Biotin labeling and quantitation of cell-surface proteins.

Cell surface receptors, such as transferrin receptors and MHC molecules, are internalized into the endocytic pathway and recycled to the plasma membrane. Previous assays used to measure endocytosis and recycling were cumbersome and often required radioactive reagents. This unit describes protocols that employ the combination of a cleavable biotin reagent to label surface molecules and a capture ELISA to detect these molecules allowing for rapid and safe quantitation of cell surface protein expression, endocytosis, and recycling.