P2X7 receptor: the regulator of glioma tumor development and survival.

P2X7 is an ionotropic nucleotide receptor, forming the cation channel upon ATP stimulation. It can also function as a large membrane pore as well as transmit ATP-dependent signal without forming a channel at all. P2X7 activity in somatic cells is well-known, but remains poorly studied in glioma tumors. The current paper presents the comprehensive study of P2X7 activity in C6 and glioma cell line showing the wide range of effects the receptor has on glioma biology. We observed that P2X7 stimulation boosts glioma cell proliferation and increases cell viability. P2X7 activation promoted cell adhesion, mitochondria depolarization, and reactive oxygen species overproduction in C6 cells. P2X7 receptor also influenced glioma tumor growth in vivo via activation of pro-survival signaling pathways and ATP release. Treatment with Brilliant Blue G, a selective P2X7 antagonist, effectively inhibited glioma tumor development; decreased the expression of negative prognostic cancer markers pro-survival and epithelial-mesenchymal transition (EMT)-related proteins; and modulated the immune response toward glioma tumor in vivo. Finally, pathway-specific enrichment analysis of the microarray data from human patients also showed an upregulation of P2X7 receptor in gliomas from grades I to III. The presented results shed more light on the role of P2X7 receptor in the biology of this disease.

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.

Cytoskeleton and Nucleotide Signaling in Glioma C6 Cells.

This chapter describes signaling pathways, stimulated by the P2Y2 nucleotide receptor (P2Y2R), that regulate cellular processes dependent on actin cytoskeleton dynamics in glioma C6 cells. P2Y2R coupled with G-proteins, in response to ATP or UTP, regulates the level of iphosphatidylinositol-4,5-bisphosphate (PIP2) which modulates a variety of actin binding proteins and is involved in calcium response and activates Rac1 and RhoA proteins. The RhoA/ROCK signaling pathway plays an important role in contractile force generation needed for the assembly of stress fibers, focal adhesions and for tail retraction during cell migration. Blocking of this pathway by a specific Rho-kinase inhibitor induces changes in F-actin organization and cell shape and decreases the level of phosphorylated myosin II and cofilin. In glioma C6 cells these changes are reversed after UTP stimulation of P2Y2R. Signaling pathways responsible for this compensation are calcium signaling which regulates MLC kinase activation via calmodulin, and the Rac1/PAK/LIMK cascade. Stimulation of the Rac1 mediated pathway via Go proteins needs additional interaction between αvß5 integrins and P2Y2Rs. Calcium free medium, or growing of the cells in suspension, prevents Gαo activation by P2Y2 receptors. Rac1 activation is necessary for cofilin phosphorylation as well as integrin activation needed for focal complexes formation and stabilization of lamellipodium. Inhibition of positive Rac1 regulation prevents glioma C6 cells from recovery of control cell like morphology.

Interaction of myosin VI and its binding partner DOCK7 plays an important role in NGF-stimulated protrusion formation in PC12 cells.

DOCK7 (dedicator of cytokinesis 7) is a guanidine nucleotide exchange factor (GEF) for Rac1 GTPase that is involved in neuronal polarity and axon generation as well in Schwann cell differentiation and myelination. Recently, we identified DOCK7 as the binding partner of unconventional myosin VI (MVI) in neuronal-lineage PC12 cells and postulated that this interaction could be important in vivo [Majewski et al. (2012) Biochem Cell Biol., 90:565-574]. Herein, we found that MVI-DOCK7 interaction takes also place in other cell lines and demonstrated that MVI cargo domain via its RRL motif binds to DOCK7 C-terminal M2 and DHR2 domains. In MVI knockdown cells, lower Rac1 activity and a decrease of DOCK7 phosphorylation on Tyr1118 were observed, indicating that MVI could contribute to DOCK7 activity. MVI and DOCK7 co-localization was maintained during NGF-stimulated PC12 cell differentiation and observed also in the outgrowths. Also, during differentiation an increase in phosphorylation of DOCK7 as well as of its downstream effector JNK kinase was detected. Interestingly, overexpression of GFP-tagged MVI cargo domain (GFP-GT) impaired protrusion formation indicating that full length protein is important for this process. Moreover, a transient increase in Rac activity observed at 5min of NGF-stimulated differentiation of PC12 cells (overexpressing either GFP or GFP-MVI) was not detected in cells overexpressing the cargo domain. These data indicate that MVI-DOCK7 interaction could have functional implications in the protrusion outgrowth, and full length MVI seems to be important for delivery and maintenance of DOCK7 along the protrusions, and exerting its GEF activity.

