Moving Closer to the Lipid Raft Proteome Using Quantitative Proteomics

Lipid rafts are small subdomains of the plasma membrane enriched in cholesterol, sphingolipids, saturated phospholipids and specific proteins. They are thought to act as coordination centres for signal transduction pathways so their protein composition is of particular biological interest. Rafts are refractory to solubilization in non-ionic detergents so they can be biochemically enriched by floatation on a sucrose density gradient but several other membranes co-migrate with rafts in such a procedure. Qualitative proteomic analysis of such detergent-resistant membranes fails to distinguish true raft proteins from co-migrating contaminants. This chapter describes a quantitative proteomic application of Stable Isotope Labelling by Amino acids in Cell culture (SILAC) for distinguishing true raft proteins in detergent-resistant preparations.