CHMP2B — Charged Multivesicular Body Protein 2B

CHMP2B — Charged Multivesicular Body Protein 2B

Introduction

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">CHMP2B — Charged Multivesicular Body Protein 2B</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>CHMP2B</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Charged Multivesicular Body Protein 2B</td>
</tr>
<tr>
<td class="label">Alternative Names</td>
<td>CHMP2B, VPS36-2, MY013</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>3p11.2</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>25978</td>
</tr>
<tr>
<td class="label">OMIM</td>
<td>609512</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000083937</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q9UQN3</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>213 amino acids</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~24 kDa</td>
</tr>
<tr>
<td class="label">Species</td>
<td>Ortholog</td>
</tr>
<tr>
<td class="label">S. cerevisiae</td>
<td>Vps2</td>
</tr>
<tr>
<td class="label">D. melanogaster</td>
<td>CHMP2B</td>
</tr>
<tr>
<td class="label">D. rerio</td>
<td>chmp2b</td>
</tr>
<tr>
<td class="label">M.

CHMP2B — Charged Multivesicular Body Protein 2B

Introduction

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">CHMP2B — Charged Multivesicular Body Protein 2B</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>CHMP2B</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Charged Multivesicular Body Protein 2B</td>
</tr>
<tr>
<td class="label">Alternative Names</td>
<td>CHMP2B, VPS36-2, MY013</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>3p11.2</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>25978</td>
</tr>
<tr>
<td class="label">OMIM</td>
<td>609512</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000083937</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q9UQN3</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>213 amino acids</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~24 kDa</td>
</tr>
<tr>
<td class="label">Species</td>
<td>Ortholog</td>
</tr>
<tr>
<td class="label">S. cerevisiae</td>
<td>Vps2</td>
</tr>
<tr>
<td class="label">D. melanogaster</td>
<td>CHMP2B</td>
</tr>
<tr>
<td class="label">D. rerio</td>
<td>chmp2b</td>
</tr>
<tr>
<td class="label">M. musculus</td>
<td>Chmp2b</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>

Pathway Diagram

CHMP2B (Charged Multivesicular Body Protein 2B) is a core subunit of the ESCRT-III (Endosomal Sorting Complex Required for Transport-III) complex, which plays critical roles in endosomal trafficking, autophagy, and membrane remodeling processes within cells. Located on chromosome 3p11.2, this gene encodes a protein that has garnered significant attention in neurodegenerative disease research due to its involvement in frontotemporal dementia (FTD-3) and amyotrophic lateral sclerosis (ALS)[@fisher2020].

CHMP2B is ubiquitously expressed with high levels in the brain, particularly in the cerebral cortex (frontal and temporal lobes), hippocampus, cerebellum, and spinal cord. These brain regions are prominently affected in neurodegenerative disorders, explaining the strong association between CHMP2B dysfunction and neurological disease["@ghanbar2021"].

The first disease-causing CHMP2B mutations were identified in 2005 in a large Danish family with hereditary frontotemporal dementia (FTD-3), linking CHMP2B to chromosome 3-linked FTD["@skibinski2005"]. Since this discovery, multiple mutations have been characterized, including the intron5 splice site mutation (c.532-11C>G) common in Danish families, nonsense mutations like Gln165X in Belgian patients, and missense variants such as Thr104Asn in ALS patients and Asn143Ser in corticobasal degeneration (CBD) patients["@isaacs2011"].

Gene Overview

Protein Structure and the ESCRT-III Complex

ESCRT-III Architecture

CHMP2B is a member of the CHMP (Charged Multivesicular Body Protein) family, which constitutes the core ESCRT-III complex[@hanson2010]. The ESCRT-III complex consists of multiple related proteins that polymerize to form membrane-scission machinery:

• CHMP2A and CHMP2B: Form heterodimers as the core ESCRT-III core
• CHMP4A, CHMP4B, and CHMP4C: Key polymerization subunits
• CHMP6: Functions as an accessory factor
• CHMP1A, CHMP1B, CHMP7: Extended family members

Structural Domains

CHMP2B contains several functional domains[@vernizzi2022]:

The protein adopts an elongated helical structure that enables formation of filamentous polymers on endosomal membranes. The C-terminal region contains an autoinhibitory alpha-helix that prevents premature polymerization until properly localized.

