The ammonia/ammonium (NH3/NH 4 + ) influx into red blood cells (RBCs) is mediated by surface glycoprotein RhAG that forms a structural complex with anion exchanger 1 (AE1, band 3). Owing to the activity of this complex, RBCs exposed to the isosmotic ammonium buffer swell and finally lyse. Isoosmotic NH 4 + -containing media alters the pH gradient in RBCs (intracellular alkalosis in response to NH3/NH 4 + influx) and triggers the AE1 activity resulting in redundant chloride and water influx and finally in cell swelling. Here we demonstrate that the ammonia/ammonium transport in human RBCs depends on the pH (pH optimum 7.4 ± 0.1), temperature (Q10 2.6 ± 0.3), HCO 3 − concentration (EC50 4.7 ± 0.3 mM), and AE1 function. The data confirm functional interactions between AE1 and RhAG. The initial velocity of cell swelling increased almost 50-fold in the isosmotic ammonium buffer containing 25 mM HCO 3 − (37°C) in comparison to the reaction in the same buffer without HCO 3 − . This indicates that the reaction is facilitated mostly by the carrier proteins, not just owing to the simple diffusion of NH3 across the erythrocyte membrane. We demonstrate that pHi reaches its maximum value much faster than the volume increase does. These data suggest that there is no direct correlation between pHi changes and the influx of NH3/NH 4 + . Taken together, our data show that the RhAG and AE1 complex activity enables erythrocytes to be ammonia/ammonium storage sites in order to maintain the physiological blood ammonia/ammonium equilibrium.

Neuroglobin is an iron-containing protein, most abundant in the vertebrate nervous system. Since neuroglobin is able to bind oxygen reversibly owing to the heme prosthetic group, it was believed that its function is an intercellular transport of oxygen in the nervous system and accumulation of oxygen for energy supply of cells in hypoxic conditions. In this work, a three-dimensional reconstruction of the neuroglobin distribution in large neurons of the rat medulla oblongata was carried out by means of immunocytochemistry and confocal laser microscopy. Positive neuroglobin immunocytochemical reaction was observed mainly in the perinuclear areas of large nerve cells exhibiting a discrete staining of the cytoplasm. Examination under the microscope at a high magnification revealed some neuroglobin-immunopositive granules, ring-like objects 1–2 μm in diameter, as well as linear and branched structures in neuronal cytoplasm and, occasionally, in the proximal segments of neuronal processes. Three-dimensional reconstruction of the neuroglobin-immunopositive structures showed that they mainly have the form of continuous lines and curves interlaced in some sites, about 1.0–1.5 μm thick, forming a complex network in the cytoplasm. The neuroglobin-immunopositive complexes found for the first time in neuronal cytoplasm are not identical to any known cytoplasmic compartments of nerve cells, but the diameter of their elements, as well as the shape and location suggest a possible link of neuroglobin with a mitochondrial network.

P-glycoprotein/ABCB1 (Pgp) is a well known protein of cell defense system. It is localized in cell membrane and pumps different drugs out of various cells using ATP energy. Its overexpression is associated with the development of multidrug resistance (MDR) in cancer cells. The data showing that Pgp also has other functions appeared recently, and this review surveys these data. In particular, (1) Pgp can protect cells from apoptosis; it suppresses the expression of endogenous protein TRAIL and decreases the activity of caspases 8 and 3; (2) Pgp is able to act as an outwardly directed flippase; (3) Pgp participates in a proper development of the innate immune response to intracellular pathogens and in the development of inflammation; (4) functionally active Pgp can be transferred from drug-resistant to drug-sensitive cells by microvesicles (MV). This is a new way of the Pgp-mediated MDR emergence in populations of tumor cells. Thus, Pgp functions as a regulator of some cellular processes. Molecular mechanisms of the Pgp influence on tumor cell viability are related not only with the drug efflux but also with some other functions.

