CHMP5

CHMP5 (Vps60/Mos10) is an ESCRT-III family protein that nucleates an alternative class of ESCRT-III copolymers and regulates late endosomal maturation and cargo trafficking to lysosomes (PMID:16567502, PMID:37768378). Loss of CHMP5 produces enlarged multivesicular endosomes that fail to deliver cargo to lysosomes, reducing degradative capacity and enhancing receptor signaling, placing CHMP5 function downstream of MVB formation rather than at the canonical ESCRT-III step (PMID:16567502, PMID:15644320). On membranes CHMP5/Vps60 seeds filaments that recruit Vps2, Vps24, Did2, and Ist1 independently of the CHMP4/Snf7 pathway, and CHMP5- and CHMP4-based filaments occupy spatially distinct sites with different dynamics, defining functionally separate ESCRT-III populations (PMID:37768378). CHMP5 controls ESCRT disassembly machinery as a negative allosteric switch: it binds the VPS4 cofactor LIP5 (Vta1) through a MIM motif, and insertion of its conserved Tyr182 into the LIP5 N-terminal domain inhibits LIP5-mediated stimulation of VPS4 ATPase activity (PMID:23105107, PMID:25637630). Through its C-terminal tail, which adopts a tandem β-hairpin fold, CHMP5 binds and recruits the Bro1-domain protein Brox to detergent-resistant membranes (PMID:22484091). Beyond trafficking, CHMP5 serves tissue-specific signaling and survival roles: in osteoclasts it cooperates with VCP/p97 to stabilize IκBα via the deubiquitinase USP15, dampening RANKL-induced NF-κB activation, and its loss causes a Paget's-like bone phenotype (PMID:26195726); in thymocytes, TCR-induced engagement of the deubiquitinase USP8 stabilizes CHMP5 protein, which promotes Bcl-2 stabilization to support post-selection T cell survival (PMID:28553951).

1. 2003 Medium

   Established that the yeast CHMP5 ortholog has a function distinct from generic endocytic/VPS machinery, hinting at a specialized cargo-targeting role rather than a redundant ESCRT step.

   Evidence Genetic screen and deletion mutant phenotyping in S. cerevisiae pseudohyphal growth

   PMID:12940986

   Open questions at the time

   • Function inferred from genetic specificity, not direct biochemistry
   • No molecular partners or mechanism defined
   • Relevance to metazoan CHMP5 trafficking not established
2. 2005 High

   Identified LIP5 as a direct CHMP5 binding partner and placed CHMP5 in MVB sorting, while flagging unexpected effects on HIV-1 budding and endocytic compartment organization.

   Evidence Co-immunoprecipitation, siRNA EGFR degradation and HIV-1 budding assays, subcellular fractionation in human cells

   PMID:15644320

   Open questions at the time

   • Molecular basis of the LIP5 interaction unresolved
   • Mechanism of HIV budding effect not defined
   • Did not distinguish CHMP5 from classical ESCRT-III function
3. 2006 High

   Defined the cellular consequence of CHMP5 loss in vivo, showing it acts downstream of MVB formation to enable cargo delivery to lysosomes, distinct from classical yeast ESCRT-III mutants.

   Evidence Conditional mouse knockout with TEM, endosomal fractionation, degradation and receptor signaling assays

   PMID:16567502

   Open questions at the time

   • Did not resolve the biochemical step CHMP5 controls
   • Filament-level activity not addressed
   • Embryonic lethality limited tissue-level analysis
4. 2012 High

   Provided the structural basis for two distinct CHMP5 protein interfaces — the Vta1/LIP5 recognition mode and the Brox-recruiting C-terminal β-hairpin — clarifying how CHMP5 engages disassembly and Bro1-domain machinery.

   Evidence NMR structure of Vps60(128-186):Vta1NTD and crystal/structural analysis of the CHMP5 C-terminal tail bound to Brox, with Co-IP and membrane fractionation

   PMID:22484091 PMID:23105107

   Open questions at the time

   • Functional consequence of Vta1 binding (ATPase modulation) not yet defined in these studies
   • Cellular role of Brox recruitment not established
   • Whether interfaces act simultaneously unknown
5. 2015 High

   Resolved how CHMP5 controls ESCRT disassembly, defining it as a negative allosteric switch that inhibits LIP5-driven VPS4 ATPase stimulation via Tyr182 insertion into LIP5NTD.

   Evidence 1 Å crystal structure of LIP5NTD with CHMP5/CHMP1B MIM motifs, ATPase assays, and Tyr182 mutagenesis

   PMID:25637630

   Open questions at the time

   • When and where this inhibition operates in vivo unclear
   • How inhibition is relieved during normal cycling not defined
   • Link to the enlarged-endosome phenotype not directly tested
6. 2015 High

   Revealed a signaling role beyond trafficking, placing CHMP5 in a VCP/p97–CHMP5–USP15–IκBα axis that restrains RANKL-induced NF-κB activation in osteoclasts.

   Evidence Conditional osteoclast knockout with genetic epistasis rescue, Co-IP, ubiquitination and NF-κB reporter assays

   PMID:26195726

   Open questions at the time

   • How ESCRT/trafficking activity connects to IκBα stabilization unresolved
   • Direct CHMP5–USP15 versus VCP-bridged interaction not fully dissected
   • Generality beyond osteoclasts unknown
7. 2017 High

   Identified a post-translational control axis in which TCR signaling stabilizes CHMP5 via USP8, and CHMP5 in turn stabilizes Bcl-2 to enable post-selection thymocyte survival.

   Evidence Conditional thymocyte knockout with Bim-KO and Bcl-2-transgene rescue, Co-IP (CHMP5–USP8), flow cytometry and Western blot

   PMID:28553951

   Open questions at the time

   • Mechanism linking CHMP5 to Bcl-2 stabilization not defined
   • Whether ESCRT activity is required for the survival role unknown
   • Direct versus indirect USP8 stabilization of CHMP5 not resolved
8. 2023 High

   Demonstrated that CHMP5/Vps60 nucleates a Snf7/CHMP4-independent ESCRT-III filament population with distinct subunit composition, localization, and dynamics, explaining its non-redundant role.

   Evidence In vitro membrane reconstitution, live-cell imaging/FRAP, EM of filaments, and subunit deletions in yeast and fibroblasts

   PMID:37768378

   Open questions at the time

   • Specific membrane-remodeling reaction served by CHMP5 filaments not defined
   • How CHMP5 and CHMP4 pathways are spatially segregated unknown
   • Cargo specificity of the alternative filament unresolved
9. 2018 Medium

   Showed CHMP5 expression is directly repressed by miR-429 and is elevated in colitis and colon cancer contexts, linking its dosage to proliferation.

   Evidence Luciferase 3′UTR reporter, qRT-PCR/Western blot, and flow cytometry in colon cancer cells and colitis models

   PMID:30334065

   Open questions at the time

   • Single-method evidence for the direct regulatory link
   • How CHMP5 level drives cell-cycle progression mechanistically not defined
   • Connection to ESCRT trafficking function not established

• How CHMP5's biochemical activities — alternative ESCRT-III filament nucleation and VPS4/LIP5 inhibition — are mechanistically coupled to its diverse signaling roles (NF-κB restraint, Bcl-2 stabilization) remains unresolved.
• No unified model linking membrane-remodeling activity to deubiquitinase-dependent protein stabilization
• Whether trafficking and signaling roles share a common molecular step is untested
• Tissue-specific partner selection not explained