P2Y1 Receptors - Properties and Functional Activities.

In this chapter we try to show a comprehensive image of current knowledge of structure, activity and physiological role of the P2Y1 purinergic receptor. The structure, distribution and changes in the expression of this receptor are summarized, as well as the mechanism of its signaling activity by the intracellular calcium mobilization. We try to show the connection between the components of its G protein activation and cellular or physiological effects, starting from changes in protein phosphorylation patterns and ending with such remote effects as receptor-mediated apoptosis. The special emphasis is put on the role of the P2Y1 receptor in cancer cells and neuronal plasticity. We concentrate on the P2Y1 receptor, it is though impossible to completely abstract from other aspects of nucleotide signaling and cross-talk with other nucleotide receptors is here discussed. Especially, the balance between P2Y1 and P2Y12 receptors, sharing the same ligand but signaling through different pathways, is presented.

[The tabernacle head does not hurt? Storage and distribution of the digital image]. / Od przybytku glowa nie boli? Przechowywanie i dystrybucja obrazu cyfrowego.

Modern life sciences become quantitative. Images created by microscopy are therefore the objects of measurement rather than a simple pictures. Saving and further storage of such images cannot change future measurements on them. Such images are the integral part of experiments. Present article try to describe what kind of data we are talking about, how should we store them and how we should not.

Hydrophobic Gating of Ion Permeation in Magnesium Channel CorA.

Ion channels catalyze ionic permeation across membranes via water-filled pores. To understand how changes in intracellular magnesium concentration regulate the influx of Mg2+ into cells, we examine early events in the relaxation of Mg2+ channel CorA toward its open state using massively-repeated molecular dynamics simulations conducted either with or without regulatory ions. The pore of CorA contains a 2-nm-long hydrophobic bottleneck which remained dehydrated in most simulations. However, rapid hydration or "wetting" events concurrent with small-amplitude fluctuations in pore diameter occurred spontaneously and reversibly. In the absence of regulatory ions, wetting transitions are more likely and include a wet state that is significantly more stable and more hydrated. The free energy profile for Mg2+ permeation presents a barrier whose magnitude is anticorrelated to pore diameter and the extent of hydrophobic hydration. These findings support an allosteric mechanism whereby wetting of a hydrophobic gate couples changes in intracellular magnesium concentration to the onset of ionic conduction.

Involvement of unconventional myosin VI in myoblast function and myotube formation.

The important role of unconventional myosin VI (MVI) in skeletal and cardiac muscle has been recently postulated (Karolczak et al. in Histochem Cell Biol 139:873-885, 2013). Here, we addressed for the first time a role for this unique myosin motor in myogenic cells as well as during their differentiation into myotubes. During myoblast differentiation, the isoform expression pattern of MVI and its subcellular localization underwent changes. In undifferentiated myoblasts, MVI-stained puncti were seen throughout the cytoplasm and were in close proximity to actin filaments, Golgi apparatus, vinculin-, and talin-rich focal adhesion as well as endoplasmic reticulum. Colocalization of MVI with endoplasmic reticulum was enhanced during myotube formation, and differentiation-dependent association was also seen in sarcoplasmic reticulum of neonatal rat cardiomyocytes (NRCs). Moreover, we observed enrichment of MVI in myotube regions containing acetylcholine receptor-rich clusters, suggesting its involvement in the organization of the muscle postsynaptic machinery. Overexpression of the H246R MVI mutant (associated with hypertrophic cardiomyopathy) in myoblasts and NRCs caused the formation of abnormally large intracellular vesicles. MVI knockdown caused changes in myoblast morphology and inhibition of their migration. On the subcellular level, MVI-depleted myoblasts exhibited aberrations in the organization of actin cytoskeleton and adhesive structures as well as in integrity of Golgi apparatus and endoplasmic reticulum. Also, MVI depletion or overexpression of H246R mutant caused the formation of significantly wider or aberrant myotubes, respectively, indicative of involvement of MVI in myoblast differentiation. The presented results suggest an important role for MVI in myogenic cells and possibly in myoblast differentiation.

