title: Cbl-c ubiquitin ligase activity is increased via the interaction of its RING finger domain with a LIM domain of the paxillin homolog, Hic 5.
abstract: Cbl proteins (Cbl, Cbl-b and Cbl-c) are ubiquitin ligases that are critical regulators of tyrosine kinase signaling. In this study we identify a new Cbl-c interacting protein, Hydrogen peroxide Induced Construct 5 (Hic-5). The two proteins interact through a novel interaction mediated by the RING finger of Cbl-c and the LIM2 domain of Hic-5. Further, this interaction is mediated and dependent on specific zinc coordinating complexes within the RING finger and LIM domain. Binding of Hic-5 to Cbl-c leads to an increase in the ubiquitin ligase activity of Cbl-c once Cbl-c has been activated by Src phosphorylation or through an activating phosphomimetic mutation. In addition, co-transfection of Hic-5 with Cbl-c leads to an increase in Cbl-c mediated ubiquitination of the EGFR. These data suggest that Hic-5 enhances Cbl-c ubiquitin ligase activity once Cbl-c has been phosphorylated and activated. Interactions between heterologous RING fingers have been shown to activate E3s. This is the first demonstration of enhancement of ubiquitin ligase activity of a RING finger ubiquitin ligase by the direct interaction of a LIM zinc coordinating domain.
authors.affiliation: Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Philip E
authors.initials: PE
authors.lastname: Ryan
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Kales
authors.forename: Rajgopal
authors.initials: R
authors.lastname: Yadavalli
authors.forename: Marion M
authors.initials: MM
authors.lastname: Nau
authors.forename: Han
authors.initials: H
authors.lastname: Zhang
authors.forename: Stanley
authors.initials: S
authors.lastname: Lipkowitz
mesh_terms: D002460:Cell Line; D066246:ErbB Receptors / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D060588:LIM Domain Proteins / Q000378:metabolism*; D054730:Protein Interaction Domains and Motifs; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D050721:Proto-Oncogene Proteins c-cbl / Q000378:metabolism* / Q000502:physiology; D054829:RING Finger Domains; D020798:Two-Hybrid System Techniques; D054875:Ubiquitination
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D060588:LIM Domain Proteins; C490351:TGFB1I1 protein, human; D050721:Proto-Oncogene Proteins c-cbl; C512478:EGFR protein, human; D066246:ErbB Receptors