The Secretory Pathway in Eukaryotic Cells

651 WordsFeb 24, 20183 Pages
The secretory pathway in eukaryotic cells is responsible for biogenesis and proper intracellular distribution of a wide range of proteins, complex carbohydrates and lipids. Trafficking in the secretory pathway is highly dynamic and tightly regulated and the Golgi complex plays a crucial role in this trafficking. This central organelle has the critical function of merging and coordinating the secretory, endocytic and recycling protein transport pathways. The Golgi complex is highly dynamic organelle that receives, modifies and sorts scores of newly synthesised proteins from the ER. Nascent proteins from the ER are first received and collected into a transitional ER-Golgi intermediate compartment (ERGIC). Subsequently this material is transported through the cis- and medial Golgi cisternae to the trans-Golgi network (TGN), during which time many post-translational modifications occur. The proteins received at the TGN, are selectively sorted and packaged into distinct carrier vesicles that are destined either for the plasma membrane or endosomal compartments. However during this transit, many proteins are selectively retained in specific cisternal compartments or returned to the ER by active transport. The bidirectional membrane traffic between the ER and the Golgi occurs via similar mechanisms. In both cases, a carrier forms on the donor organelle and then tethers to and fuses with the target organelle. Distinct machineries facilitate the formation of carriers for the
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