The emergence of clathrin-independent pinocytic pathways.

Receptor-mediated endocytosis via clathrin-coated vesicles is by far the best characterized example of pinocytosis. It has been suggested that clathrin-coated vesicles mediate all pinocytosis in mammalian cells. This is still a matter of debate, however, and recent results provide strong evidence for 'clathrin-independent' pinocytic pathways. The selective regulation of these alternate endocytic pathways and the identification of receptors targeted to them provide new tools for the functional and mechanistic characterization of clathrin-independent pinocytosis.