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Novel mechanism of Sprouty2-mediated inhibition of EGFR downregulation
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm , Ludwig Institute for Cancer Research.
(English)Manuscript (Other academic)
URN: urn:nbn:se:uu:diva-91756OAI: oai:DiVA.org:uu-91756DiVA: diva2:164589
Available from: 2004-04-23 Created: 2004-04-23 Last updated: 2011-03-02Bibliographically approved
In thesis
1. Ubiquitination and Receptor Endocytosis
Open this publication in new window or tab >>Ubiquitination and Receptor Endocytosis
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Protein ubiquitination is an evolutionary conserved mechanism that controls a wide variety of cellular functions. Polyubiquitinated proteins are generally degraded in the proteasome, whereas monoubiquitination controls various other cellular processes, including endocytosis and endosomal sorting.

Termination of signaling by activated receptor tyrosine kinases (RTKs) largely occurs via their endocytosis and subsequent lysosomal degradation, processes accompanied by receptor ubiquitination. Cbl family proteins are major ubiquitin ligases that promote RTK ubiquitination and downregulation. We showed that epidermal growth factor (EGF) and platelet derived growth factor (PDGF) receptors are monoubiquitinated at multiple sites following their ligand-induced activation and that a single ubiquitin is sufficient for both receptor internalization and degradation. Cbl also controls EGF receptor (EGFR) downregulation by binding to CIN85, which recruits endophilins to EGFR/Cbl complexes. In the complex with activated EGFRs, Cbl directs monoubiquitination of CIN85, and the entire complex is targeted for degradation in the lysosome. We propose that multiple monoubiquitination of activated receptors and associated protein complexes ensures proper receptor sorting towards the lysosome. Importantly, the functions of Cbl are also negatively controlled in order to maintain cellular homestasis. Sprouty2 blocks EGFR downregulation by sequestering Cbl from activated EGFRs. We showed that Sprouty2 also associates with CIN85 and that this binding is required for efficient inhibition of EGFR ubiquitination and endocytosis.

Cbl is also implicated in other aspects of RTK signaling, including organization of the actin cytoskeleton. We found that growth factor receptor signals promote lamellipodia formation in neuronal cells via a complex containing Cbl, the adaptor protein ArgBP2 and Pyk2. The lamellipodia formation required intact lipid rafts and the recruitment of Crk and PI(3)K to tyrosine phosphorylated Cbl.

In conclusion, our findings contribute to a better understanding of monoubiquitin signals in downregulation of RTKs and point at a role of Cbl in the regulation of cytoskeleton dynamics.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 79 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 0282-7476 ; 1351
Cell and molecular biology, Ubiquitination, receptor tyrosine kinase, endocytosis, Cbl, CIN85, EGFR, Cell- och molekylärbiologi
National Category
Biochemistry and Molecular Biology
urn:nbn:se:uu:diva-4259 (URN)91-554-5965-X (ISBN)
Public defence
2004-05-14, B22, Biomedical Center (BMC), Husargatan 3, Uppsala, 13:15
Available from: 2004-04-23 Created: 2004-04-23Bibliographically approved

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