Summary of events in protein trafficking from the frans-Golgi network (TGN). The tubulovesicular array of the TGN serves as the sorting station for transporting vesicles that deliver proteins to four major locations in the cell. The constitutive secretory pathway to the basolateral plasma membrane (red arrows) uses clathrin-coated vesicles. The endosomal pathway (green arrows) is an organelle-specific protein delivery system. Another constitutive secretory pathway to the apical plasma membrane (purple arrows) also uses clathrin-coated vesicles. The regulated secretory pathway (orange arrows) directs protein to the apical region of the cell, where proteins are stored in large secretory vesicles. These vesicles eventually fuse with the plasma membrane and release the secretory product by exocytosis.
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