The chlamydial inclusion membrane is extensively modified by the insertion of type III secreted effector proteins [1]. These inclusion membrane proteins (Incs) have two major characteristics: an N-terminal type III secretion signal that is necessary for their secretion out of the bacterium and a hydrophobic region consisting of at least two trans-membrane helices that allows insertion into the inclusion membrane. Generally, both the N- and C-terminal regions of the Inc are exposed to the host cell cytosol [2]. This family has members such as the IncE (also known as CT116) proteins found in Chlamydia trachomatis. IncE Interacts with Retromer-Associated Sorting Nexins (SNXs) directly binding the PX-domains of SNX5/6. It is expressed within the first 2 hours of C. trachomatis infection. IncE region 101-132 is the binding site for SNX5/6 causing re-localization of SNX5/6 from endosomes to the inclusion membrane. IncE101-132 expression was shown to be sufficient to maintain CI-MPR (Cation-Independent Mannose-6-Phosphate Receptor) in retromer-containing compartments, thereby disrupting efficient CI-MPR trafficking to the trans-Golgi. It has been suggested that SNX5/6 bind directly to IncE independently of phosphoinositides and that the predicted IncE C-terminal beta-hairpin is required. IncE-mediated sequestration of retromer SNX-BAR proteins may promote Golgi fragmentation, a process that facilitates lipid acquisition by C. trachomatis and enhances progeny production [3].

1: Role for chlamydial inclusion membrane proteins in inclusion membrane structure and biogenesis. Mital J, Miller NJ, Dorward DW, Dooley CA, Hackstadt T; PLoS One. 2013;8:e63426. PMID:23696825

2: Characterization of interactions between inclusion membrane proteins from Chlamydia trachomatis. Gauliard E, Ouellette SP, Rueden KJ, Ladant D; Front Cell Infect Microbiol. 2015;5:13. PMID:25717440

3: Global Mapping of the Inc-Human Interactome Reveals that Retromer Restricts Chlamydia Infection. Mirrashidi KM, Elwell CA, Verschueren E, Johnson JR, Frando A, Von Dollen J, Rosenberg O, Gulbahce N, Jang G, Johnson T, Jager S, Gopalakrishnan AM, Sherry J, Dunn JD, Olive A, Penn B, Shales M, Cox JS, Starnbach MN, Derre I, Valdivia R, Krogan NJ, Engel J; Cell Host Microbe. 2015;18:109-121. PMID:26118995