Calcium Signaling System Research Articles

Influence of extremely low frequency magnetic fields on Ca2+ signaling and double messenger system in mice hippocampus and reversal function of procyanidins extracted from lotus seedpod.

This research investigated the influence of extremely low frequency magnetic fields (ELF-MF; 50 Hz, 8 mT, 4 h per day, for 28 days) on calcium ion signaling and the double messenger system in the hippocampus of mice. Messengers that were studied included: G-protein, Ins(1,4,5)P3 (IP3 ), diacylglycerol (DAG), cAMP-dependent protein kinase (PKA), and Ca2+ -dependent protein kinase C (PKC). The results showed that ELF-MF caused an increase in the levels of Gi protein, IP3, DAG, PKA and PKC beta, calcium and calmodulin-dependent protein phosphatase calcineuring (PP2B), and intracellular Ca2+ content, and a decrease in calcium/calmodulin-dependent protein kinase II (CaMK II) and PKC alpha. In addition, ELF-MF exposure decreased the level of brain-derived neurotrophic factor (BDNF), which played a key role in hippocampal neuronal cell death. However, oral administration of procyanidins from lotus seedpod (LSPCs) (especially 90 mg kg-1 ) significantly recovered these changes, and nearly reached normal levels. All these showed that LSPCs may mediate calcium signal and double messenger system through Ca2+ /CaMK II/CREB/BDNF and DG/PKC/MAPK signaling pathways to reverse the alteration caused by ELF-MF. Bioelectromagnetics. 38:436-446, 2017. © 2017 Wiley Periodicals, Inc.

Increase of anthraquinone content in Rubia cordifolia cells transformed by native and constitutively active forms of the AtCPK1 gene.

Overexpression of both native and mutant forms of AtCPK1 in Rubia cordifolia cells increased anthraquinone production and transcript abundance of the RcIPPI, RcOSBL, RcOSBS , and RcICS genes to different extents. Calcium-dependent protein kinases (CDPKs) are involved in various cell processes and are regulated by a calcium signal system. CDPKs also function in plant defense against stress factors such as pathogens, temperature, and salinity. In this study, we compared the effect of heterologous expression of two forms of the Arabidopsis AtCPK1 gene, native and constitutively active (Ca(2+)-independent), on anthraquinone production in transgenic Rubia cordifolia cells. Significant qualitative and quantitative differences were found in the content of anthraquinone derivatives in control and AtCPK1-transgenic calli. Expression of the AtCPK1 gene increased anthraquinone production by 3 and 12 times for native and constitutively active forms, respectively, compared with control cells. In addition, we identified and quantified the expression of genes encoding key enzymes of the anthraquinone biosynthesis pathway, including isochorismate synthase (ICS), o-succinylbenzoate synthase (OSBS), o-succinylbenzoate ligase (OSBL), and isopentenyl diphosphate isomerase (IPPi). In all AtCPK1-transgenic cell lines, expression of ICS, OSBS, OSBL, and IPPi increased considerably at 14-15days of subculture and decreased at the end of cultivation (30days). The results suggest that both native and constitutively active AtCPK1 forms induced anthraquinone accumulation at the logarithmic growth stage via enhancement of expression of genes involved in the metabolism of anthraquinones or their regulatory mechanisms.

Responses of plant calmodulin to endocytosis induced by rare earth elements

The wide application of rare earth elements (REEs) have led to their diffusion and accumulation in the environment. The activation of endocytosis is the primary response of plant cells to REEs. Calmodulin (CaM), as an important substance in calcium (Ca) signaling systems, regulating almost all of the physiological activities in plants, such as cellular metabolism, cell growth and division. However, the response of CaM to endocytosis activated by REEs remains unknown. By using immunofluorescence labeling and a confocal laser scanning microscope, we found that trivalent lanthanum [La(III)], an REE ion, affected the expression of CaM in endocytosis. Using circular dichroism, X-ray photoelectron spectroscopy and computer simulations, we demonstrated that a low concentration of La(III) could interact with extracellular CaM by electrostatic attraction and was then bound to two Ca-binding sites of CaM, making the molecular structure more compact and orderly, whereas a high concentration of La(III) could be coordinated with cytoplasmic CaM or bound to other Ca-binding sites, making the molecular structure more loose and disorderly. Our results provide a reference for revealing the action mechanisms of REEs in plant cells.

