module: dmel_basement_membrane_network
title: Basement membrane laminin and collagen network in Drosophila melanogaster
label: Basement membrane network
module_type: CELLULAR_COMPONENT
description: >-
  Basement membranes are sheet-like extracellular matrices beneath epithelia
  and around muscles and organs. Their two self-assembling networks are made of
  laminin and type IV collagen. Drosophila has two laminin trimers, each made
  of one alpha chain (LanA or Wing blister) with the shared beta (LanB1) and
  gamma (LanB2) chains; laminins polymerise at the cell surface and initiate
  basement membrane assembly. Type IV collagen trimers of Col4a1 and Viking are
  made mainly by the fat body and hemocytes and then incorporated into
  basement membranes, where they form a cross-linked network that gives
  strength and shapes organs. Multiplexin (the collagen XV/XVIII homolog) and
  Pericardin (a collagen IV-like protein of the cardiac extracellular matrix)
  are additional collagens grouped with them.
summary: >-
  Laminin trimers and type IV collagen networks, with the collagens
  Multiplexin and Pericardin, that form Drosophila basement membranes.
concepts:
  - {id: GO:0005604, label: basement membrane}
parts:
  - id: laminins
    label: Laminin trimers
    role: laminin network that initiates basement membrane assembly
    module_type: PROTEIN_COMPLEX
    variant_sets:
      - id: laminin_alpha_variants
        label: Laminin trimers with different alpha chains
        selection: ONE_OR_MORE
        variants:
          - id: laminin_lana
            label: Laminin A trimer (LanA-LanB1-LanB2)
            module_type: PROTEIN_COMPLEX
            complex: true
            genes: [LanA, LanB1, LanB2]
            complex_term: {id: GO:0043256, label: laminin trimer}
            function: {id: GO:0005201, label: extracellular matrix structural constituent}
          - id: laminin_wb
            label: Laminin W trimer (Wb-LanB1-LanB2)
            module_type: PROTEIN_COMPLEX
            complex: true
            genes: [wb, LanB1, LanB2]
            complex_term: {id: GO:0043256, label: laminin trimer}
            function: {id: GO:0005201, label: extracellular matrix structural constituent}
  - id: collagen_iv
    label: Type IV collagen trimer
    role: collagen IV network
    module_type: PROTEIN_COMPLEX
    complex: true
    genes: [Col4a1, vkg]
    complex_term: {id: GO:0005587, label: collagen type IV trimer}
    function: {id: GO:0030020, label: extracellular matrix structural constituent conferring tensile strength}
  - id: other_collagens
    label: Multiplexin and Pericardin
    role: additional basement membrane and cardiac matrix collagens
    module_type: MODULE
    genes: [Mp, prc]
    function: {id: GO:0005201, label: extracellular matrix structural constituent}
    unit_functions:
      Mp: null
    roles:
      Mp: collagen XV/XVIII homolog
      prc: collagen IV-like protein of the heart extracellular matrix
connections:
  - source: laminins
    target: collagen_iv
    connection_type: PRECEDES
    description: Laminin polymers are needed for subsequent incorporation of collagen IV into the basement membrane.
notes: >-
  Boundary. The module joins the FlyBase collagen and laminin groups. Other
  core basement membrane components, perlecan (trol), nidogen (Ndg) and SPARC,
  are not in these groups and are not added; the collagen IV cross-linking
  peroxidasin (Pxn) and the collagen-processing enzymes are also outside the
  module. The laminin alpha-chain composition is shown as two variants that share
  LanB1 and LanB2. Pericardin is grouped by FlyBase as a collagen and is found
  mainly in the cardiac and pericardial matrix rather than in all basement
  membranes. The connection from laminin to collagen IV summarises the
  assembly order shown for Drosophila embryos and is not a metabolic step.