial control of Ca2+ signaling was mediated by ATP production, which, when reduced by mitochondrial depolarization or ATP synthase inhibition, eliminated local IP3-mediated Ca2+ release events. ROS buffering did not significantly alter local Ca2+ release events. These results highlight the importance of mitochondrial ATP production in providing long-range control of endothelial signaling via IP3-evoked local Ca2+ release in intact endothelium.
| S-EPMC6341391 | biostudies-literature
Project description:The effects of a whole series of adenine nucleotides on Ins(1,4,5)P3-induced Ca2+ release were characterized in permeabilized A7r5 smooth-muscle cells. Several adenine nucleotides activated the Ins(1, 4,5)P3 receptor. It was observed that 3'-phosphoadenosine 5'-phosphoulphate, CoA, di(adenosine-5')tetraphosphate (Ap4A) and di(adenosine-5')pentaphosphate (Ap5A) were more effective than ATP. Ap4A and Ap5A also interacted with a lower EC50 than ATP. In order to find out how these adenine nucleotides affected Ins(1,4, 5)P3-induced Ca2+ release, we have measured their effect on the response of permeabilized A7r5 cells to a progressively increasing Ins(1,4,5)P3 concentration. Stimulatory ATP and Ap5A concentrations had no effect on the threshold Ins(1,4,5)P3 concentration for initiating Ca2+ release, but they stimulated Ca2+ release in the presence of supra-threshold Ins(1,4,5)P3 concentrations by increasing the co-operativity of the release process. Inhibition of the Ins(1,4,5)P3-induced Ca2+ release at higher ATP concentrations was associated with a further increase in co-operativity and also with a shift in threshold towards higher Ins(1,4,5)P3 concentrations. ATP had no effect on the non-specific Ca2+ leak in the absence of Ins(1,4,5)P3. We conclude that the adenine-nucleotide-binding site can be activated by many different adenine nucleotides. Binding of these compounds to the transducing domain of the Ins(1,4,5)P3 receptor increases the efficiency of transmitting Ins(1,4,5)P3 binding to channel opening. The inhibition by high ATP concentrations is exerted at a different site, related to Ins(1,4,5)P3 binding.
| S-EPMC1218609 | biostudies-other
Project description:Receptor-mediated oscillations in cytosolic Ca(2+) concentration ([Ca(2+)]i) could originate either directly from an autonomous Ca(2+) feedback oscillator at the inositol 1,4,5-trisphosphate (IP3) receptor or as a secondary consequence of IP3 oscillations driven by Ca(2+) feedback on IP3 metabolism. It is challenging to discriminate these alternatives, because IP3 fluctuations could drive Ca(2+) oscillations or could just be a secondary response to the [Ca(2+)]i spikes. To investigate this problem, we constructed a recombinant IP3 buffer using type-I IP3 receptor ligand-binding domain fused to GFP (GFP-LBD), which buffers IP3 in the physiological range. This IP3 buffer slows hormone-induced [IP3] dynamics without changing steady-state [IP3]. GFP-LBD perturbed [Ca(2+)]i oscillations in a dose-dependent manner: it decreased both the rate of [Ca(2+)]i rise and the speed of Ca(2+) wave propagation and, at high levels, abolished [Ca(2+)]i oscillations completely. These data, together with computational modeling, demonstrate that IP3 dynamics play a fundamental role in generating [Ca(2+)]i oscillations and waves.
| S-EPMC6469397 | biostudies-literature
Project description:An important role in the regulation of apoptotic calcium release is played by the ubiquitously expressed family of inositol 1,4,5-trisphosphate receptor (IP(3)R) channels. One model for IP(3)R activation during apoptosis is cleavage by the apoptotic protease caspase 3. Here we show that early elevations in cytosolic calcium during apoptosis do not require caspase 3 activity. We detected a robust increase in calcium levels in response to staurosporine treatment in primary human fibroblasts and HeLa cells in the presence of the caspase inhibitor Z-VAD, indicating that calcium release during the initiation of apoptosis occurs independently of caspase 3. Similar results were obtained with MCF-7 cells which lack caspase 3 expression. Stable expression of caspase 3 in MCF-7 cells and TAT-based transduction of the active recombinant caspase 3 directly into living MCF-7 cells had marginal effects on the early events leading to cytosolic calcium elevations and irreversible commitment to apoptotic cell death. Significantly, blocking IP(3) binding to the IP(3)R with an IP(3) sponge resulted in suppression of staurosporine-induced calcium release and cell death. Collectively, our results suggest that generation of IP(3) is sufficient for the initiation of apoptotic calcium signaling, and caspase 3-mediated truncation of IP(3)R channel is a consequence, not causative, of apoptotic calcium release.
| S-EPMC3572306 | biostudies-literature
Project description:Swiss-mouse 3T3 cells permeabilized with saponin were used to study the specificity of the inositol trisphosphate-induced release of 45Ca2+ from their intracellular stores. Inositol 1,4,5-trisphosphate was the most potent compound studied (dose giving half-maximal effect 0.3 microM). 45Ca2+ was also released by inositol 2,4,5-trisphosphate, glycerophosphoinositol 4,5-bisphosphate and inositol 4,5-bisphosphate, with doses giving half-maximal effect of respectively 1.6 microM, 1.6 microM and 20 microM, but not by inositol 1,4-bisphosphate (50 microM). These data suggest that the trans-vicinal phosphates on the 4- and 5-positions are essential for the Ca2+-mobilizing effect of inositol trisphosphate, and that in addition there is a requirement for a phosphate group on the opposite side of the molecule, with a preference for the 1-position.