The effects of hydrophobic and hydrophilic bile acids as inducers of Ca2+-dependent permeability of the inner membrane were studied on isolated liver mitochondria. It is shown that in the absence of the inorganic phosphate (Pi)–a modulator of the mitochondrial pore–hydrophobic bile acids (lithocholic, deoxycholic, chenodeoxycholic) at concentrations of 20–50 μM, as well as a hydrophilic cholic acid at a concentration of 800 μM, induce swelling of liver mitochondria loaded with Ca2+. This effect is completely eliminated by a specific inhibitor of mitochondrial pore cyclosporin A (CsA). The effect of the bile acids as inducers of Ca2+-dependent CsA-sensitive mitochondrial pore is not associated with the modulation of the Pi effects. In contrast to other tested bile acids, a hydrophilic ursodeoxycholic acid (UDCA) at a concentration of 400 μM is able to induce Ca2+-dependent CsA-sensitive pore opening in liver mitochondria only in the presence of Pi or in the absence of potassium chloride in the incubation medium. In the presence of potassium chloride but in the absence of Pi, UDCA effects associated with the induction of the inner membrane permeability (swelling of mitochondria, drop in Δψ, and Ca2+ release from the matrix) are also observed in the presence of CsA. This Ca2+-dependent permeability of the inner membrane, in contrast to the “classical” CsA-sensitive pore, is characterized by a lower intensity of the mitochondrial swelling, a total drop in Δψ, and Ca2+ release from the matrix and is blocked by Pi. We suggest that the induction of the CsA-insensitive permeability in the inner mitochondrial membrane by UDCA is associated with activation of electrophoretic influx of K+ into the matrix and Ca2+ release from the matrix in exchange to H+. The effect of Pi as a blocker of such permeability is discussed.

Human trophoblastic β1-glycoprotein (PSG) was studied in vitro as a differentiation factor of T-regulatory lymphocytes (Treg) and IL-17-producing lymphocytes. The role of CD9 molecules in realization of PSG effects was evaluated using anti-CD9 monoclonal antibodies. A human heterogeneous PSG was produced according to the original authors’ technique. It was revealed that PSG (10 or 100 μg/mL) increased the number of Treg (CD4+FOXP3+) and promoted the expression of CTLA-4 and GITR in these cells. It was found that PSG (10 and 100 μg/mL) impeded differentiation of the CD4+ cells into Th-17 lymphocytes (ROR-γt+IL-17A+). Some of the effects exerted by PSG (100 μg/mL) on the Treg/Th-17 differentiation was abolished upon the blockade of CD9 by antibodies; this concerned, in particular, the expression of FOXP3, CTLA-4, GITR, and ROR-γt. However, the depressing effects of PSG (100 μg/mL) on the expression and production of IL-17A did not depend on CD9. Thus, PSG favors the differentiation of CD4+ cells into Treg and suppresses the induction of Th17; some of the effects require the involvement of CD9.

A number of processes in living cells are accompanied by significant changes of the geometric curvature of lipid membranes. In turn, heterogeneity of the lateral curvature can lead to spatial redistribution of membrane components, most important of which are transmembrane proteins and liquid-ordered lipid-protein domains. These components have a so-called hydrophobic mismatch: the length of the transmembrane domain of the protein, or the thickness of the bilayer of the domain differ from the thickness of the surrounding membrane. In this work we consider redistribution of membrane components with hydrophobic mismatch in membranes with non-uniform geometric curvature. Dependence of the components’ energy on the curvature is calculated in terms of theory of elasticity of liquid crystals adapted to lipid membranes. According to the calculations, transmembrane proteins prefer regions of the membrane with zero curvature. Liquid-ordered domains having a size of a few nm distribute mainly into regions of the membrane with small negative curvature appearing in the cell plasma membrane in the process of endocytosis. The distribution of domains of a large radius is determined by a decrease of their perimeter upon bending; these domains distribute into membrane regions with relatively large curvature.

