Browse
Submit Data
Databases
API
Help

Dataset Information

19 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

The ESCRT-III isoforms CHMP2A and CHMP2B display different effects on membranes upon polymerization.

ABSTRACT:

Background

ESCRT-III proteins are involved in many membrane remodeling processes including multivesicular body biogenesis as first discovered in yeast. In humans, ESCRT-III CHMP2 exists as two isoforms, CHMP2A and CHMP2B, but their physical characteristics have not been compared yet.

Results

Here, we use a combination of techniques on biomimetic systems and purified proteins to study their affinity and effects on membranes. We establish that CHMP2B binding is enhanced in the presence of PI(4,5)P2 lipids. In contrast, CHMP2A does not display lipid specificity and requires CHMP3 for binding significantly to membranes. On the micrometer scale and at moderate bulk concentrations, CHMP2B forms a reticular structure on membranes whereas CHMP2A (+CHMP3) binds homogeneously. Thus, CHMP2A and CHMP2B unexpectedly induce different mechanical effects to membranes: CHMP2B strongly rigidifies them while CHMP2A (+CHMP3) has no significant effect.

Conclusions

We therefore conclude that CHMP2B and CHMP2A exhibit different mechanical properties and might thus contribute differently to the diverse ESCRT-III-catalyzed membrane remodeling processes.

SUBMITTER: Alqabandi M

PROVIDER: S-EPMC8033747 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Targeting the ESCRT-III component CHMP2A for noncanonical Caspase-8 activation on autophagosomal membranes.

Project description:Autophagosomal membranes can serve as activation platforms for intracellular death-inducing signaling complexes (iDISCs) to initiate Caspase-8-dependent apoptosis. In this study, we explore the impact of ESCRT-III-dependent phagophore closure on iDISC assemblies and cell death in osteosarcoma and neuroblastoma cells. Inhibition of phagophore closure by conditional depletion of CHMP2A, an ESCRT-III component, stabilizes iDISCs on immature autophagosomal membranes and induces Caspase-8-dependent cell death. Importantly, suppression of the iDISC formation via deletion of ATG7, an E1 enzyme for ubiquitin-like autophagy-related proteins, blocks Caspase-8 activation and cell death following CHMP2A depletion. Although DR5 expression and TRAIL-induced apoptosis are enhanced in CHMP2A-depleted cells, the canonical extrinsic pathway of apoptosis is not responsible for the initiation of cell death by CHMP2A depletion. Furthermore, the loss of CHMP2A impairs neuroblastoma tumor growth associated with decreased autophagy and increased apoptosis in vivo. Together, these findings indicate that inhibition of the ESCRT-III-dependent autophagosome sealing process triggers noncanonical Caspase-8 activation and apoptosis, which may open new avenues for therapeutic targeting of autophagy in cancer.

| S-EPMC7862398 | biostudies-literature

Regulation of postsynaptic function by the dementia-related ESCRT-III subunit CHMP2B.

Project description:The charged multivesicular body proteins (Chmp1-7) are an evolutionarily conserved family of cytosolic proteins that transiently assembles into helical polymers that change the curvature of cellular membrane domains. Mutations in human CHMP2B cause frontotemporal dementia, suggesting that this protein may normally control some neuron-specific process. Here, we examined the function, localization, and interactions of neuronal Chmp2b. The protein was highly expressed in mouse brain and could be readily detected in neuronal dendrites and spines. Depletion of endogenous Chmp2b reduced dendritic branching of cultured hippocampal neurons, decreased excitatory synapse density in vitro and in vivo, and abolished activity-induced spine enlargement and synaptic potentiation. To understand the synaptic effects of Chmp2b, we determined its ultrastructural distribution by quantitative immuno-electron microscopy and its biochemical interactions by coimmunoprecipitation and mass spectrometry. In the hippocampus in situ, a subset of neuronal Chmp2b was shown to concentrate beneath the perisynaptic membrane of dendritic spines. In synaptoneurosome lysates, Chmp2b was stably bound to a large complex containing other members of the Chmp family, as well as postsynaptic scaffolds. The supramolecular Chmp assembly detected here corresponds to a stable form of the endosomal sorting complex required for transport-III (ESCRT-III), a ubiquitous cytoplasmic protein complex known to play a central role in remodeling of lipid membranes. We conclude that Chmp2b-containing ESCRT-III complexes are also present at dendritic spines, where they regulate synaptic plasticity. We propose that synaptic ESCRT-III filaments may function as a novel element of the submembrane cytoskeleton of spines.

| S-EPMC4331633 | biostudies-literature

An autophagy assay reveals the ESCRT-III component CHMP2A as a regulator of phagophore closure.