Signaling systems of rhizobia (Rhizobiaceae) and leguminous plants (Fabaceae) upon the formation of a legume-rhizobium symbiosis (Review)

Data from the literature and our own data on the participation and interrelation of bacterial signaling Nod-factors and components of the calcium, NADPH-oxidase, and NO-synthase signaling systems of a plant at the preinfection and infectious stages of the formation of a legume-rhizobium symbiosis are summarized in this review. The physiological role of Nod-factors, reactive oxygen species (ROS), calcium (Ca2+), NADPH-oxidase, nitric oxide (NO), and their cross influence on the processes determining the formation of symbiotic structures on the roots of the host plant is discussed.

Interaction among the vacuole, the mitochondria, and the oxidative stress response is governed by the transient receptor potential channel in Candida albicans

Candida albicans is one of the most important opportunistic pathogens, causing both mucosal candidiasis and life-threatening systemic infections. To survive in the host immune defense system, this pathogen uses an elaborate signaling network to recognize and respond to oxidative stress, which is essential for its pathogenicity. However, the exact mechanisms that this fungus employs to integrate the oxidative stress response (OSR) with functions of various organelles remain uncharacterized. Our previous work implicated a connection between the calcium signaling system and the OSR. In this study, we find that the vacuolar transient receptor potential (TRP) channel Yvc1, one of the calcium signaling members, plays a critical role in cell tolerance to oxidative stress. We further provide evidence that this channel is required not only for activation of Cap1-related transcription of OSR genes but also for maintaining the stability of both the mitochondria and the vacuole in a potassium- and calcium-dependent manner. Element assays reveal that this TRP channel affects calcium influx and potassium transport from the vacuole to the mitochondria. Therefore, the TRP channel governs the novel interaction among the OSR, the vacuole, and the mitochondria by mediating ion transport in this pathogen under oxidative stress.

Convergence of Ionotropic and Metabotropic Signal Pathways upon Activation of P2X Receptors in Vascular Smooth Muscle Cells

Ionotropic P2X receptors (P2XRs) are involved in sympathetic control of the vascular tone; they mediate entry of Ca2+ in smooth muscle cells (SMCs), which results in depolarization of the latter and activation of voltage-gated L-type calcium channels. In addition, Ca2+ ions, after their entry into the cell, trigger Ca2+ release from the sarcoplasmic reticulum (SR) of SMCs via ryanodine receptors (RyRs), and this amplifies calcium signals. We found earlier that Ca2+ release mediated by inositol triphosphate (IP3) receptors (IP3Rs) also provides a considerable contribution to P2XR-mediated calcium signaling. Thus, a metabotropic signal pathway is a component of the calcium signaling system triggered by ionotropic P2XRs. Using confocal detection of changes in the intracellular Ca2+ concentration ([Ca2+] i ) and applications of the inhibitors of calcium channels (nicardipine, 5 μM), sarco-endoplasmic Ca2+ ATPase SERCA (CPA, 10 μM), IP3Rs (2-APB, 30 μM), RyRs (tetracaine, 100 μM), and phosphalipase C (PLC; U-73122, 2.5 μM), we estimated relative contributions of the above-mentioned four components to increase in the [Ca2+] i induced by the action of an agonist of P2XRs, α,β-meATP. The contributions of transmembrane Ca2+ entry via channels of P2XRs and calcium channels were comparable (11.0 ± 1.4 %, n = 14 and 8.0 ± 1.4 %, n = 14, respectively). The contribution of Ca2+ release via IP3Rs was found to be three times greater than that via RyRs (41 ± 5 %, n = 26 and 14 ± 7 %, n = 16, respectively). Blocking of calcium channels resulted in a sevenfold decrease in the contribution of IP3R-mediated Ca2+ release (from 41.0 to 5.6%); in this case, the contribution of RyR-mediated Ca2+ release underwent no significant changes. This fact allows us to suppose that there is a functional relation between activation of calcium channels and functioning of a metabotropic PLC/IP3-mediated signal cascade. The efficiency of inhibition of α,β-meATP-induced calcium responses by the blocker of PLC, on the one hand, and by the IP3R blocker and nicardipine, on the other hand, is comparable, and this fact agrees with the above hypothesis. According to our data, P2XR activation-induced increase in [Ca2+] I results not only from P2XR-mediated Ca2+ entry that triggers Ca2+ release via RyRs but also from Ca2+ release via IP3Rs. The latter process is realized due to the functioning of the PLC-mediated pathway, is in close relation with activation of calcium channels, and provides a dominant contribution in Ca2+ release from the stores after activation of the above ionotropic receptors.

