Engineering hydrogen bonding at tyrosine-201 in the orange carotenoid protein using halogenated analogues.

The Orange Carotenoid Protein (OCP) is a unique water-soluble photoactive protein that plays a critical role in regulating the balance between light harvesting and photoprotective responses in cyanobacteria. The challenge in understanding OCP´s photoactivation mechanism stems from the heterogeneity of the initial configurations of its embedded ketocarotenoid, which in the dark-adapted state can form up to two hydrogen bonds to critical amino acids in the protein's C-terminal domain, and the extremely low quantum yield of primary photoproduct formation. While a series of experiments involving point mutations within these contacts helped us to identify these challenges, they did not resolve them.

Antioxidant properties of the soluble carotenoprotein AstaP and its feasibility for retinal protection against oxidative stress.

Photodamage to the outer segments of photoreceptor cells and their impaired utilization by retinal pigment epithelium (RPE) cells contribute to the development of age-related macular degeneration (AMD) leading to blindness. Degeneration of photoreceptor cells and RPE cells is triggered by reactive oxygen species (ROS) produced by photochemical reactions involving bisretinoids, by-products of the visual cycle, which accumulate in photoreceptor discs and lipofuscin granules of RPE. Carotenoids, natural antioxidants with high potential efficacy against a wide range of ROS, may protect against the cytotoxic properties of lipofuscin.

Accumulation of Li Ions Triggers Changes in , , , and Transcription in the LiCl-Treated Human Umbilical Vein Endothelial Cells (HUVEC).

Changes in intracellular concentrations of Na and K are shown to alter gene expression. Another monovalent cation, Li, is well known as a medicine for treatment of psychiatric disorders, but mechanism of its action is obscure. Thus, it is important to evaluate the effect of Li on gene expression in endothelial cells.

G-Quadruplexes as Sensors of Intracellular Na+/K Ratio: Potential Role in Regulation of Transcription and Translation.

Data on the structure of G-quadruplexes, noncanonical nucleic acid forms, supporting an idea of their potential participation in regulation of gene expression in response to the change in intracellular Na+/K+ ratio are considered in the review. Structural variety of G-quadruplexes, role of monovalent cations in formation of this structure, and thermodynamic stability of G-quadruplexes are described. Data on the methods of their identification in the cells and biological functions of these structures are presented.

Sodium Ions as Regulators of Transcription in Mammalian Cells.

The maintenance of an uneven distribution of Na+ and K+ ions between the cytoplasm and extracellular medium is the basis for the functioning of any animal cell. Changes in the intracellular ratio of these cations occur in response to numerous stimuli and are important for the cell activity regulation. Numerous experimental data have shown that gene transcription in mammalian cells can be regulated by changes in the intracellular [Na+]/[K+] ratio.

Increased Extracellular Sodium Concentration as a Factor Regulating Gene Expression in Endothelium.

Hyperosmotic stimulation of endothelial cells often leads to its dysfunction accompanied, among other things, by proinflammatory response. The mechanisms of this phenomenon are not fully understood. It may arise due to increase in the plasma Na+ concentration, due to increase in the extracellular osmolarity, increase in the intracellular Na+/K+ ratio, and/or change in the cell stiffness.

Antimicrobial properties of a new polymeric material based on poly(2-hydroxyethyl methacrylate).

Background And Aim: Оne of the promising areas is the development of synthetic wound dressings with programmed release of active substances that can affect various elements in the pathogenesis of the wound process. The aim was to study the antimicrobial properties of a new polymeric material based on poly(2-hydroxyethyl methacrylate).

Methods: 2-hydroxyethyl methacrylate, dimethacrylate triethylene glycol as crosslinking agent, polymerization initiator of azobisizobutyronitrile along with a porogen and one of the antimicrobial agents, including decamethoxin, chlorhexidine bigluconate, silver nitrate, octenidine, furacilin, metronidazole, dioxidine, and gentamicin were used to synthesize a new material with antimicrobial activity.

Effect of Dynamic and Static Load on the Concentration of Myokines in the Blood Plasma and Content of Sodium and Potassium in Mouse Skeletal Muscles.

Modulation of cytokine production by physical activity is of considerable interest, since it might be a promising strategy for correcting metabolic processes at both cellular and systemic levels. The content of IL-6, IL-8, and IL-15 in the plasma and the concentration of monovalent cations in the skeletal muscles of trained and untrained mice were studied at different periods after static and dynamic exercises. Dynamic loads caused an increase in the IL-6 content and decrease in the IL-15 content in the plasma of untrained mice, but produced no effect on the concentration of IL-8.

