VPS4B

VPS4B is an AAA-ATPase that drives the ATP-dependent disassembly and recycling of ESCRT-III filaments, a function central to multiple membrane-remodeling events including cytokinetic abscission and nuclear envelope repair (PMID:33326793, PMID:39540606). Its N-terminal MIT domain adopts an up-and-down three-helix bundle that presents a crevice between helices A and C for engaging ESCRT-III subunits, and a natural I58M variant destabilizes this fold (PMID:16018968). Through its C-terminal region VPS4B binds the Vta1p homologue SBP1 and the ESCRT-III subunit mVps2/CHMP2A, and its ATPase activity governs membrane association and assembly of a large SBP1-containing hetero-oligomeric complex required for endosomal/lysosomal transport (PMID:15173323); recruitment of the Ca2+-binding protein ALG-2 to ESCRT-decorated endosomes is Ca2+-dependent (PMID:16004603). VPS4B and its paralog VPS4A are synthetic-lethal: loss of either alone is tolerated, but co-depletion causes ESCRT-III filament accumulation, cytokinesis failure, nuclear deformation, G2/M arrest, and apoptosis, with attendant release of immunomodulatory molecules (PMID:33326793, PMID:31930723). Beyond ESCRT-III turnover, VPS4B controls EGFR trafficking and degradation—its loss causing EGFR accumulation and hyperactivated EGFR/AP-1 signaling—and is itself targeted for proteasomal degradation under hypoxia, coupling oxygen status to receptor abundance (PMID:22252323). VPS4B further supports autophagic flux that limits granzyme B accumulation and tumor-cell susceptibility to cytotoxic T cells (PMID:35379808), and its ATPase activity is required for retroviral (HTLV-1 Gag) budding (PMID:17601348) and for early embryonic development, with homozygous knockout causing lethality around E9.5 (PMID:33682352). A splicing mutation reducing VPS4B expression and mislocalizing the protein causes dentin dysplasia type I, with VPS4B acting upstream of Wnt/β-catenin signaling in odontogenesis (PMID:27247351).

1. 2004 High

   Established that VPS4B physically engages the ESCRT machinery and that its ATPase activity governs assembly of a membrane-associated regulatory complex, defining its biochemical role in endosomal transport.

   Evidence Yeast two-hybrid, GST pull-down with deletion mapping, and dominant-negative E235Q overexpression with fractionation

   PMID:15173323

   Open questions at the time

   • Did not resolve the structural basis of ESCRT-III recognition
   • Stoichiometry and architecture of the SBP1-containing complex not determined
2. 2005 High

   Defined the structural module by which VPS4B docks onto ESCRT-III, showing the MIT domain is a three-helix bundle with a candidate binding crevice and that a natural SNP destabilizes it.

   Evidence NMR solution structure and thermal stability assay of the I58M variant

   PMID:16018968

   Open questions at the time

   • No co-structure with an ESCRT-III partner
   • Functional consequence of I58M instability in cells untested
3. 2005 Medium

   Showed that recruitment of regulatory factors to VPS4B-marked endosomes is calcium-gated, linking Ca2+ signaling to ESCRT machinery localization.

   Evidence Immunofluorescence with GFP-SKD1(E235Q), Ca2+ chelation, and Ca2+-binding-defective ALG-2 mutant

   PMID:16004603

   Open questions at the time

   • Whether ALG-2 binds VPS4B directly versus other ESCRT components unresolved
   • Functional output of Ca2+-dependent recruitment not established
4. 2007 Medium

   Demonstrated that VPS4B-dependent ESCRT activity is co-opted for retroviral budding, generalizing its membrane-scission role to viral egress.

   Evidence Dominant-negative VPS4B expression and HTLV-1 Gag virus-like particle release assay

   PMID:17601348

   Open questions at the time

   • Single dominant-negative readout without endogenous loss-of-function
   • Direct VPS4B–Gag/ESCRT contacts not mapped
5. 2012 Medium

   Connected VPS4B function to receptor signaling control and to hypoxic regulation, showing VPS4B limits EGFR abundance and is destabilized under low oxygen.

