The Effector TepP Mediates Recruitment and Activation of Phosphoinositide 3-Kinase on Early Chlamydia trachomatis Vacuoles.

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2017-07

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Abstract

Chlamydia trachomatis delivers multiple type 3 secreted effector proteins to host epithelial cells to manipulate cytoskeletal functions, membrane dynamics, and signaling pathways. TepP is the most abundant effector protein secreted early in infection, but its molecular function is poorly understood. In this report, we provide evidence that TepP is important for bacterial replication in cervical epithelial cells, activation of type I IFN genes, and recruitment of class I phosphoinositide 3-kinases (PI3K) and signaling adaptor protein CrkL to nascent pathogen-containing vacuoles (inclusions). We also show that TepP is a target of tyrosine phosphorylation by Src kinases but that these modifications do not appear to influence the recruitment of PI3K or CrkL. The translocation of TepP correlated with an increase in the intracellular pools of phosphoinositide-(3,4,5)-triphosphate but not the activation of the prosurvival kinase Akt, suggesting that TepP-mediated activation of PI3K is spatially restricted to early inclusions. Furthermore, we linked PI3K activity to the dampening of transcription of type I interferon (IFN)-induced genes early in infection. Overall, these findings indicate that TepP can modulate cell signaling and, potentially, membrane trafficking events by spatially restricted activation of PI3K. IMPORTANCE This article shows that Chlamydia recruits PI3K, an enzyme important for host cell survival and internal membrane functions, to the pathogens inside cells by secreting a scaffolding protein called TepP. TepP enhances Chlamydia replication and dampens the activation of immune responses.

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10.1128/mSphere.00207-17

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Carpenter, Victoria, Yi-Shan Chen, Lee Dolat and Raphael H Valdivia (2017). The Effector TepP Mediates Recruitment and Activation of Phosphoinositide 3-Kinase on Early Chlamydia trachomatis Vacuoles. mSphere, 2(4). 10.1128/mSphere.00207-17 Retrieved from https://hdl.handle.net/10161/15148.

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Valdivia

Raphael H. Valdivia

Nanaline H. Duke Distinguished Professor of Molecular Genetics and Microbiology

My laboratory is interested in microbes that influence human health, both in the context of host-pathogen and host-commensal interactions. For many pathogens, and certainly for most commensal microbes, we have an incomplete molecular understanding of how host and microbial factors contribute to health and disease. My research group focuses on two experimental systems:

Chlamydia trachomatis infections are responsible for the bulk of sexually transmitted bacterial diseases and are the leading cause of infectious blindness (trachoma) in the world. Chlamydia  resides within a membrane bound compartment (“inclusion”). From this location, the pathogen manipulates the cytoskeleton, inhibits lysosomal recognition of the inclusion, activates signaling pathways, re-routes lipid transport, and prevents the onset of programmed cell death. Our laboratory focuses on identifying and characterizing the bacterial factors that are secreted into the host cell cytoplasm to manipulate eukaryotic cellular functions. We use a combination of cell biology, biochemistry, genetics, genomics, proteomics and molecular biology to determining the function of virulence factors that reveal novel facets of the host-pathogen interaction. Our goal is to understand how these obligate intracellular bacterial pathogens manipulate host cellular functions to replicate, disseminate and cause disease, and in the process develop strategies to ameliorate the damage caused by these infections to the female reproductive organs.

Akkermansia muciniphila is prevalent member of the gut microbiota that proliferates in the mucus layers of our lower gastrointestinal tract and contribute to nutrient homeostasis and human immunological health. My research group developed genetic tools to characterize these microbes to define the mechanisms used to colonize the human gut and identify the molecular and cellular pathways that underscore Akkermansia's impact on immune homeostasis.  In the process, we seek to engineer strains of Akkermansia that enhance their probiotic potential.


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