Discovery of a novel STING-binding peptide associated with reduced cGAMP-induced inflammatory gene expression

cGAMP-induced STING activation contributes to inflammatory and interferon-related signalling, making STING a relevant target for inhibitor development. In this study, a 59,319-sequence peptide library was screened against STING by molecular docking, and four top-ranked peptides were selected for evaluation. MST analysis demonstrated that Peptides 1-4 bound to recombinant STING, with Peptide-1 showing the highest affinity (K_d = 0.15 ± 0.01 μM). Docking and simulation analyses suggested that binding was mediated by hydrogen bonding and hydrophobic contacts. Molecular dynamics, MM/PBSA, and free energy landscape analyses suggested stable binding with favourable calculated energetics. Peptide-1 showed no apparent cytotoxicity up to 10 μM in RAW264.7 macrophages and primary BMDMs, while dose-dependently reducing cGAMP-induced IFN-β and IL-6 expression at both protein and mRNA levels. This inhibitory effect was accompanied by reduced STING and IRF3 phosphorylation. Collectively, these findings suggest that Peptide-1 may bind STING and attenuate cGAMP-induced IFN-β and IL-6 expression.