Transcriptomic Changes in Endothelial Cells Triggered by Na,K-ATPase Inhibition: A Search for Upstream Na/K Sensitive Genes.

Stimulus-dependent elevation of intracellular Ca affects gene expression via well-documented calmodulin-mediated signaling pathways. Recently, we found that the addition of extra- and intracellular Ca chelators increased, rather than decreased, the number of genes expressed, and that this is affected by the elevation of [Na]/[K]-ratio. This assumes the existence of a novel Na/K-mediated Ca-independent mechanism of excitation-transcription coupling.

Ouabain-Induced Cell Death and Survival. Role of α1-Na,K-ATPase-Mediated Signaling and [Na]/[K]-Dependent Gene Expression.

Ouabain is of cardiotonic steroids (CTS) family that is plant-derived compounds and is known for many years as therapeutic and cytotoxic agents. They are specific inhibitors of Na,K-ATPase, the enzyme, which pumps Na and K across plasma membrane of animal cells. Treatment of cells by CTS affects various cellular functions connected with the maintenance of the transmembrane gradient of Na and K.

Na,K-ATPase as a target for endogenous cardiotonic steroids: What's the evidence?

With an exception of few reports, the plasma concentration of ouabain and marinobufagenin, mostly studied cardiotonic steroids (CTS) assessed by immunoassay techniques, is less than 1 nM. During the last 3 decades, the implication of these endogenous CTS in the pathogenesis of hypertension and other volume-expanded disorders is widely disputed. The threshold for inhibition by CTS of human and rodent α1-Na,K-ATPase is ∼1 and 1000 nM, respectively, that rules out the functioning of endogenous CTS (ECTS) as natriuretic hormones and regulators of cell adhesion, cell-to-cell communication, gene transcription and translation, which are mediated by dissipation of the transmembrane gradients of monovalent cations.

Correction to: Measles virus hemagglutinin triggers intracellular signaling in CD150-expressing dendritic cells and inhibits immune response.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Elevation of Intracellular Na Contributes to Expression of Early Response Genes Triggered by Endothelial Cell Shrinkage.

Background/aims: Prolonged hyperosmotic shrinkage evokes expression of osmoprotective genes via nuclear factor NFAT5-mediated pathway and activates Na influx via hypertonicity-induced cation channels (HICC). In human umbilical vein endothelial cells (HUVEC) elevation of intracellular sodium concentration ([Na]) triggers transcription of dozens of early response genes (ERG). This study examined the role of monovalent cations in the expression of Na-sensitive ERGs in iso- and hyperosmotically shrunken HUVEC.

Ubiquitous and cell type-specific transcriptomic changes triggered by dissipation of monovalent cation gradients in rodent cells: Physiological and pathophysiological implications.

Elevation of [Na]/[K]-ratio is considered as one of the major signals triggering transcriptomic changes in various cells types. In this study, we identified ubiquitous and cell type-specific [Formula: see text] -sensitive genes by comparative analysis of transcriptomic changes in ouabain-treated rat aorta smooth muscle cells and rat aorta endothelial cells (RASMC and RAEC, respectively), rat cerebellar granule cells (RCGC), and mouse C2C12 myoblasts. Exposure of the cells to ouabain increased intracellular Na content by ~14, 8, 7, and 6-fold and resulted in appearance of 7577, 2698, 2120, and 1146 differentially expressed transcripts in RAEC, RASMC, C2C12, and RCGC, respectively.

SLAMF1/CD150 in hematologic malignancies: Silent marker or active player?

SLAMF1/CD150 receptor is a founder of signaling lymphocyte activation molecule (SLAM) family of cell-surface receptors. It is widely expressed on cells within hematopoietic system. In hematologic malignancies CD150 cell surface expression is restricted to cutaneous T-cell lymphomas, few types of B-cell non-Hodgkin's lymphoma, near half of cases of chronic lymphocytic leukemia, Hodgkin's lymphoma, and multiple myeloma.

Transcriptomic changes in C2C12 myotubes triggered by electrical stimulation: Role of Ca-mediated and Ca-independent signaling and elevated [Na]/[K] ratio.

Elevation of Ca and AMP-activated protein kinase (AMPK) are considered as major signals triggering transcriptomic changes in exercising skeletal muscle. Electrical pulse stimulation (EPS) of cultured myotubes is widely employed as an in vitro model of muscle contraction. This study examines the impact of Ca-mediated and Ca-independent signaling in transcriptomic changes in EPS-treated C2C12 myotubes.