DNAtraffic--a new database for systems biology of DNA dynamics during the cell life.

DNAtraffic (http://dnatraffic.ibb.waw.pl/) is dedicated to be a unique comprehensive and richly annotated database of genome dynamics during the cell life. It contains extensive data on the nomenclature, ontology, structure and function of proteins related to the DNA integrity mechanisms such as chromatin remodeling, histone modifications, DNA repair and damage response from eight organisms: Homo sapiens, Mus musculus, Drosophila melanogaster, Caenorhabditis elegans, Saccharomyces cerevisiae, Schizosaccharomyces pombe, Escherichia coli and Arabidopsis thaliana. DNAtraffic contains comprehensive information on the diseases related to the assembled human proteins. DNAtraffic is richly annotated in the systemic information on the nomenclature, chemistry and structure of DNA damage and their sources, including environmental agents or commonly used drugs targeting nucleic acids and/or proteins involved in the maintenance of genome stability. One of the DNAtraffic database aim is to create the first platform of the combinatorial complexity of DNA network analysis. Database includes illustrations of pathways, damage, proteins and drugs. Since DNAtraffic is designed to cover a broad spectrum of scientific disciplines, it has to be extensively linked to numerous external data sources. Our database represents the result of the manual annotation work aimed at making the DNAtraffic much more useful for a wide range of systems biology applications.

[Nucleotide receptors and the cell motility]. / Receptory nukleotydowe a ruch komórek.

The ability to active motility is one of the fundamental features of both normal and pathologically transformed cells. The current paper de- scribes the role of nucleotide receptors in regulation of cell motility in higher organisms. Author focuses on those cells which actively move in the nucleotide gradients: immune system cells as well as glia cells. The impact of individual receptors in motility and current opinions on the role of signaling pathways activated by those receptors will be described. The source of nucleotides regulating motility will be proposed and role of extracellular nucleotides such as ATP, ADP, UTP and adenosine will be indicated. The role of ectoenzymes in creation of secondary nucleotide gradients regulating cell motility will also be indicated. Finally, the role of nucleotides in regulation of brain tumor cells will be described and perspective of possible therapeutic role of modulation nucleotide signaling influencing cell motility will be suggested.

The protective effect of silver nanoparticles' on epithelial cornea cells against ultraviolet is accompanied by changes in calcium homeostasis and a decrease of the P2X7 and P2Y2 receptors.

PURPOSE: The aim of the study was to evaluate the effect of silver nanoparticles hydrocolloids (AgNPs) on human corneal epithelial cells. Epithelial cells form the outermost and the most vulnerable to environmental stimuli layer of the cornea in the eye. Mechanical stress, UV radiation, and pathogens such as bacteria, viruses, and parasites challenge the fragile homeostasis of the eye. To help combat stress, infection, and inflammation wide portfolio of interventions is available. One of the oldest treatments is colloidal silver. Silver nanoparticle suspension in water is known for its anti-bacterial anti-viral and antiprotozoal action. However, AgNPs interact also with host cells, and the character of the interplay between corneal cells and silver seeks investigation. METHODS: The human epithelial corneal cell line (HCE-2) was cultured in vitro, treated with AgNPs, and subjected to UV. The cell's viability, migration, calcium concentration, and expression/protein level of selected proteins were investigated by appropriate methods including cytotoxicity tests, "wound healing" assay, Fluo8/Fura2 AM staining, qRT-PCR, and western blot. RESULTS: Incubation of human corneal cells (HCE-2) with AgNP did not affect cells viability but limited cells migration and resulted in altered calcium homeostasis, decreased the presence of ATP-activated P2X7, P2Y2 receptors, and enhanced the expression of PACAP. Furthermore, AgNPs pretreatment helped restrain some of the deleterious effects of UV irradiation. Interestingly, AgNPs had no impact on the protein level of ACE2, which is important in light of potential SARS-CoV-2 entrance through the cornea. CONCLUSIONS: Silver nanoparticles are safe for corneal epithelial cells in vitro.

