Role In Ion Transport Research Articles

P2X6 Knockout Mice Exhibit Normal Electrolyte Homeostasis.

ATP-mediated signaling is an important regulator of electrolyte transport in the kidney. The purinergic cation channel P2X6 has been previously localized to the distal convoluted tubule (DCT), a nephron segment important for Mg2+ and Na+ reabsorption, but its role in ion transport remains unknown. In this study, P2x6 knockout (P2x6-/-) mice were generated to investigate the role of P2X6 in renal electrolyte transport. The P2x6-/- animals displayed a normal phenotype and did not differ physiologically from wild type mice. Differences in serum concentration and 24-hrs urine excretion of Na+, K+, Mg2+ and Ca2+ were not detected between P2x6+/+, P2x6+/- and P2x6-/- mice. Quantitative PCR was applied to examine potential compensatory changes in renal expression levels of other P2x subunits and electrolyte transporters, including P2x1-5, P2x7, Trpm6, Ncc, Egf, Cldn16, Scnn1, Slc12a3, Slc41a1, Slc41a3, Cnnm2, Kcnj10 and Fxyd2. Additionally, protein levels of P2X2 and P2X4 were assessed in P2x6+/+ and P2x6-/- mouse kidneys. However, significant changes in expression were not detected. Furthermore, no compensatory changes in gene expression could be demonstrated in heart material isolated from P2x6-/- mice. Except for a significant (P<0.05) upregulation of P2x2 in the heart of P2x6-/- mice compared to the P2x6+/+ mice. Thus, our data suggests that purinergic signaling via P2X6 is not significantly involved in the regulation of renal electrolyte handling under normal physiological conditions.

Role of ion transporters in the bile acid-induced esophageal injury

Barrett's esophagus (BE) is considered to be the most severe complication of gastro-esophageal reflux disease (GERD), in which the prolonged, repetitive episodes of combined acidic and biliary reflux result in the replacement of the squamous esophageal lining by columnar epithelium. Therefore, the acid-extruding mechanisms of esophageal epithelial cells (EECs) may play an important role in the defense. Our aim was to identify the presence of acid/base transporters on EECs and to investigate the effect of bile acids on their expressions and functions. Human EEC lines (CP-A and CP-D) were acutely exposed to bile acid cocktail (BAC) and the changes in intracellular pH (pHi) and Ca(2+) concentration ([Ca(2+)]i) were measured by microfluorometry. mRNA and protein expression of ion transporters was investigated by RT-PCR, Western blot, and immunohistochemistry. We have identified the presence of a Na(+)/H(+) exchanger (NHE), Na(+)/HCO3 (-) cotransporter (NBC), and a Cl(-)-dependent HCO3 (-) secretory mechanism in CP-A and CP-D cells. Acute administration of BAC stimulated HCO3 (-) secretion in both cell lines and the NHE activity in CP-D cells by an inositol triphosphate-dependent calcium release. Chronic administration of BAC to EECs increased the expression of ion transporters compared with nontreated cells. A similar expression pattern was observed in biopsy samples from BE compared with normal epithelium. We have shown that acute administration of bile acids differently alters ion transport mechanisms of EECs, whereas chronic exposure to bile acids increases the expression of acid/base transporters. We speculate that these adaptive processes of EECs represent an important mucosal defense against the bile acid-induced epithelial injury.

Plant roots: new challenges in a changing world

Plant roots: new challenges in a changing world

Role of Ion Transporters in Salinity Resistance in Plants

Role of Ion Transporters in Salinity Resistance in Plants

Transcriptomic analysis reveals specific osmoregulatory adaptive responses in gill mitochondria-rich cells and pavement cells of the Japanese eel.

