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WW domain HECT E3s target Cbl RING finger E3s for proteasomal degradation
Alessandra Magnifico1, Seth Ettenberg, Cuihong Yang
1Regulation of Protein Function Laboratory, Center for Cancer Research, NCI-Frederick, Frederick, MD 21702, USA.
The Journal of Biological Chemistry
|August 9, 2003
Summary
WW domain HECT E3 ubiquitin ligases, Nedd4 and Itch, degrade Cbl proteins, impacting tyrosine kinase regulation. This reveals a new regulatory pathway for Cbl substrates, including growth factor receptors and Src kinases.
Area of Science:
- Molecular and Cellular Biology
- Biochemistry
- Signal Transduction
Background:
- Cbl proteins are RING finger E3 ubiquitin ligases crucial for down-regulating tyrosine kinases.
- The precise regulation of Cbl protein activity and stability is essential for cellular signaling pathways.
Purpose of the Study:
- To investigate the role of WW domain HECT E3 ubiquitin ligases in the regulation of Cbl proteins.
- To determine if Nedd4 and Itch can target Cbl proteins for degradation and elucidate the mechanism.
Main Methods:
- Co-immunoprecipitation assays to detect protein interactions.
- Western blotting to assess protein levels and ubiquitylation status.
- Cell-based assays using epidermal growth factor receptor (EGFR) and Src kinase signaling models.
Main Results:
- Nedd4 and Itch directly bind to Cbl proteins and mediate their proteasomal degradation.
- This degradation is dependent on the HECT E3 ligase activity of Nedd4/Itch, not on Cbl's own E3 activity.
- Nedd4 antagonizes Cbl-b-mediated down-regulation and ubiquitylation of EGFR and reverses Cbl-mediated degradation of active Src kinase.
Conclusions:
- WW domain HECT E3s (Nedd4, Itch) act as negative regulators of Cbl proteins, targeting them for degradation.
- This finding introduces a novel regulatory mechanism where HECT E3s ubiquitylate RING finger E3s, impacting signaling pathways involving tyrosine kinases.
- This adds a new layer of control to Cbl substrate regulation, affecting receptor tyrosine kinases and non-receptor tyrosine kinases like Src.