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 P2Y(1) and P2Y(12) 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.

Cytoskeleton and nucleotide signaling in glioma C6 cells.

This chapter describes signaling pathways stimulated by the P2Y(2) nucleotide receptor (P2Y(2)R), that regulate cellular processes dependent on actin cytoskeleton dynamics in glioma C6 cells. P2Y(2)R coupled with G-proteins, in response to ATP or UTP, regulates the level of phosphatidylinositol-4,5-bisphosphate (PIP(2)) which modulates a variety of actin binding proteins and is involved in calcium response and activates Rac1 and RhoA proteins. The RhoA/ROCK signaling pathway plays an important role in contractile force generation needed for the assembly of stress fibers, focal adhesions and for tail retraction during cell migration. Blocking of this pathway by a specific Rho-kinase inhibitor induces changes in F-actin organization and cell shape and decreases the level of phosphorylated myosin II and cofilin. In glioma C6 cells these changes are reversed after UTP stimulation of P2Y(2)R. Signaling pathways responsible for this compensation are connected with calcium signaling. Stimulation of the Rac1 mediated pathway via G(o) proteins needs additional interaction between α(v)ß(5) integrins and P2Y(2)Rs. Rac1 activation is necessary for cofilin phosphorylation as well as integrin activation needed for focal complexes formation and stabilization of lamellipodium. Inhibition of positive Rac1 regulation prevents glioma C6 cells from recovery of control cell like morphology.

[See the signal--methods for calcium imaging in the cell]. / Zobaczyc sygnal--metody obrazowania zmian stezenia jonów wapnia w komórce.

Calcium ions are among the most universal secondary messengers existing in the living world. In the past thirty years the set of methods allowing the calcium signal visualization have been developed. Those in vivo methods allow us to observe the level of the free calcium ions in cells, tissues and organisms. The following text presents calcium imaging research tools available today as well as the calcium imaging methods and image calibration procedures.

P2X7 receptor in normal and cancer cells in the perspective of nucleotide signaling.

Nucleotides are the most common compounds produced constantly by living organisms. They are involved in most cellular processes like the synthesis of other nucleotides and nucleic acids, generation of energy needed for the maintenance of cells, and molecular signaling. In the 70s sir. Geoffrey Burstock discovered a new class of transmembrane proteins - nucleotide receptors responding to nucleotides and their derivatives. For historical reasons, we distinguish two main classes of nucleotide receptors: P1 - which are G protein-coupled adenosine receptors, and P2 - nucleotide receptors that respond to ATP and its derivatives. Additionally, the P2 receptors family can be divided into two subgroups: P2Y - G protein-coupled receptors and P2X cation channel receptors. This paper focuses mainly on the most researched receptor in the nucleotide receptors family - the P2X7 receptor - presenting it in the background of the nucleotide signaling landscape. Almost thirty years of extensive studies on the receptor contributed to understanding protein structure, splicing variants, and mechanism of action in somatic cells. Despite such a wide spectrum of research, the role of the receptor in cancer progression is still undetermined. In many reports, we can find information about the anti-tumorigenic role of this receptor caused by activation of the cell death mechanism after membrane pore formation. These results, however, contradict other studies in which the same receptor is known to promote cancer development through stimulation of proliferation and activation of pro-survival pathways. Ultimately, all this gathered knowledge points to two faces of the receptor in tumor progression. Therefore, we do provide a comprehensive overview of the topic. Finally, we also try to systemize previous and recent literature about the role of this receptor in somatic and cancer cells and provide access to it in the form of a convenient table.

Microscope-based techniques to study cell adhesion and migration.

Modern light microscopy has evolved to provide a variety of quantitative imaging techniques and also the capability to perturb structure-function relationships in living cells. The advances have been especially useful in the study of cell adhesion and migration. This review will focus on how such microscopy-based techniques can be useful in situ to study the molecular interactions and dynamics, to locally perturb actin-based structures and to measure the traction forces exerted by motile cells.

