The Small GTPase Rab7 Regulates Antigen Processing in B Cells in a Possible Interplay with Autophagy Machinery.

In B cells, antigen processing and peptide-antigen (pAg) presentation is essential to ignite high-affinity antibody responses with the help of cognate T cells. B cells efficiently internalize and direct specific antigens for processing and loading onto MHCII. This critical step, which enables pAg presentation, occurs in MHCII compartments (MIICs) which possess the enzymatic machinery for pAg loading on MHCII.

B cell receptor-induced protein dynamics and the emerging role of SUMOylation revealed by proximity proteomics.

Successful B cell activation, which is critical for high-affinity antibody production, is controlled by the B cell antigen receptor (BCR). However, we still lack a comprehensive protein-level view of the very dynamic multi-branched cellular events triggered by antigen binding. Here, we employed APEX2 proximity biotinylation to study antigen-induced changes, 5-15 min after receptor activation, at the vicinity of the plasma membrane lipid rafts, wherein BCR enriches upon activation.

Small Cellular Particles from European Spruce Needle Homogenate.

Small cellular particles (SCPs) are being considered for their role in cell-to-cell communication. We harvested and characterized SCPs from spruce needle homogenate. SCPs were isolated by differential ultracentrifugation.

Autologous Platelet and Extracellular Vesicle-Rich Plasma as Therapeutic Fluid: A Review.

The preparation of autologous platelet and extracellular vesicle-rich plasma (PVRP) has been explored in many medical fields with the aim to benefit from its healing potential. In parallel, efforts are being invested to understand the function and dynamics of PVRP that is complex in its composition and interactions. Some clinical evidence reveals beneficial effects of PVRP, while some report that there were no effects.

AutoCoEv-A High-Throughput In Silico Pipeline for Predicting Inter-Protein Coevolution.

Protein-protein interactions govern cellular processes via complex regulatory networks, which are still far from being understood. Thus, identifying and understanding connections between proteins can significantly facilitate our comprehension of the mechanistic principles of protein functions. Coevolution between proteins is a sign of functional communication and, as such, provides a powerful approach to search for novel direct or indirect molecular partners.

Analysis of Intracellular Vesicles in B Lymphocytes: Antigen Traffic in the Spotlight.

All eukaryotic cells are delimited by the plasma membrane, separating the cell from its environment. Two critical cellular pathways, the endocytic and the exocytic vesicle networks, shuttle material in and out the cell, respectively. The substantial development of cell biological imaging techniques, along with improved fluorescent probes and image analysis tools, has been instrumental in increasing our understanding of various functions and regulatory mechanisms of various intracellular vesicle subpopulations and their dynamics.

Minimizing isotropic and deviatoric membrane energy - An unifying formation mechanism of different cellular membrane nanovesicle types.

Tiny membrane-enclosed cellular fragments that can mediate interactions between cells and organisms have recently become a subject of increasing attention. In this work the mechanism of formation of cell membrane nanovesicles (CNVs) was studied experimentally and theoretically. CNVs were isolated by centrifugation and washing of blood cells and observed by optical microscopy and scanning electron microscopy.

Missing-in-Metastasis/Metastasis Suppressor 1 Regulates B Cell Receptor Signaling, B Cell Metabolic Potential, and T Cell-Independent Immune Responses.

Efficient generation of antibodies by B cells is one of the prerequisites of protective immunity. B cell activation by cognate antigens via B cell receptors (BCRs), or pathogen-associated molecules through pattern-recognition receptors, such as Toll-like receptors (TLRs), leads to transcriptional and metabolic changes that ultimately transform B cells into antibody-producing plasma cells or memory cells. BCR signaling and a number of steps downstream of it rely on coordinated action of cellular membranes and the actin cytoskeleton, tightly controlled by concerted action of multiple regulatory proteins, some of them exclusive to B cells.

B cells rapidly target antigen and surface-derived MHCII into peripheral degradative compartments.

