Browse
Submit Data
Databases
API
Help

Dataset Information

21 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Cholera toxin B subunit induces local curvature on lipid bilayers.

ABSTRACT: The B subunit of the bacterial cholera toxin (CTxB) is responsible for the toxin binding to the cell membrane and its intracellular trafficking. CTxB binds to the monosialotetrahexosyl ganglioside at the plasma membrane of the target cell and mediates toxin internalization by endocytosis. CTxB induces a local membrane curvature that is essential for its clathrin-independent uptake. Using all-atom molecular dynamics, we show that CTxB induces local curvature, with the radius of curvature around 36 nm. The main feature of the CTxB molecular structure that causes membrane bending is the protruding alpha helices in the middle of the protein. Our study points to a generic protein design principle for generating local membrane curvature through specific binding to their lipid anchors.

SUBMITTER: Pezeshkian W

PROVIDER: S-EPMC5666388 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Cholera toxin B subunit induces local curvature on lipid bilayers.

Pezeshkian Weria W Nåbo Lina J LJ Ipsen John H JH

FEBS open bio 20171010 11

The B subunit of the bacterial cholera toxin (CTxB) is responsible for the toxin binding to the cell membrane and its intracellular trafficking. CTxB binds to the monosialotetrahexosyl ganglioside at the plasma membrane of the target cell and mediates toxin internalization by endocytosis. CTxB induces a local membrane curvature that is essential for its clathrin-independent uptake. Using all-atom molecular dynamics, we show that CTxB induces local curvature, with the radius of curvature around 3 ...[more]

PMID: 29123973

Similar Datasets

Uptake and intracellular fate of cholera toxin subunit b-modified mesoporous silica nanoparticle-supported lipid bilayers (aka protocells) in motoneurons.

Project description:Cholera toxin B (CTB) modified mesoporous silica nanoparticle supported lipid bilayers (CTB-protocells) are a promising, customizable approach for targeting therapeutic cargo to motoneurons. In the present study, the endocytic mechanism and intracellular fate of CTB-protocells in motoneurons were examined to provide information for the development of therapeutic application and cargo delivery. Pharmacological inhibitors elucidated CTB-protocells endocytosis to be dependent on the integrity of lipid rafts and macropinocytosis. Using immunofluorescence techniques, live confocal and transmission electron microscopy, CTB-protocells were primarily found in the cytosol, membrane lipid domains and Golgi. There was no difference in the amount of motoneuron activity dependent uptake of CTB-protocells in neuromuscular junctions, consistent with clathrin activation at the axon terminals during low frequency activity. In conclusion, CTB-protocells uptake is mediated principally by lipid rafts and macropinocytosis. Once internalized, CTB-protocells escape lysosomal degradation, and engage biological pathways that are not readily accessible by untargeted delivery methods.

| S-EPMC7754615 | biostudies-literature

Nonadditive Compositional Curvature Energetics of Lipid Bilayers.

Project description:The unique properties of the individual lipids that compose biological membranes together determine the energetics of the surface. The energetics of the surface, in turn, govern the formation of membrane structures and membrane reshaping processes, and thus they will underlie cellular-scale models of viral fusion, vesicle-dependent transport, and lateral organization relevant to signaling. The spontaneous curvature, to the best of our knowledge, is always assumed to be additive. We describe observations from simulations of unexpected nonadditive compositional curvature energetics of two lipids essential to the plasma membrane: sphingomyelin and cholesterol. A model is developed that connects molecular interactions to curvature stress, and which explains the role of local composition. Cholesterol is shown to lower the number of effective Kuhn segments of saturated acyl chains, reducing lateral pressure below the neutral surface of bending and favoring positive curvature. The effect is not observed for unsaturated (flexible) acyl chains. Likewise, hydrogen bonding between sphingomyelin lipids leads to positive curvature, but only at sufficient concentration, below which the lipid prefers negative curvature.

| S-EPMC5134905 | biostudies-literature

Lipid rafts alter the stability and activity of the cholera toxin A1 subunit.

Project description:Cholera toxin (CT) travels from the cell surface to the endoplasmic reticulum (ER) as an AB holotoxin. ER-specific conditions then promote the dissociation of the catalytic CTA1 subunit from the rest of the toxin. CTA1 is held in a stable conformation by its assembly in the CT holotoxin, but the dissociated CTA1 subunit is an unstable protein that spontaneously assumes a disordered state at physiological temperature. This unfolding event triggers the ER-to-cytosol translocation of CTA1 through the quality control mechanism of ER-associated degradation. The translocated pool of CTA1 must regain a folded, active structure to modify its G protein target which is located in lipid rafts at the cytoplasmic face of the plasma membrane. Here, we report that lipid rafts place disordered CTA1 in a functional conformation. The hydrophobic C-terminal domain of CTA1 is essential for binding to the plasma membrane and lipid rafts. These interactions inhibit the temperature-induced unfolding of CTA1. Moreover, lipid rafts could promote a gain of structure in the disordered, 37 °C conformation of CTA1. This gain of structure corresponded to a gain of function: whereas CTA1 by itself exhibited minimal in vitro activity at 37 °C, exposure to lipid rafts resulted in substantial toxin activity at 37 °C. In vivo, the disruption of lipid rafts with filipin substantially reduced the activity of cytosolic CTA1. Lipid rafts thus exhibit a chaperone-like function that returns disordered CTA1 to an active state and is required for the optimal in vivo activity of CTA1.

| S-EPMC3436369 | biostudies-literature

Single Lipid Molecule Dynamics on Supported Lipid Bilayers with Membrane Curvature.

