title: A novel and conserved protein-protein interaction domain of mammalian Lin-2/CASK binds and recruits SAP97 to the lateral surface of epithelia.
abstract: Mammalian Lin-2 (mLin-2)/CASK is a membrane-associated guanylate kinase (MAGUK) and contains multidomain modules that mediate protein-protein interactions important for the establishment and maintenance of neuronal and epithelial cell polarization. The importance of mLin-2/CASK in mammalian development is demonstrated by the fact that mutations in mLin-2/CASK or SAP97, another MAGUK protein, lead to cleft palate in mice. We recently identified a new protein-protein interaction domain, called the L27 domain, which is present twice in mLin-2/CASK. In this report, we further define the binding of the L27C domain of mLin-2/CASK to the L27 domain of mLin-7 and identify the binding partner for L27N of mLin-2/CASK. Biochemical analysis reveals that this L27N domain binds to the N terminus of SAP97, a region that was previously reported to be essential for the lateral membrane recruitment of SAP97 in epithelia. Our colocalization studies, using dominant-negative mLin-2/CASK, show that the association with mLin-2/CASK is crucial for lateral localization of SAP97 in MDCK cells. We also report the identification of a novel isoform of Discs Large, a Drosophila melanogaster orthologue of SAP97, which contains a region highly related to the SAP97 N terminus and which binds Camguk, a Drosophila orthologue of mLin-2/CASK. Our data identify evolutionarily conserved protein-protein interaction domains that link mLin-2/CASK to SAP97 and account for their common phenotype when mutated in mice.
authors.affiliation: Department of Biological Chemistry, Howard Hughes Medical Institute, University of Michigan Medical School, 1150 W. Medical Center Dr., Ann Arbor, MI 48109, USA.
authors.forename: Seonok
authors.initials: S
authors.lastname: Lee
authors.forename: Shuling
authors.initials: S
authors.lastname: Fan
authors.forename: Olya
authors.initials: O
authors.lastname: Makarova
authors.forename: Samuel
authors.initials: S
authors.lastname: Straight
authors.forename: Ben
authors.initials: B
authors.lastname: Margolis
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D017124:Conserved Sequence; D000074288:Discs Large Homolog 1 Protein; D004285:Dogs; D004331:Drosophila melanogaster; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D051528:Guanylate Kinases; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D009703:Nucleoside-Phosphate Kinase / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D033921:Vesicular Transport Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C513314:DLG1 protein, human; D000074288:Discs Large Homolog 1 Protein; C119588:LIN-7 protein, mammalian; C486532:LIN7A protein, human; C486531:LIN7C protein, human; D046911:Macromolecular Substances; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D033921:Vesicular Transport Proteins; C106868:CASK kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases