Analysis of Cellular Tyrosine Phosphorylation via Chemical Rescue of Conditionally Active Abl Kinase

Identifying
direct substrates targeted by protein kinases is important
in understanding cellular physiology and intracellular signal transduction.
Mass spectrometry-based quantitative proteomics provides a powerful
tool for comprehensively characterizing the downstream substrates
of protein kinases. This approach is efficiently applied to receptor
kinases that can be precisely, directly, and rapidly activated by
some agent, such as a growth factor. However, nonreceptor tyrosine
kinase Abl lacks the experimental advantage of extracellular
growth factors as immediate and direct stimuli. To circumvent this
limitation, we combine a chemical rescue approach with quantitative
phosphoproteomics to identify targets of Abl and their phosphorylation
sites with enhanced temporal resolution. Both known and novel putative
substrates are identified, presenting opportunities for studying unanticipated
functions of Abl under physiological and pathological conditions.