Quantitative proteomic analysis of compartmentalized signaling networks.

Ras proteins operate predominantly from the plasma membrane; however, they have also been localized to most intracellular compartments. Various functions and signaling outputs have been ascribed to endomembranous Ras although systematic comparison and measurement of potential outputs have not yet been carried out. We describe the methodology for isolating and measuring compartment-specific signaling networks using quantitative proteomics. This approach reveals the potential of a subcellular platform for supporting specific outputs and will inform subsequent studies of endogenous isoform-specific Ras signaling.