Figure 4

Schematic representation of GP82 and GP90 pathways toward the cell surface during differentiation. Intermediate forms in which these proteins start to be expressed are represented. GP90 (red squares) mRNAs sequences encode an N-terminal signal peptide and a C-terminal signal anchor driving polypeptide through the ER-Golgi secretory pathway (1-2) to be glycosylated and receive GPI anchor. GP90 proteins leave the Golgi complex in secretory vesicles that fuse with the flagellar pocket membrane (3) and are distributed along the parasite plasma membrane (4). GP82 (green triangles) mRNAs also encode N-terminal and C-terminal signal sequences that drive polypeptide through the ER-Golgi pathway (1-2) to receive post-translational modifications (glycosylation and GPI anchor). However, instead of being addressed straight to the plasma membrane via flagellar pocket, GP82 leave the Golgi complex in vesicles that concentrate in lysosome-related organelles (LROs) (3). Further in the differentiation process, sorting mechanisms occurring at LROs and organelle repositioning allow vesicles carrying GP82 to fuse with the flagellar pocket membrane (4) and distribute the protein along the plasma membrane (5). N: nucleus, K: kinetoplast.