The Emerging Role of STING in Insect Innate Immune Responses and Pathogen Evasion Strategies

Abstract

Emerging evidence reveals that the stimulator of the interferon genes (STING) signaling pathway in insects and other animal cells helps them to sense and effectively respond to infection caused by numerous types of microbial pathogens. Recent studies have shown that genomic material from microbial pathogens induces the STING signaling pathway for the production of immune factors to attenuate infection. In contrast, microbial pathogens are equipped with various factors that assist them in evading the STING signaling cascade. Here we discuss the STING signaling pathway different animal groups compared to human and then focus on its crucial biological roles and application in the microbial infection of insects. In addition, we examine the negative and positive modulators of the STING signaling cascade. Finally, we describe the microbial pathogen strategies to evade this signaling cascade for successful invasion.

Keywords: STING; host defense; immune factors; insect immunity; microbial infection.

Figure 1

The Schematic presentation of cGAS-STING signaling cascade activation in response to different kinds of pathogens.

Figure 2

The anti-microbial defense signaling pathway (cGAS-STING pathway) in insects. Nucleic acid (DNA or RNA) is not usually occurred in the cytoplasm of the insect cells. When the enzymatic protein cGAS (cGLR or unknown molecule) recognize nucleic acid, they lead to trigger the synthesize of secondary messenger molecules (e.g., 2’3’-cGAMP). Following the synthesize of secondary molecules, STING protein is induced, which then binds with the Relish and promotes its translocation, by which in induces anti-microbial factors.

Figure 3

the Schematic representation of the molecular mechanism through which Rel-NF-_KB-dependent STING expression induces anti-viral autophagy in insects.

Figure 4

The regulation of cGAS–STING signaling pathway by proteins at various levels.