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J Proteome Res. 2015 Sep 4;14(9):3882-3891. doi: 10.1021/acs.jproteome.5b00302. Epub 2015 Aug 20.

Activating Mutations in PIK3CA Lead to Widespread Modulation of the Tyrosine Phosphoproteome.

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McKusick-Nathans Institute of Genetic Medicine and Department of Biological Chemistry, Johns Hopkins University School of Medicine, 733 North Broadway Street, Baltimore, Maryland 21205, United States.
The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins University School of Medicine, 401 North Broadway Street, Baltimore, Maryland 21231, United States.
Institute of Bioinformatics, International Tech Park, Bangalore, 560066 India.
College of Arts and Sciences, University of Delaware, 4 Kent Way, Newark, Delaware 19716, United States.
Departments of Oncology and Pathology, Johns Hopkins University School of Medicine, 401 North Broadway Street, Baltimore, Maryland 21231, United States.
Contributed equally


The human oncogene PIK3CA is frequently mutated in human cancers. Two hotspot mutations in PIK3CA, E545K and H1047R, have been shown to regulate widespread signaling events downstream of AKT, leading to increased cell proliferation, growth, survival, and motility. We used quantitative mass spectrometry to profile the global phosphotyrosine proteome of isogenic knock-in cell lines containing these activating mutations, where we identified 824 unique phosphopeptides. Although it is well understood that these mutations result in hyperactivation of the serine/threonine kinase AKT, we found a surprisingly widespread modulation of tyrosine phosphorylation levels of proteins in the mutant cells. In the tyrosine kinome alone, 29 tyrosine kinases were altered in their phosphorylation status. Many of the regulated phosphosites that we identified were located in the kinase domain or the canonical activation sites, indicating that these kinases and their downstream signaling pathways were activated. Our study demonstrates that there is frequent and unexpected cross-talk that occurs between tyrosine signaling pathways and serine/threonine signaling pathways activated by the canonical PI3K-AKT axis.

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