Eph receptor tyrosine kinases play a critical role in embryonic patterning and angiogenesis. In the adult, they are involved in carcinogenesis and pathological neovascularization. However, the mechanisms underlying their role in tumor formation and metastasis remain to be defined. Here, we demonstrated that stimulation of EphB1 with ephrinB1/Fc led to a marked downregulation of EphB1 protein, a process blocked by the lysosomal inhibitor bafilomycin. Following ephrinB1 stimulation, the ubiquitin ligase Cbl was recruited by EphB1 and then phosphorylated. Both Cbl phosphorylation and EphB1 ubiquitination were blocked by the Src inhibitor PP2. Overexpression of wild-type Cbl, but not of 70Z mutant lacking ligase activity, enhanced EphB1 ubiquitination and degradation. This negative regulation required the tyrosine kinase activity of EphB1 as kinase-dead EphB1-K652R was resistant to Cbl. Glutathione S-transferase binding experiments showed that Cbl bound to EphB1 through its tyrosine kinase-binding domain. In aggregate, we demonstrated that Cbl induces the ubiquitination and lysosomal degradation of activated EphB1, a process requiring EphB1 and Src kinase activity. To our knowledge, this is the first study dissecting the molecular mechanisms leading to EphB1 downregulation, thus paving the way to new means of modulating their angiogenic and tumorigenic properties.
We have not found any resources mentioned in this publication.
SciCrunch is a data sharing and display platform. Anyone can create a custom portal where they can select searchable subsets of hundreds of data sources, brand their web pages and create their community. SciCrunch will push data updates automatically to all portals on a weekly basis. User communities can also add their own data to SciCrunch, however this is not currently a free service.