CHMP2B Protein

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CHMP2B Protein

<div class="infobox infobox-protein">
<h3>CHMP2B Protein</h3>
<table>
<tr><th>Gene</th><td>[CHMP2B](/genes/chmp2b)</td></tr>
<tr><th>UniProt</th><td><a href="https://www.uniprot.org/uniprot/Q9UQN3" target="_blank">Q9UQN3</a></td></tr>
<tr><th>PDB Structures</th><td><a href="https://www.rcsb.org/structure/2J0N" target="_blank">2J0N</a>, <a href="https://www.rcsb.org/structure/5TQO" target="_blank">5TQO</a></td></tr>
<tr><th>Molecular Weight</th><td>~24 kDa</td></tr>
<tr><th>Protein Length</th><td>213 amino acids</td></tr>
<tr><th>Subcellular Localization</th><td>Endosomal membrane, multivesicular body, nucleus</td></tr>
<tr><th>Protein Family</th><td>ESCRT-III family, CHMP2 subgroup</td></tr>
<tr><th>Chromosomal Location</th><td>3p11.2</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">Alzheimer</a>, <a href="/wiki/amyotrophic-lateral-sclerosis" style="color:#ef9a9a">Amyotrophic Lateral Sclerosis</a>, <a href="/wiki/dementia" style="color:#ef9a9a">Dementia</a></td>
</tr>
<tr>
<td class="label">SciDEX Hypotheses</td>
<td><a href="/hypothesis/h-8986b8af" style="color:#ce93d8" title="Score: 0.43">Lysosomal Membrane Repair Enhancement...</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">188 edges</a></td>
</tr>
</table>
</div>

Overview

...

CHMP2B Protein

Overview

CHMP2B (Charged Multivesicular Body Protein 2B) is a core subunit of the ESCRT-III (Endosomal Sorting Complex Required for Transport-III) complex, playing critical roles in endosomal trafficking, autophagy, and membrane remodeling[@fisher2020]. CHMP2B is encoded by the [CHMP2B](/genes/chmp2b) gene on chromosome 3p11.2 and is expressed throughout the brain, with highest levels in the frontal and temporal cortex, hippocampus, and spinal cord — the regions most affected in [frontotemporal dementia](/diseases/frontotemporal-dementia) and [amyotrophic lateral sclerosis](/diseases/amyotrophic-lateral-sclerosis)[@ghanbar2021].

Mutations in CHMP2B cause autosomal dominant familial frontotemporal dementia (FTD-3) and familial ALS. The most well-characterized mutation is the intron5 splice site mutation (c.532-11C>G) found in Danish FTD-3 families. CHMP2B dysfunction disrupts the autophagosome-lysosome fusion step of autophagy, leading to accumulation of protein aggregates and neuronal death[@skibinski2005].

Protein Structure

Structural Architecture

CHMP2B adopts an elongated helical conformation that enables polymerization into filamentous structures[@vernizzi2022]:

| Domain | Residues | Function |
|--------|----------|----------|
| N-terminal membrane interface | 1-80 | Initiates membrane interaction and polymerization |
| Central helical domain | 80-160 | Core helical region enabling filament formation |
| C-terminal autoinhibitory helix | 160-213 | Regulates polymerization state, released upon interaction |

The C-terminal autoinhibitory helix (residues 183-213) folds back onto the helical core, preventing premature polymerization in the cytoplasm. This autoinhibition is relieved upon membrane recruitment or interaction with VPS4[@hanson2010].

ESCRT-III Polymerization

CHMP2B polymerizes into helical filaments on endosomal membranes:

Nucleation: CHMP2B-CHMP2A heterodimers initiate polymerization

Elongation: CHMP4B/C filaments assemble on the CHMP2A/B core

Constriction: Polymerization drives membrane neck constriction

Scission: VPS4 ATPase disassembles the filaments after scission

Interaction Network

CHMP2B interacts with multiple ESCRT and regulatory proteins[@fisher2020]:

CHMP2A: Forms essential heterodimers for ESCRT-III function
CHMP4B / CHMP4C: Core polymerization partners in ESCRT-III filaments
VPS4A / VPS4B: AAA+ ATPases that catalyze filament disassembly
ALIX (ALG-2-interacting protein X): ESCRT accessory factor bridging upstream events
IST1: Regulatory subunit influencing ESCRT dynamics
BRO1 (ALIX): Scaffold for ESCRT-III recruitment

Cellular Functions

Multivesicular Body Biogenesis

CHMP2B is essential for the formation of intraluminal vesicles (ILVs) within multivesicular bodies (MVBs)[@filimonenko2007]:

Mermaid diagram (expand to render)

Cargo Recognition: ESCRT-0 (HGS/STAM2) and ESCRT-I (TSG101/VPS37) recognize ubiquitinated cargo

Concentration: ESCRT-II and ESCRT-III concentrate cargo at budding sites

Scission: CHMP2B polymerization drives membrane constriction

ILV Release: Intraluminal vesicles form containing sequestered cargo

Autophagosome Maturation

CHMP2B plays a critical role in the late stages of [autophagy](/mechanisms/autophagy)[@cox2020]:

Autophagosome-Lysosome Fusion: The ESCRT-III complex, including CHMP2B, mediates the final fusion step between autophagosomes and lysosomes. Loss of CHMP2B function leads to accumulation of unfused autophagosomes.

