Sorting in the Prelysosomal Compartment (CURL)
Adsorptive endocytosis provides cells with a means of specifically internalizing exogenous substances (ligands). The specificity for each ligand’s delivery is conferred by the nature of the specific receptors on the recipient cell. The initial interaction between ligands and cells is initiated at the extracytoplasmic surface of the plasma membrane. One class of such interactions, receptor-mediated endocytosis (RME), defines a sequence of events that leads to the targeting of the internalized ligands to specific intracellular destinations. It is now well established that during RME clathrin-coated pits at the plasma membrane accumulate receptor-ligand complexes. These specialized structures then pinch off from the surface to form coated vesicles, which have a lifetime of only about 1 min (Petersen and van Deurs, 1983). The subsequent destination of each ligand and receptor then depends on the nature of the receptor system. In many systems ligands are transported to the lysosomes for degradation, whereas the receptors are spared this fate. These receptors are rerouted back to the plasma membrane via poorly understood mechanisms and pathways for subsequent endocytotic cycles. Examples of such receptor systems are those for asialoglycoproteins (Schwartz, 1984), lysosomal enzymes (Sly and Fischer, 1982), and low-density lypoproteins(Brown et al., 1983).
KeywordsLysosomal Enzyme Golgi Complex Bile Canaliculus Coated Vesicle Colloidal Gold Particle
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