title: Grb10/Nedd4-mediated multiubiquitination of the insulin-like growth factor receptor regulates receptor internalization.
abstract: The adaptor protein Grb10 is an interacting partner of the IGF-I receptor (IGF-IR) and the insulin receptor (IR). Previous work from our laboratory has established the role of Grb10 as a negative regulator of IGF-IR-dependent cell proliferation. We have shown that Grb10 binds the E3 ubiquitin ligase Nedd4 and promotes IGF-I-stimulated ubiquitination, internalization, and degradation of the IGF-IR, thereby giving rise to long-term attenuation of signaling. Recent biochemical evidence suggests that tyrosine-kinase receptors (RTK) may not be polyubiquitinated but monoubiquitinated at multiple sites (multiubiquitinated). However, the type of ubiquitination of the IGF-IR is still not defined. Here we show that the Grb10/Nedd4 complex upon ligand stimulation mediates multiubiquitination of the IGF-IR, which is required for receptor internalization. Moreover, Nedd4 by promoting IGF-IR ubiquitination and internalization contributes with Grb10 to negatively regulate IGF-IR-dependent cell proliferation. We also demonstrate that the IGF-IR is internalized through clathrin-dependent and-independent pathways. Grb10 and Nedd4 remain associated with the IGF-IR in early endosomes and caveosomes, where they may participate in sorting internalized receptors. Grb10 and Nedd4, unlike the IGF-IR, which is targeted for lysosomal degradation are not degraded and likely directed into recycling endosomes. These results indicate that Grb10 and Nedd4 play a critical role in mediating IGF-IR down-regulation by promoting ligand-dependent multiubiquitination of the IGF-IR, which is required for receptor internalization and regulates mitogenesis.
authors.affiliation: Department of Urology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
authors.forename: Giada
authors.initials: G
authors.lastname: Monami
authors.forename: Velia
authors.initials: V
authors.lastname: Emiliozzi
authors.forename: Andrea
authors.initials: A
authors.lastname: Morrione
mesh_terms: D000818:Animals; D051242:Caveolin 1 / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation; D002966:Clathrin / Q000235:genetics / Q000378:metabolism; D056827:Endosomal Sorting Complexes Required for Transport; D011992:Endosomes / Q000378:metabolism; D051383:GRB10 Adaptor Protein / Q000235:genetics / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism; D051379:Mice; D046912:Multiprotein Complexes / Q000378:metabolism; D000075702:Nedd4 Ubiquitin Protein Ligases; D025821:Polyubiquitin / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017526:Receptor, IGF Type 1 / Q000235:genetics / Q000378:metabolism*; D011972:Receptor, Insulin / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D051242:Caveolin 1; D002966:Clathrin; D056827:Endosomal Sorting Complexes Required for Transport; D046912:Multiprotein Complexes; D034741:RNA, Small Interfering; D033921:Vesicular Transport Proteins; C093846:early endosome antigen 1; D025821:Polyubiquitin; D051383:GRB10 Adaptor Protein; C000618479:NEDD4L protein, rat; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618484:Nedd4 protein, rat; C000618461:Nedd4l protein, mouse; D044767:Ubiquitin-Protein Ligases; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin