title: Phosphorylation of the Usher syndrome 1G protein SANS controls Magi2-mediated endocytosis.
abstract: The human Usher syndrome (USH) is a complex ciliopathy with at least 12 chromosomal loci assigned to three clinical subtypes, USH1-3. The heterogeneous USH proteins are organized into protein networks. Here, we identified Magi2 (membrane-associated guanylate kinase inverted-2) as a new component of the USH protein interactome, binding to the multifunctional scaffold protein SANS (USH1G). We showed that the SANS-Magi2 complex assembly is regulated by the phosphorylation of an internal PDZ-binding motif in the sterile alpha motif domain of SANS by the protein kinase CK2. We affirmed Magi2's role in receptor-mediated, clathrin-dependent endocytosis and showed that phosphorylated SANS tightly regulates Magi2-mediated endocytosis. Specific depletions by RNAi revealed that SANS and Magi2-mediated endocytosis regulates aspects of ciliogenesis. Furthermore, we demonstrated the localization of the SANS-Magi2 complex in the periciliary membrane complex facing the ciliary pocket of retinal photoreceptor cells in situ. Our data suggest that endocytotic processes may not only contribute to photoreceptor cell homeostasis but also counterbalance the periciliary membrane delivery accompanying the exocytosis processes for the cargo vesicle delivery. In USH1G patients, mutations in SANS eliminate Magi2 binding and thereby deregulate endocytosis, lead to defective ciliary transport modules and ultimately disrupt photoreceptor cell function inducing retinal degeneration.
authors.affiliation: Cell and Matrix Biology, Institute of Zoology, Focus Program Translational Neurosciences (FTN), Johannes Gutenberg University of Mainz, 55122 Mainz, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Bauß
authors.affiliation: Cell and Matrix Biology, Institute of Zoology, Focus Program Translational Neurosciences (FTN), Johannes Gutenberg University of Mainz, 55122 Mainz, Germany.
authors.forename: Barbara
authors.initials: B
authors.lastname: Knapp
authors.affiliation: Cell and Matrix Biology, Institute of Zoology, Focus Program Translational Neurosciences (FTN), Johannes Gutenberg University of Mainz, 55122 Mainz, Germany.
authors.forename: Pia
authors.initials: P
authors.lastname: Jores
authors.affiliation: Department of Human Genetics, Institute for Genetic and Metabolic Disease, Nijmegen Centre for Molecular Life Sciences and.
authors.forename: Ronald
authors.initials: R
authors.lastname: Roepman
authors.affiliation: Department of Human Genetics, Department of Otorhinolaryngology, Head and Neck Surgery, Nijmegen Centre for Molecular Life Sciences and Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen Medical Centre, 6500 HB, Nijmegen, Netherlands.
authors.forename: Hannie
authors.initials: H
authors.lastname: Kremer
authors.affiliation: Department of Human Genetics, Department of Otorhinolaryngology, Head and Neck Surgery, Nijmegen Centre for Molecular Life Sciences and Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen Medical Centre, 6500 HB, Nijmegen, Netherlands.
authors.forename: Erwin V
authors.initials: EV
authors.lastname: Wijk
authors.affiliation: Cell and Matrix Biology, Institute of Zoology, Focus Program Translational Neurosciences (FTN), Johannes Gutenberg University of Mainz, 55122 Mainz, Germany.
authors.forename: Tina
authors.initials: T
authors.lastname: Märker
authors.affiliation: Cell and Matrix Biology, Institute of Zoology, Focus Program Translational Neurosciences (FTN), Johannes Gutenberg University of Mainz, 55122 Mainz, Germany wolfrum@uni-mainz.de.
authors.forename: Uwe
authors.initials: U
authors.lastname: Wolfrum
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002966:Clathrin / Q000235:genetics / Q000378:metabolism; D004705:Endocytosis; D005786:Gene Expression Regulation; D051528:Guanylate Kinases; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism* / Q000473:pathology; D061251:Primary Cell Culture; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction; D052245:Usher Syndromes / Q000235:genetics* / Q000378:metabolism / Q000473:pathology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D002966:Clathrin; D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering; C477452:USH1G protein, human; D051528:Guanylate Kinases; C485777:MAGI2 protein, human