Biochemistry (Moscow), Supplement Series A: Membrane and Cell Biology最新文献

The effect of exogenous auxin on changes in the fatty acid composition of the total lipids of leaves and roots of spring wheat (Triticum aestivum L.) seedlings was studied. It was found that the diversity of fatty acids in vegetative organs (leaf and root) depended not only on the concentration of auxin, but also on the donor of nitric oxide (N₂ and NO₃). With an increase in the concentration of exogenous auxin, there was an increase in microviscosity and a decrease in the permeability of membranes of vegetative organs of wheat, which was confirmed by a decrease in the double bond index (DBI). At the same time, there was an increase in the concentration of saturated fatty acids (palmitic and stearic), which were used as precursors for the formation of very long-chain fatty acids (VLCFA). It was found that exogenous auxin led to an increase in the total content of VLCFA in leaves with a deficit (8.4%) and an excess of NO donors (12.3%). The introduction of exogenous auxin eliminated significant differences in desaturase activity in wheat roots at different levels of nitric oxide donors. It was suggested that the biosynthesis of docosadienoic acid (C_22:2) in leaves is one of the key stages in the formation of the adaptive response of cell membranes to the effects of abiotic stresses during plant ontogenesis. An increase in the NO level promoted the movement of auxin from the roots to the shoots, which can serve as a regulator of the activity of elongases and desaturases during the synthesis of VLCFA.

The activator of the large-conductance Ca²⁺-activated K⁺ channel (BK_Ca) NS1619 is known to have a pleiotropic action and is able to affect the functioning of other transport systems of the cell and its organelles. In this work, we have studied the effect of this benzimidazole derivative on the functioning of isolated mouse skeletal muscle mitochondria. NS1619 has been shown to dose-dependently inhibit respiration and oxidative phosphorylation of mouse skeletal muscle mitochondria fuelled by glutamate/malate (complex I substrates) or succinate (complex II substrate). This action of NS1619 is based on the inhibition of the activity of complexes I, III, and IV of the respiratory chain of organelles, as well as ATP synthase and is accompanied by a dose-dependent decrease in the membrane potential of organelles fuelled by the above substrates or ATP. In addition, NS1619 significantly reduces the ability of mitochondria to uptake and retain calcium ions in the matrix. At the same time, we noted the antioxidant effect of NS1619 expressed in a decrease in the production of hydrogen peroxide by skeletal muscle mitochondria fuelled by glutamate and malate. The mechanisms of the possible toxic effects of NS1619 on skeletal muscle mitochondrial function and its contribution to the side effects observed in the treatment of muscle pathologies in vivo are discussed.

The processes of electronic transport in chloroplasts of two contrasting species of Tradescantia, the shade-tolerant species Tradescantia fluminensis and the light loving species T. sillamontana, grown in moderate or strong light conditions were investigated. The parameters of fast (OJIP test) and slow induction of fluorescence (SIF) of chlorophyll a in chloroplasts in vivo and in situ were used as indicators reflecting the photochemical activity of photosystem 2 (PS2). The coefficient of nonphotochemical quenching of chlorophyll a fluorescence, which provides protection of the photosynthetic apparatus from light stress, was determined from the SIF kinetics. The functioning of photosystem 1 (PS1) was monitored by the kinetics of photoinduced changes in the redox state of P₇₀₀, the reaction center of PS1, recorded by electron paramagnetic resonance. A significant difference in the dynamics of changes in photosynthetic parameters of shade-tolerant and light loving tradescantia species under conditions of prolonged acclimation of plants (up to 5 months) to moderate (50–125 µmol photons m^–2 s^–1) or strong (850–1000 µmol photons m^–2 s^–1) illumination with photosynthetically active white light was observed. In the light loving species T. sillamontana, photosynthetic parameters of chloroplasts changed slightly during acclimation of plants to moderate and strong light. Photosynthetic characteristics of leaves of shade-tolerant species T. fluminenesis were sensitive to the conditions of illumination, which indicated a weakening of photochemical activity with an increase in light intensity during acclimation of plants. The effect of attenuation of photosynthetic parameters of the leaves was reversible, that is, the fluorescence parameters returned to the initial level after attenuation of light.

