Lipid rafts are defined as plasma membrane microdomains enriched with glycosphingolipids and cholesterol which render them insoluble in non-ionic detergents. Many surface receptors are constitutively or inducibly associated with lipid rafts, and it has been suggested that the rafts function as platforms regulating the induction of signaling pathways. The signaling capacity of lipid rafts has been extensively studied in rat basophilic leukemia cells. An aggregation of lipid raft components, such as glycosylphosphatidylinositol (GPI)-anchored glycoproteins (Thy-1 or TEC-21), triggers cell activation events which are similar to, but not identical with activation via the high-affinity IgE receptor (FcepsilonRI). Although FcepsilonRI in resting cells is not associated with lipid rafts, its aggregation induces a weak association with rafts and subsequent activation events. The properties of lipid rafts as well as the molecular mechanisms of their involvement in signal transduction are poorly understood. This review presents a critical analysis of recent results on structure-function relationship of lipid rafts and their regulatory role in signal transduction in mast cells.

• MeSH
• antigeny Thy-1 analýza   MeSH
• cholesterol fyziologie   MeSH
• detergenty farmakologie   MeSH
• krysa rodu Rattus MeSH
• mastocyty imunologie   MeSH
• membránové mikrodomény chemie   účinky léků   fyziologie   MeSH
• receptory IgE metabolismus   MeSH
• signální transdukce * MeSH
• skupina kinas odvozených od src-genu analýza   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• antigeny Thy-1 MeSH
• cholesterol MeSH
• detergenty MeSH
• lyn protein-tyrosine kinase MeSH Prohlížeč
• receptory IgE MeSH
• skupina kinas odvozených od src-genu MeSH

When the ancestors of men moved from aquatic habitats to the drylands, their evolutionary strategy to restrict water loss is to seal the skin surface with lipids. It is unknown how these rigid ceramide-dominated lipids with densely packed chains squeeze through narrow extracellular spaces and how they assemble into their complex multilamellar architecture. Here it is shown that the human corneocyte lipid envelope, a monolayer of ultralong covalently bound lipids on the cell surface protein, templates the functional barrier assembly by partly fluidizing and rearranging the free extracellular lipids in its vicinity during the sculpting of a functional skin lipid barrier. The lipid envelope also maintains the fluidity of the extracellular lipids during mechanical stress. This local lipid fluidization does not compromise the permeability barrier. The results provide new testable hypotheses about epidermal homeostasis and the pathophysiology underlying diseases with impaired lipid binding to corneocytes, such as congenital ichthyosis. In a broader sense, this lipoprotein-mediated fluidization of rigid (sphingo)lipid patches may also be relevant to lipid rafts and cellular signaling events and inspire new functional materials.

• Klíčová slova
• barrier, lipid assembly, membrane remodeling, permeability, template,
• MeSH
• lidé MeSH
• lipidy chemie   MeSH
• membránové proteiny * metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• lipidy MeSH
• membránové proteiny * MeSH

Recent data suggest that initiation of signal transduction via type 1 Fc epsilon receptor (Fc epsilon RI) and other immunoreceptors is spatially constrained to lipid rafts. In order to better understand the complexity and function of these structures, we prepared mAb against lipid rafts from the rat basophilic leukemia cell line, RBL-2H3, which is extensively used for analysis of Fc epsilon RI-mediated activation. One of the antibodies was found to recognize a novel glycosylphosphatidylinositol-anchored plasma membrane glycoprotein of 250 amino acids, designated TEC-21, containing a cysteine-rich domain homologous to those found in the urokinase plasminogen activator receptor/Ly-6/snake neurotoxin family. TEC-21 is abundant on the surface of RBL-2H3 cells (>10 (6) molecules/cell), but is absent in numerous rat tissues except for testes. Aggregation of TEC-21 on RBL-2H3 cells induced a rapid increase in tyrosine phosphorylation of several substrates including Syk kinase and LAT adaptor, calcium flux, and release of secretory components. Similar but more profound activation events were observed in cells activated via Fc epsilon RI. However, aggregation of TEC-21 did not induce changes in density of IgE-Fc epsilon RI complexes, tyrosine phosphorylation of Fc epsilon RI beta and gamma subunits, and co-aggregation of Lyn kinase. TEC-21-induced activation events were also observed in Fc epsilon RI(-) mutants of RBL-2H3 cells. Thus, TEC-21 is a novel lipid raft component of RBL-2H3 cells whose aggregation induces activation independently of Fc epsilon RI.

