ABSTRACT
Glycosylphosphatidylinositol (GPI)-anchored proteins comprise a diverse class of membrane molecules. They protect cells from complement-mediated lysis, control cell to cell adhesion, activate T cells, and play a role in the etiology of slow viral diseases. Despite their functional diversity, GPI-anchored proteins are all attached to the plasma membrane by a common glycolipid anchor. We will examine one aspect of GPI-anchor metabolism, namely, the processing of the molecule after it arrives at the plasma membrane. After biosynthesis and transport to the plasma membrane, the GPI-anchored protein can be endocytosed and degraded or cleaved and released. The enzymatic machinery controlling the catabolism of GPI-anchored molecules at the plasma membrane is likely to play a central role in regulating the cell surface expression of these molecules