Quantitative phospho-proteomics to investigate the polo-like kinase 1-dependent phospho-proteome

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Polo-like kinase 1 (PLK1) is crucial for cell division and mitotic progression.
• PLK1 inhibitors are being investigated for cancer therapy.
• The full range of PLK1 substrates remains largely unknown.

Purpose of the Study:

• To conduct a proteome-wide identification of PLK1-regulated phosphorylation sites in mitotic human cells.
• To discover novel substrates and regulatory roles of PLK1.

Main Methods:

• Quantitative mass spectrometry was employed to compare phosphorylation sites in HeLa cells with and without PLK1 inhibitor (BI 4834) treatment.
• Peptide labeling, strong cation exchange chromatography, and immobilized metal affinity chromatography were used for sample preparation and enrichment.

Main Results:

• Identified 4070 unique mitotic phosphorylation sites on 2069 proteins.
• Discovered 401 proteins with phosphorylation sites whose abundance decreased upon PLK1 inhibition.
• Found novel PLK1 substrates involved in DNA damage, spindle formation, checkpoint signaling, and chromosome segregation.
• Identified two potential novel variants of the PLK1 consensus motif.

Conclusions:

• This study significantly expands the known landscape of PLK1 substrates.
• The findings provide new insights into PLK1's diverse roles in mitosis and potential therapeutic targets.
• The identified novel motifs may refine future studies on PLK1 substrate specificity.