Interaction Network

CHMP2B interacts with multiple ESCRT components[@fisher2020]:

• CHMP2A: Forms heterodimers essential for ESCRT-III function
• CHMP4B/C: Core ESCRT-III complex polymerization
• VPS4: ATPase that catalyzes disassembly of ESCRT-III filaments
• ALIX: ESCRT accessory factor that bridges upstream events
• IST1: Regulatory subunit influencing ESCRT dynamics

Cellular Functions

Multivesicular Body Formation

CHMP2B is essential for the formation of multivesicular bodies (MVBs), which are critical for receptor downregulation and protein sorting[@filimonenko2007]:

Autophagosome Maturation

CHMP2B plays a critical role in autophagy, particularly in the maturation of autophagosomes to autolysosomes[@cox2020]:

• Autophagosome-Lysosome Fusion: ESCRT-III mediates the final degradation step
• Cargo Recruitment: Selective autophagy receptors recruit CHMP2B to autophagosomes
• Endosomal Integration: Coordinate ESCRT and autophagy pathway functions

Nuclear Envelope Reformation

During cell division, CHMP2B participates in nuclear envelope reformation, ensuring proper nuclear compartmentalization in post-mitotic neurons.

Neuronal Synaptic Function

In neurons, CHMP2B contributes to[@ghanbar2021]:

• Synaptic Vesicle Trafficking: Essential for presynaptic function and neurotransmitter release
• Axonal Endosomal Trafficking: Regulates trafficking of signaling receptors in axons
• Dendritic Spine Morphogenesis: Involved in postsynaptic structure formation

Disease Associations

Frontotemporal Dementia (FTD-3)

CHMP2B mutations cause familial frontotemporal dementia (FTD-3) with characteristic features[@ghazinoori2012]:

Inheritance Pattern: Autosomal dominant, with Danish families representing the largest cohort

Age of Onset: Typically 40-60 years

Clinical Features:

• Behavioral variant FTD (bvFTD) with prominent personality changes
• Progressive loss of social conduct and disinhibition
• Language impairment including progressive aphasia
• Motor features in later stages

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

• Intron5 splice mutation (c.532-11C>G): Most common in Danish families
• Gln165X (p.Gln165*): Nonsense mutation in Belgian patients
• Asn143Ser: Missense variant in CBD patients

Amyotrophic Lateral Sclerosis (ALS)

CHMP2B mutations cause familial ALS with characteristic features[@lee2015]:

Inheritance: Autosomal dominant inheritance

Age of Onset: Typically 40-60 years

Phenotype:

• Mixed bulbar and spinal onset
• Rapid progression

Neuropathology:

• TDP-43 positive inclusions in motor neurons
• Bunina bodies in some cases
• Spinal cord motor neuron loss

• Thr104Asn (p.Thr104Asn): Missense mutation in Scandinavian ALS families
• p.Ser185Leu: Identified in ALS-FTD spectrum cases

Other Neurodegenerative Conditions

• Parkinson's Disease: Endo-lysosomal dysfunction relevant to pathogenesis
• Huntington's Disease: Protein clearance impairments
• Alzheimer's Disease: ESCRT alterations reported in some studies
• Corticobasal Degeneration: CHMP2B missense variants identified

Molecular Mechanisms in Neurodegeneration

Endosomal Sorting and Autophagy Dysfunction

CHMP2B mutations disrupt ESCRT-III function, leading to[@fisher2020]:

Neuronal Vulnerability

Motor neurons and cortical neurons show particular susceptibility due to[@ghanbar2021]:

• Axonal Transport Requirements: High dependency on endosomal trafficking
• Synaptic Vesicle Cycling: Continuous presynaptic activity
• Protein Turnover: Long-lived proteins require efficient clearance
• Nuclear Pore Integrity: ESCRT functions in nuclear envelope maintenance

TDP-43 Pathology

CHMP2B dysfunction contributes to TDP-43 proteinopathy—the hallmark pathology of most ALS and many FTD cases:

• TDP-43 Mislocalization: Cytoplasmic aggregation
• Splicing Dysregulation: Altered TDP-43 autoregulation
• Stress Granule Formation: Impaired stress response

Therapeutic Implications

Small Molecule Approaches

• ESCRT Modulators: Enhance residual ESCRT function
• Autophagy Inducers: Bypass CHMP2B dysfunction
• Lysosomal Enhancers: Improve clearance capacity
• Neuroprotective Agents: Target downstream pathways

Gene Therapy Strategies

• Wild-type CHMP2B Delivery: AAV-mediated expression
• CRISPR Correction: Repair pathogenic mutations
• RNAi Approaches: Reduce toxic mutant expression
• Antisense Oligonucleotides: Allele-specific targeting

Biomarker Development

• CSF CHMP2B: Disease-specific alterations in levels
• Blood-based Markers: Peripheral biomarkers
• Imaging Markers: Neuroimaging correlates

Research Models

Cellular Models

• Patient Fibroblasts: Show endosomal abnormalities
• iPSC-derived Neurons: Motor neuron models with CHMP2B mutations
• Knockdown Studies: Loss-of-function characterization

Animal Models

• Transgenic Mice: CHMP2B mutant expression shows neurodegeneration
• Zebrafish: Motor neuron development studies
• Drosophila: Genetic interaction screens

Key Publications

External Resources

• [NCBI Gene: CHMP2B](https://www.ncbi.nlm.nih.gov/gene/25978)
• [UniProt: Q9UQN3](https://www.uniprot.org/uniprot/Q9UQN3)
• [Ensembl: ENSG00000083937](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000083937)
• [OMIM: 609512](https://www.omim.org/entry/609512)
• [Allen Human Brain Atlas - CHMP2B Expression](https://human.brain-map.org/microarray/search/show?search_term=CHMP2B)

See Also

• [Genes Index](/genes)
• [Frontotemporal Dementia](/diseases/frontotemporal-dementia)
• [Amyotrophic Lateral Sclerosis (ALS)**](/diseases/amyotrophic-lateral-sclerosis)
• [ESCRT Pathway](/mechanisms/escr-pathway)
• [Autophagy Pathway](/mechanisms/autophagy)
• [TDP-43 Proteinopathy](/mechanisms/tdp-43-proteinopathy)

Additional Research Insights

CHMP2B and Lysosomal Function

CHMP2B plays a critical role in lysosomal biology, which is central to neurodegenerative disease pathogenesis:

Lysosomal Biogenesis: ESCRT-III function is essential for proper lysosome formation and function. CHMP2B mutations impair lysosomal maturation, leading to accumulation of lipofuscin and other lysosomal storage materials.

Cathepsin Processing: CHMP2B influences the processing and activation of lysosomal cathepsins, proteolytic enzymes critical for protein degradation.

Autophagic Flux: The CHMP2B-autophagy axis is essential for autophagic flux. Disruption leads to accumulation of autophagosomes and failure to clear protein aggregates.

CHMP2B in Neuronal Trafficking

Neurons have unique trafficking requirements due to their morphology:

Axonal Transport: CHMP2B localizes to axonal endosomes and regulates the trafficking of signaling receptors, neurotrophin receptors, and synaptic proteins along axons.

Synaptic Vesicle Cycling: At presynaptic terminals, CHMP2B participates in synaptic vesicle endocytosis and recycling.

Dendritic Trafficking: In dendrites, CHMP2B regulates trafficking of AMPA and NMDA receptors, influencing synaptic plasticity.

CHMP2B and Neuroinflammation

The relationship between CHMP2B dysfunction and neuroinflammation is bidirectional:

Microglial Activation: CHMP2B mutations lead to altered microglial morphology and function. Activated microglia show enhanced inflammatory responses.

Cytokine Production: Dysregulated ESCRT function affects cytokine production and secretion by both neurons and glia.

Peripheral Immune Cross-talk: CHMP2B-related endosomal dysfunction may affect peripheral immune cell function and CNS infiltration.

CHMP2B Post-translational Modifications

CHMP2B activity is regulated by multiple post-translational modifications:

Phosphorylation: Multiple phosphorylation sites regulate CHMP2B polymerization and disassembly. Casein kinase 2 (CK2) and other kinases phosphorylate CHMP2B.

Ubiquitination: CHMP2B is ubiquitinated, which influences its subcellular localization and interactions with ESCRT components.