• MeSH
• akutní bazofilní leukemie patologie   MeSH
• antigeny povrchové chemie   izolace a purifikace   fyziologie   MeSH
• klonování DNA MeSH
• krysa rodu Rattus MeSH
• membránové glykoproteiny * MeSH
• membránové mikrodomény fyziologie   MeSH
• molekulární sekvence - údaje MeSH
• nádorové buňky kultivované MeSH
• receptory IgE fyziologie   MeSH
• sekvence aminokyselin MeSH
• sekvence nukleotidů MeSH
• signální transdukce MeSH
• skupina kinas odvozených od src-genu metabolismus   MeSH
• vápník metabolismus   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antigeny povrchové MeSH
• lyn protein-tyrosine kinase MeSH Prohlížeč
• membránové glykoproteiny * MeSH
• receptory IgE MeSH
• skupina kinas odvozených od src-genu MeSH
• TEC-21 antigen, rat MeSH Prohlížeč
• vápník MeSH

Lipid membranes can spontaneously organize their components into domains of different sizes and properties. The organization of membrane lipids into nanodomains might potentially play a role in vital functions of cells and organisms. Model membranes represent attractive systems to study lipid nanodomains, which cannot be directly addressed in living cells with the currently available methods. This review summarizes the knowledge on lipid nanodomains in model membranes and exposes how their specific character contrasts with large-scale phase separation. The overview on lipid nanodomains in membranes composed of diverse lipids (e.g., zwitterionic and anionic glycerophospholipids, ceramides, glycosphingolipids) and cholesterol aims to evidence the impact of chemical, electrostatic, and geometric properties of lipids on nanodomain formation. Furthermore, the effects of curvature, asymmetry, and ions on membrane nanodomains are shown to be highly relevant aspects that may also modulate lipid nanodomains in cellular membranes. Potential mechanisms responsible for the formation and dynamics of nanodomains are discussed with support from available theories and computational studies. A brief description of current fluorescence techniques and analytical tools that enabled progress in lipid nanodomain studies is also included. Further directions are proposed to successfully extend this research to cells.

• MeSH
• fluorescence MeSH
• membránové lipidy chemie   MeSH
• membránové mikrodomény chemie   MeSH
• nanostruktury chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• membránové lipidy MeSH

Lipid rafts are defined as detergent-resistant membrane microdomains of specific lipid and protein composition. They are involved in many aspects of cell biology, including T-cell activation and immunoreceptor signaling. This review discusses current controversies around lipid rafts and summarizes recent developments in the area.

• MeSH
• aktivace lymfocytů fyziologie   MeSH
• lidé MeSH
• membránové mikrodomény chemie   fyziologie   MeSH
• receptory antigenů T-buněk fyziologie   MeSH
• signální transdukce fyziologie   MeSH
• T-lymfocyty fyziologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• receptory antigenů T-buněk MeSH

An advantageous alternative to the use of detergents in biochemical studies on membrane proteins are the recently developed styrene-maleic acid (SMA) amphipathic copolymers. In our recent study [1] we demonstrated that using this approach, most T cell membrane proteins were fully solubilized (presumably in small nanodiscs), while two types of raft proteins, GPI-anchored proteins and Src family kinases, were mostly present in much larger (>250 nm) membrane fragments markedly enriched in typical raft lipids, cholesterol and lipids containing saturated fatty acid residues. In the present study we demonstrate that disintegration of membranes of several other cell types by means of SMA copolymer follows a similar pattern and we provide a detailed proteomic and lipidomic characterization of these SMA-resistant membrane fragments (SRMs).