| S-EPMC1144170 | biostudies-other
Project description:RationaleThe mechanisms underlying atrial fibrillation (AF), the most common clinical arrhythmia, are poorly understood. Nucleoplasmic Ca2+ regulates gene expression, but the nature and significance of nuclear Ca2+-changes in AF are largely unknown.ObjectiveTo elucidate mechanisms by which AF alters atrial-cardiomyocyte nuclear Ca2+ ([Ca2+]Nuc) and CaMKII (Ca2+/calmodulin-dependent protein kinase-II)-related signaling.Methods and resultsAtrial cardiomyocytes were isolated from control and AF dogs (kept in AF by atrial tachypacing [600 bpm × 1 week]). [Ca2+]Nuc and cytosolic [Ca2+] ([Ca2+]Cyto) were recorded via confocal microscopy. Diastolic [Ca2+]Nuc was greater than [Ca2+]Cyto under control conditions, while resting [Ca2+]Nuc was similar to [Ca2+]Cyto; both diastolic and resting [Ca2+]Nuc increased with AF. IP3R (Inositol-trisphosphate receptor) stimulation produced larger [Ca2+]Nuc increases in AF versus control cardiomyocytes, and IP3R-blockade suppressed the AF-related [Ca2+]Nuc differences. AF upregulated nuclear protein expression of IP3R1 (IP3R-type 1) and of phosphorylated CaMKII (immunohistochemistry and immunoblot) while decreasing the nuclear/cytosolic expression ratio for HDAC4 (histone deacetylase type-4). Isolated atrial cardiomyocytes tachypaced at 3 Hz for 24 hours mimicked AF-type [Ca2+]Nuc changes and L-type calcium current decreases versus 1-Hz-paced cardiomyocytes; these changes were prevented by IP3R knockdown with short-interfering RNA directed against IP3R1. Nuclear/cytosolic HDAC4 expression ratio was decreased by 3-Hz pacing, while nuclear CaMKII phosphorylation was increased. Either CaMKII-inhibition (by autocamtide-2-related peptide) or IP3R-knockdown prevented the CaMKII-hyperphosphorylation and nuclear-to-cytosolic HDAC4 shift caused by 3-Hz pacing. In human atrial cardiomyocytes from AF patients, nuclear IP3R1-expression was significantly increased, with decreased nuclear/nonnuclear HDAC4 ratio. MicroRNA-26a was predicted to target ITPR1 (confirmed by luciferase assay) and was downregulated in AF atrial cardiomyocytes; microRNA-26a silencing reproduced AF-induced IP3R1 upregulation and nuclear diastolic Ca2+-loading.ConclusionsAF increases atrial-cardiomyocyte nucleoplasmic [Ca2+] by IP3R1-upregulation involving miR-26a, leading to enhanced IP3R1-CaMKII-HDAC4 signaling and L-type calcium current downregulation. Graphic Abstract: A graphic abstract is available for this article.
| S-EPMC8243404 | biostudies-literature
Project description:Thymocyte-expressed, positive selection-associated 1 (Tespa1) is important in T cell receptor (TCR)-driven thymocyte development. Downstream of the TCR, Tespa1 is a crucial component of the linker for activation of T cells (LAT) signalosome, facilitating calcium signalling and subsequent MAPK activation. However, it is unknown how Tespa1 elicits calcium signalling. Here, we show that inositol 1,4,5-trisphosphate receptor type 1 (IP3R1) is crucial for Tespa1-optimized, TCR-induced Ca2+ flux and thymocyte development. Upon TCR stimulation, Tespa1 directly interacts with IP3R1 and recruits it to the TCR complex, where IP3R1 is phosphorylated at Y353 by Fyn. This Tespa1-IP3R1 interaction is mediated by the F187 and F188 residues of Tespa1 and the amino-terminus of IP3R1. Tespa1-F187A/F188A mutant mice phenocopy Tespa1-deficient mice with impaired late thymocyte development due to reduced IP3R1 translocation to the TCR-proximal region. Our work elucidates the function of Tespa1 in T cell development and the regulation of TCR-induced Ca2+ signalling through IP3R1.
| S-EPMC5472764 | biostudies-literature
Project description:Thimerosal inhibits calcium uptake in skeletal muscle sarcoplasmic reticulum and rat cerebellar microsomes by inhibiting the Ca(2+)-ATPase. In the presence of 5 mM dithiothreitol (DTT), Ca2+ uptake and ATPase activity were not inhibited by thimerosal, indicating that thimerosal modifies cysteine residues of the Ca(2+)-ATPase. Low thimerosal concentrations (2 microM) sensitize the inositol 1,4,5-trisphosphate (InsP3)-sensitive Ca2+ channel, making it open at lower InsP3 concentrations. Higher concentrations of thimerosal, however, cause inhibition of InsP3-induced Ca2+ release. Both sensitization and inhibition of the InsP3 receptor by thimerosal can be prevented by DTT. The binding and metabolism of InsP3 by cerebellar microsomes is not affected by thimerosal. The amount of InsP3-induced Ca2+ release is co-operatively linked to the InsP3 concentration with a Hill coefficient of 2.0 +/- 0.3. This is decreased to 1.0 +/- 0.2 at inhibitory concentrations of thimerosal. Under our experimental conditions, we observed no dependence of quantal Ca2+ release on intraluminal Ca2+ concentration.
| S-EPMC1132258 | biostudies-other