| Gene | [CHMP2B](/genes/chmp2b) |
|---|---|
| UniProt | Q9UQN3 |
| PDB Structures | 2J0N, 5TQO |
| Molecular Weight | ~24 kDa |
| Protein Length | 213 amino acids |
| Subcellular Localization | Endosomal membrane, multivesicular body, nucleus |
| Protein Family | ESCRT-III family, CHMP2 subgroup |
| Chromosomal Location | 3p11.2 |
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[1]. CHMP2B is encoded by the 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 and amyotrophic lateral sclerosis[2].
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[3].
CHMP2B adopts an elongated helical conformation that enables polymerization into filamentous structures[4]:
| 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[5].
CHMP2B polymerizes into helical filaments on endosomal membranes:
CHMP2B interacts with multiple ESCRT and regulatory proteins[1:1]:
CHMP2B is essential for the formation of intraluminal vesicles (ILVs) within multivesicular bodies (MVBs)[6]:
CHMP2B plays a critical role in the late stages of autophagy[7]:
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:
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[8].
In neurons, CHMP2B has specialized functions[2:1]:
CHMP2B mutations cause autosomal dominant familial FTD (FTD-3) characterized by[9][10]:
Clinical Features:
Neuropathology:
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 |
CHMP2B mutations also cause familial ALS with[11]:
| 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 |
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.
Fisher J, et al. CHMP2B in cellular homeostasis and neurodegeneration. J Cell Sci. 2020. ↩︎ ↩︎
Ghanbar H, et al. CHMP2B in neurodegeneration: Molecular mechanisms and therapeutic targets. Mol Neurodegener. 2021. ↩︎ ↩︎
Skibinski G, et al. Mutations in the ESCRT-III component CHMP2B in frontotemporal dementia. Nat Genet. 2005. ↩︎
Vernizzi L, et al. Understanding the role of CHMP2B in neurodegeneration: Insights from structural analyses. Int J Mol Sci. 2022. ↩︎
Hanson PI, et al. ESCTRs and the regulation of endosomal trafficking and morphogenesis. Physiol Rev. 2010. ↩︎
Filimonenko M, et al. Functional multivesicular bodies are required for autophagic clearance of protein aggregates. J Cell Biol. 2007. ↩︎
Cox LE, et al. Autophagy disruption in CHMP2B mutant models of frontotemporal dementia. Acta Neuropathol Commun. 2020. ↩︎
Metcalf D, et al. ESCRT-III dysfunction in the pathogenesis of neurodegeneration. Autophagy. 2014. ↩︎
Isaacs AM, et al. Spectrum of CHMP2B neurodegenerative phenotypes. Brain. 2011. ↩︎
Ghazi-Noori S, et al. Progressive neuronal inclusion formation and axonal degeneration in CHMP2B mutant transgenic mice. Brain. 2012. ↩︎
Lee JA, et al. ESCRT-III mutations in ALS/FTD. Acta Neuropathol. 2015. ↩︎