Generation Of Calcium Signals Research Articles

Phosphatidylinositol-specific phospholipase C-associated phospholipid metabolism mediates DcGLRs channel to promote calcium influx under CaCl2 treatment in shredded carrots during storage

The rapid activation of phosphatidylinositol-specific phospholipase C (PI-PLC) occurs early after the stimulation of biotic and abiotic stress in plants, which directly associated with the calcium channel-induced calcium ion (Ca2+) influx. Exogenous calcium chloride (CaCl2) mediates the calcium signaling transduction to promote the γ-aminobutyric acid accumulation and nutritional quality in shredded carrots whereas the generation mechanism remains uncertain. Therefore, the involvement of PI-PLC-associated phospholipid metabolism was investigated in present study. Our result revealed that CaCl2 treatment promoted the expression and activity of PI-PLC and increased the inositol 1,4,5-trisphosphate and hexakisphosphate content in shredded carrots. The transcripts of multi-glutamate receptor-like channels (DcGLRs), the glutamate and γ-aminobutyric acid (GABA) content, and Ca2+ influx were induced by CaCl2 treatment in shredded carrots during storage. However, PI-PLC inhibitor (U73122) treatment inhibited the activation of PI-PLC, the increase of many DcGLRs family genes expression levels, and Ca2+ influx. Moreover, the identification of DcPI-PLC4/6 and DcGLRs proteins, along with the analysis of characteristic domains such as PLCXc, PLCYc, C2 domain, transmembranous regions, and ligand binding domain, suggests their involvement in phospholipid catalysis and calcium transport in carrots. Furthermore, DcPI-PLC4/6 overexpression in tobacco leaves induced the Ca2+ influx by activating the expressions of NtGLRs and the accumulation of glutamate and GABA. These findings collectively indicate that CaCl2 treatment-induced PI-PLC activation influences DcGLRs expression levels to mediate cytosolic Ca2+ influx, thus, highlighting the “PI-PLC-GLRs-Ca2+” pathway in calcium signaling generation and GABA biosynthesis in shredded carrots.

Centripetal integration of past events in hippocampal astrocytes regulated by locus coeruleus.

An essential feature of neurons is their ability to centrally integrate information from their dendrites. The activity of astrocytes, in contrast, has been described as mostly uncoordinated across cellular compartments without clear central integration. Here we report conditional integration of calcium signals in astrocytic distal processes at their soma. In the hippocampus of adult mice of both sexes, we found that global astrocytic activity, as recorded with population calcium imaging, reflected past neuronal and behavioral events on a timescale of seconds. Salient past events, indicated by pupil dilations, facilitated the propagation of calcium signals from distal processes to the soma. Centripetal propagation to the soma was reproduced by optogenetic activation of the locus coeruleus, a key regulator of arousal, and reduced by pharmacological inhibition of α1-adrenergic receptors. Together, our results suggest that astrocytes are computational units of the brain that slowly and conditionally integrate calcium signals upon behaviorally relevant events.

Supralinear Dependence of the IP3 Receptor-to-Mitochondria Local Ca2+ Transfer on the Endoplasmic Reticulum Ca2+ Loading.

Calcium signal propagation from endoplasmic reticulum (ER) to mitochondria regulates a multitude of mitochondrial and cell functions, including oxidative ATP production and cell fate decisions. Ca2+ transfer is optimal at the ER-mitochondrial contacts, where inositol 1,4,5-trisphosphate (IP3) receptors (IP3R) can locally expose the mitochondrial Ca2+ uniporter (mtCU) to high [Ca2+] nanodomains. The Ca2+ loading state of the ER (Ca2 + ER) can vary broadly in physiological and pathological scenarios, however, the correlation between Ca2 + ER and the local Ca2+ transfer is unclear. Here, we studied IP3-induced Ca2+ transfer to mitochondria at different Ca2 + ER in intact and permeabilized RBL-2H3 cells via fluorescence measurements of cytoplasmic [Ca2+] ([Ca2+]c) and mitochondrial matrix [Ca2+] ([Ca2+]m). Preincubation of intact cells in high versus low extracellular [Ca2+] caused disproportionally greater increase in [Ca2+]m than [Ca2+]c responses to IP3-mobilizing agonist. Increasing Ca2 + ER by small Ca2+ boluses in suspensions of permeabilized cells supralinearly enhanced the mitochondrial Ca2+ uptake from IP3-induced Ca2+ release. The IP3-induced local [Ca2+] spikes exposing the mitochondrial surface measured using a genetically targeted sensor appeared to linearly correlate with Ca2 + ER, indicating that amplification happened in the mitochondria. Indeed, overexpression of an EF-hand deficient mutant of the mtCU gatekeeper MICU1 reduced the cooperativity of mitochondrial Ca2+ uptake. Interestingly, the IP3-induced [Ca2+]m signal plateaued at high Ca2 + ER, indicating activation of a matrix Ca2+ binding/chelating species. Mitochondria thus seem to maintain a "working [Ca2+]m range" via a low-affinity and high-capacity buffer species, and the ER loading steeply enhances the IP3R-linked [Ca2+]m signals in this working range.