BackgroundHomeostasis of ions and water is important for the maintenance of cellular functions. The regulation of the homeostasis is particularly important in euryhaline fish that migrate between freshwater (FW) and seawater (SW) environments. The fish gill, the major tissue that forms an interface separating the extracellular fluids and external water environment, has an effective transport system to maintain and regulate a constant body osmolality. In fish gills, the two major epithelial cells, pavement cells (PVCs) and mitochondria-rich cells (MRCs), are known to play key and complementary roles in ion transport at the interface. Discovering the robust mechanisms underlying the two cell types’ response to osmotic stress would benefit our understanding of the fundamental mechanism allowing PVCs and MRCs to handle osmotic stress. Owing to the limited genomic data available on estuarine species, existing knowledge in this area is slim. In this study, transcriptome analyses were conducted using PVCs and MRCs isolated from Japanese eels adapted to FW or SW environments to provide a genome-wide molecular study to unravel the fundamental processes at work.ResultsThe study identified more than 12,000 transcripts in the gill cells. Interestingly, remarkable differential expressed genes (DEGs) were identified in PVCs (970 transcripts) instead of MRCs (400 transcripts) in gills of fish adapted to FW or SW. Since PVCs cover more than 90 % of the gill epithelial surface, the greater change in gene expression patterns in PVCs in response to external osmolality is anticipated. In the integrity pathway analysis, 19 common biological functions were identified in PVCs and MRCs. In the enriched signaling pathways analysis, most pathways differed between PVCs and MRCs; 14 enriched pathways were identified in PVCs and 12 in MRCs. The results suggest that the osmoregulatory responses in PVCs and MRCs are cell-type specific, which supports the complementary functions of the cells in osmoregulation.ConclusionsThis is the first study to provide transcriptomic analysis of PVCs and MRCs in gills of eels adapted to FW or SW environments. It describes the cell-type specific transcriptomic network in different tonicity. The findings consolidate the known osmoregulatory pathways and provide molecular insight in osmoregulation. The presented data will be useful for researchers to select their targets for further studies.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2271-0) contains supplementary material, which is available to authorized users.

Short-Term &lt;I&gt;in Situ Action&lt;/I&gt; of Melatonin on Ion Transport in Mice Kept at Restraint Stress

Melatonin, a pleiotropic hormone, is involved in many physiological functions including combating oxidative stress. However, its role in ion transport during stress response is not yet understood. The dose-dependent effect of in situ melatonin was examined in Swiss albino mice. Perfusion of melatonin at 10 -7 M for 20 minutes produced a significant decrease in Na + , K + -ATPase activity in the kidney, liver, stomach and intestinal tissues. A dose-responsive decrease in cytosolic and mitochondrial H + ATPase activity was found in these tissues after melatonin perfusion. Likewise, the cytosolic and mitochondrial Ca 2+ ATPase activities decreased in the kidney, liver, stomach and intestine. The mitochondrial Mg 2+ ATPase activity decreased in the tested tissues in a dose-responsive manner. Subjecting mice to restraint stress for seven days increased the Na + , K + -ATPase, H + ATPase, Ca 2+ ATPase and Mg 2+ ATPase activities to significant levels in kidney, liver, stomach and intestinal tissues. On the contrary, in-situ perfusion of melatonin to stressed mice at 10 -9 M caused decrease in the stress-induced hyperactivity of these transmembrane ion transporters. These results provide evidence for a role of melatonin in ion transporter activity and point to a protective role of melatonin in ion transport during stress response in mice.

WNK3‐SPAK/OSR1‐NKCC1 Signaling Pathway in Ischemic Brain Injury

Ischemia-mediated activation of Na-K-Cl cotransporter (NKCC1) leads to Na+ overload, cytotoxic edema, and cell death. However, the molecular mechanisms underlying these processes are not understood. Here we investigated the role of WNK (with no lysine = K)-SPAK/OSR1 kinase signaling pathway in regulating the function of NKCC1 in cerebral ischemia. We show that genetic deletion of WNK3, a WNK family member highly expressed in brain, or siRNA-mediated knockdown of SPAK or OSR1, protects against ischemic neuroglial death triggered by oxygen-glucose deprivation/reoxygenation. Using phospho specific antibodies, we detected robust up regulation of p-NKCC1 as well as p-SPAK/p-OSR1expression in peri-infarct cortex, striatum and corpus callosum in wild type mice subjected to transient middle cerebral artery occlusion. In WNK3 knockout mice, ischemia-induced hyper-phosphorylations of both the SPAK/OSR1 catalytic T-loop and NKCC1 are abolished, infarct volume and axonal demyelination are reduced, and neurobehavioral recovery is accelerated. These data provide fresh insight into the roles of ion transporters and their regulatory kinases in ischemic neuroglial injury, and identify the WNK3-SPAK/OSR1 kinase complex as a compelling target for novel neuroprotective strategies following stroke. Support: NIH R01NS38118