In order to study the structural and functional specificity of different fragments of extracellular domains of the membrane receptors, their immunological blockade and analysis of changes in brain function in health and disease were carried out. Effects of the immunization against unstructured fragments of the neurotrophin receptor (p75 NTR) containing binding sites for a nerve growth factor, amyloid-beta, and proneurotrophin were studied. It was shown that immunization of NMRI mice with synthetic peptides with amino-acid residue sequences corresponding to the p75 NTR fragments 86–93 and 146–153 exerted an adverse effect both on the morpho-functional state of the cortical and hippocampal neurons and on the spatial memory of animals. In contrast, the immunization by the p75 NTR synthetic fragment 167–176 was accompanied by an improvement of these characteristics. The results of the structural-functional mapping of the extracellular domain in neuronal membrane receptors in vivo were in line with the published data of the X-ray analysis. The immunological approach developed in this work provides insight into the peculiarities of the receptor functioning in the course of the Alzheimer’s type neurodegeneration process and favors the development of effective immunological ways for selective therapy of the Alzheimer’s disease.

The distribution of initiation factor eIF3 in the cytoplasm of peripheral blood neutrophils in Alzheimer disease (AD) was investigated. Using a specially developed image analysis protocol, we found a significant increase in the heterogeneity of the eIF3 distribution in AD neutrophils as compared with control cells. We also obtained an evidence that the increase in the eIF3 heterogeneity in AD neutrophils is associated with the formation of stress granules–non-membrane structures that emerge in the cytoplasm of eukaryotic cells in response to the environmental stress.

The origin of the nuclear envelope is a milestone in the eukaryotic evolution. The nuclear envelope separates the nucleus from cytoplasm and provides selective traffic between them. It is the most prominent structure in modern eukaryotes, which has no analogues in prokaryotes. Here, we overview different theories of eukaryogenesis and contemplate the data concerning possible ways of the formation of the nuclear envelope and nuclear pore complex.

The influence of β-adrenoceptor activation and inhibition by isoprenaline and propranolol on the specific binding of nonselective α1- and α2-adrenoceptor antagonists [3H]prazosin and [3H]RX821002 in rat cerebral cortex subcellular membrane fractions was studied. It was established that for the α1- and α2-adrenoceptors the ligand–receptor interaction corresponds to the model of one affinity pool of receptors and binding of two ligand molecules by one dimer receptor. The parameters of [3H]prazosin binding to α1-adrenoceptors were: K d = 1.85 ± 0.16 nM, B max = 31.14 ± 0.35 fmol/mg protein, n = 2. The parameters of [3H]RX821002 binding to α2-adrenoceptors were: K d = 1.57 ± 0.27 nM, B max = 7.2 ± 1.6 fmol/mg protein, n = 2. When β-adrenoceptors were activated by isoprenaline, the binding of radiolabelled ligands with α1- and α2-adrenoceptors occurred according to the same model. The affinity to [3H]prazosin and the concentration of active α1-adrenoceptors increased by 27% (K d = 1.36 ± 0.03 nM) and 84% (B max = 57.37 ± 0.28 fmol/mg protein), respectively. The affinity of α2-adrenoceptors to [3H]RX821002 decreased by 56% (K d = 3.55 ± 0.02 nM), and the concentration of active receptors increased by 69% (B max = 12.24 ± 0.06 fmol/mg protein). Propranolol alters the binding character of both ligands. For [3H]prazosin and [3H]RX821002, two pools of receptors were detected with the following parameters: K d1 = 1.13 ± 0.09, K d2 = 6.07 ± 1.06 nM, B m1 = 11.36 ± 1.77, Bm2 = 51.09 ± 0.41 fmol/mg protein, n = 2 and K d1 = 0.61 ± 0.02, K d2 = 3.41 ± 0.13 nM, B m1 = 1.88 ± 0.028, B m2 = 9.27 ± 0.08 fmol/mg protein, n = 2, respectively. The concentration of active receptors (B max) increased twofold for both ligands. It was suggested that α1- and α2-adrenoceptors in rat cerebral cortex subcellular membrane fractions exist as dimers. A modulating influence of isoprenaline and propranolol on the specific binding of the antagonists to α1- and α2- adrenoceptors was revealed, which was manifested in the activating effect on the [3H]prazosin binding parameters, in the inhibitory effect on the [3H]RX821002 binding parameters, and in a change of the general character of binding for both ligands.