Role of mitochondria in the operation of calcium signaling system in heat-stressed plants

Mild heat stress induces the expression of heat shock proteins (HSPs) that protect plants from death during damaging heat treatments. It was assumed that the appearance in the cell of denatured proteins triggers the expression of HSP; however, recent results show that protein denaturation is not a prerequisite for this process. In this work we discuss a hypothetical mechanism for activation under heat stress of HSP expression promoted by short-term elevation of cytosolic Ca2+ level. According to our hypothesis, a prolonged elevation of Ca2+ has a negative influence on HSP expression. Therefore, calcium is transported from the cytosol into intracellular compartments, including mitochondria. The Ca2+ entry into mitochondria is accompanied by hyperpolarization of the inner mitochondrial membrane and by the increased production of reactive oxygen species (ROS). The increased ROS production contributes to the activation of HSP expression under mild heat stress but leads to plant death under severe heat shock. Thus, mitochondria and, possibly, other organelles play the crucial role in determining life or death fate of heat-treated plant cells by controlling the cytosolic Ca2+ content and ROS production.

Excessive Signal Transduction of Gain-of-Function Variants of the Calcium-Sensing Receptor (CaSR) Are Associated with Increased ER to Cytosol Calcium Gradient

In humans, gain-of-function mutations of the calcium-sensing receptor (CASR) gene are the cause of autosomal dominant hypocalcemia or type 5 Bartter syndrome characterized by an abnormality of calcium metabolism with low parathyroid hormone levels and excessive renal calcium excretion. Functional characterization of CaSR activating variants has been so far limited at demonstrating an increased sensitivity to external calcium leading to lower Ca-EC50. Here we combine high resolution fluorescence based techniques and provide evidence that for the efficiency of calcium signaling system, cells expressing gain-of-function variants of CaSR monitor cytosolic and ER calcium levels increasing the expression of the Sarco-Endoplasmic Reticulum Calcium-ATPase (SERCA) and reducing expression of Plasma Membrane Calcium-ATPase (PMCA). Wild-type CaSR (hCaSR-wt) and its gain-of-function (hCaSR-R990G; hCaSR-N124K) variants were transiently transfected in HEK-293 cells. Basal intracellular calcium concentration was significantly lower in cells expressing hCaSR-wt and its gain of function variants compared to mock. In line, FRET studies using the D1ER probe, which detects [Ca2+]ER directly, demonstrated significantly higher calcium accumulation in cells expressing the gain of function CaSR variants compared to hCaSR-wt. Consistently, cells expressing activating CaSR variants showed a significant increase in SERCA activity and expression and a reduced PMCA expression. This combined parallel regulation in protein expression increases the ER to cytosol calcium gradient explaining the higher sensitivity of CaSR gain-of-function variants to external calcium. This control principle provides a general explanation of how cells reliably connect (and exacerbate) receptor inputs to cell function.

