TransGolgiNetzwerk

TransGolgiNetzwerk (Trans-Golgi Network, TGN) is a major sorting and dispatch station of the eukaryotic secretory pathway. Located at the trans face of the Golgi apparatus, the TGN receives cargo that has traversed earlier Golgi compartments and serves as the primary hub where proteins and lipids are sorted into distinct itineraries: lysosomal carriers, secretory granules, and plasma membrane or endosome-directed pathways. In addition to sorting, the TGN hosts enzymes that complete post-translational modifications and maturation steps necessary for correct function of secreted and membrane proteins.

Cargo recognition relies on adaptor protein complexes such as AP-1 and GGAs, along with clathrin and accessory factors. Sorting receptors, notably the mannose-6-phosphate receptor, direct lysosomal enzymes from the TGN to endosomes and lysosomes; other cargoes are packaged into constitutive secretory vesicles or regulated secretory granules. Budding vesicles depart the TGN and are targeted to endosomes, lysosomes, or the plasma membrane; SNAREs, Rab GTPases, and tethering factors coordinate vesicle docking and fusion.

Although the TGN is a central sorting station in most animal cells, its role varies among organisms. In plants, the TGN can also function as an early endosome; in yeast, the organization of the Golgi and TGN differs but a similar sorting function is maintained.

Disruption of TGN function can cause protein mis-sorting and disease, including lysosomal storage disorders when lysosomal enzymes fail to reach lysosomes.