An integrated comparative phosphoproteomic and bioinformatic approach reveals a novel class of MPM-2 motifs upregulated in EGFRvIII-expressing glioblastoma cells.
Glioblastoma (GBM, WHO grade IV) is an aggressively proliferative and invasive brain tumor that carries a poor clinical prognosis with a median survival of 9 to 12 months. In a prior phosphoproteomic study performed in the U87MG glioblastoma cell line, we identified tyrosine phosphorylation events that are regulated as a result of titrating EGFRvIII, a constitutively active mutant of the epidermal growth factor receptor (EGFR) associated with poor prognosis in GBM patients. In the present study, we have used the phosphoserine/phosphothreonine-specific antibody MPM-2 (mitotic protein monoclonal #2) to quantify serine/threonine phosphorylation events in the same cell lines. By employing a bioinformatic tool to identify amino acid sequence motifs regulated in response to increasing oncogene levels, a set of previously undescribed MPM-2 epitope sequence motifs orthogonal to the canonical "pS/pT-P" motif was identified. These motifs contain acidic amino acids in combinations of the -5, -2, +1, +3, and +5 positions relative to the phosphorylated amino acid. Phosphopeptides containing these motifs are upregulated in cells expressing EGFRvIII, raising the possibility of a general role for a previously unrecognized acidophilic kinase (e.g. casein kinase II (CK2)) in cell proliferation downstream of EGFR signaling.
Joughin
Brian A
BA
The David H. Koch Institute for Integrative Cancer Research at MIT, Cambridge, MA, USA.
Naegle
Kristen M
KM
Huang
Paul H
PH
Yaffe
Michael B
MB
Lauffenburger
Douglas A
DA
White
Forest M
FM
D020816:Amino Acid Motifs; D000906:Antibodies / Q000276:immunology*; D000918:Antibody Specificity; D000941:Antigens / Q000737:chemistry / Q000276:immunology; D045744:Cell Line, Tumor; D019295:Computational Biology; D066246:ErbB Receptors / Q000378:metabolism*; D005909:Glioblastoma / Q000276:immunology* / Q000378:metabolism*; D006801:Humans; D010750:Phosphoproteins / Q000032:analysis* / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D015854:Up-Regulation
D000906:Antibodies; D000941:Antigens; D010750:Phosphoproteins; C410723:epidermal growth factor receptor VIII; D066246:ErbB Receptors