Fifty Years of the Fluid–Mosaic Model of Biomembrane Structure and Organization and Its Importance in Biomedicine with Particular Emphasis on Membrane Lipid Replacement

Exosomes as a Therapeutic Strategy in Cancer: Potential Roles as Drug Carriers and Immune Modulators

Exosome-based cancer immunotherapy is advancing quickly on the concept of artificially activating the immune system to combat cancer. They can mechanistically change the tumor microenvironment, increase immune responses, and function as efficient drug delivery vehicles because of their inherent bioactivity, low toxicity, and immunogenicity. Accurate identification of the mechanisms of action of exosomes in tumor environments, along with optimization of their isolation, purification, and characterization methods, is necessary to increase clinical applications. Exosomes can be modified through cargo loading and surface modification to enhance their therapeutic applications, either before or after the donor cells' isolation. These engineered exosomes can directly target tumor cells at the tumor site or indirectly activate innate and adaptive immune responses in the tumor microenvironment. This approach is particularly effective when combined with traditional cancer immunotherapy techniques such as vaccines, immune checkpoints, and CAR-T cells. It can improve anti-tumor responses, induce long-term immunity, and address the limitations of traditional therapies, such as poor penetration in solid tumors and immunosuppressive environments. This review aims to provide a comprehensive and detailed overview of the direct role of engineered exosomes as drug delivery systems and their immunomodulatory effects on tumors as an indirect approach to fighting cancer. Additionally, it will discuss novel immunotherapy options.

Toxicity mechanism of microplastics on the growth traits and metabolic pathways of Vallisneria natans under different light environments

Freshwater plants are threatened by microplastics (MPs). While many studies have reported the effects of MPs on aquatic plants and animals, few have examined the effects of MPs on plant metabolism at different light intensities. We explore cellular, metabolic, and stress responses of Vallisneria natans at different light intensities (0, 20, 90, 160, 280 μmol·m-2·s-1), without and with (50 mg·L-1) MPs. The experiment showed that that the strong light promotes adsorption and accumulation of MPs on leaf and root tissues, affected growth rate, and changed metabolic pathways, inhibited photosynthetic processes, and enhanced oxidative stress responses in V. natans. Metabolomic analysis and experimental validation revealed that the combination of 280 μmol m-2·s-1 and MPs interfered most severely with plant carbon and nitrogen metabolism, lipid metabolism, and amino acid metabolism pathways compared with the combination of 90 μmol m-2·s-1 and MPs. This condition also significantly inhibited the activities of photosynthesis and energy transfer-related regulators and proteins, as well as stimulated oxidative stress-related pathways and exacerbated oxidative stress toxicity responses. The results of the research indicate that the highest light intensity tested can increase the accumulation of MPs, leading to V. natans cell damage, inhibition of photosynthetic metabolism, and the risk of oxidative toxic stress. Our results provide a basis for the analysis of the growth and metabolism processes and risk assessment of aquatic plants under the action of light and MPs.

Metabolomic analysis of plant-derived nanovesicles and extracellular vesicles from Pinellia ternata: insights into a temporary immersion bioreactor system

Plant-derived nanovesicles (PDNVs) and extracellular vesicles (EVs) represent a promising area of research due to their unique properties and potential therapeutic applications. Pinellia ternata (P. ternata) is well-known for its pharmacological properties but the PDNVs and EVs derived from it have been largely understudied. Previous studies have shown that a Temporary Immersion Bioreactor System (TIBS) plays an important role in controlling plant growth in order to obtain reproducible EVs and PDNVs. PDNVs were isolated from P. ternata plants and EVs were collected in the TIBS medium via ultra-high-speed differential centrifugation. Particle size, Zeta potentials and particle concentrations were assessed for PDNVs and EVs. Furthermore, non-targeted metabolomics was used to assess metabolic compositional differences between EVs and PDNVs, enabling the evaluation of the TIBS's quality control efficacy. Metabolomic profiling revealed 1072 metabolites in PDNVs and EVs, including 426 differential metabolites (DMs) distinguishing PDNVs from EVs: 362 DMs were positively correlated with PDNVs and 64 DMs were positively correlated with EVs; they were enriched across 17 KEGG pathways. PCA, PLS-DA, and metabolite sample correlation analyses showed high consistency between the replicates (PDNVs >0.87, EVs >0.93). This study demonstrated that TIBS is a performant system allowing consistency in generating PDNVs and EVs from P. ternata. We also highlighted the metabolic differences between PDNVs and EVs, guiding researchers in finding the bet system to produce efficient nanodrugs containing P. ternata pharmacological compounds.

