Acanthamoeba castellanii STAT protein

Legionella pneumophila inhibits type I interferon signaling to avoid cell-intrinsic host cell defense

The host type I interferon (IFN) response protects against Legionella pneumophila infections. Other bacterial pathogens inhibit type I IFN-mediated cell signaling; however, the interaction between this signaling pathway and L. pneumophila has not been well described. Here, we demonstrate that L. pneumophila inhibits the IFN-β signaling pathway but does not inhibit IFN-γ-mediated cell signaling. The addition of IFN-β to L. pneumophila-infected macrophages limited bacterial growth independently of NOS2 and reactive nitrogen species. The type IV secretion system of L. pneumophila is required to inhibit IFN-β-mediated cell signaling. Finally, we show that the inhibition of the IFN-β signaling pathway occurs downstream of STAT1 and STAT2 phosphorylation. In conclusion, our findings describe a novel host cell signaling pathway inhibited by L. pneumophila via its type IV secretion system.

Structural and mutational analysis of member-specific STAT functions

BACKGROUND

The STAT family of transcription factors control gene expression in response to signals from various stimulus. They display functions in diseases ranging from autoimmunity and chronic inflammatory disease to cancer and infectious disease.

SCOPE OF REVIEW

This work uses an approach informed by structural data to explore how domain-specific structural variations, post-translational modifications, and the cancer genome mutational landscape dictate STAT member-specific activities.

MAJOR CONCLUSIONS

We illustrated the structure-function relationship of STAT proteins and highlighted their effect on member-specific activity. We correlated disease-linked STAT mutations to the structure and cancer genome mutational landscape and proposed rational drug targeting approaches of oncogenic STAT pathway addiction.

GENERAL SIGNIFICANCE

Hyper-activated STATs and their variants are associated with multiple diseases and are considered high value oncology targets. A full understanding of the molecular basis of member-specific STAT-mediated signaling and the strategies to selectively target them requires examination of the difference in their structures and sequences.

STAT3 but not STAT4 is critical for γδT17 cell responses and skin inflammation

The transcription factors STAT3 and STAT4 are essential for lymphocyte differentiation and function. Interleukin (IL)-17 producing γδ T (γδT17) cells are innate lymphocytes important for anti-bacterial and inflammatory responses at barrier surfaces. Herein, we examine the role of STAT3 and STAT4 in regulating the homeostasis, activation, and pathogenicity of γδT17 cells. We show that STAT3 sustains γδT17 numbers in the skin but not in the lymph nodes, while STAT4 deficiency does not affect their homeostasis. Similarly, STAT3 but not STAT4 is essential for IL-23-induced IL-22 production by γδT17 cells. Concomitantly, mice lacking STAT3 expression in γδT17 cells develop significantly reduced psoriasis-like inflammation. STAT3-deficient γδT17 cells fail to expand and to upregulate IL-17A, IL-17F, and IL-22 in response to psoriatic stimuli. Although STAT4-deficient animals develop psoriasis-like disease, γδT17 cells in these mice are defective in IL-17F production. Collectively, our data demonstrate for the first time a critical role for STAT3 in orchestrating the homeostasis and pathogenicity of γδT17 cells and provide evidence for the requirement of STAT4 for optimal cytokine responses during inflammation.

Free-living amoebae and squatters in the wild: ecological and molecular features

Free-living amoebae are protists frequently found in water and soils. They feed on other microorganisms, mainly bacteria, and digest them through phagocytosis. It is accepted that these amoebae play an important role in the microbial ecology of these environments. There is a renewed interest for the free-living amoebae since the discovery of pathogenic bacteria that can resist phagocytosis and of giant viruses, underlying that amoebae might play a role in the evolution of other microorganisms, including several human pathogens. Recent advances, using molecular methods, allow to bring together new information about free-living amoebae. This review aims to provide a comprehensive overview of the newly gathered insights into (1) the free-living amoeba diversity, assessed with molecular tools, (2) the gene functions described to decipher the biology of the amoebae and (3) their interactions with other microorganisms in the environment.

Protective effect of naringin against ankylosing spondylitis via ossification, inflammation and oxidative stress in mice

Naringin is an abundant flavanone in pomelo, grapefruit as well as lime and its variants, has been shown to exhibit certain antioxidative, anti-inflammatory, anti-cancer and hypoglycemic effects. The aim of the current study was to evaluate the protective effects of naringin against ankylosing spondylitis (AS) and to elucidate the potential underlying mechanism. Firstly, a mouse model of ankylosing spondylitis (AS) was established. Next, osteocalcin (OC), alkaline phosphatase (ALP) and triglyceride (TG) activity values, inflammatory factor and oxidative stress were evaluated in the AS mice. Then, the Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) protein expression levels in the AS mice were investigated using western blot analysis. The results showed that naringin increased OC, ALP and TG activity values in the AS mouse model. Furthermore, inflammatory factor and oxidative stress levels in the AS mice were restrained by treatment with naringin. Furthermore, JAK2 and STAT3 protein expression levels were reduced by treatment with naringin. In conclusion, the present results indicated that the protective effects of naringin against AS are exerted via the induction of ossification, suppression of inflammation and oxidative stress and the downregulation of JAK2/STAT3 in mice.