Neurospora crassa ncs-1, mid-1 and nca-2 double-mutant phenotypes suggest diverse interaction among three Ca2 + -regulating gene products

The calcium (Ca2+) signalling system in the filamentous fungus Neurospora crassa is unique and significantly different from that in plants and animals, mainly with regard to the second messenger systems involved in Ca2+-release from internal stores (Galagan et al. 2003). The complex Ca2+ signalling system in N. crassa contains 48 Ca2+ signalling proteins including a Ca2+ and/or CaM binding protein called neuronal calcium sensor-1 (NCS-1), a Ca2+-permeable channel MID-1 and a PMCA-type Ca2+-ATPase NCA-2 (Zelter et al. 2004; Tamuli et al. 2013). Here, we show that ncs-1, mid-1 and nca-2 interactions affect growth, carotenoid accumulation, Ca2+ stress tolerance, ultraviolet (UV) survival and circadian-regulated conidiation in N. crassa. The N. crassa homologue of NCS-1 has a role in growth, Ca2+ stress tolerance and UV survival (Deka et al. 2011; Tamuli et al. 2011). MID-1 is necessary for Ca2+homeostasis in N. crassa (Lew et al. 2008). Mid-1 in Gibberella zeae has a role in growth, development and ascospore discharge (Cavinder et al. 2011). NCA-2 is responsible for adaptation to stress conditions and functions to pump Ca2+ out of the cell in N. crassa (Benito et al. 2000; Bowman et al. 2011). In Schizosaccharomyces pombe, Ncs1p, the homologue of NCS-1, promotes Ca2+-induced closure of Yam8p Ca2+ channel, a homologue of the MID1 (Hamasaki-Katagiri and Ames 2010). The Ca2+-sensitive phenotype of the ncs1 deletion mutant is rescued by a yam8 deletion, indicating that Ncs1p negatively regulates Yam8p in S. pombe

The synthesis and investigation of vasoactive properties of new phosphorylated peptidomimetics

The paper presents the synthesis of new phosphorylated peptidomimetics and their action on the isolated rat aorta. It has been shown that derivatives of diethyl 5-amino-2-phthalimidoalkyl-1,3-oxazol-4-ylphosphonates can be employed in the synthesis of phosphorylated peptidomimetics containing a phosphonoglycine residue. For this purpose derivatives of 1,3-oxazol-4-ylphosphonates were decomposed hydrolytically in the acidic medium. The reaction of diethyl 5-alkylamino-2-aminoalkyl-1,3-oxazol-4-ylphosphonates with unsaturated azlactones was used to obtain phosphorylated peptidomimetics with dehydroamino acid groups. The method developed is very convenient and preparative because reactions proceed in mild conditions without formation of undesirable byproducts. Peptidomimetics are isolated with high yields and their separation does not require chromatography. Biological research has revealed the vasodilating activity of new derivatives of phosphorylated peptidomimetics depending on their chemical structure when acting on the rat’s isolated aorta. The possible molecular mechanisms of this activity with participation of the plasma membrane Ca2+-channels of vascular smooth muscle cells are discussed. The data of impact of an inhibitor of voltage-dependent Ca2+-channels of L-type of nitrendipine on the vascular tone are reported. It has been found that the concentration dependences of the vasodilating activity of the diethyl esters of 5-alkylamino-2-{N-[N-benzoyl-(4-methylbenzylidene)glycyl]aminomethyl}-1,3-oxazol- 4-ylphosphonates synthesized and nitrendipine are similar. It can testify about the indirect detection of the vasodilatory effect of these compounds associated with inhibition of the calcium signal system. The study shows a direct effect of the compounds synthesized on the muscle cells of blood vessels.

Presenilins and Calcium Signaling—Systems Biology to the Rescue

Mutations in presenilins result in familial Alzheimer's disease (FAD). Presenilins encode a catalytic subunit of the γ-secretase complex, and FAD mutations in presenilins alter γ-secretase activity. Many FAD mutations in presenilins also affect intracellular calcium signaling. To explain these results, it was proposed that presenilins also function as endoplasmic reticulum (ER) calcium leak channels and that this function is disrupted by FAD mutations. Although this hypothesis has been controversial, new research supports the calcium leak channel hypothesis. One group reported the presence of putative ion-conduction pore in the high-resolution crystal structure of bacterial presenilin homolog PSH1. Another group identified an essential role for presenilins in mediating ER calcium leak in a cell-based screen for calcium homeostasis modulators. These results should enable the field to move forward and to focus on exploring connections between FAD mutations in presenilins, changes in γ-secretase and ER Ca(2+) leak functions, and development of the disease.