Presenilin-dependent expression of STIM proteins and dysregulation of capacitative Ca2+ entry in familial Alzheimer's disease.

Mutations in presenilin 1 (PS1), which are the major cause of familial Alzheimer's disease (FAD), are involved in perturbations of cellular Ca2+ homeostasis. Attenuation of capacitative Ca2+ entry (CCE) is the most often observed alteration of Ca2+ homeostasis in cells bearing FAD PS1 mutations. However, molecular mechanisms underlying this CCE impairment remains elusive. We demonstrate that cellular levels of STIM1 and STIM2 proteins, which are key players in CCE, depend on presenilins. We found increased level of STIM1 and decreased level of STIM2 proteins in mouse embryonic fibroblasts lacking presenilins. Fura-2 ratiometric assays revealed that CCE is enhanced in these cells after Ca2+ stores depletion by thapsigargin treatment. In turn, overexpression of PS1 with FAD mutations in HEK293 cells led to an attenuation of CCE. Although, no changes in STIM protein levels were observed in these HEK293 cells, FAD mutations in endogenous PS1 in human B lymphocytes resulted in a decreased expression of STIM2 in parallel to an attenuation of CCE. Our experiments showing that knock-out of presenilins in MEF cells and FAD mutations in endogenous PS1 in lymphocytes affect both CCE and the cellular level of STIM proteins open new perspectives for studies on CCE in FAD.

P2X7 receptor activity landscape in rat and human glioma cell lines.

P2X7 is a commonly expressed purinergic receptor, which functions as a cation-permeable channel in the plasma membrane. In certain circumstances, the receptor may also form a large transmembrane pore what results in cell death. P2X7 receptors control numerous physiological and pathological cellular processes and their overexpression is often associated with cancer progression. As nucleotides are important signaling molecules in the central nervous system, P2X7 plays also an important but ambiguous role in glioma biology with contrary observations originating from different glioma models. Therefore, the aim of our research was to investigate P2X7 receptor expression and functions in three human (U-87 MG, U-138 MG, U-251 MG) and one rat (C6) glioma cell lines. Although the receptor mRNA and protein were present in all the studied cells, we found profound differences in their level. We also encountered a problem with one human cell lines authenticity (U-87 MG) and excluded it from most of the experiments. Interestingly, there was no clear dependency between P2X7 receptor level, calcium signal and pore formation ability in the studied glioma lines. In U-138 human cell line, the receptor seemed to be inactive, while in U-251 human and C6 rat cell line its activation resulted in calcium influx and large pore formation. However, the viability of studied cells upon the administration of specific P2X7 agonist - BzATP - was not affected for U-138 and U-251, whereas for C6 cells a stimulatory effect was observed. Our results stress the variability of P2X7 signaling in glioma models and the need for future research which would take into account the complicated landscape of the receptor signaling in the brain.

Formation of Aberrant Myotubes by Myoblasts Lacking Myosin VI Is Associated with Alterations in the Cytoskeleton Organization, Myoblast Adhesion and Fusion.

We have previously postulated that unconventional myosin VI (MVI) could be involved in myoblast differentiation. Here, we addressed the mechanism(s) of its involvement using primary myoblast culture derived from the hindlimb muscles of Snell's waltzer mice, the natural MVI knockouts (MVI-KO). We observed that MVI-KO myotubes were formed faster than control heterozygous myoblasts (MVI-WT), with a three-fold increase in the number of myosac-like myotubes with centrally positioned nuclei. There were also changes in the levels of the myogenic transcription factors Pax7, MyoD and myogenin. This was accompanied by changes in the actin cytoskeleton and adhesive structure organization. We observed significant decreases in the levels of proteins involved in focal contact formation, such as talin and focal adhesion kinase (FAK). Interestingly, the levels of proteins involved in intercellular communication, M-cadherin and drebrin, were also affected. Furthermore, time-dependent alterations in the levels of the key proteins for myoblast membrane fusion, myomaker and myomerger, without effect on their cellular localization, were observed. Our data indicate that in the absence of MVI, the mechanisms controlling cytoskeleton organization, as well as myoblast adhesion and fusion, are dysregulated, leading to the formation of aberrant myotubes.