In order to mount high-affinity antibody responses, B cells internalise specific antigens and process them into peptides loaded onto MHCII for presentation to T helper cells (T cells). While the biochemical principles of antigen processing and MHCII loading have been well dissected, how the endosomal vesicle system is wired to enable these specific functions remains much less studied. Here, we performed a systematic microscopy-based analysis of antigen trafficking in B cells to reveal its route to the MHCII peptide-loading compartment (MIIC).

Visualization and Quantitative Analysis of the Actin Cytoskeleton Upon B Cell Activation.

The formation of the immunological synapse upon B cell activation critically depends on the rearrangement of the submembranous actin cytoskeleton. Polymerization of actin monomers into filaments provides the force required for B cell spreading on the antigen-presenting cell (APC). Interestingly, the actin network also participates in cellular signaling at multiple levels.

Effect of shear stress in the flow through the sampling needle on concentration of nanovesicles isolated from blood.

During harvesting of nanovesicles (NVs) from blood, blood cells and other particles in blood are exposed to mechanical forces which may cause activation of platelets, changes of membrane properties, cell deformation and shedding of membrane fragments. We report on the effect of shear forces imposed upon blood samples during the harvesting process, on the concentration of membrane nanovesicles in isolates from blood. Mathematical models of blood flow through the needle during sampling with vacuumtubes and with free flow were constructed, starting from the Navier-Stokes formalism.

Effect of carbon black nanomaterial on biological membranes revealed by shape of human erythrocytes, platelets and phospholipid vesicles.

Background: We studied the effect of carbon black (CB) agglomerated nanomaterial on biological membranes as revealed by shapes of human erythrocytes, platelets and giant phospholipid vesicles. Diluted human blood was incubated with CB nanomaterial and observed by different microscopic techniques. Giant unilamellar phospholipid vesicles (GUVs) created by electroformation were incubated with CB nanomaterial and observed by optical microscopy.

Molecular control of B cell activation and immunological synapse formation.

B cells form an essential part of the adaptive immune system by producing specific antibodies that can neutralize toxins and target infected or malignant cells for destruction. During B cell activation, a fundamental role is played by a specialized intercellular structure called the immunological synapse (IS). The IS serves as a platform for B cell recognition of foreign, often pathogenic, antigens on the surface of antigen-presenting cells (APC).

Effects of magnetic cobalt ferrite nanoparticles on biological and artificial lipid membranes.

Background: The purpose of this work is to provide experimental evidence on the interactions of suspended nanoparticles with artificial or biological membranes and to assess the possibility of suspended nanoparticles interacting with the lipid component of biological membranes.

Methods: 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid vesicles and human red blood cells were incubated in suspensions of magnetic bare cobalt ferrite (CoFe2O4) or citric acid (CA)-adsorbed CoFe2O4 nanoparticles dispersed in phosphate-buffered saline and glucose solution. The stability of POPC giant unilamellar vesicles after incubation in the tested nanoparticle suspensions was assessed by phase-contrast light microscopy and analyzed with computer-aided imaging.

Suppression of membrane vesiculation as anticoagulant and anti-metastatic mechanism. Role of stability of narrow necks.

Nanovesicles that are pinched off from biological membranes in the final stage of budding constitute a cell-cell communication system. Recent studies indicate that in vivo they are involved in blood clot formation and in cancer progression. The bud is connected to the mother membrane by a thin neck so it dwells close to the mother membrane.

Visualization of internalization of functionalized cobalt ferrite nanoparticles and their intracellular fate.

In recent years, nanoparticles (NPs) and related applications have become an intensive area of research, especially in the biotechnological and biomedical fields, with magnetic NPs being one of the promising tools for tumor treatment and as MRI-contrast enhancers. Several internalization and cytotoxicity studies have been performed, but there are still many unanswered questions concerning NP interactions with cells and NP stability. In this study, we prepared functionalized magnetic NPs coated with polyacrylic acid, which were stable in physiological conditions and which were also nontoxic short-term.

A 32-month follow-up study of nanovesicle concentrations in blood from 12 patients with gastrointestinal stromal tumour treated with imatinib.

