Phosphoproteomic Analyses of NRAS(G12) and NRAS(Q61) Mutant Melanocytes Reveal Increased CK2α Kinase Levels in NRAS(Q61) Mutant Cells

J Invest Dermatol. 2016 Oct;136(10):2041-2048. doi: 10.1016/j.jid.2016.05.098. Epub 2016 May 29.


In melanoma, mutant and thereby constantly active neuroblastoma rat sarcoma (NRAS) affects 15-20% of tumors, contributing to tumor initiation, growth, invasion, and metastasis. Recent therapeutic approaches aim to mimic RAS extinction by interfering with critical signaling pathways downstream of the mutant protein. This study investigates the phosphoproteome of primary human melanocytes bearing mutations in the two hot spots of NRAS, NRAS(G12) and NRAS(Q61). Stable isotope labeling by amino acids in cell culture followed by mass spectrometry identified 14,155 spectra of 3,371 unique phosphopeptides mapping to 1,159 proteins (false discovery rate < 2%). Data revealed pronounced PI3K/AKT signaling in NRAS(G12V) mutant cells and pronounced mitogen-activated protein kinase (MAPK) signaling in NRAS(Q61L) variants. Computer-based prediction models for kinases involved, revealed that CK2α is significantly overrepresented in primary human melanocytes bearing NRAS(Q61L) mutations. Similar differences were found in human NRAS(Q61) mutant melanoma cell lines that were also more sensitive to pharmacologic CK2α inhibition compared with NRAS(G12) mutant cells. Furthermore, CK2α levels were pronounced in patient samples of NRAS(Q61) mutant melanoma at the mRNA and protein level. The preclinical findings of this study reveal that codon 12 and 61 mutant NRAS cells have distinct signaling characteristics that could allow for the development of more effective, mutation-specific treatment modalities.

MeSH terms

  • Casein Kinase II / metabolism
  • GTP Phosphohydrolases / genetics*
  • Humans
  • Mass Spectrometry / methods
  • Melanocytes / metabolism*
  • Melanoma / genetics
  • Melanoma / pathology*
  • Membrane Proteins / genetics*
  • Mitogen-Activated Protein Kinases / metabolism
  • Mutation
  • Phosphatidylinositol 3-Kinase / metabolism
  • Phosphopeptides / metabolism
  • Proteomics / methods*
  • Proto-Oncogene Proteins c-akt / metabolism
  • RNA, Messenger / metabolism
  • Signal Transduction
  • Skin Neoplasms / genetics
  • Skin Neoplasms / pathology*


  • Membrane Proteins
  • Phosphopeptides
  • RNA, Messenger
  • Phosphatidylinositol 3-Kinase
  • CSNK2A1 protein, human
  • Casein Kinase II
  • Proto-Oncogene Proteins c-akt
  • Mitogen-Activated Protein Kinases
  • GTP Phosphohydrolases
  • NRAS protein, human