title: Isoform-specific monoubiquitination, endocytosis, and degradation of alternatively spliced ErbB4 isoforms.
abstract: Endocytosis and subsequent lysosomal degradation serve as a well characterized mechanism to fine-tune and down-regulate EGFR signaling. However, other members of the EGFR/ErbB receptor family have been reported to be endocytosis-impaired. Here we demonstrate that endocytosis of ErbB4 is regulated in an isoform-specific manner: CYT-1 isoforms were efficiently endocytosed whereas CYT-2 isoforms were endocytosis-impaired. CYT-1 isoforms in endocytic vesicles colocalized with Rab5 and Rab7 indicating trafficking via early endosomes to late endosomal/lysosomal structures. A PPXY motif within the CYT-1-specific sequence that lacks from CYT-2 was necessary both for ubiquitination and endocytosis of CYT-1 isoforms and provided a binding site for a WW domain-containing ubiquitin ligase Itch. Itch catalyzed ubiquitination of ErbB4 CYT-1, promoted its localization into intracellular vesicles, and stimulated degradation of ErbB4 CYT-1. Dominant negative Itch suppressed ErbB4 CYT-1 endocytosis and degradation. These data indicate that ErbB4 isoforms differ in endocytosis and degradation by a mechanism mediated by CYT-1-specific PPXY motif interacting with a WW domain-containing E3 ubiquitin ligase.
authors.affiliation: MediCity Research Laboratory and Department of Medical Biochemistry and Molecular Biology, University of Turku, FIN-20520 Turku, Finland.
authors.forename: Maria
authors.initials: M
authors.lastname: Sundvall
authors.forename: Anna
authors.initials: A
authors.lastname: Korhonen
authors.forename: Ilkka
authors.initials: I
authors.lastname: Paatero
authors.forename: Eugenio
authors.initials: E
authors.lastname: Gaudio
authors.forename: Gerry
authors.initials: G
authors.lastname: Melino
authors.forename: Carlo M
authors.initials: CM
authors.lastname: Croce
authors.forename: Rami I
authors.initials: RI
authors.lastname: Aqeilan
authors.forename: Klaus
authors.initials: K
authors.lastname: Elenius
mesh_terms: D017398:Alternative Splicing / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D066246:ErbB Receptors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D066247:Receptor, ErbB-4; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D054875:Ubiquitination
chemical_list: D007527:Isoenzymes; D044767:Ubiquitin-Protein Ligases; C587689:ERBB4 protein, human; D066246:ErbB Receptors; C587690:Erbb4 protein, mouse; D066247:Receptor, ErbB-4