Selective Autophagy: CHMP2B is recruited to selective autophagy substrates through interactions with autophagy receptors (p62/SQSTM1, NDP52, T6BP).

Consequences of Dysfunction:

Accumulation of LC3-II positive autophagosomes
Impaired degradation of autophagy substrates
p62/SQSTM1-positive aggregate formation
Unsealed autophagosomes with incomplete closure

Nuclear Envelope Reformation

During cell division, CHMP2B participates in nuclear envelope (NE) reformation after mitosis. ESCRT-III/CHMP2B mediates closure of the nuclear envelope, which is particularly important in post-mitotic neurons that cannot re-enter the cell cycle[@metcalf2014].

Synaptic Function

In neurons, CHMP2B has specialized functions[@ghanbar2021]:

Presynaptic Vesicle Cycling: CHMP2B regulates synaptic vesicle endocytosis and recycling at presynaptic terminals
Axonal Endosomal Trafficking: Critical for trafficking neurotrophin receptors (TrkA, TrkB, p75^NTR) and signaling molecules in axons
Dendritic Spine Morphogenesis: Regulates AMPA and NMDA receptor trafficking in dendrites, affecting [synaptic plasticity](/mechanisms/synaptic-plasticity-mechanisms)

Role in Neurodegenerative Disease

Frontotemporal Dementia (FTD-3)

CHMP2B mutations cause autosomal dominant familial FTD (FTD-3) characterized by[@isaacs2011][@ghazinoori2012]:

Clinical Features:

Behavioral variant FTD with prominent personality changes (disinhibition, apathy)
Language impairment (progressive aphasia, semantic variant)
Age of onset: 40-60 years
Mean disease duration: 8-12 years

Neuropathology:

TDP-43 positive inclusions (Type B pathology) — cytosolic mislocalization
Neuronal loss in frontal and temporal cortices
Spongiform changes in subcortical white matter
Subtle cerebellar involvement

Characterized Mutations:
| Mutation | Type | Population | Effect |
|----------|------|-----------|--------|
| c.532-11C>G (Intron5) | Splice site | Danish families | Truncated protein |
| p.Gln165* | Nonsense | Belgian patients | Early termination |
| p.Asn143Ser | Missense | CBD patients | Reduced function |
| p.Thr104Asn | Missense | Scandinavian ALS | Impaired ESCRT |

Amyotrophic Lateral Sclerosis

CHMP2B mutations also cause familial ALS with[@lee2015]:

Mixed bulbar and spinal onset
Rapid progression
High frequency of ALS-FTD overlap
TDP-43 pathology in motor neurons
Bunina bodies in some cases

Mechanism of Neurodegeneration

Mermaid diagram (expand to render)

Therapeutic Strategies

Small Molecule Approaches

| Strategy | Target | Agent | Status |
|----------|--------|-------|--------|
| ESCRT modulation | Residual ESCRT function | UDCA (Ursodeoxycholic acid) | Preclinical |
| Autophagy induction | Bypass ESCRT defect | Rapamycin, Lithium | Preclinical |
| Lysosomal enhancement | Lysosomal function | Trehalose | Preclinical |
| TDP-43 targeting | Aggregation | HSP70 inducers | Research |
| Neuroprotection | Downstream pathways | Gene therapy | Preclinical |

Gene Therapy

AAV-CHMP2B: Adeno-associated virus delivery of wild-type CHMP2B to restore ESCRT function
CRISPR-Cas9: Correction of pathogenic mutations using base editing
ASOs: Antisense oligonucleotides to modulate CHMP2B splicing or reduce toxic transcripts
RNAi: Allele-specific silencing of mutant CHMP2B

Biomarkers

CSF CHMP2B: Altered levels in FTD/ALS patients vs. controls
Blood biomarkers: PBMC CHMP2B expression as peripheral marker
Imaging: PET tracers targeting endosomal-lysosomal dysfunction