Highly flexible cell membranes are the key to efficient production of lipophilic compounds

Lipophilic compounds have a variety of positive effects on human physiological functions and exhibit good effects in the prevention and treatment of clinical diseases. This has led to significant interest in the technical applications of synthetic biology for the production of lipophilic compounds. However, the strict selective permeability of the cell membrane and the hydrophobic nature of lipophilic compounds pose significant challenges to their production. During fermentation, lipophilic compounds tend to accumulate within cell membrane compartments rather than being secreted extracellularly. The toxic effects of excessive lipophilic compound accumulation can threaten cell viability, while the limited space within the cell membrane restricts further increases in production yield. Consequently, to achieve efficient production of lipophilic compounds, research is increasingly focused on constructing robust and multifunctional microbial cell factories. Utilizing membrane engineering techniques to construct highly flexible cell membranes is considered an effective strategy to break through the upper limit of lipophilic compound production. Currently, there are two main approaches to cell membrane modification: constructing artificial storage compartments for lipophilic compounds and engineering the cell membrane structure to facilitate product outflow. This review summarizes recent cell membrane engineering strategies applied in microbial cell factories for the production of liposoluble compounds, discussing the challenges and future prospects. These strategies enhance membrane flexibility and effectively promote the production of liposoluble compounds.

Molecular Insights into the Effect of Cholesterol on the Binding of Bicarbonate Ions in Band 3 Protein

Band 3, or anion exchanger 1 (AE1), is one of the indispensable transmembrane proteins involved in the effective respiratory process of the human body and is primarily responsible for the exchange of bicarbonate and chloride anions across the plasma membrane of erythrocyte. However, the molecular mechanism of ion transport of Band 3 is not completely understood, yet. In this work, we systematically investigate the key binding sites of bicarbonate ions in Band 3 and the impact of cholesterol (CHOL) in lipid bilayers on bicarbonate ion binding using all-atom molecular dynamics (MD) simulations. We examine the dynamics of interactions of bicarbonate ions with Band 3 in the microsecond time scale and calculate the binding free energy of the anion in Band 3. The results indicate that the residue R730 of Band 3 is the most probable binding site for bicarbonate ions. CHOL enhances the bicarbonate ion binding by influencing the conformational stability of Band 3 and compressing the volume of the Band 3 cavity. These findings provide some insights into the bicarbonate ion binding in Band 3 and are helpful for understanding the anion exchange of Band 3.

The intricate link between membrane lipid structure and composition and membrane structural properties in bacterial membranes

It is now evident that the cell manipulates lipid composition to regulate different processes such as membrane protein insertion, assembly and function. Moreover, changes in membrane structure and properties, lipid homeostasis during growth and differentiation with associated changes in cell size and shape, and responses to external stress have been related to drug resistance across mammalian species and a range of microorganisms. While it is well known that the biomembrane is a fluid self-assembled nanostructure, the link between the lipid components and the structural properties of the lipid bilayer are not well understood. This perspective aims to address this topic with a view to a more detailed understanding of the factors that regulate bilayer structure and flexibility. We describe a selection of recent studies that address the dynamic nature of bacterial lipid diversity and membrane properties in response to stress conditions. This emerging area has important implications for a broad range of cellular processes and may open new avenues of drug design for selective cell targeting.

Charge of a transmembrane peptide alters its interaction with lipid membranes

Transmembrane (TM) proteins interact closely with the surrounding membrane lipids. Lipids in the vicinity of TM proteins were reported to have hindered mobility, which has been associated with lipids being caught up in the rough surface of the TM domains. These reports, however, neglect one important factor that largely influences the membrane behavior - electrostatics of the TM peptides that are usually positively charged at their cytosolic end. Here, we study on the example of a neutral and a positively charged WALP peptide, how the charge of a TM peptide influences the membrane. We investigate both its dynamics and mechanics by: (i) time dependent fluorescent shift in combination with classical and FRET generalized polarization to evaluate the mobility of lipids at short and long-range distance from the peptide, (ii) atomic force microscopy to observe the mechanical stability of the peptide-containing membranes, and (iii) molecular dynamics simulations to analyze the peptide-lipid interactions. We show that both TM peptides lower lipid mobility in their closest surroundings. The peptides cause lateral heterogeneity in lipid mobility, which in turn prevents free lipid rearrangement and lowers the membrane ability to seal ruptures after mechanical indentations. Introduction of a positive charge to the peptide largely enhances these effects, affecting the whole membrane. We thus highlight that unspecific peptide-lipid interactions, especially the electrostatics, should not be overlooked as they have a great impact on the mechanics and dynamics of the whole membrane.