• Klíčová slova
• Jurkat cell line, Lipidomics, Membrane rafts, Proteomics, SMA copolymer,
• MeSH
• buněčná membrána chemie   MeSH
• maleáty analýza   chemie   MeSH
• mastné kyseliny analýza   MeSH
• membránové mikrodomény MeSH
• membránové proteiny chemie   MeSH
• polystyreny * chemie   MeSH
• proteomika * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• maleáty MeSH
• maleic acid MeSH Prohlížeč
• mastné kyseliny MeSH
• membránové proteiny MeSH
• polystyreny * MeSH
• styrofoam MeSH Prohlížeč

Membrane rafts and signaling molecules associated with them are thought to play important roles in immunoreceptor signaling. Rafts differ in their lipid and protein compositions from the rest of the membrane and are relatively resistant to solubilization by Triton X-100 or similar detergents, producing buoyant, detergent-resistant membranes (DRMs) that can be isolated by density gradient ultracentrifugation. One of the key signaling molecules present in T cell DRMs is the transmembrane adaptor protein LAT (linker for activation of T cells). In contrast to previous results, a recent study demonstrated that a LAT construct not present in the buoyant DRMs is fully able to support TCR signaling and development of T cells in vivo. This finding caused doubts about the real physiological role of rafts in TCR signaling. In this study, we demonstrate that these results can be explained by the existence of a novel type of membrane raft-like microdomains, producing upon detergent solubilization "heavy DRMs" containing a number of membrane molecules. At a moderate level of expression, LAT supported TCR signaling more efficiently than constructs targeted to the microdomains producing heavy DRMs or to nonraft membrane. We suggest that different types of membrane microdomains provide environments regulating the functional efficiencies of signaling molecules present therein.

• MeSH
• adaptorové proteiny signální transdukční imunologie   metabolismus   MeSH
• aktivace lymfocytů imunologie   MeSH
• Jurkat buňky MeSH
• lidé MeSH
• membránové mikrodomény chemie   imunologie   MeSH
• membránové proteiny chemie   imunologie   izolace a purifikace   metabolismus   MeSH
• receptory antigenů T-buněk imunologie   metabolismus   MeSH
• signální transdukce imunologie   MeSH
• T-lymfocyty chemie   imunologie   metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adaptorové proteiny signální transdukční MeSH
• LAT protein, human MeSH Prohlížeč
• membránové proteiny MeSH
• receptory antigenů T-buněk MeSH

A considerable amount of evidence supports the idea that lipid rafts are involved in many cellular processes, including protein sorting and trafficking. We show that, in this process, also a non-raft lipid, phosphatidylethanolamine (PE), has an indispensable function. The depletion of this phospholipid results in an accumulation of a typical raft-resident, the arginine transporter Can1p, in the membranes of Golgi, while the trafficking of another plasma membrane transporter, Pma1p, is interrupted at the level of the ER. Both these transporters associate with a Triton (TX-100) resistant membrane fraction before their intracellular transport is arrested in the respective organelles. The Can1p undelivered to the plasma membrane is fully active when reconstituted to a PE-containing vesicle system in vitro. We further demonstrate that, in addition to the TX-100 resistance at 4 degrees C, Can1p and Pma1pa exhibit different accessibility to nonyl glucoside (NG), which points to distinct intimate lipid surroundings of these two proteins. Also, at 20 degrees C, these two proteins are extracted by TX-100 differentially. The features above suggest that Pma1p and Can1p are associated with different compartments. This is independently supported by the observations made by confocal microscopy. In addition we show that PE is involved in the stability of Can1p-raft association.

• MeSH
• detergenty MeSH
• fosfatidylethanolaminy chemie   metabolismus   MeSH
• membránové mikrodomény chemie   metabolismus   MeSH
• membránové proteiny chemie   metabolismus   MeSH
• protonové ATPasy izolace a purifikace   metabolismus   MeSH
• Saccharomyces cerevisiae - proteiny izolace a purifikace   metabolismus   MeSH
• Saccharomyces cerevisiae metabolismus   MeSH
• sbalování proteinů MeSH
• transportní systémy pro bazické aminokyseliny izolace a purifikace   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• CAN1 protein, S cerevisiae MeSH Prohlížeč
• detergenty MeSH
• fosfatidylethanolaminy MeSH
• membránové proteiny MeSH
• phosphatidylethanolamine MeSH Prohlížeč
• PMA1 protein, S cerevisiae MeSH Prohlížeč
• protonové ATPasy MeSH
• Saccharomyces cerevisiae - proteiny MeSH
• transportní systémy pro bazické aminokyseliny MeSH

