Polyubiquitination of insulin-like growth factor I receptor (IGF-IR) activation loop promotes antibody-induced receptor internalization and down-regulation.
J Biol Chem
; 286(48): 41852-41861, 2011 Dec 02.
Article
en En
| MEDLINE
| ID: mdl-21994939
ABSTRACT
Ubiquitination has been implicated in negatively regulating insulin-like growth factor I receptor (IGF-IR) activity. Because of the relative stability of IGF-IR in the presence of ligand stimulation, IGF-IR ubiquitination sites have yet to be mapped and characterized, thus preventing a direct demonstration of how the receptor ubiquitination contributes to downstream molecular cascades. We took advantage of an anti-IGF-IR antibody (h10H5) that induces more efficient receptor down-regulation to show that IGF-IR is promptly and robustly ubiquitinated. The ubiquitination sites were mapped to the two lysine residues in the IGF-IR activation loop (Lys-1138 and Lys-1141) and consisted of polyubiquitin chains formed through both Lys-48 and Lys-29 linkages. Mutation of these ubiquitinated lysine residues resulted in decreased h10H5-induced IGF-IR internalization and down-regulation as well as a reduced cellular response to h10H5 treatment. We have therefore demonstrated that IGF-IR ubiquitination contributes critically to the down-regulating and antiproliferative activity of h10H5. This finding is physiologically relevant because insulin-like growth factor I appears to mediate ubiquitination of the same major sites as h10H5 (albeit to a lesser extent), and ubiquitination is facilitated by pre-existing phosphorylation of the receptor in both cases. Furthermore, identification of a breast cancer cell line with a defect in IGF-IR ubiquitination suggests that this could be an important tumor resistance mechanism to evade down-regulation-mediated negative regulation of IGF-IR activity in cancer.
Texto completo:
1
Banco de datos:
MEDLINE
Asunto principal:
Regulación hacia Abajo
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Receptor IGF Tipo 1
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Anticuerpos Monoclonales de Origen Murino
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Recubrimiento Inmunológico
Tipo de estudio:
Prognostic_studies
Límite:
Animals
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Humans
Idioma:
En
Año:
2011
Tipo del documento:
Article