CHMP2A

CHMP2A is a core ESCRT-III subunit that drives membrane remodeling and fission as part of the minimal CHMP2A-CHMP3-VPS4 machinery (PMID:36604498). Cryo-EM of membrane-coated filaments shows that CHMP2A and CHMP3 assemble as heterodimers in the open ESCRT-III conformation into helical filaments whose partially positive surface engages the membrane, with N-terminal motifs positioned for membrane interaction and C-terminal VPS4 target sequences facing the tube interior; electrostatic inter-filament contacts permit VPS4-driven sliding, constriction, and tube cleavage (PMID:36604498). CHMP2A itself lacks intrinsic lipid specificity and depends on CHMP3 to bind membranes, and it does not appreciably alter membrane rigidity, distinguishing it from CHMP2B (PMID:33832485). Engagement of the AAA-ATPase VPS4/SKD1 occurs independently of the N-terminal coiled-coil, which is instead required for assembly into ESCRT-III membrane structures (PMID:15173323), and yeast ortholog analysis confirms that spiral formation, lateral heteropolymerization, and VPS4 binding are the minimal functional features of this subunit (PMID:34028356). During cytokinetic abscission CHMP2A acts as a hierarchical organizer of ESCRT-III assembly, with CHMP4B, CHMP3, and CHMP1B depending on it for correct localization (PMID:40928930). Beyond cytokinesis, CHMP2A mediates phagophore/autophagosome closure: its depletion stabilizes intracellular death-inducing signaling complexes on immature autophagosomal membranes and triggers ATG7-dependent Caspase-8 apoptosis (PMID:32807832), and it functions downstream of PTEN to support autophagy flux and protection after ischemia/reperfusion injury (PMID:34789720). In tumor cells CHMP2A restrains antitumor immunity by suppressing NF-κB-driven chemokine secretion and by promoting extracellular-vesicle-mediated NK cell apoptosis, with its loss broadly enhancing immune-cell-mediated tumor control (PMID:35393416, PMID:38702144).

1. 2004 Medium

   Established that mammalian CHMP2A physically engages the VPS4-family ATPase and depends on its N-terminal coiled-coil for assembly onto endosomal membranes, separating its ATPase-binding function from its membrane-targeting function.

   Evidence Yeast two-hybrid, co-IP, and immunofluorescence with the dominant-negative SKD1(E235Q) in mammalian cells

   PMID:15173323

   Open questions at the time

   • Did not resolve the structural basis of the CHMP2A-VPS4 interaction
   • No direct demonstration of membrane fission
2. 2020 Medium

   Placed CHMP2A in autophagosome closure by showing its loss stabilizes death-inducing complexes on immature membranes and triggers Caspase-8 apoptosis, linking ESCRT-III membrane closure to cell-death control.

   Evidence Conditional knockdown/knockout, ATG7-deletion epistasis, Caspase-8 assays, xenograft model

   PMID:32807832

   Open questions at the time

   • Molecular composition and membrane attachment of iDISCs not fully resolved
   • Mechanism of phagophore sealing by CHMP2A not directly visualized
3. 2021 High

   Demonstrated that CHMP2A lacks intrinsic lipid specificity and requires CHMP3 for membrane binding, defining its biophysical role relative to the membrane-rigidifying CHMP2B paralog.

   Evidence In vitro reconstitution with purified proteins on biomimetic membranes and membrane mechanics measurements

   PMID:33832485

   Open questions at the time

   • Did not establish the filament architecture underlying binding
   • Physiological membrane substrate composition not addressed
4. 2021 Medium

   Reduced the subunit to three minimal functional requirements—spiral formation, lateral heteropolymerization, and VPS4 binding—using the yeast ortholog, defining the conserved logic of ESCRT-III function.

   Evidence Mutagenesis, genetic complementation, and engineered selection in S. cerevisiae Vps2

   PMID:34028356

   Open questions at the time

   • Inferred from yeast ortholog rather than human CHMP2A
   • Did not test membrane fission directly
5. 2021 Medium

   Positioned CHMP2A downstream of PTEN in autophagy regulation, showing CHMP2A is required for PTEN-mediated autophagy flux and tissue protection after ischemia/reperfusion.

   Evidence PTEN transgenic mice, proteomics, CHMP2A siRNA rescue, autophagy flux assays

   PMID:34789720

   Open questions at the time

   • Mechanism by which PTEN upregulates CHMP2A unclear
   • Direct role of CHMP2A in autolysosome formation not visualized
6. 2022 Medium

   Identified CHMP2A as a tumor immune-evasion factor that suppresses NF-κB-driven chemokine secretion and drives NK-cell-killing via MICA/B- and TRAIL-bearing extracellular vesicles.

   Evidence Genome-wide CRISPR screen, CHMP2A KO, NF-κB analysis, EV characterization, NK killing assays, xenografts

   PMID:35393416

   Open questions at the time

   • How ESCRT-III membrane activity connects mechanistically to NF-κB is unresolved
   • EV cargo loading mechanism not defined
7. 2023 High

   Provided the atomic structural mechanism: CHMP2A-CHMP3 open-conformation heterodimers form helical membrane-coating filaments cleaved by VPS4, establishing CHMP2A-CHMP3-VPS4 as a minimal fission machine.

   Evidence Cryo-EM at 3.3/3.6 Å, high-speed AFM, fluorescence microscopy

   PMID:36604498

   Open questions at the time

   • In-cell relevance of the reconstituted geometry not tested
   • Stoichiometry with other ESCRT-III subunits in physiological filaments unresolved
8. 2024 Medium

   Extended the immune-evasion role in vivo, showing CHMP2A loss broadens antitumor immunity (more T and NK cells, fewer MDSCs) and confirmed the effect is immune-dependent.

   Evidence CRISPR KO, syngeneic immunocompetent vs immunodeficient orthotopic transplantation, immune profiling

   PMID:38702144

   Open questions at the time

   • Cell-intrinsic mechanism altering MDSC and T-cell recruitment not defined
   • Whether effect is EV-dependent in vivo not isolated
9. 2024 Low

   Began mapping CHMP2A lipid environment during division by capturing associated lipid species in dividing cells.

   Evidence Lipid-trap mass spectrometry (GFP-CHMP2A IP plus lipidomics) in dividing HeLa cells (preprint)

   PMID:bio_10.1101_2024.12.13.627510

   Open questions at the time

   • Single method, preprint, no functional validation of specific lipid interactions
   • Direct binding vs co-purification not distinguished
10. 2025 Medium

    Defined CHMP2A as a hierarchical organizer of abscission, with downstream ESCRT-III subunits depending on it for correct localization while abscission is delayed rather than abolished.

    Evidence Live imaging, SIM, correlative light-electron microscopy in CHMP2A KO cells

    PMID:40928930

    Open questions at the time

    • Redundancy compensating for CHMP2A loss not identified
    • Order of subunit recruitment relative to VPS4 not fully resolved

• How CHMP2A's membrane-fission activity is mechanistically coupled to its signaling roles (NF-κB modulation, EV-mediated immune suppression, PTEN-dependent autophagy) remains unresolved.
• No direct link established between filament/fission activity and NF-κB control
• Mechanism of immune-relevant EV biogenesis by CHMP2A undefined