Structural and functional analysis of salivary intercalated duct cells reveals a secretory phenotype.

Currently, all salivary ducts (intercalated, striated and collecting) are assumed to function broadly in a similar manner, reclaiming ions that were secreted by the secretory acinar cells while preserving fluid volume and delivering saliva to the oral cavity. Nevertheless, there has been minimal investigation into the structural and functional differences between distinct types of salivary duct cells. Therefore, in this study, the expression profile of proteins involved in stimulus-secretion coupling, as well as the function of the intercalated duct (ID) and striated duct cells, was examined. Particular focus was placed on defining differences between distinct duct cell populations. To accomplish this, immunohistochemistry and in situ hybridization were utilized to examine the localization and expression of proteins involved in reabsorption and secretion of ions and fluid. Further, in vivo calcium imaging was employed to investigate cellular function. Based on the protein expression profile and functional data, marked differences between the IDs and striated ducts were observed. Specifically, the ID cells express proteins native to the secretory acinar cells while lacking proteins specifically expressed in the striated ducts. Further, the ID and striated duct cells display different calcium signalling characteristics, with the IDs responding to a neural stimulus in a manner similar to the acinar cells. Overall, our data suggest that the IDs have a distinct role in the secretory process, separate from the reabsorptive striated ducts. Instead, based on our evidence, the IDs express proteins found in secretory cells, generate calcium signals in a manner similar to acinar cells, and, therefore, are likely secretory cells. KEY POINTS: Current studies examining salivary intercalated duct cells are limited, with minimal documentation of the ion transport machinery and the overall role of the cells in fluid generation. Salivary intercalated duct cells are presumed to function in the same manner as other duct cells, reclaiming ions, maintaining fluid volume and delivering the final saliva to the oral cavity. Here we systematically examine the structure and function of the salivary intercalated duct cells using immunohistochemistry, in situ hybridization and by monitoring in vivo Ca2+ dynamics. Structural data revealed that the intercalated duct cells lack proteins vital for reabsorption and express proteins necessary for secretion. Ca2+ dynamics in the intercalated duct cells were consistent with those observed in secretory cells and resulted from GPCR-mediated IP3 production.

Capture at the ER-mitochondrial contacts licenses IP3 receptors to stimulate local Ca2+ transfer and oxidative metabolism

Endoplasmic reticulum-mitochondria contacts (ERMCs) are restructured in response to changes in cell state. While this restructuring has been implicated as a cause or consequence of pathology in numerous systems, the underlying molecular dynamics are poorly understood. Here, we show means to visualize the capture of motile IP3 receptors (IP3Rs) at ERMCs and document the immediate consequences for calcium signaling and metabolism. IP3Rs are of particular interest because their presence provides a scaffold for ERMCs that mediate local calcium signaling, and their function outside of ERMCs depends on their motility. Unexpectedly, in a cell model with little ERMC Ca2+ coupling, IP3Rs captured at mitochondria promptly mediate Ca2+ transfer, stimulating mitochondrial oxidative metabolism. The Ca2+ transfer does not require linkage with a pore-forming protein in the outer mitochondrial membrane. Thus, motile IP3Rs can traffic in and out of ERMCs, and, when ‘parked’, mediate calcium signal propagation to the mitochondria, creating a dynamic arrangement that supports local communication.

Epidemic-Like Calcium Signaling in Mobile Molecular Communication Networks.

Molecular Communication is an emerging technology enabling communications in nano-networks. Ca2+ signal is one promising option of MC due to the important role in bio-metabolisms and the available characteristics in communication engineering. So far, scientists analyze Ca2+ signaling via bio-experiments and simulations. Current researches lack a mathematical model for quantitative analysis of Ca2+ signal propagation on the network scale. In this work, we investigate the propagation patterns of Ca2+ signals in bio-cellular network. Firstly, we propose an improved Ca2+ dynamics model to describe Ca2+ signals considering movements of cells and attenuation of Ca2+ concentration. Then, we perform multi-modal analysis through the waveform characteristics, and classify cells according to their states. Moreover, a mathematical model is put forward to analyze the propagation of calcium signals based on typical epidemic model. The proposed model fully considers the similarity between: 1) epidemic disease propagates among mobile individuals; 2) Ca2+ signal propagates among mobile cells. The proposed model is amended to fit the case considering unique characters of Ca2+ signal. Finally, simulation results show that the proposed Ca2+ propagation model is coincident with Monte Carlo simulation results, indicating that the model is helpful for understanding how far and how fast Ca2+ signal can propagate.

The unfolding and activation of STIM1 in store-operated calcium signal generation

• Single molecule FRET studies reveal details of the folding of STIM1 in its resting state and unfolding activated by Ca 2+ store-depletion. • STIM1 is folded with SOAR inverted and held between the CC1α helices in a domain-swapping configuration close to the ER membrane. • Store-depletion causes the STIM1 TM-helices to bind together, squeezing SOAR from between the CC1α1 helices, allowing it to flip up and activate Orai channels SEE ABSTRACT in Query Response

Plant Viruses Can Alter Aphid-Triggered Calcium Elevations in Infected Leaves.

Alighting aphids probe a new host plant by intracellular test punctures for suitability. These induce immediate calcium signals that emanate from the punctured sites and might be the first step in plant recognition of aphid feeding and the subsequent elicitation of plant defence responses. Calcium is also involved in the transmission of non-persistent plant viruses that are acquired by aphids during test punctures. Therefore, we wanted to determine whether viral infection alters calcium signalling. For this, calcium signals triggered by aphids were imaged on transgenic Arabidopsis plants expressing the cytosolic FRET-based calcium reporter YC3.6-NES and infected with the non-persistent viruses cauliflower mosaic (CaMV) and turnip mosaic (TuMV), or the persistent virus, turnip yellows (TuYV). Aphids were placed on infected leaves and calcium elevations were recorded by time-lapse fluorescence microscopy. Calcium signal velocities were significantly slower in plants infected with CaMV or TuMV and signal areas were smaller in CaMV-infected plants. Transmission tests using CaMV-infected Arabidopsis mutants impaired in pathogen perception or in the generation of calcium signals revealed no differences in transmission efficiency. A transcriptomic meta-analysis indicated significant changes in expression of receptor-like kinases in the BAK1 pathway as well as of calcium channels in CaMV- and TuMV-infected plants. Taken together, infection with CaMV and TuMV, but not with TuYV, impacts aphid-induced calcium signalling. This suggests that viruses can modify plant responses to aphids from the very first vector/host contact.

Commentary to Baraniak et al. “Orai channel C-terminal peptides are key modulators of STIM-Orai coupling and calcium signal generation” published in cell reports 35: 109322.

Commentary to Baraniak et al. “Orai channel C-terminal peptides are key modulators of STIM-Orai coupling and calcium signal generation” published in cell reports 35: 109322.

Orai channel C-terminal peptides are key modulators of STIM-Orai coupling and calcium signal generation.

SUMMARYJunctional coupling between endoplasmic reticulum (ER) Ca2+-sensor STIM proteins and plasma membrane (PM) Orai channels mediates Ca2+ signals in most cells. We reveal that PM-tethered, fluorescently tagged C-terminal M4x (fourth transmembrane helix contains a cytoplasmic C-terminal extension) peptides from Orai channels undergo a Leu-specific signature of direct interaction with the STIM1 Orai-activating region (SOAR), exactly mimicking STIM1 binding to gate Orai channels. The 20-amino-acid Orai3-M4x peptide associates avidly with STIM1 within ER-PM junctions, functions to competitively block native Ca2+ signals, and mediates a key modification of STIM-Orai coupling induced by 2-aminoethoxydiphenyl borate. By blocking STIM-Orai coupling, the Orai3-M4x peptide reveals the critical role of Orai channels in driving Ca2+ oscillatory signals and transcriptional control through NFAT. The M4x peptides interact independently with SOAR dimers consistent with unimolecular coupling between Orai subunits and STIM1 dimers. We reveal the critical role of M4x helices in defining the coupling interface between STIM and Orai proteins to mediate store-operated Ca2+ signals.

Modeling Working Memory in a Spiking Neuron Network Accompanied by Astrocytes.

