Label-Free Immunoprecipitation Mass Spectrometry Workflow for Large-scale Nuclear Interactome Profiling

Area of Science:

• Proteomics
• Molecular Biology
• Biochemistry

Background:

• Immunoaffinity purification mass spectrometry (IP-MS) is a powerful technique for identifying protein-protein interactions.
• Identifying low-abundance protein interactions, particularly within specific subcellular compartments like the nucleus, remains challenging.
• Understanding nuclear protein interactions is vital for deciphering complex cellular processes such as gene regulation.

Purpose of the Study:

• To present a comprehensive interaction proteomics workflow for identifying low-abundance protein-protein interactions from subcellular compartments, with a focus on the nucleus.
• To optimize existing IP-MS methods for enhanced sensitivity and specificity in detecting challenging protein interactions.
• To provide a detailed protocol applicable to various subcellular compartments and protein types.

Main Methods:

• The workflow integrates subcellular fractionation, immunoprecipitation, meticulous sample preparation, offline cleanup, and single-shot label-free mass spectrometry.
• It emphasizes the immunoprecipitation of endogenous proteins from fractionated subcellular compartments to enrich for low-abundance interactions.
• Downstream computational analysis and data visualization tools are employed for robust data interpretation and quality assessment.

Main Results:

• The developed protocol successfully identifies low-abundance, compartmentalized protein interactions, exemplified by the investigation of the nuclear interactome of DYRK1A.
• The workflow demonstrates improved detection of interactions that are difficult to identify from whole cell lysates.
• Guidelines for data quality evaluation are provided to differentiate true positives from nonspecific interactions.

Conclusions:

• This optimized IP-MS workflow significantly enhances the ability to identify low-abundance protein-protein interactions within specific subcellular compartments, particularly the nucleus.
• The presented methodology offers a robust and adaptable approach for interaction proteomics, advancing the study of nuclear protein networks.
• The findings contribute to a better understanding of protein functions and cellular mechanisms involving low-abundance nuclear proteins.