module: dmel_escrt_machinery
title: ESCRT machinery in Drosophila melanogaster
label: ESCRT machinery
module_type: PROTEIN_COMPLEX
description: >-
  The endosomal sorting complexes required for transport (ESCRTs) sort
  ubiquitylated membrane proteins into intralumenal vesicles of multivesicular
  bodies and drive membrane scission that buds away from the cytoplasm. ESCRT-0
  (Hrs, Stam) binds ubiquitylated cargo on endosomes; ESCRT-I and ESCRT-II bind
  cargo and membrane and nucleate ESCRT-III, whose subunits polymerize into
  spirals that constrict the bud neck. The AAA ATPase Vps4, with its cofactor
  Vta1, disassembles ESCRT-III and recycles it. The same ESCRT-III and Vps4
  machinery acts in cytokinetic abscission, nuclear envelope sealing and
  membrane repair. In Drosophila, loss of ESCRT function causes accumulation of
  signalling receptors such as Notch on endosomes and neoplastic overgrowth in
  epithelia.
summary: >-
  ESCRT-0, -I, -II and -III with Vps4-Vta1 that sort ubiquitylated cargo into
  multivesicular bodies and drive outward membrane scission.
concepts:
  - {id: GO:0032509, label: endosome transport via multivesicular body sorting pathway}
cellular_components:
  - {id: GO:0010008, label: endosome membrane}
notes: >-
  Decomposition. The five ESCRT subcomplexes are modelled as ordered parts,
  following the sequential recruitment established for the MVB pathway. The
  two ESCRT-I variants that differ in their Vps37 paralog are alternatives.
  Accessory factors such as ALiX are outside the module.
parts:
  - id: escrt_0
    label: ESCRT-0
    role: ubiquitylated cargo clustering
    group: ESCRT-0
    complex_term: {id: GO:0033565, label: ESCRT-0 complex}
  - id: escrt_i
    label: ESCRT-I
    role: cargo binding and ESCRT-II recruitment
    variant_sets:
      - id: escrt_i_variants
        label: ESCRT-I Vps37A or Vps37B variant
        selection: ONE_OR_MORE
        variants:
          - {id: escrt_ia, label: ESCRT-I Vps37A variant, group: ESCRT-IA, complex_term: {id: GO:0000813, label: ESCRT I complex}}
          - {id: escrt_ib, label: ESCRT-I Vps37B variant, group: ESCRT-IB, complex_term: {id: GO:0000813, label: ESCRT I complex}}
  - id: escrt_ii
    label: ESCRT-II
    role: ESCRT-III nucleation
    group: ESCRT-II
    complex_term: {id: GO:0000814, label: ESCRT II complex}
  - id: escrt_iii
    label: ESCRT-III
    role: membrane-constricting polymer
    group: ESCRT-III
    complex_term: {id: GO:0000815, label: ESCRT III complex}
    processes:
      - {id: GO:0090148, label: membrane fission}
  - id: vps4_vta1
    label: Vps4-Vta1
    role: ESCRT-III disassembly ATPase
    group: VSP4C
    unit_functions:
      Vps4: {id: GO:0016887, label: ATP hydrolysis activity}
connections:
  - {source: escrt_0, target: escrt_i, connection_type: PRECEDES, description: ESCRT-0 recruits ESCRT-I to cargo-containing endosomal membrane.}
  - {source: escrt_i, target: escrt_ii, connection_type: PRECEDES, description: ESCRT-I engages ESCRT-II.}
  - {source: escrt_ii, target: escrt_iii, connection_type: PRECEDES, description: ESCRT-II nucleates ESCRT-III polymerization.}
  - {source: escrt_iii, target: vps4_vta1, connection_type: PRECEDES, description: Vps4-Vta1 is recruited by ESCRT-III and disassembles it.}