期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2003
卷号：100
期号：11
页码：6505-6510
DOI：10.1073/pnas.1031790100
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Ligand activation of the epidermal growth factor receptor (EGFR) causes the binding of Cbls, which leads to EGFR polyubiquitination and internalization through endophilin complexes that contain the adaptor protein SH3-domain encoding, expressed in tumorigenic astrocytes/Cbl-interacting protein of 85 kDa/regulator of ubiquitous kinase (SETA/CIN85/Ruk). In cells grown at high density, high levels of SETA interfered in the recruitment of Casitas B-lineage (Cbl) proteins to the EGFR and reduced its polyubiquitination, suggesting that SETA has a regulatory function in the formation of the EGFR-Cbl-endophilin complex and in EGFR down-regulation. In a situation where there is EGFR signaling but no internalization or down-regulation, as is the case with the EGFR with exons 2-7 deleted ({Delta}EGFR) oncogene, these proteins were absent altogether. By using mAb 806, which recognizes an EGFR-activation state and preferentially immunoprecipitates {Delta}EGFR, we show that {Delta}EGFR did not interact with Cbls, SETA, or endophilin A1, providing a mechanistic explanation for its lack of internalization. As would be expected by the absence of Cbl proteins in the {Delta}EGFR complex, the mutant receptor was also not polyubiquitinated. The intracellular C terminus and tyrosine autophosphorylation pattern of {Delta}EGFR are similar to wild-type EGFR, but it signals at a lower intensity as determined by levels of EGFR phosphotyrosine. To test the implication that the lack of interaction with the Cbl-SETA-endophilin complex is because of differences in signal intensity, EGFR-expressing cells were treated with tyrphostin AG1478 EGFR inhibitor. Attenuation of wild-type EGFR signal to levels similar to that found in {Delta}EGFR resulted in the dissociation of SETA and Cbl proteins and a concomitant attenuation of receptor internalization.
