Fig. 1

Autophagy and endocytic pathways can culminate in lysosomes. Endocytosis enables the transport of substances from the external environment and includes the clathrin-dependent pathway as well as clathrin-independent pathways such as phagocytosis. Phagocytosis is the endocytosis of large molecules or intact microorganisms. Protrusions of plasma membrane surround and internalize the extracellular cargo into single-membrane structures called phagosomes, which are then transported to the lysosome for degradation. Endocytosis (clathrin-mediated endocytosis is shown here) involves invagination of the plasma membrane and biogenesis of small intracellular vesicles that contain constituents of the plasma membrane and extracellular components. These small vesicles fuse and establish the compartment called the early endosome (EE). EE cargo can be recycled to the plasma membrane via recycling endosomes, transported to or from the Golgi apparatus via the retromer complex, or routed to lysosomes via multivesicular bodies (MVBs). During macroautophagy, double-membrane structures called autophagosomes are formed to deliver autophagic cargo to lysosomes or to fuse with MVBs. Autophagy and endocytic pathways cooperate at some stages and share many components of the molecular machinery