Plant growth regulators involved in abiotic stress: preface

An ever-expanding world population and globally changing diet preferences have put considerable pressure on the worldwide agricultural community to produce more food, feed and bio-energy crops. As a result, marginal land areas will need to be used to meet the increasing requirement of future generations, especially in developing countries. These marginal areas commonly impose abiotic stresses on crops due to factors such as salinity, drought, temperature extremes, flooding, low nutrients and aluminium or heavy metal toxicity. As a consequence, the growth and yield of crops from such areas is typically low and their quality poor, limiting farmer income. Therefore, it is important to gain knowledge and insight of the intrinsic flexibility by which plants respond to these abiotic stresses. Throughout evolution, plants have developed a dazzling array of complex strategies for coping with abiotic stresses and adapting to a wide range of environments. Biochemical, physiological and molecular genetic studies of these strategies have been initiated, and, as in many plant research fields, those on Arabidopsis pave the way. However, the contributions in this special issue illustrate the progress made on other species and highlight the insights into this research field. The calcineurin B-like (CBL) and CBL-interacting protein kinase (CIPK) signalling pathway is a flexible, Ca signalling network that allows plants to fine-tune their stress mitigation responses. Thoday-Kennedy et al. (2015) provide a critical account of our current knowledge of CBL and CIPK interactions and their roles in ion transport under abiotic stress. Han et al. (2014) review the signalling pathways and key mechanisms of sodium detoxification mediated by ion transporters and antiporters, and give an overview of practical strategies and methodologies for functional characterisation of high-affinity potassium transporters. In addition, they discuss how to alleviate salt stress through the exogenous application of gibberellins and nitric oxide. Li et al. (2014a) focus on salt cress (Thellungiella halophila), a close relative of Arabidopsis, a species that has emerged as a model halophyte for the molecular elucidation of abiotic stress tolerance. Its seed germination is highly regulated by environmental and hormonal signals; thus, it provides opportunities to study how such external conditions are sensed. The mung bean (Vigna radiata) is salinity-sensitive and suffers considerably from soil salinity; as a consequence, reductions in germination, chlorophyll content, vigour and yield have been reported. Patel et al. (2014) draw attention to interactions that occur with this species in the rhizosphere and report on those with halotolerant Bacillus spp. These species were isolated from saline habitats and alleviate salt stress in mung beans thereby increasing germination and partially restoring root and shoot growth. Xuan et al. (2014) characterise the response of seedlings of yellowand black-seeded rape to salt and cadmium stresses, and show how tolerance is associated with flavonoid content. Li et al. (2014b) demonstrate how improvement of endogenous polyamine levels by exogenous spermidine application may promote drought tolerance of plants. Waterlogging is also a major constraint to crop production in many parts of the world due to anoxic conditions in the root zone. Najeeb et al. (2015) investigate the mechanisms of waterlogging tolerance in cotton induced by aminoethoxyvinylglycine and show the how leaf growth and fruit production can be enhanced under these & Stefaan P. O. Werbrouck Stefaan.Werbrouck@UGent.be

The role of the CBL–CIPK calcium signalling network in regulating ion transport in response to abiotic stress