Cross-Pathway Connections

[Autophagy Pathway](/mechanisms/autophagy) — Central to CHMP2B dysfunction
[Endosomal-Lysosomal Pathway](/mechanisms/endosomal-lysosomal-pathway) — Primary site of CHMP2B action
[TDP-43 Proteinopathy](/mechanisms/tdp-43-proteinopathy) — Downstream consequence of CHMP2B loss
[Protein Homeostasis](/mechanisms/protein-homeostasis) — Impaired by ESCRT dysfunction
[Synaptic Dysfunction](/mechanisms/synaptic-dysfunction) — Neuronal consequence
[ESCRT Pathway](/mechanisms/escr-pathway) — Broader ESCRT system

[Frontotemporal Dementia](/diseases/frontotemporal-dementia) — FTD-3 caused by CHMP2B
[Amyotrophic Lateral Sclerosis (ALS)](/diseases/amyotrophic-lateral-sclerosis) — CHMP2B-associated ALS
[Corticobasal Degeneration](/diseases/corticobasal-syndrome) — CHMP2B variants identified
[Parkinson's Disease](/diseases/parkinsons-disease) — Endosomal dysfunction commonality

[CHMP2A](/proteins/chmp2a-protein) — Essential CHMP2B partner
[VPS4A](/proteins/vps4-protein) — ATPase disassembly partner
[p62/SQSTM1](/proteins/p62-protein) — Autophagy receptor
[TDP-43 (TARDBP)](/proteins/tardbp-protein) — Pathological aggregate

Summary

CHMP2B is a critical ESCRT-III subunit whose mutations cause FTD-3 and familial ALS. The protein's roles in autophagosome maturation, endosomal trafficking, and synaptic function make it essential for neuronal protein homeostasis. Loss of CHMP2B function leads to autophagosome accumulation, TDP-43 pathology, and progressive neurodegeneration. Therapeutic approaches include ESCRT modulators, autophagy enhancers, and gene therapy strategies.

References

[Fisher J, et al., CHMP2B in cellular homeostasis and neurodegeneration (2020)](https://pubmed.ncbi.nlm.nih.gov/32409567/)

[Ghanbar H, et al., CHMP2B in neurodegeneration: Molecular mechanisms (2021)](https://pubmed.ncbi.nlm.nih.gov/34059063/)

[Filimonenko M, et al., Functional multivesicular bodies for autophagic clearance (2007)](https://pubmed.ncbi.nlm.nih.gov/17960148/)

[Skibinski G, et al., Mutations in ESCRT-III component CHMP2B in frontotemporal dementia (2005)](https://pubmed.ncbi.nlm.nih.gov/16034160/)

[Isaacs AM, et al., Spectrum of CHMP2B neurodegenerative phenotypes (2011)](https://pubmed.ncbi.nlm.nih.gov/21881189/)

[Ghazi-Noori S, et al., Progressive neuronal inclusion formation in CHMP2B mice (2012)](https://pubmed.ncbi.nlm.nih.gov/22116196/)

[Cox LE, et al., Autophagy disruption in CHMP2B mutant models (2020)](https://pubmed.ncbi.nlm.nih.gov/32677982/)

[Vernizzi L, et al., Structural insights into CHMP2B neurodegeneration (2022)](https://pubmed.ncbi.nlm.nih.gov/35907840/)

[Hanson PI, et al., ESCTRs and endosomal trafficking regulation (2010)](https://pubmed.ncbi.nlm.nih.gov/20068178/)

[Metcalf D, et al., ESCRT-III dysfunction in neurodegeneration (2014)](https://pubmed.ncbi.nlm.nih.gov/24813547/)

[Lee JA, et al., ESCRT-III mutations in ALS/FTD (2015)](https://pubmed.ncbi.nlm.nih.gov/25823586/)

From the [SciDEX Exchange](/exchange) — scored by multi-agent debate

[Lysosomal Membrane Repair Enhancement](/hypothesis/h-8986b8af) — <span style="color:#ffd54f;font-weight:600">0.43</span> · Target: CHMP2B

Pathway Diagram

The following diagram shows the key molecular relationships involving CHMP2B Protein discovered through SciDEX knowledge graph analysis:

Mermaid diagram (expand to render)

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CHMP2B Protein

CHMP2B Protein

Overview

CHMP2B Protein

Overview

Protein Structure

Structural Architecture

ESCRT-III Polymerization

Interaction Network

Cellular Functions

Multivesicular Body Biogenesis

Autophagosome Maturation

Nuclear Envelope Reformation

Synaptic Function

Role in Neurodegenerative Disease

Frontotemporal Dementia (FTD-3)

Amyotrophic Lateral Sclerosis

Mechanism of Neurodegeneration

Therapeutic Strategies

Small Molecule Approaches

Gene Therapy

Biomarkers

Cross-Pathway Connections

Related Mechanisms

Related Diseases

Related Proteins

Summary

References

Related Hypotheses

Pathway Diagram