Large-scale characterization of HeLa cell nuclear phosphoproteins

TLDR

Determining phosphorylation sites is essential for understanding kinase–substrate relationships and signaling pathways, yet large‑scale identification remains unsolved. The study applies existing technology to isolate and identify phosphorylation sites. Phosphopeptides were enriched from HeLa nuclear lysate via strong cation exchange chromatography and identified by tandem MS. The study identified 2,002 phosphorylation sites across 967 proteins, enabling a comprehensive analysis of kinase motifs and substrates.

Abstract

Determining the site of a regulatory phosphorylation event is often essential for elucidating specific kinase–substrate relationships, providing a handle for understanding essential signaling pathways and ultimately allowing insights into numerous disease pathologies. Despite intense research efforts to elucidate mechanisms of protein phosphorylation regulation, efficient, large-scale identification and characterization of phosphorylation sites remains an unsolved problem. In this report we describe an application of existing technology for the isolation and identification of phosphorylation sites. By using a strategy based on strong cation exchange chromatography, phosphopeptides were enriched from the nuclear fraction of HeLa cell lysate. From 967 proteins, 2,002 phosphorylation sites were determined by tandem MS. This unprecedented large collection of sites permitted a detailed accounting of known and unknown kinase motifs and substrates.