Plants are sessile organisms and have multiple tolerance mechanisms which allow them to adapt to the environmental stresses to which they may be exposed. Key to a plant’s tolerance of abiotic stresses is the ability to rapidly detect stress and activate the appropriate stress response mechanism. The calcineurin B-like (CBL) and CBL-interacting protein kinase (CIPK) signalling pathway is a flexible Ca2+ signalling network which allows a plant to fine tune its response to stress, via both pre- and post-translational mechanisms. Genes encoding CBLs and CIPKs have now been identified in a variety of plant species. Plants have been found to have large gene families of CBLs and CIPKs, each encoding proteins with specific upstream and downstream targets, thus providing the flexibility required to allow a plant to adapt to a variety of stresses. Characterisation of CBL and CIPK mutants have shown them to be important for a plant to survive cold, drought, heat, salinity and low nutrient stresses. Many CBLs and CIPKs have been shown to be involved in the transport of ions through a plant, either limiting the supply of toxic ions to certain tissues or maximising the uptake of beneficial nutrients from the soil. This review will provide an update into the current knowledge of CBL and CIPK interactions and their role in ion transport during abiotic stress.

Role of Ca2+ in the change in the structure type and the fluoride-ion conductivity in crystals upon transition from β-ErF3 to Er0.715Ca0.285F2.715

The symmetry-dependent structural differences and the fluoride-ion conductivity of the β-ErF3 crystal (the orthorhombic β-YF3 type) and the phase Er0.715Ca0.285F2.715 (the hexagonal tysonite modification α-LaF3) are revealed. A change in the β-YF3 structure type is caused by the partial replacement of Er3+ by Ca2+. It was shown that the contribution of Ca2+ to the conductivity of the phases R1 − yCayF3 − y is not limited to the creation of VF+ anion vacancies. The crystals of Er0.715Ca0.285F2.715 characterized by cation-composition heterogeneity have structural features (different from the vacancies in the anionic sublattice), which can exert a positive effect on the mobility of fluoride anions. This factor may play a more important role in ion transport than the concentration of anion vacancies.

Carbonic Anhydrases: Nature's Way to Balance CO2 Concentration.

Citation: Aggarwal M, McKenna R. Carbonic Anhydrases: Nature’s Way to Balance CO2 Concentration. Biochem Mol Biol J. 2016, 1:1. The carbonic anhydrases (CAs; EC 4.2.1.1) are a family of structurally diverse (in both fold and oligomeric state), yet efficient metalloenzymes that catalyze the reversible hydration of CO2 and bicarbonate. They are categorized into five distinct classes (α, β, γ, δ, and ζ). Among these, the αCAs are found primarily in vertebrates, the βCAs are dominantly expressed in higher plants and some prokaryotes, while γCAs are present only in archaebacteria, and the δ and ζ classes have thus far been only isolated in diatoms. These ubiquitous enzymes equilibrate the reaction between three simple chemical molecules: CO2, bicarbonate, and protons; hence, they have important roles in ion transport, acid-base regulation, gas exchange, photosynthesis, and CO2 fixation (Figures 1A-1C) [1]. As such, structural studies of how this family of enzyme binds CO2 and convert it to bicarbonate may help in the understanding and designing of bio-industrial technologies for carbon sequestration. Recently, high-pressure cryo-crystallography studies have been successful in “trapping” CO2 in the active sites of an αCA and a βCA (Figures 1D and 1E) [2,3]. Note, Figure 1E shows a model of a γCA-CO2 complex which is based on the structural similarities observed between the αCA and βCA-CO2 complexes. These studies are significant for several reasons: (1) they demonstrate a substrate (with a kcat/KM approaching diffusion controlled limits of 108 M-1s-1) can be captured in an enzyme active site, (2) they show the mechanistic orientation of CO2 in a hydrophobic pocket, positioned and poised for the nucleophilic attack of a zinc-bound hydroxide to produce bicarbonate, but most importantly (3) they demonstrate that structurally distinct Carbonic Anhydrases: Nature’s Way to Balance CO2 Concentration

Effects of MEK inhibitors GSK1120212 and PD0325901 in vivo using 10-plex quantitative proteomics and phosphoproteomics.