One of the key receptors on the surface of platelets, non-nuclear cells responsible for preventing blood loss when blood vessels are damaged, is the receptor for the extracellular matrix protein collagen, glycoprotein VI (GPVI). GPVI triggers tyrosine kinase signaling in platelets, simultaneously initiating calcium signaling via phospholipase Cγ2 (PLCγ2) and phosphoinositide signaling via phosphoinositide-3-kinase (PI3K). Previously, our group demonstrated that among healthy donors there is more than a twofold variability in calcium response to activation through the GPVI receptor. Here, a computer model of platelet activation through the GPVI receptor is proposed to explain this phenomenon. This model is a system of ordinary differential equations integrated with the LSODA method. The model equations were derived from our previously published model of platelet activation via the CLEC-2 receptor. Using the developed model, a monotonic dependence of the degree of platelet activation on the number of GPVI receptors was predicted. An analysis of the sensitivity of the model to its parameters showed that the platelet response to activation through GPVI is determined by the number of GPVI receptors, as well as the catalytic parameters of tyrosine kinases, while a twofold change in the number of receptors is sufficient to explain the observed phenomenon. Thus, it was theoretically predicted that the variability of calcium responses of platelets to their stimulation through the GPVI receptor could be determined by the variability in the number of GPVI receptors on the platelet surface of healthy donors.

Stimulation of mitochondrial respiration in state 4 without changes in passive proton leakage is known to be accompanied by a decrease in the H⁺/O ratio. In the present work, it was found that during the oxidation of succinate by liver mitochondria, N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) and α,ω-hexadecanedioic acid (HDA) effectively stimulate respiration in state 4, and their action is, unlike the protonophore uncoupler DNP, is not caused by an increase in the proton conductivity of the inner membrane. Under these conditions, TMPD and HDA do not significantly affect the efficiency of oxidative ATP synthesis and energy transformation by complex IV (cytochrome c oxidase). The data obtained are considered as evidence that during the oxidation of succinate by liver mitochondria, TMPD and HDA selectively switch off ETC complex III from energy transformation. It is theoretically substantiated that, under these conditions, the H⁺/O ratio can be determined based on the ratio of respiratory rates in the absence and presence of TMPD and HDA. Based on this model, we considered the change in the H⁺/O ratio depending on the stimulation of mitochondrial respiration in state 4 by TMPD and HDA. It has been established that under the influence of TMPD or HDA, the value of the H⁺/O ratio decreases during the oxidation of succinate from 6 to the limiting values of 2. We conclude that in liver mitochondria during free respiration, in contrast to the oxidative ATP synthesis, the values of the H⁺/O ratio are 4 and 2 for complexes III and IV, respectively.

Cannabinoid receptors (CBRs) play a key role in various physiological processes, including neurogenesis, synaptic plasticity, immune modulation, cell apoptosis, metabolism regulation, cardiovascular and reproductive systems activity. Since activation of CBRs suppresses hyperexcitation and protects cells from death, their modulation may have therapeutic prospects in the treatment of such pathologies of the nervous system as mental disorders, epilepsy, Parkinson’s and Huntington’s disease, multiple sclerosis, spinal cord and brain injuries. This paper presents experimental data on the effects of the cannabinoid receptor agonist WIN 55,212-2 on the induced oscillations of intracellular Ca²⁺ concentration ([Ca²⁺]_i) in two in vitro models of epileptiform activity. To study the neuroprotective properties of WIN 55,212-2, hyperexcitation was induced by the application of a GABA(A) receptor antagonist, bicuculline, or depolarizing doses of ammonium chloride. As experiments have shown, WIN 55,212-2 at a concentration of 100 nM and above significantly suppresses the [Ca²⁺]_i oscillations frequency and reduces the basal [Ca²⁺]_i level. At the same time, the amplitude of calcium oscillations also decreased in the presence of the agonist. WIN 55,212-2 at a concentration of 2 μM suppressed NH₄Cl-induced [Ca²⁺]_i oscillations in all neurons but caused a transient biphasic increase in the basal [Ca²⁺]_i level in 20% of astrocytes. Thus, in this work, using various models of hyperexcitation of neuronal networks, we have demonstrated a potential antiepileptic effect of the cannabinoid receptor agonist WIN 55,212-2.

