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

Adsorption and photochemical reactions of pyranine on a bilayer lipid membrane (BLM) have been studied by measuring electrostatic potentials at the membrane–water interface. The dependence of the electrostatic potentials due to the adsorption of pyranine on its concentration in solution is described by the Gouy–Chapman theory assuming that anions with three charged groups are adsorbed on the membrane. No significant changes in the boundary potential were found when BLM with pyranine adsorbed on it was illuminated. Significant changes in the potential were observed if molecules of styryl dyes di-4-ANEPPS or RH-421 were adsorbed on BLM in addition to pyranine. The sign and magnitude of these changes correspond to the disappearance of the dipole potential created by styryl dye molecules on the BLM. The rate of potential disappearance was proportional to pyranine concentration and illumination intensity. The disappearance of the potential can be caused either by the binding of protons released from the pyranine molecule to the dye mo-lecules with their subsequent desorption from the BLM or by their destruction. Pyranine and styryl dye molecules can form complexes at the BLM boundary. This is evidenced by experiments in which the sum of the potential changes caused by their adsorption separately differed significantly from the change in the boundary potential during their simultaneous adsorption. The kinetics of the disappearance of the dipole potential of BLM with styryl dyes upon excitation of pyranine turned out to be similar to that observed earlier with another compound, 2-methoxy-5-nitrophenyl sodium sulfate, which releases protons at the membrane boundary upon illumination (Konstantinova et al., 2021. Biochem. (Mosc.), Suppl. Series A: Membr. Cell Biol. 15 (2), 142–146). This suggests that it is associated with the desorption of dye molecules from the membrane, due to the binding of protons released from excited pyranin molecules to them.

In this work the effect of changing extracellular potassium concentration ([K⁺]_o) on spontaneous and evoked burst activity of glutamatergic neurons in the mouse hippocampus was investigated using the whole-cell patch clamp technique. It was shown that the increase of [K⁺]_o from 3 to 8.5 mM (potassium load): (1) induced spontaneous tonic and pacemaker burst activity in CA1 pyramidal cells (20% and 10% of total cells, respectively) but did not result in the emergence of pacemaker granule cells in the dentate gyrus (DG). (2) Similarly, potassium load increased the evoked burst activity of CA1 pyramidal cells and, paradoxically, suppressed the burst activity of DG granule cells over the entire range of current steps from 10 to 200 pA. (3) Potassium load caused a rightward shift of the current–voltage (I/V) curves in both cell types, decreasing the reversal potential E_rev and increasing the slope of the I/V curves (amplitudes of inward currents at voltages from –100 mV to –70 mV) in the CA1 and DG neurons 2–3- and 4–5-fold, respectively. (4) Potassium load produced an opposite effect on outward currents, causing a significant increase in current amplitude in pyramidal cells and a decrease in granule cells (at membrane voltages above 0 mV). The inward and outward currents of DG neurons were 4–4.5 times higher than those of CA1 neurons. The possible involvement of potassium-activated and other potassium-conducting channels in different excitability responses of glutamatergic CA1 and DG neurons under potassium load is discussed. The high sensitivity of CA1 pyramidal cells to potassium load compared to DG granule cells may play an important role in hyperexcitation of neuronal networks during epileptogenesis.

The review considers the data available in the literature on myoglobin expression in various tumors and cell lines of non-muscle tumor cells and on the influence of hypoxia, reactive oxygen and nitrogen species, hormones, growth factors, gender, and age on this process. The effect of tumor myoglobin on cellular processes such as oxidative stress, inhibition of mitochondrial respiration by nitric oxide, and fatty acid metabolism is also analyzed, both during endogenous expression of small amounts (~1 μM) of myoglobin and overexpression of the protein (~150 μM) due to incorporation of the myoglobin gene into the tumor cell genome. It is concluded that hypoxia-induced intrinsic expression of low concentrations of myoglobin, due to its ability to utilize reactive oxygen and nitrogen species that can damage tumor cells, ensures their better survival by promoting tumor progression and metastasis. Accordingly, this expression of myoglobin is generally associated with a more aggressive tumor type, poor prognosis for the course and outcome of the disease, and may thus serve as a “marker” of an aggressive malignancy. In contrast, artificial overexpression of myoglobin can significantly inhibit tumor development and improve disease course by switching cancer cell metabolism from tumor-specific glycolysis to oxidative phosphorylation inherent in healthy tissue. Myoglobin overexpression may thus be an effective therapeutic tool in oncology.

