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Phosphorylation of Crk at Tyrosine 251 in the RT loop of the SH3C domain downstream of EGFR: Novel Role in Abl Transactivation
Author(s) -
Sriram Ganapathy,
Reichman Charles,
Machida Kazuya,
Mayer Bruce,
Kalodimos Charalampos,
Birge Raymond B
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.563.9
The Crk family of adaptor proteins composed of tandem SH2 and SH3 domains regulate key cellular processes including cell migration and phagocytosis. CrkI and CrkII over‐expression has been associated with several human cancers with roles in promoting cell invasion and migration. Abl is known to be activated downstream of EGFR by a hitherto unkown mechanism and has been recently reported to be activated in several breast cancer cell lines contributing to enhanced cell migration. We have identified Y251 in the RT‐loop of the human CrkII SH3C domain as a novel phosphorylation site. Phosphopeptides corresponding to this motif bind to the Abl SH2 and activate Abl 1b in vitro . A hCrkII Y251F mutant significantly abrogates transactivation of Abl 1b in vitro and in vivo . Also, hCrkII fails to transactivate the Abl SH2 domain mutant, R171L. Our results suggest that the phosphotyrosine motif pY251 in the hCrkII SH3C promotes transactivation of Abl 1b by SH2 domain displacement. Interestingly, phosphorylation at Y251 is induced by EGF treatment of human breast‐cancer derived MDA‐MB‐468 cells (which overexpress EGFR) in an imatinib‐insensitive manner suggesting that pY251 on hCrkII maybe a mediator of Abl activation downstream of EGFR. Further, SH2 domain profiling reveals several potential binding partners of pY251. Therefore, our study identifies Y251 as a phosphorylation site in the hCrkII SH3C with a role in Abl transactivation thereby suggesting a mechanism for Abl activation downstream of EGFR and also reveals potential novel modes of signal transduction by hCrkII. This research was supported by the National Institutes of Health (USA).