title: Nedd4 mediates ErbB4 JM-a/CYT-1 ICD ubiquitination and degradation in MDCK II cells.
abstract: ErbB4, a type I transmembrane receptor tyrosine kinase, is a member of the epidermal growth factor receptor family. Its cleavage releases an intracellular C-terminal domain (ICD), which can be either degraded following ubiqitination or translocated to the nucleus and regulate gene expression. There are 2 ErbB4 ICD isoforms: CYT-1 and CYT-2. We and others have previously reported that following cleavage, CYT-2 selectively translocates to the nucleus. In the current study we found that following cleavage, the intracellular levels of CYT-1 ICD decreased rapidly, while levels of CYT-2 ICD remained relatively stable. CYT-1 ICD degradation could be prevented by administration of either the proteasome inhibitor lactacystin or the lysosome inhibitor chloroquine, indicating both proteasomal and lysosomal degradation. Further studies implicated Nedd4, an E3 ubiquitin ligase, as a mediator of CYT-1 ubiquitination and degradation. The interaction of Nedd4 with CYT-1 was shown by coimmnunoprecipitation, an in vitro direct binding assay, and an in vitro ubiquitination assay. Three PPxY or PY motifs present in the CYT-1 C terminus are necessary for binding by Nedd4 WW domains, because impaired interactions are seen in mutation of any of the PY motifs. Nedd4-CYT-1 binding was associated with increased CYT-1 ubiquitination following proteasome inhibitor treatment. Impaired Nedd4 binding to CYT-1 by PY motif mutations led to increased CYT-1 ICD stability, whereas only one of the PY motif mutations (Y1056A), which disrupts the binding sites for both a WW domain and an SH2 domain of PI3 kinase, demonstrated enhanced nuclear translocation following HB-EGF treatment. These studies indicate that Nedd4 mediates ErbB4 CYT-1 ICD ubiquitination and degradation, and the prevention of both WW binding and PI3 kinase activity are required for ErbB4 nuclear translocation.
authors.affiliation: Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University, Nashville, TN 37232, USA.
authors.forename: Fenghua
authors.initials: F
authors.lastname: Zeng
authors.forename: Jie
authors.initials: J
authors.lastname: Xu
authors.forename: Raymond C
authors.initials: RC
authors.lastname: Harris
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D002478:Cells, Cultured; D004285:Dogs; D056827:Endosomal Sorting Complexes Required for Transport; D004791:Enzyme Inhibitors / Q000378:metabolism; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D000075702:Nedd4 Ubiquitin Protein Ligases; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D066247:Receptor, ErbB-4; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D056827:Endosomal Sorting Complexes Required for Transport; D004791:Enzyme Inhibitors; D061988:Proteasome Inhibitors; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D025801:Ubiquitin; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618483:Nedd4 protein, human; D044767:Ubiquitin-Protein Ligases; C587689:ERBB4 protein, human; D066246:ErbB Receptors; D066247:Receptor, ErbB-4; D046988:Proteasome Endopeptidase Complex; D013755:Tetradecanoylphorbol Acetate