Pseudomonas aeruginosa-derived DnaJ functions as a novel immunomodulator inducing IFNβ via CME–SGK1–IRF3 axis in macrophages

Abstract

Abstract Type I interferons (IFNs), particularly IFNβ, play a pivotal role in coordinating innate and adaptive immune responses during microbial infections. Pseudomonas aeruginosa ( P. aeruginosa ), a clinically significant opportunistic pathogen, is able to induce IFNβ expression; however, the specific microbial factors responsible for this induction remain poorly characterized. In this study, we identify DnaJ, a heat shock protein 40 (HSP40) homolog derived from P. aeruginosa , as a novel microbial inducer of IFNβ expression in macrophages. Among the bacterial HSP homologs tested, DnaJ elicits the most robust IFNβ production via a mechanism dependent on Toll-like receptor 4 (TLR4) and the TRIF–TBK1–IRF3 signaling axis. Mechanistic analysis revealed that clathrin-mediated endocytosis (CME) is required for DnaJ-induced IRF3 activation, and that serum/glucocorticoid regulated kinase 1 (SGK1) functions downstream of CME to promote IRF3 phosphorylation and subsequent IFNβ expression. Consistent with these findings, human HSP40 similarly induced IFNβ expression through the conserved CME–SGK1–IRF3 pathway, indicating that both bacterial and host-derived HSP40 proteins can serve as immune modulators. Collectively, these findings identify P. aeruginosa DnaJ as a potent immunomodulatory ligand capable of inducing IFNβ expression. DnaJ may therefore represent a promising candidate for therapeutic modulation of innate immunity or as an adjuvant in antimicrobial immunotherapy.