title: Interactions between the three CIN85 SH3 domains and ubiquitin: implications for CIN85 ubiquitination.
abstract: CIN85 is an adaptor protein linking the ubiquitin ligase Cbl and clathrin-binding proteins in clathrin-mediated receptor endocytosis. The SH3 domains of CIN85 bind to a proline-rich region of Cbl. Here we show that all three SH3 domains of CIN85 bind to ubiquitin. We also present a data-based structural model of the CIN85 SH3-C domain in complex with ubiquitin. In this complex, ubiquitin binds to the canonical interaction surface of the SH3 domain for proline-rich ligands and mimics the PPII helix, and we provide evidence that ubiquitin competes with these ligands for binding. We demonstrate that disruption of ubiquitin binding results in constitutive ubiquitination of CIN85 and an increased level of ubiquitination of EGFR in the absence of EGF stimulation. These results suggest that competition between Cbl and ubiquitin binding to CIN85 regulates Cbl function and EGFR endocytosis.
authors.affiliation: Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, Canada M5S 1A8.
authors.forename: Irina
authors.initials: I
authors.lastname: Bezsonova
authors.forename: M Christine
authors.initials: MC
authors.lastname: Bruce
authors.forename: Silke
authors.initials: S
authors.lastname: Wiesner
authors.forename: Hong
authors.initials: H
authors.lastname: Lin
authors.forename: Daniela
authors.initials: D
authors.lastname: Rotin
authors.forename: Julie D
authors.initials: JD
authors.lastname: Forman-Kay
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D050721:Proto-Oncogene Proteins c-cbl / Q000737:chemistry / Q000378:metabolism; D025801:Ubiquitin / Q000737:chemistry / Q000378:metabolism*; D054875:Ubiquitination; D018909:src Homology Domains
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C433810:SH3KBP1 protein, human; D025801:Ubiquitin; D050721:Proto-Oncogene Proteins c-cbl