Self-assembly of peptide nanomaterials at biointerfaces: molecular design and biomedical applications

Self-assembly is an important strategy for constructing ordered structures and complex functions in nature. Based on this, people can imitate nature and artificially construct functional materials with novel structures through the supermolecular self-assembly pathway of biological interfaces. Among the many assembly units, peptide molecular self-assembly has received widespread attention in recent years. In this review, we introduce the interactions (hydrophobic interaction, hydrogen bond, and electrostatic interaction) between peptide nanomaterials and biological interfaces, summarizing the latest advancements in multifunctional self-assembling peptide materials. We systematically demonstrate the assembly mechanisms of peptides at biological interfaces, such as proteins and cell membranes, while highlighting their application potential and challenges in fields like drug delivery, antibacterial strategies, and cancer therapy.

Research Advances of Engineered Exosomes as Drug Delivery Carrier

Exosomes are nanoscale vesicles secreted by living cells that have similar membrane composition to parental cells and carry a variety of proteins, lipids, and nucleic acids. Therefore, exosomes have certain biological activities and play an important role in intercellular communication. On the basis of its potential as a carrier for drug delivery systems, exosomes have been engineered to compensate for the shortage of natural exosomes through various engineering strategies for improving drug delivery efficiency, enhancing targeting to tissues and organs, and extending the circulating half-life of exosomes. This review focuses on the engineered exosomes loading drugs through different strategies, discussions on exosome surface modification strategies, and summarizes the advantages and disadvantages of different strategies. In addition, this review provides an overview of the recent applications of engineered exosomes in a number of refractory and relapsable diseases. This review has the potential to provide a reference for further research and development of engineered exosomes.

Evolution of the Concepts of Architecture and Supramolecular Dynamics of the Plasma Membrane

The plasma membrane (PM) has undergone important conceptual changes during the history of scientific research, although it is undoubtedly a cellular organelle that constitutes the first defining characteristic of cellular life. Throughout history, the contributions of countless scientists have been published, each one of them with an enriching contribution to the knowledge of the structure-location and function of each structural component of this organelle, as well as the interaction between these and other structures. The first published contributions on the plasmatic membrane were the transport through it followed by the description of the structure: lipid bilayer, associated proteins, carbohydrates bound to both macromolecules, association with the cytoskeleton and dynamics of these components.. The data obtained experimentally from each researcher were represented in graphic configurations, as a language that facilitates the understanding of cellular structures and processes. This paper presents a review of some of the concepts and models proposed about the plasma membrane, emphasizing the components, the structure, the interaction between them and the dynamics. The work is illustrated with resignified 3D diagrams to visualize the changes that occurred during the history of the study of this organelle. Schemes were redrawn in 3D from the original articles...

(Patho)Physiology of Glycosylphosphatidylinositol-Anchored Proteins I: Localization at Plasma Membranes and Extracellular Compartments

Glycosylphosphatidylinositol (GPI)-anchored proteins (APs) are anchored at the outer leaflet of plasma membranes (PMs) of all eukaryotic organisms studied so far by covalent linkage to a highly conserved glycolipid rather than a transmembrane domain. Since their first description, experimental data have been accumulating for the capability of GPI-APs to be released from PMs into the surrounding milieu. It became evident that this release results in distinct arrangements of GPI-APs which are compatible with the aqueous milieu upon loss of their GPI anchor by (proteolytic or lipolytic) cleavage or in the course of shielding of the full-length GPI anchor by incorporation into extracellular vesicles, lipoprotein-like particles and (lyso)phospholipid- and cholesterol-harboring micelle-like complexes or by association with GPI-binding proteins or/and other full-length GPI-APs. In mammalian organisms, the (patho)physiological roles of the released GPI-APs in the extracellular environment, such as blood and tissue cells, depend on the molecular mechanisms of their release as well as the cell types and tissues involved, and are controlled by their removal from circulation. This is accomplished by endocytic uptake by liver cells and/or degradation by GPI-specific phospholipase D in order to bypass potential unwanted effects of the released GPI-APs or their transfer from the releasing donor to acceptor cells (which will be reviewed in a forthcoming manuscript).