We propose a novel biologically plausible computational model of working memory (WM) implemented by a spiking neuron network (SNN) interacting with a network of astrocytes. The SNN is modeled by synaptically coupled Izhikevich neurons with a non-specific architecture connection topology. Astrocytes generating calcium signals are connected by local gap junction diffusive couplings and interact with neurons via chemicals diffused in the extracellular space. Calcium elevations occur in response to the increased concentration of the neurotransmitter released by spiking neurons when a group of them fire coherently. In turn, gliotransmitters are released by activated astrocytes modulating the strength of the synaptic connections in the corresponding neuronal group. Input information is encoded as two-dimensional patterns of short applied current pulses stimulating neurons. The output is taken from frequencies of transient discharges of corresponding neurons. We show how a set of information patterns with quite significant overlapping areas can be uploaded into the neuron-astrocyte network and stored for several seconds. Information retrieval is organized by the application of a cue pattern representing one from the memory set distorted by noise. We found that successful retrieval with the level of the correlation between the recalled pattern and ideal pattern exceeding 90% is possible for the multi-item WM task. Having analyzed the dynamical mechanism of WM formation, we discovered that astrocytes operating at a time scale of a dozen of seconds can successfully store traces of neuronal activations corresponding to information patterns. In the retrieval stage, the astrocytic network selectively modulates synaptic connections in the SNN leading to successful recall. Information and dynamical characteristics of the proposed WM model agrees with classical concepts and other WM models.

Using Volumetric 3D Microscopy Techniques to Characterize Astrocyte Morphologies over Large Spatial Scales

Astrocytes are a type of glia found in the central nervous system with many roles, and have recently been reported to be directly involved in modulating and scaling synaptic transmission. Neurotransmitters released in synaptic activity induce astrocyte calcium signaling, which then induces the release gliotransmitters that can act on neighbouring pre- and postsynaptic neuronal elements. Astrocytes are highly 3-dimensional and form large syncytium of diffusion-coupled cells via their many long protrusions. It has been proposed that astrocytes may use these large networks to communicate and correlate to distant synapses. When studying astrocyte network interactions, it is important to establish astrocyte morphology at the the level of single cells and of populations, as this structure is directly related to the astrocytes’ ability for intercellular communication, and speed and frequency of calcium signal propagation. On-going advances in volumetric 3D imaging techniques, such as light-sheet microscopy, now allow for imaging complete murine brain sections, and obtaining a better understanding of how astrocytes are organized and interact in situ on a larger spatial scale. Here, a pipeline for characterizing morphology for both single astrocytes and their networks using volumetric 3D microscopy techniques was optimized using 500 µm and 1 mm thick mouse cortex slices. Various structural features were measured and quantified including territorial volume, cell orientations, number of connections, process arborisations and lengths. This characterization pipeline can be extended to cortical organoids, larger tissue sections, or other brain regions, and is a helpful tool for studying astrocyte network structure and functionality.

Essential Functions of the Transcription Factor Npas4 in Neural Circuit Development, Plasticity, and Diseases.

Signaling from the synapse to nucleus is mediated by the integration and propagation of both membrane potential changes (postsynaptic potentials) and intracellular second messenger cascades. The electrical propagation of postsynaptic potentials allows for rapid neural information processing, while propagating second messenger pathways link synaptic activity to the transcription of genes required for neuronal survival and adaptive changes (plasticity) underlying circuit formation and learning. The propagation of activity-induced calcium signals to the cell nucleus is a major synapse-to-nucleus communication pathway. Neuronal PAS domain protein 4 (Npas4) is a recently discovered calcium-dependent transcription factor that regulates the activation of genes involved in the homeostatic regulation of excitatory–inhibitory balance, which is critical for neural circuit formation, function, and ongoing plasticity, as well as for defense against diseases such as epilepsy. Here, we summarize recent findings on the neuroprotective functions of Npas4 and the potential of Npas4 as a therapeutic target for the treatment of acute and chronic diseases of the central nervous system.

Stimulation of the Gαq/phospholipase Cβ1 signaling pathway returns differentiated cells to a stem-like state.