Multiplexed isobaric tag based quantitative proteomics and phosphoproteomics strategies can comprehensively analyze drug treatments effects on biological systems. Given the role of mitogen-activated protein/extracellular signal-regulated kinase (MEK) signaling in cancer and mitogen-activated protein kinase (MAPK)-dependent diseases, we sought to determine if this pathway could be inhibited safely by examining the downstream molecular consequences. We used a series of tandem mass tag 10-plex experiments to analyze the effect of two MEK inhibitors (GSK1120212 and PD0325901) on three tissues (kidney, liver, and pancreas) from nine mice. We quantified ∼ 6000 proteins in each tissue, but significant protein-level alterations were minimal with inhibitor treatment. Of particular interest was kidney tissue, as edema is an adverse effect of these inhibitors. From kidney tissue, we enriched phosphopeptides using titanium dioxide (TiO2 ) and quantified 10 562 phosphorylation events. Further analysis by phosphotyrosine peptide immunoprecipitation quantified an additional 592 phosphorylation events. Phosphorylation motif analysis revealed that the inhibitors decreased phosphorylation levels of proline-x-serine-proline (PxSP) and serine-proline (SP) sites, consistent with extracellular-signal-regulated kinase (ERK) inhibition. The MEK inhibitors had the greatest decrease on the phosphorylation of two proteins, Barttin and Slc12a3, which have roles in ion transport and fluid balance. Further studies will provide insight into the effect of these MEK inhibitors with respect to edema and other adverse events in mouse models and human patients.

The role of Cl‐ channels in ion transport across the apical and basolateral sides of the mouse retinal pigment epithelium

AbstractPurpose The retinal pigment epithelium (RPE) is important in transporting water from the subretinal space to the choroid of the eye. The water transport across the RPE is supposed to be mediated by Cl‐ channels situated at the basolateral side of the RPE tissue. The purpose of this study was to assess the function of Cl‐ channels at the apical and basolateral side of mouse RPE.Methods RPE of healthy mice (C57BL/6J) was mounted in Ussing chambers. The short‐circuit current (Isc) was measured in μAmp/cm2. The non‐specific Cl‐ channel blocker NPPB (4 mM) was applied to both sides. The CFTR blocker CFTRinh‐172 (0.8 mM) was added to the apical side. The Ca++ dependent Cl‐ channel blocker CaCCinh‐A01 (1.15 mM ) was added to the apical side. Each dose of the blockers was tested for 30 minutes. The results are presented as mean ± SEM, n = 6 in all experiments.Results NPPB (4 mM) on the basolateral side produced no significant change (p = 0.36; 30 min), but 4 mM NPPB on the apical side reversed the Isc (μAmp/cm2) from ‐4,8 ± 5,9 to +19.9 ± 7,3 (p = 0.004) at 5 min which stabilised at +2.9 ± 4,9 (p = 0.03) at 30 min. CFTRinh‐172 (0.8 mM) caused a transient increase, ‐13 ± 3,5 to ‐15,1 ± 3,3 (p = 0.02) at 5 min. CaCCinh‐A01 (1.15 mM) reversed the Isc from ‐10,6 ± 2,1 to +5,5 ± 3,9 (p = 0.0002) at 10 min, which stabilized at ‐0.10 ± 3,0 (p = 0.002) at 30 min.Conclusion The results indicate that Cl‐ channels are situated on the apical side of the RPE and drive a part of the ion transport across the mouse RPE. The channels may play a lesser role in ion transport across the basolateral side.

Role of pHi, and proton transporters in oncogene-driven neoplastic transformation