Project description:The plasma membrane is a highly compartmentalized, dynamic material and this organization is essential for a wide variety of cellular processes. Nanoscale domains allow proteins to organize for cell signaling, endo- and exocytosis, and other essential processes. Even in the absence of proteins, lipids have the ability to organize into domains as a result of a variety of chemical and physical interactions. One feature of membranes that affects lipid domain formation is membrane curvature. To directly test the role of curvature in lipid sorting, we measured the accumulation of two similar lipids, 1,2-Dihexadecanoyl-sn-glycero-3-phosphoethanolamine (DHPE) and hexadecanoic acid (HDA), using a supported lipid bilayer that was assembled over a nanopatterned surface to obtain regions of membrane curvature. Both lipids studied contain 16 carbon, saturated tails and a head group tag for fluorescence microscopy measurements. The accumulation of lipids at curvatures ranging from 28 nm to 55 nm radii was measured and fluorescein labeled DHPE accumulated more than fluorescein labeled HDA at regions of membrane curvature. We then tested whether single biotinylated DHPE molecules sense curvature using single particle tracking methods. Similar to groups of fluorescein labeled DHPE accumulating at curvature, the dynamics of single molecules of biotinylated DHPE was also affected by membrane curvature and highly confined motion was observed.

| S-EPMC5371976 | biostudies-literature

Curvature-Driven Migration of Colloids on Tense Lipid Bilayers.

Project description:Inspired by proteins that generate membrane curvature, sense the underlying membrane geometry, and migrate driven by curvature gradients, we explore the question: Can colloids, adhered to lipid bilayers, also sense and respond to membrane geometry? We report the migration of Janus microparticles adhered to giant unilamellar vesicles elongated to present spatially varying curvatures. In our experiments, colloids migrate only when the membranes are tense, suggesting that they migrate to minimize membrane area. By determining the energy dissipated along a trajectory, the energy field is inferred to depend on the local deviatoric curvature, like curvature driven capillary migration on interfaces between immiscible fluids. In this latter system, energy gradients are larger, so colloids move deterministically, whereas the paths traced by colloids on vesicles have significant fluctuations. By addressing the role of Brownian motion, we show that the observed migration is analogous to curvature driven capillary migration, with membrane tension playing the role of interfacial tension. Since this motion is mediated by membrane shape, it can be turned on and off by dynamically deforming the vesicle. While particle-particle interactions on lipid membranes have been considered in many contributions, we report here an exciting and previously unexplored modality to actively direct the migration of colloids to desired locations on lipid bilayers.

| S-EPMC5706785 | biostudies-literature

Lipid flip-flop and desorption from supported lipid bilayers is independent of curvature.

Project description:Flip-flop of lipids of the lipid bilayer (LBL) constituting the plasma membrane (PM) plays a crucial role in a myriad of events ranging from cellular signaling and regulation of cell shapes to cell homeostasis, membrane asymmetry, phagocytosis, and cell apoptosis. While extensive research has been conducted to probe the lipid flip flop of planar lipid bilayers (LBLs), less is known regarding lipid flip-flop for highly curved, nanoscopic LBL systems despite the vast importance of membrane curvature in defining the morphology of cells and organelles and in maintaining a variety of cellular functions, enabling trafficking, and recruiting and localizing shape-responsive proteins. In this paper, we conduct molecular dynamics (MD) simulations to study the energetics, structure, and configuration of a lipid molecule undergoing flip-flop and desorption in a highly curved LBL, represented as a nanoparticle-supported lipid bilayer (NPSLBL) system. We compare our findings against those of a planar substrate supported lipid bilayer (PSSLBL). Our MD simulation results reveal that despite the vast differences in the curvature and other curvature-dictated properties (e.g., lipid packing fraction, difference in the number of lipids between inner and outer leaflets, etc.) between the NPSLBL and the PSSLBL, the energetics of lipid flip-flop and lipid desorption as well as the configuration of the lipid molecule undergoing lipid flip-flop are very similar for the NPSLBL and the PSSLBL. In other words, our results establish that the curvature of the LBL plays an insignificant role in lipid flip-flop and desorption.

| S-EPMC7773258 | biostudies-literature

Spray-Dried Formulation of Epicertin, a Recombinant Cholera Toxin B Subunit Variant That Induces Mucosal Healing.