Clinical studies have indicated that the NV (nanovesicle) concentration in blood samples is a potential indicator of clinical status and can be used to follow the development of the disease. For 32 months, we monitored the effect of imatinib treatment on NV concentrations in blood samples from 12 patients with GIST (gastrointestinal stromal tumour). The NV concentration before the treatment increased with respect to control by a factor of 3.

Effect of engineered TiO2 and ZnO nanoparticles on erythrocytes, platelet-rich plasma and giant unilamelar phospholipid vesicles.

Background: Massive industrial production of engineered nanoparticles poses questions about health risks to living beings. In order to understand the underlying mechanisms, we studied the effects of TiO2 and ZnO agglomerated engineered nanoparticles (EPs) on erythrocytes, platelet-rich plasma and on suspensions of giant unilamelar phospholipid vesicles.

Results: Washed erythrocytes, platelet-rich plasma and suspensions of giant unilamelar phospholipid vesicles were incubated with samples of EPs.

Morphology, biophysical properties and protein-mediated fusion of archaeosomes.

As variance from standard phospholipids of eubacteria and eukaryotes, archaebacterial diether phospholipids contain branched alcohol chains (phytanol) linked to glycerol exclusively with ether bonds. Giant vesicles (GVs) constituted of different species of archaebacterial diether phospholipids and glycolipids (archaeosomes) were prepared by electroformation and observed under a phase contrast and/or fluorescence microscope. Archaebacterial lipids and different mixtures of archaebacterial and standard lipids formed GVs which were analysed for size, yield and ability to adhere to each other due to the mediating effects of certain plasma proteins.

Nanoparticles isolated from blood: a reflection of vesiculability of blood cells during the isolation process.

Background: Shedding of nanoparticles from the cell membrane is a common process in all cells. These nanoparticles are present in body fluids and can be harvested by isolation. To collect circulating nanoparticles from blood, a standard procedure consisting of repeated centrifugation and washing is applied to the blood samples.

Post-prandial rise of microvesicles in peripheral blood of healthy human donors.

Background: Microvesicles isolated from body fluids are membrane - enclosed fragments of cell interior which carry information on the status of the organism. It is yet unclear how metabolism affects the number and composition of microvesicles in isolates from the peripheral blood.

Aim: To study the post - prandial effect on microvesicles in isolates from the peripheral blood of 21 healthy donors, in relation to blood cholesterol and blood glucose concentrations.

Isolated microvesicles from peripheral blood and body fluids as observed by scanning electron microscope.

Microvesicles are sub-micron structures shed from the cell membrane in a final step of the budding process. After being released into the microenvironment they are free to move and carry signaling molecules to distant cells, thereby they represent a communication system within the body. Since all cells shed microvesicles, it can be expected that they will be found in different body fluids.

Mechanisms for the formation of membranous nanostructures in cell-to-cell communication.

Cells interact by exchanging material and information. Two methods of cell-to-cell communication are by means of microvesicles and by means of nanotubes. Both microvesicles and nanotubes derive from the cell membrane and are able to transport the contents of the inner solution.

Time lapse monitoring of CaCo-2 cell shapes and shape dependence of the distribution of integrin β1 and F-actin on their basal membrane.

CaCo-2 cell line is a model system for cell differentiation. For the effective use of CaCo-2 cells, it is important to understand how their growth depends on environmental conditions. The authors grew them on laminin-1, fibronectin, and collagen-1 adsorbed to glass and polystyrene.

Suppression of membrane microvesiculation--a possible anticoagulant and anti-tumor progression effect of heparin.

Heparins (unfractionated and low molecular weight (LMWH) heparins) primarily used as anticoagulants, were found to be effective also in slowing down the development of some types of cancer. On the other hand, the number of microvesicles in the peripheral blood originating from the budding of cell membranes (mostly platelets) is increased in hypercoagulabile states as well as in cancer, indicating a possible common underlying mechanism. It was hypothesized that by mediating an attractive interaction between phospholipid membranes heparin suppresses microvesiculation and thereby acts as an anticoagulant and anti-tumor agent.