Multiplexed Phosphoproteomic Profiling Using Titanium Dioxide and Immunoaffinity Enrichments Reveals Complementary...

Area of Science:

• Cell Biology
• Proteomics
• Biochemistry

Background:

• Understanding protein phosphorylation is vital for cell biology.
• Mass spectrometry-based proteomics offers a powerful approach to study phosphorylation.
• The full scope of the phosphoproteome remains incompletely understood.

Purpose of the Study:

• To evaluate the complementarity of titanium dioxide (TiO2) enrichment and phosphorylation motif-specific immunoaffinity precipitation (IAP) for phosphopeptide enrichment.
• To assess the coverage and characteristics of phosphoproteomes obtained by these distinct enrichment strategies.

Main Methods:

• Phosphopeptide enrichment using titanium dioxide (TiO2) chromatography.
• Phosphopeptide enrichment using immunoaffinity precipitation (IAP) with four different antibodies.
• Mass spectrometry-based proteomics for phosphopeptide identification and quantification.

Main Results:

• Both TiO2 and IAP methods identified approximately 2000 phosphoproteins each.
• TiO2 enrichment identified over 10,000 unique phosphorylation sites, while IAP identified over 3900 sites, with less than 5% overlap.
• Distinct phosphorylation site ratios (pS:pT:pY) were observed: ~90:10:<1 for TiO2 and 51:29:20 for IAP.

Conclusions:

• TiO2 and IAP enrichment methods capture distinct populations of phosphopeptides.
• The observed differences highlight the complementarity of these enrichment strategies.
• Utilizing multiple enrichment methods is essential for a comprehensive analysis of the phosphoproteome.