Human serum albumin (HSA) is an endogenous inhibitor of angiotensin-I-converting enzyme (ACE), which is an integral membrane protein catalyzing the cleavage of decapeptide angiotensin I to octapeptide angiotensin II. By inhibiting ACE, HSA plays an important role in the renin-angiotensin-aldosterone system (RAAS). However, little is known about the mechanism of interaction between these proteins, and the structure of the HSA–ACE complex has not yet been experimentally obtained. The aim of the presented work is to investigate the interaction of HSA with ACE by molecular modeling methods. Ten possible HSA–ACE complexes were obtained by macromolecular docking method. The leader complex was selected according to the number of steric and polar contacts between the proteins, and its stability was tested by molecular dynamics (MD) simulation. The possible effect of modifications in the albumin molecule on its interaction with ACE was analyzed. A comparative analysis of the structure of the obtained HSA–ACE complex with the known crystal structure of the HSA complex with neonatal Fc receptor (FcRn) was performed. The obtained results of molecular modeling define a direction for further in vitro studies of the mechanisms of HSA–ACE interaction. Information about these mechanisms will help in the design and improvement of pharmacotherapy aimed at modulating the physiological activity of ACE.

A mathematical model of glycolysis in mammalian skeletal muscles is presented for the first time, in which stationary concentrations of intermediate metabolites of glycolysis are in good agreement with experimental data obtained in resting muscles. The correspondence between model and experimental values of metabolite concentrations was achieved due to the increased inhibitory effect of ATP on pyruvate kinase and a significant decrease in the [NAD⁺]/[NADH] concentration ratio in the cytoplasm of skeletal muscles. At the same time, activation of muscle pyruvate kinase by fructose-1,6-diphosphate was introduced into the model to allow glycolysis to provide the rate of ATP production required during muscle load activation.

The paper describes an extended mathematical model for the regulation of the key stages of electron transfer in the photosynthetic chain of electron transport and the associated processes of trans-thylakoid proton transfer and ATP synthesis in chloroplasts. This model includes primary plastoquinone PQ_A, associated with photosystem 2 (PS2), and secondary plastoquinone PQ_B, exchanging with plastoquinone molecules that are part of the pool of electronic carriers between PS2 and photosystem 1 (PS1). The model adequately describes the multiphase non-monotonic curves of chlorophyll fluorescence induction and the kinetics of P₇₀₀ redox transformations (photoreaction center PS1), plastoquinone, changes in ATP and pH concentrations in lumen (pH_i) and stroma (pH_o) depending on the illuminating conditions of chloroplasts (variation in intensity and spectral composition of light). The results of computer simulation are consistent with experimental data on the kinetics of photoinduced P₇₀₀ transformations in the leaves of higher plants and the induction of chlorophyll a fluorescence. The obtained data are discussed in the context of “short-term” mechanisms of pH-dependent regulation of electron transport in intact chloroplasts (non-photochemical quenching of excitation in PS2 and activation of the Calvin–Benson cycle reactions).

Phosphatidylserine- (PS-) positive platelets play an important role in thrombosis and hemostasis. They have high procoagulant activity, the ability to vesiculate, and can aggregate with activated PS-negative platelets. They are found in growing thrombus in vitro, but numerous mysteries remain regarding them. In particular, intracellular signaling and cytoskeletal reorganization in these platelets is poorly studied, since they have the ability to be destroyed by permeabilization, which is necessary for the penetration of antibodies to intracellular markers into the cell. In this work, we propose an approach that allows the analysis of intracellular signaling in calcium ionophore A23187-induced PS-positive platelets using flow cytometry or confocal microscopy. We used the mildest permeabilization of fixed PS-positive platelets using saponin and showed that such permeabilization allows us to significantly preserve PS-positive platelets. As an example, we analyzed the state of the polymerized form of actin in PS-positive platelets and showed that, despite the significant rearrangement of the cytoskeleton that occurs upon activation in such platelets, actin in them is partially presented in a polymerized form.

