Activation of epidermal growth factor receptor is required for Chlamydia trachomatis development

Abstract

BackgroundChlamydia trachomatis (C. trachomatis) is a clinically significant human pathogen and one of the leading causative agents of sexually transmitted diseases. As obligate intracellular bacteria, C. trachomatis has evolved strategies to redirect the host’s signaling and resources for its own survival and propagation. Despite the clinical notoriety of Chlamydia infections, the molecular interactions between C. trachomatis and its host cell proteins remain elusive.ResultsIn this study, we focused on the involvement of the host cell epidermal growth factor receptor (EGFR) in C. trachomatis attachment and development. A combination of molecular approaches, pharmacological agents and cell lines were used to demonstrate distinct functional requirements of EGFR in C. trachomatis infection. We show that C. trachomatis increases the phosphorylation of EGFR and of its downstream effectors PLCγ1, Akt and STAT5. While both EGFR and platelet-derived growth factor receptor-β (PDGFRβ) are partially involved in bacterial attachment to the host cell surface, it is only the knockdown of EGFR and not PDGFRβ that affects the formation of C. trachomatis inclusions in the host cells. Inhibition of EGFR results in small immature inclusions, and prevents C. trachomatis-induced intracellular calcium mobilization and the assembly of the characteristic F-actin ring at the inclusion periphery. By using complementary approaches, we demonstrate that the coordinated regulation of both calcium mobilization and F-actin assembly by EGFR are necessary for maturation of chlamydial inclusion within the host cells. A particularly important finding of this study is the co-localization of EGFR with the F-actin at the periphery of C. trachomatis inclusion where it may function to nucleate the assembly of signaling protein complexes for cytoskeletal remodeling required for C. trachomatis development.ConclusionCumulatively, the data reported here connect the function of EGFR to C. trachomatis attachment and development in the host cells, and this could lead to new venues for targeting C. trachomatis infections and associated diseases.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-014-0277-4) contains supplementary material, which is available to authorized users.

Chlamydia cell biology and pathogenesis

“…Consistent with this notion, the growing inclusion becomes encased in F-actin and intermediate filaments that form a dynamic scaffold, which provides structural stability and limits the access of bacterial products to the host cytosol 7,49 . The recruitment and assembly of F-actin involves RHO-family GTPases 49 , septins 94 , EGFR signalling 95 and at least one bacterial effector, InaC 81 . Microtubules are also actively reorganized around the inclusion by IPAM in C. trachomatis , which hijacks a centrosome protein, the centrosomal protein of 170 kDa (CEP170) 96 .…”

Infection of HeLa cells with Chlamydia trachomatis inhibits protein synthesis and causes multiple changes to host cell pathways

“…Activation of the EGFR‐signalling pathways has been noted before upon C . trachomatis infection, and RNAi against the EGFR reduced chlamydial development (Patel et al, ). Enhanced signalling through pathways downstream of EGFR has further been documented during infection with C .…”

Chlamydia‐infected cells shed Gp96 to prevent chlamydial re‐infection

“…Loss of Gp96 results in the loss of proper folding and function of these proteins. In addition, recent data indicate that cell surface receptors such as EphA2 and EGFR remain active and associated with the inclusion after endocytosis of Ctr (Patel et al ., ; Subbarayal et al ., ). This could explain why Gp96 depletion or inhibition of its activity also affected the intracellular development of Ctr .…”