Phosphoproteome profiling using a fluorescent phosphosensor dye in two-dimensional polyacrylamide gel electrophoresis

Area of Science:

• Biochemistry
• Proteomics
• Molecular Biology

Background:

• Protein phosphorylation is a critical post-translational modification regulating cellular processes.
• Sensitive and specific detection methods for phosphoproteins are essential for phosphoproteomics research.

Purpose of the Study:

• To validate the novel PhosphoQUANTI SolidBlue Complex (PQSC) dye for sensitive fluorescent detection of phosphorylated proteins.
• To assess the compatibility of PQSC staining with subsequent proteomic analyses, including mass spectrometry.

Main Methods:

• Polyacrylamide gel electrophoresis (PAGE) and two-dimensional gel electrophoresis (2DE) were employed.
• PQSC dye was used for sensitive fluorescent staining of phosphoproteins.
• Enzymatic dephosphorylation and phosphoprotein enrichment were performed to demonstrate specificity.
• Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF-MS) was used for protein identification.

Main Results:

• PQSC demonstrated sensitive detection limits for phosphorylated proteins (e.g., 15.6 ng of ß-casein).
• Fluorescence intensity correlated with the number of phosphorylated residues.
• PQSC staining signals were significantly reduced after enzymatic dephosphorylation, confirming specificity.
• Phosphoproteome analysis of Swiss 3T3 cells identified over 135 protein spots, with 15 identified by MALDI TOF-MS.

Conclusions:

• PQSC is a novel, sensitive, and specific fluorescent dye for detecting phosphoproteins in gel electrophoresis.
• The PQSC staining method is simple, reversible, and compatible with MALDI TOF-MS, facilitating downstream proteomic identification.