module: dmel_pp2a_holoenzymes
title: Protein phosphatase 2A holoenzymes in Drosophila melanogaster
label: PP2A holoenzymes
module_type: PROTEIN_COMPLEX
description: >-
  Protein phosphatase 2A (PP2A) is a major serine/threonine phosphatase formed by a
  core dimer of a scaffold (A) subunit and a catalytic (C) subunit, joined by one of
  several regulatory B subunits that select substrates and subcellular location. In
  Drosophila the catalytic subunit is Microtubule star (Mts) and the scaffold is
  Pp2A-29B. The B55-family subunit Twins (Tws) directs PP2A to mitotic substrates
  and regulates mitotic exit, while the B56 subunits Widerborst (Wdb) and Well
  rounded (Wrd) act in planar cell polarity, Hedgehog and Wingless signaling,
  insulin signaling and synapse development.
summary: >-
  Mts-Pp2A-29B core with alternative Tws, Wdb or Wrd regulatory subunits.
concepts:
  - {id: GO:0000159, label: protein phosphatase type 2A complex}
parts:
  - id: pp2a_core_enzyme
    label: PP2A core enzyme
    role: catalytic and scaffold subunits
    genes: [mts, Pp2A-29B]
    complex_label: PP2A A-C core dimer
    unit_functions:
      mts: {id: GO:0004722, label: protein serine/threonine phosphatase activity}
  - id: pp2a_regulatory_subunit
    label: PP2A regulatory B subunit
    role: substrate-targeting subunit
    variant_sets:
      - id: pp2a_b_subunit_variants
        label: B55 or B56 regulatory subunit
        selection: EXACTLY_ONE
        variants:
          - {id: tws_b55, label: Twins (B55), genes: [tws], function: {id: GO:0019888, label: protein phosphatase regulator activity}}
          - {id: wdb_b56, label: Widerborst (B56), genes: [wdb], function: {id: GO:0019888, label: protein phosphatase regulator activity}}
          - {id: wrd_b56, label: Well rounded (B56), genes: [wrd], function: {id: GO:0019888, label: protein phosphatase regulator activity}}
connections:
  - source: pp2a_regulatory_subunit
    target: pp2a_core_enzyme
    connection_type: POSITIVELY_REGULATES
    description: The B subunit targets the core enzyme to specific substrates and sites.
notes: >-
  FlyBase defines three holoenzymes (WRD-PP2A, TWS-PP2A, WDB-PP2A) that share the
  A and C subunits; they are modelled as one core part plus an EXACTLY_ONE B-subunit
  choice. The striatin-containing PP2A of STRIPAK is a separate module
  (dmel_stripak_complex). The B'' subunit and PP2A inhibitors are not in the FlyBase
  group and are not modelled.
group: PP2A