C. trachomatis L2 inclusion proteome

Chlamydia trachomatis is an important human pathogen that replicates inside the infected host cell in a unique vacuole, the inclusion. The formation of this intracellular bacterial niche is essential for productive Chlamydia infections. Despite its importance for Chlamydia biology, a holistic view on the protein composition of the inclusion, including its membrane, is currently missing. Here we describe a newly established method to purify inclusions from C. trachomatis infected epithelial cells and the analysis of the host cell-derived proteome by a combination of label free and stable isotope labeling -based quantitative proteomics. Computational analysis of the proteome data indicated that the inclusion is a complex intracellular trafficking platform that interacts with host cells' antero- and retrograde trafficking pathways. Furthermore, the inclusion is highly enriched for sorting nexins of the SNX-BAR retromer, a complex essential for retrograde trafficking. Functional studies showed that in particular SNX5 controls the C. trachomatis infection and that retrograde trafficking is essential for infectious progeny formation. In summary, our findings suggest that the inclusion of C. trachomatis is well embedded in the hosts' endomembrane system and hijacks retrograde trafficking pathways for effective infection.