A Large-Scale Quantitative Proteomic Approach To Identifying Sulfur Mustard-Induced Protein Phosphorylation Cascades

Sulfur mustard [SM, bis-(2-chloroethyl) sulfide] is a potent alkylating
agent and chemical weapon. While there are no effective treatments
for SM-induced injury, current research focuses on understanding the
molecular changes upon SM exposure. Indeed, efforts that seek a more
comprehensive analysis of proteins and post-translational modifications
are critical for understanding SM-induced toxicity on a more global
scale. Furthermore, these studies can uncover proteins previously
uncharacterized in SM-exposed cells, which in turn leads to potential
targets for therapeutic intervention. Here, we apply a quantitative
proteomic approach termed stable isotope-labeling with amino acids
in cell culture combined with immobilized metal affinity chromatography
to study the large-scale protein phosphorylation changes resulting
from SM exposure in a human keratinocyte cell culture model. This
resulted in the characterization of over 2300 nonredundant phosphorylation
sites, many of which exhibit altered levels in response to SM. Our
results point toward several proteins previously implicated in SM-induced
toxicity as well as many additional proteins previously uncharacterized.
Further de novo analysis of these phosphoproteins using interaction
mapping software revealed both known and novel pathways that may serve
as future therapeutic targets of SM exposure.