MARQUIS: a multiplex method for absolute quantification of peptides and posttranslational modifications

Area of Science:

• Proteomics
• Mass Spectrometry
• Signal Transduction

Background:

• Absolute quantification of protein expression and post-translational modifications (PTMs) like phosphorylation is challenging.
• The large dynamic range of phosphorylation response complicates accurate measurement.

Purpose of the Study:

• To develop a novel mass spectrometry-based approach for absolute quantification of protein phosphorylation.
• To enable quantitative comparison of phosphorylation dynamics in signaling networks.

Main Methods:

• Developed MARQUIS (Multiplex Absolute Regressed Quantification with Internal Standards).
• Utilized isobaric tags and heavy-labeled standard peptides to create internal standard curves.
• Applied to quantify phosphorylation dynamics in the EGFR network and patient-derived xenografts.

Main Results:

• MARQUIS enabled absolute quantification of phosphorylation dynamics in the EGFR network.
• Demonstrated qualitatively similar but quantitatively distinct EGFR phosphorylation for different ligands.
• Quantified the effect of EGFR kinase inhibition on glioblastoma xenografts.

Conclusions:

• MARQUIS is a versatile and broadly applicable method for absolute protein quantification.
• The method is extendable to multiple mass spectrometry platforms.
• Enables precise measurement of phosphorylation dynamics in complex biological systems.