We compared oxidative and osmotic stress-induced changes in sterol content in plasma membranes and tonoplasts isolated from stored beet (Beta vulgaris L.) roots. The most significant differences between the membranes under all studied stresses were observed in the cholesterol content: it decreased in the plasmalemma, but increased 4-6 times in the tonoplast. Similar changes were observed for other sterols, but in different ways under different types of stress. Particularly noticeable differences were noted under hyperosmotic stress. The increase in the content of sterols was much more pronounced in the vacuolar membrane compared to the plasmalemma. This observation allows us to conclude that tonoplast plays a more significant role in protection of the plant cell from stress compared to plasmalemma.

A variety of surface receptors and intracellular signaling systems are involved in cell-to-cell communication and paracrine/autocrine regulation of cellular functions. Being most numerous, the family of G‑protein coupled receptors (GPCRs) is involved in the regulation of almost all physiological processes due to coupling to multiple and diverse intracellular signaling cascades. Among them, the ubiquitous contributors are the adenylate cyclase cascade, which controls the intracellular cAMP level, and the phosphoinositide cascade determining many aspects of intracellular Ca²⁺ signaling. Existing evidence suggests that the adenylate cyclase and phosphoinositide cascades are cross regulated. It therefore can be expected that agonists of adenylate cyclase-coupled GPCRs also are capable of affecting intracellular Ca²⁺, and in turn, Ca²⁺-mobilizing ligands could initiate a change in the cAMP level. Thus, simultaneous monitoring of cAMP and Ca²⁺ in the cell cytosol is rational as potentially providing new insights into intracellular signaling processes initiated by agonists. Currently, solely genetically encoded fluorescent sensors enable the on line monitoring of intracellular cAMP, and apart from Ca²⁺ dyes, such sensors are also evaluable for the analysis of intracellular Ca²⁺ signals. Based on maternal HEK-293 cells, here we generated a monoclonal line of HEK-PF/GG cells that co-expressed molecular fluorescent sensors for cAMP (Pink Flamindo) and Ca²⁺ (GEM-GECO1). Physiological tests showed that this cell line provides the possibility of simultaneous monitoring of cAMP and Ca²⁺ with sufficient sensitivity. Such a tool can increase the efficacy of studying agonist-induced intracellular processes and, in particular, the analysis of crosstalk between the cAMP and Ca²⁺ signaling systems.

This work aimed to produce mixed liposomes based on natural amino acids as vehicles for delivery of anticancer drugs and nucleic acids. Liposomes were formed from cationic lipids based on L-alanine and L-serine, a cerasome-forming lipid based on L-ornithine, and phospholipids phosphatidylcholine (PC) or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE). For the developed agents, particle size, zeta potential, and stability were determined, and the biological activity was studied on the MCF-7 and HEK 293 cell lines. Liposomes based on L-serine demonstrated the ability to accumulate in the endoplasmic reticulum of cells within 1 h, and their transfection activity significantly exceeded that of the commercial drug Lipofectamine-2000. At the same time, the proposed system had a slight toxic effect (IC₅₀, 0.475 mg/mL and the safe working concentration, 0.24 mg/mL). Thus, the results suggest that mixed liposomes based on L-serine can serve as an efficient delivery system of drugs into cells.