Abnormal change of calcium signal system on consecutive monoculture problem of Rehmannia glutinosa

Based on the early transcriptome and digital differentially expressed profiling library construction in consecutive monoculture (two-year culturing) Rehmannia glutinosa, we screened and chose the twelve differentially expressed protein genes which might be related with calcium signal system. The spatiotemporal expression of these genes was measured by the real-time quantitative PCR, and the relative expression values of the genes related with calcium signal system in different development stages and tissues of normal growth (one-year culturing) and succession cropping of R. glutinosa (two-year culturing) was elaborated in detail. In addition, disposed succession cropping of R. glutinosa was treated with different levels of calcium signal blocking agents in order to verify the mode of action of calcium signal system on consecutive monoculture problem in R. glutinosa. Among the twelve genes, two calcium channels away from the cytoplasm were down-regulated expressed, while the ten calcium channels toward the cytoplasm were up-regulated expressed. The results implied that succession cropping caused calcium ions flowing from endoplasmic reticulum to cytoplasm. While the key genes in calcium signal respond components such as CBL, CBP, CIBP, PLC, etc. were down-regulated expressed significantly in succession cropping of R. glutinosa which were disposed with calcium signal blocking agents, the extent of the damage was relieved, and approached the normal growth (one-year culturing) level. This result strongly showed that calcium signal system participated in the perceiving, conducting and magnifying processes of succession cropping obstacles of R. glutinosa.

Regulation Mechanism of Intracellular IP3-Ca 2+ on Photosynthesis in Maize Seedlings under UV-B Stress

使用外加0.15 Wm-2 UV-B及不同钙效应剂处理玉米幼苗，研究细胞Ca2＋信号系统对UV-B辐射下玉米幼苗光合作用的调控机理。结果表明，UV诱导的胞内Ca2＋荧光增强受胞内IP3通道阻断剂肝素（Heparin）、胞内CaM活性抑制剂三氟啦嗪（TFP）抑制，降低玉米幼苗Chl a、Chl b及Chl T含量、原初光能转化效率（Fv/Fm）、PSII活性（Fv/Fo）、Hill反应活力、水分利用效率（WUE），提高胞间二氧化碳浓度（Ci），最终导致净光合速率（Pn）下降；细胞质膜钙通道阻断剂氯化镧（LaCl3）引发的此效应较小。据此提出，UV-B辐射下，玉米幼苗叶片细胞IP3动员胞内钙库释放Ca2＋，调节光合色素合成、Hill反应活性、WUE，CaM介导的下游反应调节Gs，是Ca2＋信号系统最终实现对Pn调控的主要机制。

Shock Waves Simulating Blast-Induced Traumatic Brain Injury Activate Purinergic Signaling in Astrocytes

While progress has been made in physically protecting individuals from experiencing bTBI, there are no countermeasures or drug treatments to ameliorate the effects of bTBI after exposure. Historically bTBI research focused on neuronal protection and the effect of neuronal trauma with less attention to the effect of injury to astrocytes. We have developed a pneumatic device that delivers shockwaves, similar to those known to induce bTBI, within a chamber optimal for fluorescence microscopy. Abrupt changes in pressure can be created with and without the presence of shear forces at the surface of cells. We discovered that exposure of primary cultures of human central nervous system cells to these transient peak pressures per se do not cause cellular excitation. Instead, it is the concomitant shear forces that reproducibly activate the cells. The resultant calcium signal is amplified and spread by cell-cell propagation arising from a small number of cells that are directly affected by the shear forces (Ravin et.al 2012). Astrocytes have long-range calcium signaling systems that propagate as calcium waves instead of action potentials and modulate neuronal and CNS activity. Blast shock waves simulating those initiating primary bTBI cause a cascade of events in human CNS dissociated cultures in which calcium is elevated mainly in astrocytes, leading to a propagation of calcium waves throughout the network, mediated by ATP signaling. We found that P2 receptor antagonists are able to reduce this response suggesting a potential therapeutic target for treating TBI.

