Phosphoproteomic Characterization of Signaling Networks Resulting from Activation of Chemokine Receptor CCR2

Leukocyte recruitment, a universal feature of tissue inflammation, is regulated by the interactions of chemokines with their G protein-coupled receptors. Activation of CC chemokine receptor 2 (CCR2) by its cognate chemokine ligands, including CCL2, plays a central role in recruitment of monocytes in several inflammatory diseases. In this study, we used phosphoproteomics to enable unbiased characterization of the signaling network resulting from CCL2 activation of CCR2. Using data-independent acquisition (DIA) mass spectrometry, both the proteome and phosphoproteome were quantified for FlpIn-HEK293T cells stably expressing CCR2, at six time points after activation with CCL2, in comparison with untreated cells. Differential expression analysis identified 699 significantly regulated phosphorylation sites located on 441 proteins. As expected, many of these proteins participate in canonical signal transduction pathways and the regulation of actin cytoskeleton dynamics, including numerous guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs). In addition, we identified regulated phosphorylation sites in numerous proteins that exert functions in the nucleus, including several constituents of the nuclear pore complex. This study provides an unprecedented level of detail about CCR2 signalling and identifies potential novel targets for regulation of CCR2 function.