Seasonal changes in fatty acid composition in four skeletal muscles of the true hibernating Yakutian long-tailed ground squirrel Urocitellus undulatus were studied. Measurements were taken on animals of four experimental groups: summer active, autumn active, winter hibernating, and winter active. An increase in total fatty acids was found in winter in the quadriceps femoris muscle (m. vastus lateralis), triceps forearm muscle (m. triceps), and lumbar muscle (m. psoas). A decrease in the total content of saturated fatty acids in all muscles was observed during the winter period. The increase in the total content of monounsaturated fatty acids in winter hibernating animals occurred in the quadriceps femoris muscle, triceps forearm muscle, and lumbar muscle. In winter active animals, the total content of polyunsaturated fatty acids increased in quadriceps femoris muscle and lumbar muscle. A statistically significant decrease in the content of palmitic acid in hibernating and winter active animals compared to summer and autumn animals was found in all muscles studied. The content of palmitoleic acid increased in hibernating animals in the quadriceps femoris muscle and lumbar muscle. In the triceps forearm muscle, the content of palmitoleic acid was increased in autumn active and winter hibernating animals. The content of oleic acid was elevated in all muscles in winter hibernating animals relative to active autumn animals. Linoleic acid content was significantly increased in winter active animals in all muscles except the calf muscle. Dihomo-gamma-linolenic acid increased in all muscles during the autumn period with a decrease in content in winter hibernating and winter active animals to the level of summer (seasonal) controls. The results obtained indicate that most of the changes in fatty acid composition have the same direction in all four studied skeletal muscles of the long-tailed ground squirrel. The possible role of seasonal changes in fatty acid composition and fatty acid participation in biochemical processes in the muscle tissue of the long-tailed ground squirrel is discussed.

Mesenchymal stromal cells (MSCs) are universal regulators of regenerative processes due to their ability to paracrine release of regulatory molecules or to replace dead cells by differentiation in the appropriate direction. Recently, another mechanism for the beneficial effects of MSCs on damaged tissues has been discovered, namely transfer of mitochondria into its cells in response to stress signals. MSCs can transfer mitochondria through tunnel nanotubes forming a connecting bridge between cells, through gap junctions, by release as part of extracellular vesicles or in the free form, as well as by complete or partial fusion with recipient cells. In the damaged cells that received mitochondria from MSCs, the disturbed energy metabolism is restored and oxidative stress is reduced, which is accompanied by increased survival, and in some cases also by increased proliferation or changes in differentiation status. Restoration of energetics after mitochondria transfer from MSCs has a beneficial effect on functional activity of recipient cells and promotes suppression of inflammatory reactions. It has been repeatedly demonstrated on models of damage of various organs in experimental animals that the transfer of mitochondria from MSCs to target cells makes a significant contribution to the therapeutic efficacy of MSCs. Therefore, methods to enhance mitochondrial donation are currently being searched for. However, it should be taken into account that MSCs are able to transfer mitochondria to malignant cells, thus stimulating tumor growth and increasing its resistance to chemotherapy. These data make us cautious about the prospects of using MSCs in cell therapy, but, on the other hand, they can serve as a basis for searching for new therapeutic targets in the treatment of cancer.

Various RNAs are among the most promising and actively developed therapeutic agents for the treatment of tumors, infectious diseases and a number of other pathologies associated with the dysfunction of specific genes. Some nanocarriers are used for the effective delivery of RNAs to target cells, including liposomes based on cationic and/or ionizable amphiphiles. Cationic amphiphiles contain a protonated amino group and exist as salts in an aqueous environment. Ionizable amphiphiles are a new generation of cationic lipids that exhibit reduced toxicity and immunogenicity and undergo ionization only in the acidic environment of the cell. In this work we developed a scheme for the preparation and carried out the synthesis of new cationic and ionizable amphiphiles based on natural amino acids (L-glutamic acid, glycine, β-alanine, and γ-aminobutyric acid). Cationic and ionizable liposomes were formed based on the obtained compounds, mixed with natural lipids (phosphatidylcholine and cholesterol), and their physicochemical characteristics (particle size, zeta potential, and storage stability) were determined. Average diameter of particles stable for 5–7 days did not exceed 100 nm. Zeta potential of cationic and ionizable liposomes was about 30 and 1 mV, respectively. The liposomal particles were used to form complexes with RNA molecules. Such RNA complexes were characterized by atomic force microscopy and their applicability for nucleic acid transport was determined.