Early Presynaptic and Postsynaptic Calcium Signaling Abnormalities Mask Underlying Synaptic Depression in Presymptomatic Alzheimer's Disease Mice

Alzheimer's disease (AD)-linked presenilin (PS) mutations result in pronounced endoplasmic reticulum calcium disruptions that occur before detectable histopathology and cognitive deficits. More subtly, these early AD-linked calcium alterations also reset neurophysiological homeostasis, such that calcium-dependent presynaptic and postsynaptic signaling appear functionally normal yet are actually operating under aberrant calcium signaling systems. In these 3xTg-AD mouse brains, upregulated ryanodine receptor (RyR) activity is associated with a shift toward synaptic depression, likely through a reduction in presynaptic vesicle stores and increased postsynaptic outward currents through small-conductance calcium-activated potassium SK2 channels. The deviant RyR-calcium involvement in the 3xTg-AD mice also compensates for an intrinsic predisposition for hippocampal long-term depression (LTD) and reduced long-term potentiation (LTP). In this study, we detail the impact of disrupted RyR-mediated calcium stores on synaptic transmission properties, LTD, and calcium-activated membrane channels of hippocampal CA1 pyramidal neurons in presymptomatic 3xTg-AD mice. Using electrophysiological recordings in young 3xTg-AD and nontransgenic (NonTg) hippocampal slices, we show that increased RyR-evoked calcium release in 3xTg-AD mice "normalizes" an altered synaptic transmission system operating under a shifted homeostatic state that is not present in NonTg mice. In the process, we uncover compensatory signaling mechanisms recruited early in the disease process that counterbalance the disrupted RyR-calcium dynamics, namely increases in presynaptic spontaneous vesicle release, altered probability of vesicle release, and upregulated postsynaptic SK channel activity. Because AD is increasingly recognized as a "synaptic disease," calcium-mediated signaling alterations may serve as a proximal trigger for the synaptic degradation driving the cognitive loss in AD.

Parallel adaptive feedback enhances reliability of the Ca 2+ signaling system

Despite large cell-to-cell variations in the concentrations of individual signaling proteins, cells transmit signals correctly. This phenomenon raises the question of what signaling systems do to prevent a predicted high failure rate. Here we combine quantitative modeling, RNA interference, and targeted selective reaction monitoring (SRM) mass spectrometry, and we show for the ubiquitous and fundamental calcium signaling system that cells monitor cytosolic and endoplasmic reticulum (ER) Ca(2+) levels and adjust in parallel the concentrations of the store-operated Ca(2+) influx mediator stromal interaction molecule (STIM), the plasma membrane Ca(2+) pump plasma membrane Ca-ATPase (PMCA), and the ER Ca(2+) pump sarco/ER Ca(2+)-ATPase (SERCA). Model calculations show that this combined parallel regulation in protein expression levels effectively stabilizes basal cytosolic and ER Ca(2+) levels and preserves receptor signaling. Our results demonstrate that, rather than directly controlling the relative level of signaling proteins in a forward regulation strategy, cells prevent transmission failure by sensing the state of the signaling pathway and using multiple parallel adaptive feedbacks.

The regulation mechanisms of contractile activity of smooth muscle cells: reactive oxygen species role

The effect of modulation of hydrogen peroxide, nitric oxide and hydrogen sulfide on contractile reactions of smooth muscle cells caused by depolarization, phenylephrine and solutions with altered osmolarity has been investigated by the mechanographical method. The new data of the fundamental nature of the role of reactive oxygen species in the operation of calcium and cGMP-mediated intracellular signaling systems, as well as in volume-dependent regulation of smooth muscle contraction.

