Comparative Analysis of Quantitative Mass Spectrometric Methods for Subcellular Proteomics

Area of Science:

• Proteomics
• Cell Biology
• Biochemistry

Background:

• Understanding protein intracellular location is crucial for elucidating protein function and organelle roles.
• Global cellular mapping integrates subcellular fractionation with quantitative mass spectrometry.
• Evaluating mass spectrometry techniques is essential for accurate proteome analysis.

Purpose of the Study:

• To assess various mass spectrometry approaches for quantitative proteomic analysis of subcellular fractions.
• To compare the performance of tandem mass tag (TMT) isobaric labeling (MS2 and MS3) and label-free methods (MS1 and data-independent acquisition - DIA).
• To determine the optimal method for high-coverage, accurate protein localization in cellular maps.

Main Methods:

• Rat liver subcellular fractions were generated using differential centrifugation and Nycodenz density gradients.
• Proteomic analysis employed TMT isobaric labeling with MS2 and MS3 reporter ion quantification.
• Label-free quantification utilized MS1 intensity-based and data-independent acquisition (DIA) approaches.
• Protein localization accuracy was assessed using a protein clustering approach with reference proteins.

Main Results:

• TMT-MS2 achieved the highest proteome coverage and lowest percentage of missing quantifiable data.
• Ratio compression in TMT-MS2 narrowed the accurate dynamic range compared to TMT-MS3, MS1, and DIA.
• All evaluated methods demonstrated good data quality for protein localization, with isobaric labeling yielding superior results.
• TMT-MS2 provided comparable protein localization accuracy to other methods despite dynamic range limitations.

Conclusions:

• TMT-MS2 is a valuable method for subcellular proteome mapping, offering extensive coverage and minimal missing values.
• While TMT-MS2 exhibits ratio compression, its performance in protein localization and data completeness is highly competitive.
• The study validates mass spectrometry-based approaches for generating comprehensive cellular maps through subcellular fractionation.