Phytotoxicity of microplastics to the floating plant Spirodela polyrhiza (L.): Plant functional traits and metabolomics

Freshwater ecosystems are gradually becoming sinks for terrestrial microplastics (MPs), posing a potential ecological risk. Although the effects of MPs on plankton and aquatic animals in freshwater ecosystems have been given increasing attention, the toxicity of MPs to the metabolism of aquatic plants remains unclear. Here, the model aquatic plant Spirodela polyrhiza (L.) Schleid. (S. polyrhiza) was exposed to polyvinyl chloride (PVC; 0, 10, 100 and 1000 mg/L) MPs, and changes in the plant functional traits and physiological metabolism were monitored. The results showed that the high dose of PVC MPs decreased the adventitious root elongation ratio by 41.68% and leaf multiplication ratio by 61.03% of S. polyrhiza, and resulted in the decrease in anthocyanin and nitrogen contents to 63.45% and 84.21% of the control group, respectively. Moreover, the widely targeted metabolomics analysis results showed 37 differential metabolites in the low-dose treatment and 119 differential metabolites in the high-dose treatment. PVC MPs interfered with organic matter accumulation by affecting carbon metabolism, nitrogen metabolism, amino acid metabolism and lipid metabolism, and S. polyrhiza resists PVC MP stress by regulating the synthesis and metabolism of secondary metabolites. PVC MPs had concentration-related toxicological effects on plant functional traits, inhibited plant growth and reproduction, affected plant nutrient metabolism, and exhibited profound effects on the nitrogen fate of aquatic plant habitats. Overall, we systematically summarized the metabolic response mechanisms of aquatic plants to PVC MP stress, providing a new perspective for studying the effects of MPs on plant trait function and ecological risks.

The Fluid-Mosaic model of cell membranes: A brief introduction, historical features, some general principles, and its adaptation to current information

The Fluid-Mosaic Membrane (FMM) model was originally proposed as a general, nanometer-scale representation of cell membranes (Singer and Nicolson, 1972). The FMM model was based on some general principles, such as thermodynamic considerations, intercalation of globular proteins into a lipid bilayer, independent protein and lipid dynamics, cooperativity and other characteristics. Other models had trimolecular structures or membrane globular lipoprotein units. These latter models were flawed, because they did not allow autonomous lipids, membrane domains or discrete lateral dynamics. The FMM model was also consistent with membrane asymmetry, cis- and trans-membrane linkages and associations of membrane components into multi-molecular complexes and domains. It has remained useful for explaining the basic organizational principles and properties of various biological membranes. New information has been added, such as membrane-associated cytoskeletal assemblies, extracellular matrix interactions, transmembrane controls, specialized lipid-protein domains that differ in compositions, rotational and lateral mobilities, lifetimes, functions, and other characteristics. The presence of dense, structured membrane domains has reduced significantly the extent of fluid-lipid membrane areas, and the FMM model is now considered to be more mosaic and dense than the original proposal.

The Structures of Heterogeneous Membranes and Their Interactions with an Anticancer Peptide: A Molecular Dynamics Study

We conduct molecular dynamics simulations of model heterogeneous membranes and their interactions with a 24-amino acid peptide-NAF-144-67. NAF-144-67 is an anticancer peptide that selectively permeates and kills malignant cells; it does not permeate normal cells. We examine three membranes with different binary mixtures of lipids, DOPC-DOPA, DOPC-DOPS, and DOPC-DOPE, with a single peptide embedded in each as models for the diversity of biological membranes. We illustrate that the peptide organization in the membrane depends on the types of nearby phospholipids and is influenced by the charge and size of the head groups. The present study sheds light on early events of permeation and the mechanisms by which an amphiphilic peptide crosses from an aqueous solution to a hydrophobic membrane. Understanding the translocation mechanism is likely to help the design of new permeants.