Augmented gene expression triggered by Na,K-ATPase inhibition: Role of Ca-mediated and -independent excitation-transcription coupling.

In rat vascular smooth muscle cells (RVSMC), 3-h Na,K-ATPase inhibition by ouabain or in K-free medium resulted in the inversion of the [Na]/[K] ratio and elevation up to 7-fold the content of Egr1, Atf3, Nr4a1 and Ptgs2 mRNAs. Ouabain increased the rate of 45Ca influx by 2-fold that was abolished by L-type voltage-gated Ca channel blocker nicardipine, but it was resistant to Na/Ca exchanger inhibitor KB-R7943. To study the role of Ca-mediated signaling in the expression of Na/K-sensitive genes we used intracellular Ca chelator BAPTA and incubated RVSMC in Ca-free medium.

The interplay of CD150 and CD180 receptor pathways contribute to the pathobiology of chronic lymphocytic leukemia B cells by selective inhibition of Akt and MAPK signaling.

Cell surface expression of CD150 and CD180 receptors in chronic lymphocytic leukemia (CLL) associates with mutational IGHV status and favourable prognosis. Here we show a direct correlation between cell surface expression and colocalization of these receptors on CLL B cells. In the absence of CD150 and CD180 on the cell surface both receptors were expressed in the cytoplasm.

Electrical pulse stimulation decreases electrochemical Na and K gradients in C2C12 myotubes.

Electrical pulse stimulation (EPS)-treated cultured myotubes are widely employed as an in vitro model of muscle contraction. Here we examined time-dependent EPS action and dose-dependent ouabain action on [Na] and [K] in C2C12 myotubes. After 2 h of EPS (40 V, 1 Hz, 10 ms) [Na] increased by ∼150% whereas [K] declined by ∼20%.

Time- and dose dependent actions of cardiotonic steroids on transcriptome and intracellular content of Na and K: a comparative analysis.

Recent studies demonstrated that in addition to Na,K-ATPase inhibition cardiotonic steroids (CTSs) affect diverse intracellular signaling pathways. This study examines the relative impact of [Na]/[K]-mediated and -independent signaling in transcriptomic changes triggered by the endogenous CTSs ouabain and marinobufagenin (MBG) in human umbilical vein endothelial cells (HUVEC). We noted that prolongation of incubation increased the apparent affinity for ouabain estimated by the loss of [K] and gain of [Na].

Early B-cell factor 1 (EBF1) is critical for transcriptional control of SLAMF1 gene in human B cells.

Signaling lymphocytic activation molecule family member 1 (SLAMF1)/CD150 is a co-stimulatory receptor expressed on a variety of hematopoietic cells, in particular on mature lymphocytes activated by specific antigen, costimulation and cytokines. Changes in CD150 expression level have been reported in association with autoimmunity and with B-cell chronic lymphocytic leukemia. We characterized the core promoter for SLAMF1 gene in human B-cell lines and explored binding sites for a number of transcription factors involved in B cell differentiation and activation.

Deoxygenation Affects Composition of Membrane-Bound Proteins in Human Erythrocytes.

Background/aims: ATP release from erythrocyte plays a key role in hypoxia-induced elevation of blood flow in systematic circulation. We have previously shown that hemolysis contributes to erythrocyte ATP release triggered by several stimuli, including hypoxia, but the molecular mechanisms of hypoxia-increased membrane fragility remain unknown.

Methods: In this study, we compared the action of hypoxia on hemolysis, ATP release and the composition of membrane-bound proteins in human erythrocytes.

Measles virus hemagglutinin triggers intracellular signaling in CD150-expressing dendritic cells and inhibits immune response.

Measles virus (MV) is highly contagious pathogen, which causes a profound immunosuppression, resulting in high infant mortality. This virus infects dendritic cells (DCs) following the binding of MV hemagglutinin (MV-H) to CD150 receptor and alters DC functions by a mechanism that is not completely understood. We have analyzed the effect of MV-H interaction with CD150-expressing DCs on the DC signaling pathways and consequent phenotypic and functional changes in the absence of infectious context.

Expression of CD150 in tumors of the central nervous system: identification of a novel isoform.

CD150 (IPO3/SLAM) belongs to the SLAM family of receptors and serves as a major entry receptor for measles virus. CD150 is expressed on normal and malignant cells of the immune system. However, little is known about its expression outside the hematopoietic system, especially tumors of the central nervous system (CNS).