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The cytotoxic type 3 secretion system 1 of Vibrio rewires host gene expression to subvert cell death and activate cell survival pathways

2017-05-16T10:57:24-07:00

Bacterial effectors potently manipulate host signaling pathways. The marine bacterium Vibrio parahaemolyticus (V. para) delivers effectors into host cells through two type 3 secretion systems (T3SSs). T3SS1 is vital for V. para survival in the environment, whereas T3SS2 causes acute gastroenteritis in human hosts. Although the natural host is undefined, T3SS1 effectors attack highly conserved cellular processes and pathways to orchestrate nonapoptotic cell death. To understand how the concerted action of T3SS1 effectors globally affects host cell signaling, we compared gene expression changes over time in primary fibroblasts infected with V. para that have a functional T3SS1 (T3SS1+) to those in cells infected with V. para lacking T3SS1 (T3SS1). Overall, the host transcriptional response to both T3SS1+ and T3SS1 V. para was rapid, robust, and temporally dynamic. T3SS1 rewired host gene expression by specifically altering the expression of 398 genes. Although T3SS1 effectors targeted host cells at the posttranslational level to cause cytotoxicity, V. para T3SS1 also precipitated a host transcriptional response that initially activated cell survival and repressed cell death networks. The increased expression of several key prosurvival transcripts mediated by T3SS1 depended on a host signaling pathway that is silenced posttranslationally later in infection. Together, our analysis reveals a complex interplay between the roles of T3SS1 as both a transcriptional and posttranslational manipulator of host cell signaling.




Science Signaling Podcast for 16 May 2017: Vibrio rewires host cells

2017-05-16T10:57:24-07:00

Abstract

This Podcast features a conversation with Kim Orth and Nicole De Nisco, authors of a Research Resource that appears in the 16 May 2017 issue of Science Signaling, about how the marine bacterium Vibrio parahaemolyticus rewires host cell signaling networks. V. parahaemolyticus thrives in warm brackish waters and infects both shellfish and finfish. This bacterium causes gastroenteritis when humans consume contaminated seafood that is raw or undercooked. V. parahaemolyticus delivers virulence factors into host cells through two different type 3 secretion systems (T3SSes). Whereas T3SS2 mediates gastroenteritis, T3SS1 is required for the bacterium to survive in its natural environment and delivers virulence factors that target conserved cellular processes. De Nisco et al. examined transcriptional changes in human cells infected with a strain of V. parahaemolyticus that lacked T3SS2 but had an intact T3SS1. They found that the virulence factors delivered through T3SS1 initially induced transcriptional changes that promoted cell survival, then later repressed prosurvival signaling to induce cell death.

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Nrf2 inactivation enhances placental angiogenesis in a preeclampsia mouse model and improves maternal and fetal outcomes

2017-05-16T10:57:24-07:00

Placental activation of the renin-angiotensin system (RAS) plays a key role in the pathogenesis of preeclampsia. Reactive oxygen species (ROS) are thought to affect placental angiogenesis, which is critical for preventing preeclampsia pathology. We examined the role of ROS in preeclampsia by genetically modifying the Keap1-Nrf2 pathway, a cellular antioxidant defense system, in a mouse model of RAS-induced preeclampsia. Nrf2 deficiency would be expected to impair cellular antioxidant responses; however, Nrf2 deficiency in preeclamptic mice improved maternal and fetal survival, ameliorated intra-uterine growth retardation, and augmented oxidative DNA damage. Furthermore, the placentas of Nrf2-deficient mice had increased endothelial cell proliferation with dense vascular networks. In contrast, the placentas of preeclamptic mice with overactive Nrf2 showed repressed angiogenesis, which was associated with decreased expression of genes encoding angiogenic chemokines and cytokines. Our findings support the notion that ROS-mediated signaling is essential for maintaining placental angiogenesis in preeclampsia and may provide mechanistic insight into the negative results of clinical trials for antioxidants in preeclampsia.







Quorum sensing to repress virulence

2017-05-16T10:57:24-07:00

A quorum-sensing system of an insect endosymbiont enables the bacterium to establish persistent infection by inhibiting the expression of virulence genes.




Papers of note in Science Translational Medicine 9 (389)

2017-05-16T10:57:24-07:00

This week’s articles highlight how tumor-associated macrophages limit the efficacy of PD-1–targeted checkpoint therapy and show that an anti-inflammatory drug may be used to treat lymphedema.




Papers of note in Science 356 (6338)

2017-05-16T10:57:24-07:00

This week’s articles demonstrate how T cells search for ligands; a role for the endoplasmic reticulum in the nonclathrin-mediated endocytosis of a growth factor receptor; and growth coupling between distant bacterial colonies that enables the cells to share limited resources.




Papers of note in Nature 545 (7653)

2017-05-16T10:57:25-07:00

This week’s articles highlight colon cancer stem cells; cooperative signaling that maintains intestinal stem cell self-renewal; a newly developed Wnt agonist; and metabolic changes in endothelial cells that promote angiogenesis.




New connections: The duality of ROS in angiogenesis

2017-05-16T10:57:25-07:00

Depending on the tissue and context, ROS can either stimulate or suppress blood vessel formation.