Over-accumulation of nuclear IGF-1 receptor in tumor cells requires elevated expression of the receptor and the SUMO-conjugating enzyme Ubc9.
Biochem Biophys Res Commun
; 404(2): 667-71, 2011 Jan 14.
Article
em En
| MEDLINE
| ID: mdl-21147068
ABSTRACT
The insulin-like growth factor 1 receptor (IGF-1R) plays crucial roles in tumor cell growth and is overexpressed in many cancers. IGF-1R's trans-membrane kinase signaling pathways have been well characterized. Very recently, we showed that SUMOylation mediates nuclear translocation of the IGF-1R, and that nuclear IGF-1R (nIGF-1R) binds to enhancer regions and activates transcription. We identified three lysine residues in the ß-subunit of the receptor and that mutation of these blocks nuclear translocation and gene activation. Furthermore, accumulation of nIGF-1R was proven strongly dependent on the specific SUMO-conjugating enzyme Ubc9. Here we show that nIGF-1R originates solely from the cell membrane and that phosphorylation of the core tyrosine residues of the receptor kinase is crucial for nuclear accumulation. We also compared the levels of nIGF-1R, measured as nuclear/membrane ratios, in tumor and normal cells. We found that the breast cancer cell line MCF-7 has 13-fold higher amounts of nIGF-1R than breast epithelial cells (IME) which showed only a small amount of nIGF-1R. In comparison, the total expression of IGF-1R was only 3.7- higher in MCF-7. Comparison of several other tumor and normal cell lines showed similar tumor cell over-accumulation of nIGF-1R, exceeding the total receptor expression substantially. Ectopic overexpression (>10-fold) of the receptor increased nIGF-1R in IME cells but not to that high level as in wild type MCF-7. The levels of Ubc9 were higher in all tumor cell lines, compared to the normal cells, and this probably contributes to over-accumulation of nIGF-1R. Over-accumulation of nIGF-1R may contribute to deregulated gene expression and therewith play a pathophysiological role in cancer cells.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Receptor IGF Tipo 1
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Enzimas de Conjugação de Ubiquitina
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Sumoilação
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Neoplasias
Tipo de estudo:
Prognostic_studies
Limite:
Humans
Idioma:
En
Revista:
Biochem Biophys Res Commun
Ano de publicação:
2011
Tipo de documento:
Article
País de afiliação:
Suécia