How GPI-anchored proteins turnover: or where do they go after arrival at the plasma membrane.

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. In this review we will examine how the GPI anchor is metabolized after arrival at the cell membrane. The conclusion is that break-down of the GPI anchor is potentially as diverse as the proteins themselves. The GPI-anchored protein can be endocytosed and degraded, cleaved and released, vesiculated, or exchanged onto another cell. The chimeric nature--lipid and protein--of the GPI-anchored molecules affords a unique window into the dynamic processes of lipid biosynthesis, movement, transport and maintenance.