Phospholipase Cβ1 is activated by Gαq to generate calcium signals in response to hormones and neurotransmitters. Besides carrying out this plasma membrane function, PLCβ1 has a cytosolic population that helps to drive the differentiation of PC12 cells by inhibiting a nuclease that promotes RNA-induced silencing (C3PO). Here, we show that down-regulating PLCβ1 or reducing its cytosolic population by activating Gαq to localize it to the plasma membrane returns differentiated PC12 and SK-N-SH cells to an undifferentiated state. In this state, PC12 cells have a spherical morphology, resume proliferation, and express the stem cell transcription factors nanog and Oct4. Similar changes are seen when C3PO is down-regulated. This return to a stem-like state is accompanied by shifts in multiple miR populations. Surprisingly, de-differentiation can be induced by extended stimulation of Gαq where cells return to a spherical morphology and levels of specific miRs return to their undifferentiated values. In complementary studies, we followed the real-time hydrolysis of a fluorescent-tagged miR in cells where PLCβ1 or C3PO were down-regulated in PC12 cells and find substantial differences in miR processing in the undifferentiated and differentiated states. Taken together, our studies suggest that PLCβ1, through its ability to regulate C3PO and endogenous miR populations, mediates the differentiation of two types of cultured neuronal cells.

The Role of TRP Channels in Allergic Inflammation and its Clinical Relevance.

Allergy refers to an abnormal adaptive immune response to non-infectious environmental substances (allergen) that can induce various diseases such as asthma, atopic dermatitis, and allergic rhinitis. In this allergic inflammation, various immune cells, such as B cells, T cells, and mast cells, are involved and undergo complex interactions that cause a variety of pathophysiological conditions. In immune cells, calcium ions play a crucial role in controlling intracellular Ca2+ signaling pathways. Cations, such as Na+, indirectly modulate the calcium signal generation by regulating cell membrane potential. This intracellular Ca2+ signaling is mediated by various cation channels; among them, the Transient Receptor Potential (TRP) family is present in almost all immune cell types, and each channel has a unique function in regulating Ca2+ signals. In this review, we focus on the role of TRP ion channels in allergic inflammatory responses in T cells and mast cells. In addition, the TRP ion channels, which are attracting attention in clinical practice in relation to allergic diseases, and the current status of the development of therapeutic agents that target TRP channels are discussed.

Bilirubin disrupts calcium homeostasis in neonatal hippocampal neurons: a new pathway of neurotoxicity.

Severe hyperbilirubinemia leads to bilirubin encephalopathy in neonates, causing irreversible neurological sequelae. We investigated the nature of neuronal selective vulnerability to unconjugated bilirubin (UCB) toxicity. The maintenance of intracellular calcium homeostasis is crucial for neuron survival. Calcium release from endoplasmic reticulum (ER) during ER-stress can lead to apoptosis trough the activation of Caspase-12. By live calcium imaging we monitored the generation of calcium signals in dissociated hippocampal neurons and glial cells exposed to increasing UCB concentrations. We showed the ability of UCB to alter intracellular calcium homeostasis, inducing the appearance of repetitive intracellular calcium oscillations. The contribution of intracellular calcium stores and the induction and activation of proteins involved in the apoptotic calcium-dependent signaling were also assessed. Thapsigargin, a specific inhibitor of Sarco/endoplasmic reticulum ATPase (SERCA) pumps, significantly reduced the duration of Ca2+ oscillation associated with UCB exposure indicating that UCB strongly interfered with the reticulum calcium stores. On the contrary, in pure astrocyte cultures, spontaneous Ca2+ transient duration was not altered by UCB. The protein content of GRP78, AT6, CHOP, Calpain and Caspase-12 of neuronal cells treated with UCB for 24h was at least twofold higher compared to controls. Calcium-dependent Calpain and Caspase-12 induction by UCB were significantly reduced by 50% and 98%, respectively when cells were pretreated with the ER-stress inhibitor 4-PBA. These results show the strong and direct interference of UCB with neuronal intracellular Ca2+ dynamics, suggesting ER Ca2+ stores as a primary target of UCB toxicity with the activation of the apoptotic ER-stress-dependent pathway.

Structured silicon for revealing transient and integrated signal transductions in microbial systems.

Bacterial response to transient physical stress is critical to their homeostasis and survival in the dynamic natural environment. Because of the lack of biophysical tools capable of delivering precise and localized physical perturbations to a bacterial community, the underlying mechanism of microbial signal transduction has remained unexplored. Here, we developed multiscale and structured silicon (Si) materials as nongenetic optical transducers capable of modulating the activities of both single bacterial cells and biofilms at high spatiotemporal resolution. Upon optical stimulation, we capture a previously unidentified form of rapid, photothermal gradient-dependent, intercellular calcium signaling within the biofilm. We also found an unexpected coupling between calcium dynamics and biofilm mechanics, which could be of importance for biofilm resistance. Our results suggest that functional integration of Si materials and bacteria, and associated control of signal transduction, may lead to hybrid living matter toward future synthetic biology and adaptable materials.