Project description:The mechanism of phagophore closure remains unclear due to technical limitations in distinguishing unclosed and closed autophagosomal membranes. Here, we report the HaloTag-LC3 autophagosome completion assay that specifically detects phagophores, nascent autophagosomes, and mature autophagic structures. Using this assay, we identify the endosomal sorting complexes required for transport (ESCRT)-III component CHMP2A as a critical regulator of phagophore closure. During autophagy, CHMP2A translocates to the phagophore and regulates the separation of the inner and outer autophagosomal membranes to form double-membrane autophagosomes. Consistently, inhibition of the AAA-ATPase VPS4 activity impairs autophagosome completion. The ESCRT-mediated membrane abscission appears to be a critical step in forming functional autolysosomes by preventing mislocalization of lysosome-associated membrane glycoprotein 1 to the inner autophagosomal membrane. Collectively, our work reveals a function for the ESCRT machinery in the final step of autophagosome formation and provides a useful tool for quantitative analysis of autophagosome biogenesis and maturation.

| S-EPMC6054611 | biostudies-literature

Membrane constriction and thinning by sequential ESCRT-III polymerization.

Project description:The endosomal sorting complexes required for transport (ESCRTs) mediate diverse membrane remodeling events. These typically require ESCRT-III proteins to stabilize negatively curved membranes; however, recent work has indicated that certain ESCRT-IIIs also participate in positive-curvature membrane-shaping reactions. ESCRT-IIIs polymerize into membrane-binding filaments, but the structural basis for negative versus positive membrane remodeling by these proteins remains poorly understood. To learn how certain ESCRT-IIIs shape positively curved membranes, we determined structures of human membrane-bound CHMP1B-only, membrane-bound CHMP1B + IST1, and IST1-only filaments by cryo-EM. Our structures show how CHMP1B first polymerizes into a single-stranded helical filament, shaping membranes into moderate-curvature tubules. Subsequently, IST1 assembles a second strand on CHMP1B, further constricting the membrane tube and reducing its diameter nearly to the fission point. Each step of constriction thins the underlying bilayer, lowering the barrier to membrane fission. Our structures reveal how a two-component, sequential polymerization mechanism drives membrane tubulation, constriction and bilayer thinning.

| S-EPMC7343221 | biostudies-literature

ESCRT-III CHMP2A and CHMP3 form variable helical polymers in vitro and act synergistically during HIV-1 budding.

Project description:The endosomal sorting complex required for transport-III (ESCRT-III) proteins are essential for budding of some enveloped viruses, for the formation of intraluminal vesicles at the endosome and for the abscission step of cytokinesis. ESCRT-III proteins form polymers that constrict membrane tubes, leading to fission. We have used electron cryomicroscopy to determine the molecular organization of pleiomorphic ESCRT-III CHMP2A-CHMP3 polymers. The three-dimensional reconstruction at 22?Å resolution reveals a helical organization of filaments of CHMP molecules organized in a head-to-tail fashion. Protease susceptibility experiments indicate that polymerization is achieved via conformational changes that increase the protomer stability. Combinatorial siRNA knockdown experiments indicate that CHMP3 contributes synergistically to HIV-1 budding, and the CHMP3 contribution is ~ 10-fold more pronounced in concert with CHMP2A than with CHMP2B. This is consistent with surface plasmon resonance affinity measurements that suggest sequential CHMP4B-CHMP3-CHMP2A recruitment while showing that both CHMP2A and CHMP2B interact with CHMP4B, in agreement with their redundant functions in HIV-1 budding. Our data thus indicate that the CHMP2A-CHMP3 polymer observed in vitro contributes to HIV-1 budding by assembling on CHMP4B polymers.

| S-EPMC3783020 | biostudies-literature

TMEM106B, a frontotemporal lobar dementia (FTLD) modifier, associates with FTD-3-linked CHMP2B, a complex of ESCRT-III.

