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

The ability of NK cells to establish antigen-specific responses has been demonstrated in various infections. NK cell receptors of the diverse family of Killer-cell Immunoglobulin-like Receptors (KIR) interact with HLA class I molecules, and this interaction is peptide-dependent. The activating receptor KIR2DS4 enables NK cell degranulation following interaction with specific peptides presented within HLA-C*05. However, the mechanism underlying the differential NK cell response depending on a peptide remains poorly understood and lacks explanation based on the structure of ligand-receptor interaction. Using AlphaFold 3, we generated models of KIR2DS4-peptide-HLA-C*05 complexes to analyze the contact interfaces. We confirmed the substantial role of the aromatic ring in the 8th amino acid residue of peptide sequences in mediating interactions with KIR2DS4. Even with the same amino acid residue at position 8, different peptides exhibited variability in polar contacts with KIR2DS4. Our results may contribute to the prediction of KIR-HLA interactions and facilitate the identification of specific peptides capable of activating NK cells.

Plasma membranes perform a barrier function in cells, preventing free exchange between the external environment and the intracellular space. The permeability of the plasma cell membrane can be artificially increased by forming through pores. The outer and inner monolayers of the plasma membranes of cells typically have different lipid compositions. Currently, a theoretical description of the poration of membranes with monolayers symmetrical in lipid composition has been developed. In the present work, we consider the process of pore formation in membranes, whose monolayers have different spontaneous curvatures due to the difference in their lipid composition. In the framework of the theory of lipid membrane elasticity and considering hydrophobic interactions, the dependence of the pore energy on the radius is calculated. It is shown that the dependences of pore energy on radius are qualitatively different in asymmetric and symmetric membranes. The pore energy in the asymmetric membrane differs from the pore energy in the symmetric membrane at any values of the spontaneous curvature of the monolayers of the symmetric membrane. Thus, it is incorrect to predict the course of the pore formation in an asymmetric membrane on the basis of data obtained on symmetric membranes; the asymmetry of lipid composition (spontaneous curvature) of monolayers should be explicitly taken into account.

Here we examined how drug-to-lipid ratio affects the fine structure of anionic liposomes with dipalmitoyl phosphatidylcholine and cardiolipin loaded with levofloxacin following with investigation of molecular details of complex formation with mannosylated chitosan. Drug loading leads to reduce of acyl chain mobility in the bilayer and redistribution of carbonyl and phosphate groups on the hydration degree, suggesting bilayer structural changes. Higher drug-to-lipid ratio provides more pronounced changes. The effects become more significant upon heating, mostly because of slowing down of phase transition. Complex formation with mannosylated chitosan mostly mitigates effects. Thus, altering drug-lipid-ratio affects the structure of anionic levofloxacin-loaded liposomes coated with mannosylated chitosan, affecting their stability and therapeutic capacity.

ATP synthase is a membrane protein complex that plays a crucial role in cellular bioenergetics. The formation of I-shaped dimers of spinach chloroplast ATP synthase in a model system (detergent micelles) with a high concentration of sodium chloride has been reported in the literature, but the presence and functional role of this mechanism in vivo remains unclear. We studied the impact of ionic strength on the thermostability and activity of spinach ATP synthase in liposomes. We measured ATP synthesis in the presence of NaCl, NaNO₃, and Na₂SO₄ at various concentrations and found that high ionic strength (~1 M) reduced ATP synthase activity by approximately 50%. Additionally, we determined the melting temperature of ATP synthase in the presence of NaCl and KCl, observing an increase from ~60.5 to ~62.0°C in solutions with high ionic strength. Our results demonstrate that salt ions affect ATP synthesis and thermostability in a non-specific manner. These findings provide support for the hypothesis that ATP synthase dimerization in vivo may serve as a regulatory mechanism for controlling its activity.

Bordetella pertussis, a gram-negative bacterium responsible for whooping cough, poses severe health risks, especially to young children. However, the disease can be prevented by immunization with whole-cell pertussis vaccines and acellular pertussis vaccines containing 2–5 purified B. pertussis antigens, of which chemically detoxified pertussis toxin is the main protective component. While current vaccines have proven effective, concerns over high reactogenicity of whole-cell pertussis vaccines and the waning immunity to acellular pertussis vaccines formulations underscore the need for improved pertussis vaccines. Genetically detoxified pertussis toxin is an attractive vaccine candidate because it retains most of the structural properties of native pertussis toxin and better preserves the protective epitopes compared to detoxified pertussis toxin. In this study, we developed a candidate vaccine based on a genetically detoxified pertussis toxin S1 subunit, gd15PTxS1. We evaluated humoral and cellular immunogenicity of gd15PTxS1 in a murine model and demonstrated significant anti-PTx IgG seroconversion and a balanced Th1/Th2/Th17 T-cell response, with gd15PTxS1 inducing robust cytotoxic and helper T-cell activation comparable to that of the whole-cell pertussis vaccines. Our results show that gd15PTxS1 is highly immunogenic in mice and is a promising vaccine candidate for further protectivity studies.

The need for new effective compounds that can serve as prototype drugs for the treatment of viral infections and various types of cancer has not diminished over the past decades. This is due to the emergence of new pathogens and the development of resistance to existing drugs. Nucleoside analogues are one of the most common classes of drugs that have long served as the basis for antiviral and anticancer therapies. The analogues' similarity to natural nucleosides, which are involved in many biological processes, allows them to inhibit key enzymes in the development of pathogenic processes. The antiviral properties of synthetic nucleosides and their analogues are of great interest in connection with the primary or re-emerging viruses with epidemic and/or pandemic potential, such as Ebola, Zika, Middle East respiratory syndrome (MERS-CoV), severe acute respiratory syndrome viruses, coronaviruses 1 and 2 (SARS and SARS-CoV-2), or new strains of influenza. The aim of our work was to create new uracil derivatives—acyclic reverse fleximers as potential antiviral and antitumor agents. The substances were obtained by the Suzuki–Miyaura reaction and characterized using modern physicochemical methods. Antiviral activity against influenza A/California/7/2009 and SARS-CoV-2 was tested, and cytotoxicity was assessed on leukemia and neuroblastoma cell cultures.

Despite significant advances in diagnosis and treatment, atrial fibrillation remains a common cardiac arrhythmia affecting up to 2% of our world’s population. Atrial fibrillation results from complex dynamic interactions between risk factors and comorbidities that trigger a variety of atrial remodeling processes. Atrial remodeling increases the persistence of atrial fibrillation while contributing to disease progression. The variability of manifestations and the wide range of mechanisms involved in the initiation, maintenance, and progression of atrial fibrillation, as well as the associated adverse outcomes, make early identification of causative factors a major challenge for modern cardiology. Computer modeling over the past 60 years has opened new avenues for understanding mechanisms, risk prediction, and personalized therapy in the treatment of atrial fibrillation. As part of our modeling of patient-specific atrial structure from gadolinium-enhanced magnetic resonance imaging data, we investigated fibrosis as a substrate for the occurrence of re-entry from a purely electrophysiological perspective. We demonstrated the effects occurring on the patient-specific atrial structure in the case of normal electrophysiology and the electrophysiology obtained in long-term atrial fibrillation. In this work, we also compared the effects of the antiarrhythmic agent Verapamil on conduction by atrial models with different electrophysiology and fibrosis distribution.

Optogenetics allows a precise control of a vast variety of cellular processes in excitable and non-excitable cells, in particular, through their organelles. Microbial rhodopsin-based optogenetic tools could be used to control ion concentrations in various compartments. Recently, induction of apoptosis by rhodopsin-based optogenetics was demonstrated: cytosol alkalization in human cells by outward proton pump Arch3 was shown to induce intrinsic, mitochondria-mediated apoptotic pathway of cell death. It is known that cytosol and mitochondrial matrix alkalization, reactive oxygen species production in mitochondria and Ca²⁺ signaling are tightly interconnected in mammalian cells, and under certain conditions they favor mitochondrial permeability transition pore opening and cell death. However, in the case of optogenetic alkalization reactive oxygen species generation has not been experimentally addressed. In this work we investigated reactive oxygen species generation which occurred under the optogenetic cytosol alkalization. Arch3 was expressed in the plasma membrane of HeLa cells, and optogenetic cytosol alkalization by Arch3 lead to mitochondrial reactive oxygen species generation as well as to elevation of the level of reactive oxygen species in cytosol. We propose that production of reactive oxygen species may be a key step in cell death induced by optogenetic alkalization of cytosol by promoting the opening of mitochondrial permeability transition pores. Our findings may help to better understand the mechanisms of apoptosis induced by reactive oxygen species and shed light on the interplay between the cytosolic pH, mitochondrial dynamics, reactive oxygen species, and some other factors promoting cell death in living cells.

Discovery of antigen epitopes and cognate T-cell receptors (TCRs) is one of the central challenges in the development of targeted immunotherapies. In vitro testing for antigen reactivity is the major protocol for these purposes. Here we have proposed an approach for multiplexing of the antigens/epitopes in one test volume with the unmixing of stimulus during the analysis. We found that B-cell marker CD20 is transferred from B-cells to T-cells surface during antigen-specific interactions. We demonstrated that anti-CD20 antibodies with different labels can be used as tracers of the specific antigens loaded into the B-cells, so that T-cells stimulated by certain antigen accept corresponding anti-CD20 antibodies. This approach can be expanded using the mixture of anti-CD20 antibodies that will increase the output and reliability of antigen discovery routine.

Investigation of the complex interrelationships of multiple intercellular processes underlying cardiac electrophysiology and pathophysiology requires the dynamic and non-invasive assessment of multiple parameters. Here, we introduce an approach to two-parametric optical mapping, which allows for studying metabolism–excitation–contraction coupling in human heart tissue. We applied this methodology for cardioplegic solution cardiotoxicity testing and to study the modulation of cardiac physiology during hypoxia. Using this approach, we determined the effects of Normacor and Custodiol cardioplegic solutions on human induced pluripotent stem cells-derived cardiomyocytes (hiPSC-CMs) physiology with possible long-term effects on cardiomyocyte excitability. We revealed a reversible shortening of the action potential during hypoxia with Normacor (326 ± 36 ms in control and 198 ± 41 ms immediately after 4-h hypoxia and hyperkalemia) and observed an irreversible loss of excitability after 4 h of hypoxia under cold ischemia.