Orai, STIM, and PMCA contribute to reduced calcium signal generation in CD8+ T cells of elderly mice.

Ca2+ is a crucial second messenger for proper T cell function. Considering the relevance of Ca2+ signals for T cell functionality it is surprising that no mechanistic insights into T cell Ca2+ signals from elderly individuals are reported. The main Ca2+ entry mechanism in T cells are STIM-activated Orai channels. Their role during lymphocyte aging is completely unknown. Here, we report not only reduced Ca2+ signals in untouched and stimulated, but also in central and effector memory CD8+ T cells from elderly (18-24 months) compared to adult (3-6 months) mice. Two mechanisms contribute to the overall reduction in Ca2+ signals of CD8+ T cells of elderly mice: 1) Reduced Ca2+ currents through Orai channels due to decreased expressions of STIMs and Orais. 2) A faster extrusion of Ca2+ owing to an increased expression of PMCA4. The reduced Ca2+ signals correlated with a resistance of the cytotoxic efficiency of CD8+ T cells to varying free [Ca2+]ext with age. In summary, reduced STIM/Orai expression and increased Ca2+ clearing rates following enhanced PMCA4 expression contribute to reduced Ca2+ signals in CD8+ T cells of elderly mice. These changes are apparently relevant to immune function as they reduce the Ca2+ dependency of CTL cytotoxicity.

Non-uniform Distribution of Inner Mitochondrial Membrane Calcium Transport Mechanisms in the Cardiac Muscle

Energy homeostasis in the cardiac muscle is critical to assure uninterrupted circulation. The primary energy source of the adult cardiomyocyte is the mitochondrial oxidative ATP production. Metabolic feedback loops and the ATP buffering creatine kinase-phosphocreatine system serve to replenish the ATP levels consumed at each heartbeat; however, they may not sufficiently support the abrupt performance increase needed during fight-or-flight or similar stress responses. To that end, a feed-forward loop has evolved that stimulates the electron donor generators for the respiratory chain, the calcium sensitive mitochondrial matrix dehydrogenases, via mitochondrial calcium uptake during the excitation-contraction coupling. This feed-forward loop, also referred as ‘excitation-bioenergetics coupling’, involves local calcium transfer at the membrane contacts formed between the sarcoplasmic reticulum calcium release units and intermyofibrillar mitochondria. These contacts are secured by protein tethers and our recent studies suggest that they are also areas with strong distribution anomalies of the primary mitochondrial calcium uptake and extrusion mechanisms of the inner mitochondrial membrane. Namely, while the contact area is a hotspot for the mitochondrial calcium uniporter complex (MCUC), the Na+/Ca2+ exchanger NCLX is largely excluded from there, even though it is abundant outside the contact area. In this talk, I will present our ideas why such a biased distribution is a favorable arrangement for effective mitochondrial matrix calcium signal generation. Furthermore, potential molecular mechanisms that are responsible for the non-uniform distribution of the MCUC components will be discussed.

Calcium Signaling in Glioma Cells: The Role of Nucleotide Receptors.

Calcium signaling is probably one of the evolutionary oldest and the most common way by which the signal can be transmitted from the cell environment to the cytoplasmic calcium binding effectors. Calcium signal is fast and due to diversity of calcium binding proteins it may have a very broad effect on cell behavior. Being a crucial player in neuronal transmission it is also very important for glia physiology. It is responsible for the cross-talk between neurons and astrocytes, for microglia activation and motility. Changes in calcium signaling are also crucial for the behavior of transformed glioma cells. The present chapter summarizes molecular mechanisms of calcium signal formation present in glial cells with a strong emphasis on extracellular nucleotide-evoked signaling pathways. Some aspects of glioma C6 signaling such as the cross-talk between P2Y1 and P2Y12 nucleotide receptors in calcium signal generation will be discussed in-depth, to show complexity of machinery engaged in formation of this signal. Moreover, possible mechanisms of modulation of the calcium signal in diverse environments there will be presented herein. Finally, the possible role of calcium signal in glioma motility is also discussed. This is a very important issue, since glioma cells, contrary to the vast majority of neoplastic cells, cannot spread in the body with the bloodstream and, at least in early stages of tumor development, may expand only by means of sheer motility.