Project description:Epicertin (EPT) is a recombinant variant of the cholera toxin B subunit, modified with a C-terminal KDEL endoplasmic reticulum retention motif. EPT has therapeutic potential for ulcerative colitis treatment. Previously, orally administered EPT demonstrated colon epithelial repair activity in dextran sodium sulfate (DSS)-induced acute and chronic colitis in mice. However, the oral dosing requires cumbersome pretreatment with sodium bicarbonate to conserve the acid-labile drug substance while transit through the stomach, hampering its facile application in chronic disease treatment. Here, we developed a solid oral formulation of EPT that circumvents degradation in gastric acid. EPT was spray-dried and packed into enteric-coated capsules to allow for pH-dependent release in the colon. A GM1-capture KDEL-detection ELISA and size-exclusion HPLC indicated that EPT powder maintains activity and structural stability for up to 9 months. Capsule disintegration tests showed that EPT remained encapsulated at pH 1 but was released over 180 min at pH 6.8, the approximate pH of the proximal colon. An acute DSS colitis study confirmed the therapeutic efficacy of encapsulated EPT in C57BL/6 mice upon oral administration without gastric acid neutralization pretreatment compared to vehicle-treated mice (p < 0.05). These results provide a foundation for an enteric-coated oral formulation of spray-dried EPT.

| S-EPMC8073836 | biostudies-literature

Cholera toxin B: one subunit with many pharmaceutical applications.

Project description:Cholera, a waterborne acute diarrheal disease caused by Vibrio cholerae, remains prevalent in underdeveloped countries and is a serious health threat to those living in unsanitary conditions. The major virulence factor is cholera toxin (CT), which consists of two subunits: the A subunit (CTA) and the B subunit (CTB). CTB is a 55 kD homopentameric, non-toxic protein binding to the GM1 ganglioside on mammalian cells with high affinity. Currently, recombinantly produced CTB is used as a component of an internationally licensed oral cholera vaccine, as the protein induces potent humoral immunity that can neutralize CT in the gut. Additionally, recent studies have revealed that CTB administration leads to the induction of anti-inflammatory mechanisms in vivo. This review will cover the potential of CTB as an immunomodulatory and anti-inflammatory agent. We will also summarize various recombinant expression systems available for recombinant CTB bioproduction.

| S-EPMC4379537 | biostudies-literature

Gas phase characterization of the noncovalent quaternary structure of cholera toxin and the cholera toxin B subunit pentamer.

Project description:Cholera toxin (CTx) is an AB5 cytotonic protein that has medical relevance in cholera and as a novel mucosal adjuvant. Here, we report an analysis of the noncovalent homopentameric complex of CTx B chain (CTx B5) using electrospray ionization triple quadrupole mass spectrometry and tandem mass spectrometry and the analysis of the noncovalent hexameric holotoxin usingelectrospray ionization time-of-flight mass spectrometry over a range of pH values that correlate with those encountered by this toxin after cellular uptake. We show that noncovalent interactions within the toxin assemblies were maintained under both acidic and neutral conditions in the gas phase. However, unlike the related Escherichia coli Shiga-like toxin B5 pentamer (SLTx B), the CTx B5 pentamer was stable at low pH, indicating that additional interactions must be present within the latter. Structural comparison of the CTx B monomer interface reveals an additional alpha-helix that is absent in the SLTx B monomer. In silico energy calculations support interactions between this helix and the adjacent monomer. These data provide insight into the apparent stabilization of CTx B relative to SLTx B.

| S-EPMC1432099 | biostudies-literature

Lipid clustering correlates with membrane curvature as revealed by molecular simulations of complex lipid bilayers.

Project description:Cell membranes are complex multicomponent systems, which are highly heterogeneous in the lipid distribution and composition. To date, most molecular simulations have focussed on relatively simple lipid compositions, helping to inform our understanding of in vitro experimental studies. Here we describe on simulations of complex asymmetric plasma membrane model, which contains seven different lipids species including the glycolipid GM3 in the outer leaflet and the anionic lipid, phosphatidylinositol 4,5-bisphophate (PIP2), in the inner leaflet. Plasma membrane models consisting of 1500 lipids and resembling the in vivo composition were constructed and simulations were run for 5 µs. In these simulations the most striking feature was the formation of nano-clusters of GM3 within the outer leaflet. In simulations of protein interactions within a plasma membrane model, GM3, PIP2, and cholesterol all formed favorable interactions with the model ?-helical protein. A larger scale simulation of a model plasma membrane containing 6000 lipid molecules revealed correlations between curvature of the bilayer surface and clustering of lipid molecules. In particular, the concave (when viewed from the extracellular side) regions of the bilayer surface were locally enriched in GM3. In summary, these simulations explore the nanoscale dynamics of model bilayers which mimic the in vivo lipid composition of mammalian plasma membranes, revealing emergent nanoscale membrane organization which may be coupled both to fluctuations in local membrane geometry and to interactions with proteins.

| S-EPMC4207469 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data