Paumet Research

Actin and microtubules are important cytoskeletal elements in eukaryotic cells. The cytoskeleton controls many cellular processes, including cell division and motility, as well as vesicle and organelle trafficking. Inside its host cell, C. trachomatis rearranges the cytoskeleton to promote its survival and enhance its pathogenicity. In particular, C. trachomatis induces the rearrangement of both actin and microtubules, which is vital for its entry, inclusion development, maintenance of the inclusion structure, and its exit from its host cell. In this context, our laboratory seeks to understand the bacterial molecular machinery that co-opts the host cytoskeleton and coordinates the reorganization of actin and microtubules. Notably, we found that the chlamydial protein CT813/InaC controls both MT stabilization and actin polymerization around the inclusion by co-opting host small GTPases. We now seek to 1) identify any additional inclusion proteins involved in these processes, 2) determine how such a molecular platform efficiently coordinates the formation of the different scaffolds, and 3) assess the impact of these inclusion proteins on C. trachomatis development and pathogenesis.

As an obligate intracellular bacterium, C. trachomatis replicates in an intracellular inclusion. When several bacteria infect the same cell, each develops in its own inclusion. Ultimately, all these inclusions undergo homotypic fusion ~15 hours post-infection. This homotypic fusion event is critical for C. trachomatis pathogenicity as natural non-fusing Chlamydia mutants have replication defects, grow more slowly than their wild-type counterparts, and cause significantly milder symptoms in humans. Recent work in our laboratory has characterized the inclusion membrane protein IncA, which is essential for membrane fusion. Furthermore, we recently discovered that inclusions form inclusion contact sites (ICSs), where specific inclusion proteins and lipids cluster. In this project, we seek to 1) identify additional lipid and protein elements that concentrate in the ICSs, 2) determine the involvement of these ICS elements in homotypic fusion, and 3) reconstitute IncA-mediated fusion in vitro in order to characterize how the various regulatory elements influence this event. Finally, we will 4) assess the role of IncA-mediated fusion in an animal model and characterize its impact on disease development.