   Evidence shRNA knockdown, dominant-negative E235Q, AP-1 reporter, and proteasome-inhibitor/hypoxia Western blots in breast cancer cells

   PMID:22252323

   Open questions at the time

   • E3 ligase mediating hypoxic degradation not identified
   • Whether EGFR effects are direct trafficking or downstream of broader ESCRT failure unclear
6. 2016 Medium

   Linked VPS4B to a Mendelian disease and a developmental signaling axis, establishing VPS4B as an upstream regulator of Wnt/β-catenin in tooth development.

   Evidence Family-based mapping of a splice mutation, localization, pathway analysis, and zebrafish morpholino rescue with human VPS4B mRNA

   PMID:27247351

   Open questions at the time

   • Molecular link between ESCRT activity and Wnt signaling not defined
   • Tissue-specificity of the dentin phenotype unexplained
7. 2020 High

   Resolved the paralog relationship, showing VPS4A and VPS4B are synthetic-lethal and that VPS4B participates in ESCRT-III disassembly required for abscission, with therapeutic implications for VPS4B-deleted cancers.

   Evidence CRISPR and RNAi screens, genetic epistasis, ESCRT-III imaging, cell-cycle analysis, transcriptomics, and xenograft models across two studies

   PMID:31930723 PMID:33326793

   Open questions at the time

   • Degree of mechanistic non-redundancy between paralogs not fully dissected
   • Basis of the immunomodulatory release upon co-depletion unresolved
8. 2021 Medium

   Established that VPS4B is individually essential in vivo despite paralog redundancy in culture, with knockout causing early embryonic lethality.

   Evidence Vps4b conditional knockout mice with timed embryo analysis and siRNA knockdown with qRT-PCR

   PMID:33682352

   Open questions at the time

   • Cause of E9.5 lethality not mechanistically resolved
   • Tissue-specific requirements not dissected
9. 2022 High

   Placed VPS4B in the autophagic degradation pathway controlling immune killing, showing its loss impairs autophagy and allows granzyme B accumulation that sensitizes tumor cells to CD8+ T cells.

   Evidence In vitro and in vivo CRISPR screens, autophagy flux assays, granzyme B accumulation, and orthotopic transplantation

   PMID:35379808

   Open questions at the time

   • Step in autophagy requiring VPS4B not pinpointed
   • Whether granzyme B clearance is direct autophagic substrate handling unclear
10. 2024 Medium

    Extended VPS4B's ESCRT-III recycling role to nuclear envelope repair, showing insufficient VPS4B impairs response to mechanical NE stress.

    Evidence VPS4B knockdown/expression comparison with nuclear deformation, DNA damage, and ESCRT-III dynamics imaging in glioblastoma cells

    PMID:39540606

    Open questions at the time

    • Limited methodology described
    • Quantitative contribution relative to VPS4A at the NE not established
11. 2025 Low

    Implicated VPS4B in adipocyte lipid droplet release through an ANXA5 interaction modulated by O-GlcNAcylation, suggesting metabolic regulation of VPS4B activity.

    Evidence Co-culture, RNA-seq/proteomics, co-IP of VPS4B–ANXA5, siRNA knockdown, and in vivo tumor models

    PMID:40410860

    Open questions at the time

    • Single-lab interaction with limited mechanistic resolution
    • Site and functional impact of O-GlcNAc modification not mapped
    • Reciprocal validation of VPS4B–ANXA5 binding not shown

• It remains unknown how VPS4B's single ESCRT-III disassembly activity is differentially deployed and regulated across its distinct membrane contexts (endosomes, midbody, nuclear envelope) and how this connects mechanistically to downstream signaling outcomes such as Wnt and EGFR pathways.
• No structural model of the active VPS4B–ESCRT-III–cofactor assembly in human cells
• Determinants of context-specific recruitment unidentified
• Direct link between membrane-scission activity and transcriptional/signaling phenotypes unresolved