The change of a normal, healthy cell to a transformed cell is the first step in the evolutionary arc of a cancer. While the role of oncogenes in this 'passage' is well known, the role of ion transporters in this critical step is less known and is fundamental to our understanding the early physiological processes of carcinogenesis. Cancer cells and tissues have an aberrant regulation of hydrogen ion dynamics leading to a reversal of the normal tissue intracellular to extracellular pH gradient (ΔpHi to ΔpHe). When this perturbation in pH dynamics occurs during carcinogenesis is less clear. Very early studies using the introduction of different oncogene proteins into cells observed a concordance between neoplastic transformation and a cytoplasmic alkalinization occurring concomitantly with a shift towards glycolysis in the presence of oxygen, i.e. 'Warburg metabolism'. These processes may instigate a vicious cycle that drives later progression towards fully developed cancer where the reversed pH gradient becomes ever more pronounced. This review presents our understanding of the role of pH and the NHE1 in driving transformation, in determining the first appearance of the cancer 'hallmark' characteristics and how the use of pharmacological approaches targeting pH/NHE1 may open up new avenues for efficient treatments even during the first steps of cancer development.

Influence of NaY on the morphology and conductivity characteristics of poly(ethylene oxide)-LiClO4 electrolyte with plasticizer EC

A novel solid-state composite polymer electrolyte (CPE), based on a polymer, poly(ethylene oxide) (PEO), alkali metal salts, and NaY molecular sieve powders with a small amount of low molecular weight plasticizer, ethylene carbonate (EC) is investigated. (PEO)16LiClO4 polymer metal salt complexes with 5 wt% EC, and different content of NaY are prepared by the solution casting technology. The crystallization characteristic, surface morphology, and ionic conductivity of the CPE systems are studied using X-ray diffractometer (XRD) analysis, scanning electron microscopy (SEM), energy dispersive spectrometer, and impedance spectroscopy. It is found that NaY incorporation has a beneficial effect on the enhancement of ionic conductivity, increasing two orders of magnitude. XRD spectra show that the NaY has a major influence on the crystallization process of polymer matrix. By incorporating NaY, the crystallinity degree of PEO matrix obviously decreases. SEM images show a dramatic modification of surface morphology, the surface spherulites of polymer matrix disappear, and ultra-branched and cross-linked framework structure forms, which play an important role in ion transport and enhancing the tensile strength (TS). The TS is achieved 2.12 MPa with the content of 35 wt% NaY, far higher than the 0.17 MPa with (PEO)16LiClO4–5 wt% EC. In addition, it is demonstrated for the first time that EC affects the network structure of the molecular sieve and leads to exhibit enhanced ionic conductivity of electrolyte maintaining for a long time.

Entropic transport in confined media: a challenge for computational studies in biological and soft-matter systems

Transport in small-scale biological and soft-matter systems typically occurs under confinement conditions in which particles proceed through obstacles and irregularities of the boundaries that may significantly alter their trajectories. A transport model that assimilates the confinement to the presence of entropic barriers provides an efficient approach to quantify its effect on the particle current and the diffusion coefficient. We review the main peculiarities of entropic transport and treat two cases in which confinement effects play a crucial role, with the appearance of emergent properties. The presence of entropic barriers modifies the mean first-passage time distribution and therefore plays a very important role in ion transport through micro- and nano-channels. The functionality of molecular motors, modeled as Brownian ratchets, is strongly affected when the motor proceeds in a confined medium that may constitute another source of rectification. The interplay between ratchet and entropic rectification gives rise to a wide variety of dynamical behaviors, not observed when the Brownian motor proceeds in an unbounded medium. Entropic transport offers new venues of transport control and particle manipulation and new ways to engineer more efficient devices for transport at the nanoscale.

Identification of antifungal natural products via Saccharomyces cerevisiae bioassay: insights into macrotetrolide drug spectrum, potency and mode of action.

Since current antifungal drugs have not kept pace with the escalating medical demands of fungal infections, new, effective medications are required. However, antifungal drug discovery is hindered by the evolutionary similarity of mammalian and fungal cells, which results in fungal drug targets having human homologs and drug non-selectivity. The group III hybrid histidine kinases (HHKs) are an attractive drug target since they are conserved in fungi and absent in mammals. We used a Saccharomyces cerevisiae reporter strain that conditionally expresses HHK to establish a high-throughput bioassay to screen microbial extracts natural products for antifungals. We identified macrotetrolides, a group of related ionophores thought to exhibit restricted antifungal activity. In addition to confirming the use of this bioassay for the discovery of antifungal natural products, we demonstrated broader, more potent fungistatic activity of the macrotetrolides against multiple Candida spp., Cryptococcus spp., and Candida albicans in biofilms. Macrotetrolides were also active in an animal model of C. albicans biofilm, but were found to have inconsistent activity against fluconazole-resistant C. albicans, with most isolates resistant to this natural product. The macrotetrolides do not directly target HHKs, but their selective activity against S. cerevisiae grown in galactose (regardless of Drk1 expression) revealed potential new insight into the role of ion transport in the mode of action of these promising antifungal compounds. Thus, this simple, high-throughput bioassay permitted us to screen microbial extracts, identify natural products as antifungal drugs, and expand our understanding of the activity of macrotetrolides.

A Novel Initiation Mechanism of Death in Streptococcus pneumoniae Induced by the Human Milk Protein-Lipid Complex HAMLET and Activated during Physiological Death

To cause colonization or infection, most bacteria grow in biofilms where differentiation and death of subpopulations is critical for optimal survival of the whole population. However, little is known about initiation of bacterial death under physiological conditions. Membrane depolarization has been suggested, but never shown to be involved, due to the difficulty of performing such studies in bacteria and the paucity of information that exists regarding ion transport mechanisms in prokaryotes. In this study, we performed the first extensive investigation of ion transport and membrane depolarization in a bacterial system. We found that HAMLET, a human milk protein-lipid complex, kills Streptococcus pneumoniae (the pneumococcus) in a manner that shares features with activation of physiological death from starvation. Addition of HAMLET to pneumococci dissipated membrane polarity, but depolarization per se was not enough to trigger death. Rather, both HAMLET- and starvation-induced death of pneumococci specifically required a sodium-dependent calcium influx, as shown using calcium and sodium transport inhibitors. This mechanism was verified under low sodium conditions, and in the presence of ionomycin or monensin, which enhanced pneumococcal sensitivity to HAMLET- and starvation-induced death. Pneumococcal death was also inhibited by kinase inhibitors, and indicated the involvement of Ser/Thr kinases in these processes. The importance of this activation mechanism was made evident, as dysregulation and manipulation of physiological death was detrimental to biofilm formation, a hallmark of bacterial colonization. Overall, our findings provide novel information on the role of ion transport during bacterial death, with the potential to uncover future antimicrobial targets.

Na(+),K (+)-ATPase as a docking station: protein-protein complexes of the Na(+),K (+)-ATPase.

The Na(+),K(+)-ATPase, or sodium pump, is well known for its role in ion transport across the plasma membrane of animal cells. It carries out the transport of Na(+) ions out of the cell and of K(+) ions into the cell and thus maintains electrolyte and fluid balance. In addition to the fundamental ion-pumping function of the Na(+),K(+)-ATPase, recent work has suggested additional roles for Na(+),K(+)-ATPase in signal transduction and biomembrane structure. Several signaling pathways have been found to involve Na(+),K(+)-ATPase, which serves as a docking station for a fast-growing number of protein interaction partners. In this review, we focus on Na(+),K(+)-ATPase as a signal transducer, but also briefly discuss other Na(+),K(+)-ATPase protein-protein interactions, providing a comprehensive overview of the diverse signaling functions ascribed to this well-known enzyme.

Role of Ion Transport in the Actuation of Cellulose Based EAPap

The application of electroative polymer devices requires the availability of their propertis at various operating conditions. Cellulose based Electro-Active Paper (EAPap) has been studied as an attractive EAP material for artificial muscles due to its low cost, availability, light weight, large displacement output, low actuation voltage and low power consumption. It is investigated which the underlying mechanism is responsible for their strain-field response. The understanding of the actuation mechanism of this material is important in order to improve the performance and also to better target the application. To physically investigate the actuation mechanism of EAPap, several tests are performed. TSC current showed an evidence of ionic migration effect. Thus, we conclude ionic migration effect associated with dipole moment of cellulose paper ingredients. These effects maybe depend on environmental condition.