The study of protein phosphorylation is critical for the advancement of our understanding of cellular responses to external and internal stimuli. Phosphorylation, the addition of phosphate groups, most often occurs on serine, threonine, or tyrosine residues due to the action of protein kinases. This structural change causes the protein to become activated (or deactivated) and enables it in turn to initiate the phosphorylation of other proteins in a cascade, eventually causing cell-wide changes such as apoptosis, cell differentiation, and growth (among others). Cellular phosphoprotein pathway dysregulation by mutation or chromosomal instability can often give the cell a selective advantage and lead to cancer. Obviously the understanding of these systems is of huge importance to the field of oncology.This chapter aims to provide a "how to" manual for one such technology, the 96-well plate-based xMAP® platform from Luminex. The system utilizes antibody-bound free-floating magnetic spheres which can easily be removed from suspension via magnetization. There are 100 unique bead sets (moving up to 500 bead sets for the most recent system) identified by the ratio of two dyes coating the microsphere. Each bead set is conjugated to a specific antibody which allows targeted protein extraction from low-concentration lysate solution. Biotinylated secondary antibodies/streptavidin-R-phycoerythrin (SAPE) complexes provide the quantification mechanism for the phosphoprotein of interest.
Keywords: Antibody; Luminex; Multiplex; Phosphoprotein; Suspension array.