MPP5, SH3 domain (IPR035601)

Short name: MPP5_SH3

Overlapping homologous superfamilies

Domain relationships

  • SH3 domain (IPR001452)
    • MPP5, SH3 domain (IPR035601)


MPP5, also called PALS1 (protein associated with Lin7) or Nagie oko protein in zebrafish [PMID: 20362667] or Stardust in Drosophila [PMID: 20861315], is a scaffolding protein which associates with Crumbs homologue 1 (CRB1), CRB2, or CRB3 through its PDZ domain and with PALS1-associated tight junction protein (PATJ) or multi-PDZ domain protein 1 (MUPP1) through its L27 domain [PMID: 22114289]. The resulting tri-protein complexes are core proteins of the Crumb complex, which localizes at tight junctions or subapical regions, and is involved in the maintenance of apical-basal polarity in epithelial cells and the morphogenesis and function of photoreceptor cells [PMID: 17920587]. MPP5 is critical for the proper stratification of the retina and is also expressed in T lymphocytes where it is important for TCR-mediated activation of NFkB [PMID: 21479189]. Drosophila Stardust exists in several isoforms, some of which show opposing functions in photoreceptor cells, which suggests that the relative ratio of different Crumbs complexes regulates photoreceptor homeostasis [PMID: 28416478]. MPP5 belongs to the membrane-associated guanylate kinase (MAGUK) p55 subfamily.

The membrane-associated guanylate kinase (MAGUK) p55 subfamily (also known as MPP subfamily) members include the Drosophila Stardust protein and its vertebrate homologues, MPP1-7. They contain the core of three domains characteristic of MAGUK (membrane-associated guanylate kinase) proteins: PDZ, SH3, and guanylate kinase (GuK). In addition, they also contain the Hook (Protein 4.1 Binding) motif in between the SH3 and GuK domains [PMID: 11414766]. MPP2-7 have two additional L27 domains at their N terminus. The GuK domain in MAGUK proteins is enzymatically inactive; instead, the domain mediates protein-protein interactions and associates intramolecularly with the SH3 domain [PMID: 17678554].

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.