AP-1 in Toxoplasma gondii Mediates Biogenesis of the Rhoptry Secretory Organelle from a Post-Golgi Compartment

• Published in: The Journal of biological chemistry 2003-02, Vol.278 (7), p.5343-5352
• Main Authors: Ngo, H M, Yang, M, Paprotka, K, Pypaert, M, Hoppe, H, Joiner, KA
• Format: Article
• Language: English
• Subjects: Adaptor Protein Complex 1 - physiology; Amino Acid Sequence; Animals; Golgi Apparatus - physiology; Membrane Proteins - physiology; Molecular Sequence Data; Protein Transport - physiology; Protozoan Proteins - physiology; Secretory Vesicles - physiology; Secretory Vesicles - ultrastructure; Sequence Alignment; Toxoplasma - physiology; Toxoplasma - ultrastructure
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M208291200

We have previously demonstrated that Toxoplasma gondii has a tyrosine-based sorting system, which mediates protein targeting to the lysosome-like rhoptry secretory organelle. We now show that rhoptry protein targeting is also dependent on a dileucine motif and occurs from a post-Golgi endocytic organelle to mature rhoptries in an adaptin-dependent fashion. The T. gondii AP-1 adaptin complex is implicated in this transport because the μ1 chain of T. gondii AP-1 ( a ) was localized to multivesicular endosomes and the limiting and luminal membranes of the rhoptries; ( b ) bound to endocytic tyrosine motifs in rhoptry proteins, but not in proteins from dense granule secretory organelles; ( c ) when mutated in predicted tyrosine-binding motifs, led to accumulation of the rhoptry protein ROP2 in a post-Golgi multivesicular compartment; and ( d ) when depleted via antisense mRNA, resulted in accumulation of multivesicular endosomes and immature rhoptries. These are the first results to implicate AP-1 in transport from a post-Golgi compartment to a mature secretory organelle and substantially expand the role for AP-1 in anterograde protein transport.