Project description:Transmembrane protein 106B (TMEM106B) has been identified as a risk factor for frontotemporal lobar degeneration, which is the second most common form of progressive dementia in people under 65 years of age. Mutations in charged multivesicular body protein 2B (CHMP2B), which is involved in endosomal protein trafficking, have been found in chromosome 3-linked frontotemporal dementia. Despite the number of studies on both CHMP2B and TMEM106B in the endolysosomal pathway, little is known about the relationship between CHMP2B and TMEM106B in the endosomal/autophagy pathway.This study found that endogenous TMEM106B was partially sequestered in CHMP2B-positive structures, suggesting its possible involvement in endosomal sorting complexes required for transport (ESCRT)-associated pathways. The role of single nucleotide polymorphisms of TMEM106B (T185, S185, or S134N) in the ESCRT-associated pathways were characterized. The T185 and S185 variants were more localized to Rab5-/Rab7-positive endosomes compared with S134N, while all of the variants were more localized to Rab7-positive endosomes compared to Rab5-positive endosomes. T185 was more associated with CHMP2B compared to S185. Autophagic flux was slightly reduced in the T185-expressing cells compared to the control or S185-expressing cells. Moreover, T185 slightly enhanced the accumulation of EGFR, impairments in autophagic flux, and neurotoxicity that were caused by CHMP2B(Intron5) compared to S185-expressing cells.These findings suggest that the T185 variant functions as a risk factor in neurodegeneration with endolysosomal defects. This study provides a better understanding of pathogenic functions of TMEM106B, which is a risk factor for the progression of neurodegenerative diseases that are associated with endosomal defects in the aged brain.

| S-EPMC4676093 | biostudies-literature

The ESCRT-III protein VPS4, but not CHMP4B or CHMP2B, is pathologically increased in familial and sporadic ALS neuronal nuclei.

Project description:Nuclear pore complex injury has recently emerged as an early and significant contributor to familial and sporadic ALS disease pathogenesis. However, the molecular events leading to this pathological phenomenon characterized by the reduction of specific nucleoporins from neuronal nuclear pore complexes remain largely unknown. This is due in part to a lack of knowledge regarding the biological pathways and proteins underlying nuclear pore complex homeostasis specifically in human neurons. We have recently uncovered that aberrant nuclear accumulation of the ESCRT-III protein CHMP7 initiates nuclear pore complex in familial and sporadic ALS neurons. In yeast and non-neuronal mammalian cells, nuclear relocalization of CHMP7 has been shown to recruit the ESCRT-III proteins CHMP4B, CHMP2B, and VPS4 to facilitate nuclear pore complex and nuclear envelope repair and homeostasis. Here, using super resolution structured illumination microscopy, we find that neither CHMP4B nor CHMP2B are increased in ALS neuronal nuclei. In contrast, VPS4 expression is significantly increased in ALS neuronal nuclei prior to the emergence of nuclear pore injury in a CHMP7 dependent manner. However, unlike our prior CHMP7 knockdown studies, impaired VPS4 function does not mitigate alterations to the NPC and the integral transmembrane nucleoporin POM121. Collectively our data suggest that while alterations in VPS4 subcellular localization appear to be coincident with nuclear pore complex injury, therapeutic efforts to mitigate this pathogenic cascade should be targeted towards upstream events such as the nuclear accumulation of CHMP7 as we have previously described.

| S-EPMC8287756 | biostudies-literature

Charged multivesicular body protein 2B (CHMP2B) of the endosomal sorting complex required for transport-III (ESCRT-III) polymerizes into helical structures deforming the plasma membrane.

