Endocytosis without clathrin coats

Endocytosis is involved in an enormous variety of cellular processes. To da te, most studies on endocytosis in mammalian cells have focused on pathways that start with uptake through clathrin-coated pits. Recently, new techniq ues and reagents have allowed a wider range of endocytic pathways to begin to be characterized. Various non-clathrin endocytic mechanisms have been id entified, including uptake through caveolae, macropinosomes and via a separ ate constitutive pathway. Many markers for clathrin-independent endocytosis are found in detergent-resistant membrane fractions, or lipid rafts. We wi ll discuss these emerging new findings and their implications for the natur e of lipid rafts themselves, as well as for the potential roles of non-clat hrin endocytic pathways in remodeling of the plasma membrane and in regulat ing the membrane composition of specific intracellular organelles.