The recently shown transmissibility of variant Creutzfeldt-Jakob disease (vCJD) by blood transfusion emphasises the need for better understanding of the cellular prion protein (PrPc) in blood. A substantial amount of cell-associated PrPc in blood resides in platelets. Platelet activation leads to up-regulation of PrPc on the platelet surface and its release on exosomes and microparticles. The sub-cellular localisation and function of platelet PrPc, however, is poorly understood. In the present study, we investigated the association of PrPc with platelet lipid rafts and the platelet cytoskeleton. Immuno-fluorescence microscopy showed that the signals of PrPc and P-selectin, both of which occupy intracellular alpha granules, were separated on the membrane, suggesting organisation in different membrane domains. A flotation assay of platelet lysates demonstrated that a relatively small portion of platelet PrPc floats with lipid rafts, regardless of platelet activation status. This was reversed by depolymerisation of the platelet cytoskeleton, which led to flotation of most platelet PrPc, suggesting that interactions with the cytoskeleton prevent flotation of PrPc rafts. This association of PrPc with the platelet cytoskeleton was confirmed by its presence in both the isolated membrane skeleton and actin cytoskeleton. Platelet activation significantly increased the amount of PrPc associated with the cytoskeleton. Our results indicate that the localisation of PrPc in platelets is complex, with the majority of PrPc present within platelet lipid rafts linked to the platelet cytoskeleton. This localisation places PrPc in a position where it can interact with proteins involved in platelet signalling and eventually with vCJD prions.

• MeSH
• aktivace trombocytů MeSH
• biopolymery MeSH
• buněčná membrána chemie   MeSH
• cytoplazmatická granula chemie   MeSH
• cytoskelet chemie   MeSH
• fluorescenční mikroskopie MeSH
• lidé MeSH
• membránové mikrodomény chemie   MeSH
• P-selektin MeSH
• PrPC proteiny krev   MeSH
• trombocyty chemie   ultrastruktura   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• biopolymery MeSH
• P-selektin MeSH
• PrPC proteiny MeSH

Changes of membrane organization upon cross-linking of its components trigger cell signaling response to various exogenous factors. Cross-linking of raft gangliosides GM1 with cholera toxin (CTxB) was shown to cause microscopic phase separation in model membranes, and the CTxB-GM1 complexes forming a minimal lipid raft unit are the subject of ongoing cell membrane research. Yet, those subdiffraction sized rafts have never been described in terms of size and dynamics. By means of two-color z-scan fluorescence correlation spectroscopy, we show that the nanosized domains are formed in model membranes at lower sphingomyelin (Sph) content than needed for the large-scale phase separation and that the CTxB-GM1 complexes are confined in the domains poorly stabilized with Sph. Förster resonance energy transfer together with Monte Carlo modeling of the donor decay response reveal the domain radius of ~8 nm, which increases at higher Sph content. We observed two types of domains behaving differently, which suggests a dual role of the cross-linker: first, local transient condensation of the GM1 molecules compensating for a lack of Sph and second, coalescence of existing nanodomains ending in large-scale phase separation.

• MeSH
• chemické modely * MeSH
• cholerový toxin chemie   MeSH
• fluidita membrány * MeSH
• G(M1) gangliosid chemie   MeSH
• lipidové dvojvrstvy chemie   MeSH
• membránové mikrodomény chemie   ultrastruktura   MeSH
• molekulární konformace MeSH
• molekulární modely MeSH
• reagencia zkříženě vázaná chemie   MeSH
• změna skupenství MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cholerový toxin MeSH
• G(M1) gangliosid MeSH
• lipidové dvojvrstvy MeSH
• reagencia zkříženě vázaná MeSH