Signal Transduction Reaction Monitoring Deciphers Site-Specific PI3K-mTOR/MAPK Pathway Dynamics in Oncogene-Induced Senescence

We report a straightforward strategy
to comprehensively monitor
signal transduction pathway dynamics in mammalian systems. Combining
targeted quantitative proteomics with highly selective phosphopeptide
enrichment, we monitor, with great sensitivity, phosphorylation dynamics
of the PI3K-mTOR and MAPK signaling networks. Our approach consists
of a single enrichment step followed by a single targeted proteomics
experiment, circumventing the need for labeling and immune purification
while enabling analysis of selected phosphorylation nodes throughout
signaling pathways. The need for such a comprehensive pathway analysis
is illustrated by highlighting previously uncharacterized phosphorylation
changes in oncogene-induced senescence, associated with diverse biological
phenotypes and pharmacological intervention of the PI3K-mTOR pathway.