Systematic analysis of protein pools, isoforms, and modifications affecting turnover and subcellular localization

Area of Science:

• Proteomics
• Molecular and Cellular Biology
• Genomics

Background:

• Many genes in higher eukaryotes produce protein isoforms with poorly understood functions.
• Characterizing these isoforms is crucial for understanding cellular processes and disease.

Purpose of the Study:

• To develop and validate systematic approaches for detecting protein isoforms with differential biological properties.
• To analyze proteome dynamics, including abundance, turnover, and subcellular distribution.

Main Methods:

• Utilized stable isotope labeling with amino acids in cell culture (SILAC) for quantitative proteomic analysis.
• Developed three data analysis strategies (candidate, rule of thirds, three in a row) to identify protein isoforms based on SILAC ratios.
• Employed SDS-PAGE fractionation and mass spectrometry (MS) for isoform detection and property evaluation.
• Analyzed the impact of protein phosphorylation on turnover rates.

Main Results:

• Successfully detected protein isoforms using the developed analytical strategies.
• Quantified protein abundance, turnover rates, and subcellular localization in HeLa cells.
• Demonstrated that protein phosphorylation influences protein turnover rates.

Conclusions:

• The presented experimental and analytical framework enables robust detection and characterization of protein isoforms.
• This approach facilitates the expansion of functional genome annotation by elucidating isoform-specific roles.