Functional Characterization of STING in Large Yellow Croaker (larimichthys Crocea), a Pivotal Regulator Associated with TRIF, TRAF3, IRF3, and IRF7 in Modulating Antiviral Signaling

STING serves as a crucial adaptor protein in cytosolic nucleic acid sensing pathways that initiate host antiviral defense mechanisms. Herein, we report the molecular cloning and functional characterization of a STING ortholog namely Lc-STING in large yellow croaker (Larimichthys crocea). The complete coding sequence of Lc-STING comprises 1,227-bp, encoding a 408-aa protein containing a TMEM173 domain and three transmembrane regions. Lc-STING exhibits ubiquitous tissue distribution, with maximal levels in the intestine and minimal in the brain. Upon challenge with poly I:C, LPS, PGN, or Pseudomonas plecoglossicida, Lc-STING expression was markedly elevated in immune-related tissues. As a cytoplasmic distribution protein, Lc-STING overexpression dose-dependently activated NF-κB, IRF3, IRF7, and type I IFN promoters. Notably, the co-expression of Lc-STING with Lc-TRIF, Lc-TRAF3, Lc-IRF3, or Lc-IRF7 substantially influenced antiviral signaling cascade, attenuating NF-κB while amplifying IRF3, IRF7, and type I IFN promoter activation. Such combinatorial expressions also significantly impacted the transcription of antiviral and inflammatory genes, encompassing IL-1β, IRF3, TNF-α, IRF7, ISG15, Mx, and ISG56. These findings collectively establish Lc-STING as a pivotal mediator of antiviral immunity in large yellow croaker, engaging in intricate crosstalk with multiple signaling components to coordinate balanced activation of interferon regulatory pathways while tempering inflammatory NF-κB responses.