Project description:The endosomal sorting complexes required for transport (ESCRT-0-III) allow membrane budding and fission away from the cytosol. This machinery is used during multivesicular endosome biogenesis, cytokinesis, and budding of some enveloped viruses. Membrane fission is catalyzed by ESCRT-III complexes made of polymers of charged multivesicular body proteins (CHMPs) and by the AAA-type ATPase VPS4. How and which of the ESCRT-III subunits sustain membrane fission from the cytoplasmic surface remain uncertain. In vitro, CHMP2 and CHMP3 recombinant proteins polymerize into tubular helical structures, which were hypothesized to drive vesicle fission. However, this model awaits the demonstration that such structures exist and can deform membranes in cellulo. Here, we show that depletion of VPS4 induces specific accumulation of endogenous CHMP2B at the plasma membrane. Unlike other CHMPs, overexpressed full-length CHMP2B polymerizes into long, rigid tubes that protrude out of the cell. CHMP4s relocalize at the base of the tubes, the formation of which depends on VPS4. Cryo-EM of the CHMP2B membrane tubes demonstrates that CHMP2B polymerizes into a tightly packed helical lattice, in close association with the inner leaflet of the membrane tube. This association is tight enough to deform the lipid bilayer in cases where the tubular CHMP2B helix varies in diameter or is closed by domes. Thus, our observation that CHMP2B polymerization scaffolds membranes in vivo represents a first step toward demonstrating its structural role during outward membrane deformation.

| S-EPMC3220537 | biostudies-literature

Expression of mutant CHMP2B, an ESCRT-III component involved in frontotemporal dementia, causes eye deformities due to Notch misregulation in Drosophila.

Project description:Endosomal sorting complexes required for transport (ESCRTs) mediate sorting of ubiquitinated membrane proteins into multivesicular bodies en route to lysosomes for degradation. A mutation in CHMP2B (CHMP2B(Intron5), an ESCRT-III component) that is associated with a hereditary form of frontotemporal dementia (FTD3) disrupts the endosomal-lysosomal pathway and causes accumulation of autophagosomes and multilamellar structures. We previously demonstrated that expression of CHMP2B(Intron5) in the Drosophila eye using GMR-Gal4 causes misregulation of the Toll receptor pathway. Here, we show that ectopic expression of CHMP2B(Intron5) using eyeless-Gal4 (ey>CHMP2B(Intron5)), a driver with different spatiotemporal expression attributes than GMR-Gal4 in the Drosophila eye, causes eye deformities when compared to expression of wild-type CHMP2B (CHMP2B(WT)) and the Drosophila homologue of CHMP2B (CG4618). In addition, ey>CHMP2B(Intron5) flies showed defects in photoreceptor cell patterning and phototactic behavior. Furthermore, ey>CHMP2B(Intron5) flies showed accumulation of Notch in enlarged endosomes and up-regulation of Notch activity. Partial loss of Notch activity in ey>CHMP2B(Intron5) flies significantly rescued eye deformities, photoreceptor patterning defect, and phototactic behavior defect, indicating that these defects are primarily due to Notch misregulation. These results demonstrate that CHMP2B(Intron5) preferentially affects different receptor signaling pathways in a cellular and developmental context-dependent manner.

| S-EPMC3898657 | biostudies-literature

Molecular and structural basis of ESCRT-III recruitment to membranes during archaeal cell division.

Project description:Members of the crenarchaeal kingdom, such as Sulfolobus, divide by binary fission yet lack genes for the otherwise near-ubiquitous tubulin and actin superfamilies of cytoskeletal proteins. Recent work has established that Sulfolobus homologs of the eukaryotic ESCRT-III and Vps4 components of the ESCRT machinery play an important role in Sulfolobus cell division. In eukaryotes, several pathways recruit ESCRT-III proteins to their sites of action. However, the positioning determinants for archaeal ESCRT-III are not known. Here, we identify a protein, CdvA, that is responsible for recruiting Sulfolobus ESCRT-III to membranes. Overexpression of the isolated ESCRT-III domain that interacts with CdvA results in the generation of nucleoid-free cells. Furthermore, CdvA and ESCRT-III synergize to deform archaeal membranes in vitro. The structure of the CdvA/ESCRT-III interface gives insight into the evolution of the more complex and modular eukaryotic ESCRT complex.

| S-EPMC3763469 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

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