SUMOylation: SUMOylation of CHMP2B affects its function in selective autophagy.

Comparative Biology of CHMP2B

CHMP2B orthologs are conserved across eukaryotes:

The conservation of CHMP2B function highlights its fundamental role in eukaryotic cell biology.

CHMP2B in Aging

The aging process affects CHMP2B function:

Age-related Changes: CHMP2B expression and localization change with age, potentially contributing to age-related neurodegeneration.

Cellular Senescence: ESCRT dysfunction can induce cellular senescence phenotypes in neurons.

Protein Homeostasis Decline: Age-related decline in proteostasis may synergize with CHMP2B dysfunction to accelerate neurodegeneration.

Therapeutic Strategies

Multiple therapeutic approaches are being explored:

Gene Replacement Therapy: AAV-mediated wild-type CHMP2B delivery to restore normal function.

Small Molecule ESCRT Modulators: Compounds that enhance residual ESCRT function or bypass CHMP2B deficiency.

Autophagy Enhancement: Pharmacological induction of autophagy to compensate for ESCRT dysfunction.

Antisense Oligonucleotides: ASO-based approaches to modulate CHMP2B splicing or expression.

Biomarker Development

CHMP2B-related biomarkers are under development:

CSF CHMP2B: Altered cerebrospinal fluid CHMP2B levels in FTD/ALS patients.

Blood Biomarkers: Peripheral blood mononuclear cell CHMP2B expression as a potential biomarker.

Imaging Markers: PET tracers targeting endosomal/lysosomal dysfunction.

Challenges in CHMP2B Research

Several challenges remain in understanding and targeting CHMP2B:

Model Systems: Creating accurate cellular and animal models that recapitulate human disease.

Therapeutic Delivery: Ensuring adequate delivery to the CNS while avoiding peripheral effects.

Biomarker Validation: Large-scale studies to validate CHMP2B as a biomarker.

Combination Therapies: Developing multi-target approaches that address both ESCRT dysfunction and downstream consequences.

CHMP2B in Neurodegenerative Disease Networks

CHMP2B intersects with multiple disease pathways:

Autophagy-Lysosome Pathway: CHMP2B is central to autophagic degradation; dysfunction leads to aggregate accumulation.

Endosomal Trafficking: CHMP2B mutations disrupt receptor trafficking and signaling in neurons.

Protein Homeostasis: ESCRT dysfunction impairs protein quality control mechanisms.

Neuroinflammation: Altered protein clearance leads to chronic neuroinflammation.

Clinical Translation of CHMP2B Research

Translating CHMP2B research into clinical applications:

Genetic Testing: CHMP2B mutation analysis is available for at-risk families.

Biomarker Development: CSF and blood CHMP2B as potential disease biomarkers.

Therapeutic Approaches: Gene therapy and small molecule approaches in development.

Clinical Trials: Planning underway for ESCRT-targeted interventions.

CHMP2B in Different Cell Types

CHMP2B function varies across cell types:

Neurons: High dependency on CHMP2B for synaptic function and protein homeostasis.

Astrocytes: CHMP2B supports astrocytic protein clearance functions.

Microglia: CHMP2B in microglial phagocytosis and inflammatory responses.

Oligodendrocytes: CHMP2B supports myelin protein processing.

Interplay Between CHMP2B and Other ESCRT Proteins

CHMP2B functions within the ESCRT system:

CHMP2A: Forms heterodimers with CHMP2B; both subunits required for function.

CHMP4 Family: Works with CHMP4B/C in ESCRT-III polymerization.

VPS4: ATPase that disassembles CHMP2B-containing filaments.

ALIX: Accessory factor that recruits CHMP2B to sites of action.

Summary

CHMP2B is an essential ESCRT-III subunit whose mutations cause familial FTD-3 and ALS. Through its roles in autophagy, endosomal trafficking, and lysosomal function, CHMP2B is critical for neuronal protein homeostasis. Understanding CHMP2B's function in neurodegeneration is enabling the development of ESCRT-targeted therapeutic approaches for FTD, ALS, and related disorders.

Related Hypotheses

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 — Charged Multivesicular Body Protein 2B discovered through SciDEX knowledge graph analysis: