Paumet Research

Contact

Professor

233 10th street
750 BLSB
Philadelphia, PA 19107

215-503-8567

Research in our laboratory focuses on host-pathogen interactions. In particular, we study the pathogenesis of Chlamydia trachomatis, which is the most frequently reported bacterial sexually transmitted disease, and the leading cause of infectious blindness worldwide. Chlamydia is particularly difficult to study, in part, due to its intracellular lifestyle. While non-intracellular bacteria can be naturally destroyed by the immune system, intracellular bacteria hide inside human cells to escape immune defenses. To achieve this, Chlamydia manipulates host cells to create an intracellular niche, the so-called inclusion, in which it can multiply. Chlamydia constitutes an outstanding model to study host-pathogen interaction as it manipulates a large number of cellular pathways to support its intracellular development. Among these pathways, Chlamydia drastically reorganizes the cytoskeleton to provide scaffolds for its inclusion. Additionally, Chlamydia co-opts cellular vesicular trafficking to acquire lipids and nutrients. Finally, this bacterium is particularly attractive to study as it also induces novel membrane fusion events using bacterial proteins.

Our laboratory uses a multidisciplinary approach to understand mechanisms at the molecular level. We combine crystallographic analysis with a variety of sophisticated biochemical and cellular functional assays to understand how chlamydial proteins interfere with their host partners. Additionally, we now have the resources to mutagenize Chlamydia to create knock-outs, knock-ins, and mutants. Ultimately, this strategy will open new avenues of research for other intracellular bacteria including Salmonella and Mycobacterium, which also manipulate their host cells to their advantage.

Research Projects

Determine how Chlamydia manipulates the host cytoskeleton during infection

Actin and microtubules are important cytoskeletal elements in eukaryotic cells. The cytoskeleton controls many cellular processes such as cell division and motility, as well as vesicle and organelle trafficking. Inside of its host cell, the human pathogen Chlamydia trachomatis rearranges the cytoskeleton to promote its survival and enhance its pathogenicity. In particular, Chlamydia induces the rearrangement of both actin and microtubules, which is vital for its entry, inclusion structure and development, and exit from its host cell. In this context, our laboratory seeks to understand the molecular machinery used by Chlamydia trachomatis to co-opt the host cytoskeleton and to coordinate the reorganization of actin and microtubules. Furthermore, we investigate the impact of such reorganization on Chlamydia development and pathogenesis.

Identify the role of the host SNARE proteins during Chlamydia infection

SNAREs are ubiquitously expressed proteins, conserved from yeast to humans, that mediate intracellular membrane fusion events. In fact, they constitute the core machinery necessary to mediate specific membrane fusion. As such, they are key regulators of all intracellular vesicle trafficking events and cargo transport steps. Therefore, manipulation of individual SNARE proteins or SNARE complexes may help Chlamydia to subvert normal trafficking patterns, while the specific recruitment of host SNAREs to the chlamydial inclusion would afford the pathogen the ability to manipulate vesicular trafficking during infection. In this project, we seek to analyze the contribution of various SNARE proteins to Chlamydia infection, notably we are creating a library of CRIPR/Cas9 knockout cell lines for specific SNAREs, which will then be screened during Chlamydia infection.

Identify how Chlamydia escapes the cell degradative pathway: involvement of bacterial SNARE-like proteins

As an obligate intracellular bacterium, Chlamydia trachomatis replicates in an intracellular inclusion. When several bacteria infect a cell, they each develop in their own inclusion, which undergo homotypic fusion around 10-12 hours post-infection. This homotypic fusion event is critical for C. trachomatis pathogenicity as natural non-fusing Chlamydia mutants have replication defects, grow slower than their wild-type counterparts, and cause significantly milder symptoms in human. Recent work in our laboratory has characterized the inclusion membrane protein IncA, which is essential for membrane fusion. IncA shares significant sequence similarities with eukaryotic SNARE proteins. In this project, we seek to establish the 3D structure of IncA and establish whether it uses an α-helical structure to promote membrane fusion, similar to the eukaryotic SNARE fusion system. We also seek to identify the entire fusion machinery responsible for this unique bacterial event.

Characterize the machinery that controls homotypic fusion of the inclusion

As an obligate intracellular bacterium, Chlamydia trachomatis replicates in an intracellular inclusion. When several bacteria infect a cell, they each develop in their own inclusion, which undergo homotypic fusion ~10-12 hours post-infection. This homotypic fusion event is critical for C. trachomatis pathogenicity as natural non-fusing Chlamydia mutants have replication defects, grow slower than their wild-type counterparts, and cause significantly milder symptoms in human. Recent work in our laboratory has characterized the inclusion membrane protein IncA, which is essential for membrane fusion. IncA shares significant sequence similarities with eukaryotic SNARE proteins. In this project, we seek to establish the 3D structure of IncA and establish whether it uses an α-helical structure to promote membrane fusion, similar to the eukaryotic SNARE fusion system. We also seek to identify the entire fusion machinery responsible for this unique bacterial event.

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