Centrosome Subversion by Chlamydial Effectors: Implications for Cellular Transformation and Oncogenesis

About This Grant

Project Summary Chlamydia trachomatis (C.t.) is the leading cause of non-congenital blindness and the most prevalent sexually transmitted bacterial infection worldwide. There is no vaccine, and reinfections are common due to the absence of long-term protective immunity. C.t. infection has been associated with supernumerary centrosomes, multipolar spindles, and multinucleation—hallmarks of most tumors, including cervical and ovarian cancers, for which prior or current C.t. infection is a recognized risk factor. However, an important gap in our understanding remains regarding how C.t., orchestrates these host cell changes and whether these events may predispose cells to oncogenic transformation. C.t. delivers an arsenal of effector proteins into the host cell via a type 3 secretion system (T3SS). While progress has been made in elucidating the role some of these proteins play in establishing C.t.’s intracellular niche, the function of most remains unknown. We recently discovered that the T3SS effector protein CteG binds to centrin-2 (CETN2), a core component of centrosomes, and that this interaction induces supernumerary centrosome formation during infection. Although our data indicate that the CteG-CETN2 interaction is necessary for centrosome amplification, it is not sufficient, nor does CteG contribute to other infection-associated cellular abnormalities, suggesting that other bacterial factors contribute. We hypothesize that C.t. employs multiple secreted effectors to disrupt centrosome duplication and to inhibit host cell cytokinesis, promoting chlamydial infection while paradoxically inducing cellular transformation events that may contribute to cellular transformation. In Aim 1, we will use proteomics and advanced microscopy to determine whether CteG mimics Sfi1-like motifs to bind to the C-terminus of CETN2, thereby disrupting canonical CETN2-interactions and promoting centrosome amplification. In Aim 2, we will leverage newly developed C.t. null strains to test whether C.t. interferes with centrosome duplication and host cell cytokinesis to enhance bacterial release via extrusion. In Aim 3, we will examine whether infection-induced cellular abnormalities contribute to transformation using novel cellular and in vivo models. Collectively, our studies will lead to an enhanced understanding of how C.t. perturbs centrosome duplication and host cell cytokinesis, and whether these changes contribute to cellular transformation. Establishing these mechanistic links will be an important step toward understanding the long- term cellular consequences of C.t. infection and their potential impact on women’s health.