EFFECT OF REACTIVE OXYGEN ON MECHANISMS COUPLING EXCITATION OF SMOOTH MUSCLE CELLS GUINEA PIG URETER: PP.21.345

Objective: Reactive oxygen species claim to the role of signaling molecules, especially towards the realization of oxidative stress. However, the methods and extent of their interaction with key intracellular signaling and effector systems of regulation of excitation-coupling in smooth muscle cells continue to actively explored. This study examines the effect of reactive oxygen species in the mechanisms of regulation by cyclic nucleotides and calcium signaling system of electrical and contractile activity of smooth muscle cells. Design and Methods: The method of double sucrose bridge to study the effect of hydrogen peroxide and nitric oxide on electrical and contractile properties of smooth muscle cells of guinea pig ureter, caused by electric stimulus. To investigate the role of C-kinase branch of the calcium and nitric oxide in the development of the action potential and contractile responses of smooth muscle using phenylephrine and sodium nitroprusside, respectively. Results: Found opposite effect of hydrogen peroxide and cyclic nucleotides on C-kinase branch of the regulation of excitation-coupling in smooth muscle cells. With additional activation protenkinase with phenylephrine changing effects of hydrogen peroxide and sodium nitroprusside: electrical and contractile activity are inhibited. Similar effects have evolved against the background of inhibitors of enzymes break down hydrogen peroxide and cyclic nucleotides. Thus, the C-kinase branch of the calcium signaling system is one of the major intracellular targets, the effect on reactive oxygen species that leads to the inhibition of electrical and contractile activity of smooth muscle cells of guinea pig ureter.

Calcium Signaling and Neurodegeneration

Neurodegenerative disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), and spinocerebellar ataxias (SCA) are very important both for fundamental science and for practical medicine. Despite extensive research into the causes of these diseases, clinical researchers have had very limited progress and, as of now, there is still no cure for any of these diseases. One of the main obstacles in the way of creating treatments for these disorders is the fact that their etiology and pathophysiology still remain unclear. This paper reviews results that support the so-called "calcium hypothesis of neurodegenerative diseases." The calcium hypothesis states that the atrophic and degenerative processes in the neurons of AD, PD, ALS, HD, and SCA patients are accompanied by alterations in calcium homeostasis. Moreover, the calcium hypothesis states that this deregulation of calcium signaling is one of the early-stage and key processes in the pathogenesis of these diseases. Based on the results we reviewed, we conclude that the calcium channels and other proteins involved in the neuronal calcium signaling system are potential drug targets for AD, PD, ALS, HD, and SCA therapy.

Identification of potential targets in biological signalling systems through network perturbation analysis

The network-based representation and analysis of biological systems contributes to a greater understanding of their structures and functions at different levels of complexity. These techniques can also be used to identify potential novel therapeutic targets based on the characterisation of vulnerable or highly influential network components. There is a need to investigate methods for estimating the impact of molecular perturbations. The prediction of high-impact or critical targets can aid in the identification of novel strategies for controlling the level of activation of specific, therapeutically relevant genes or proteins. Here, we report a new computational strategy for the analysis of the vulnerability of cellular signalling networks based on the quantitative assessment of the impact of large-scale, dynamic perturbations. To show the usefulness of this methodology, two complex signalling networks were analysed: the caspase-3 and the adenosine-regulated calcium signalling systems. This allowed us to estimate and rank the perturbation impact of the components defining these networks. Testable hypotheses about how these targets could modify the dynamic operation of the systems are provided. In the case of the caspase-3 system, the predictions and rankings were in line with results obtained from previous experimental validations of computational predictions generated by a relatively more computationally complex technique. In the case of the adenosine-regulated calcium system, we offer new testable predictions on the potential effect of different targets on the control of calcium flux. Unlike previous methods, the proposed approach provides perturbation-specific scores for each network component. The proposed perturbation assessment methodology may be applied to other systems to gain a deeper understanding of their dynamic operation and to assist the discovery of new therapeutic targets and strategies.