Thioredoxin 1 inhibits GCRV replication by maintaining redox homeostasis in grass carp (Ctenopharyngodon idella).

Abstract

Thioredoxin (Trx) is a conserved redox regulatory protein that plays critical roles in maintaining cellular redox homeostasis and immune defense. However, its molecular characteristics and antiviral functions in grass carp (Ctenopharyngodon idella) remain largely unknown. In this study, thioredoxin 1 (trx1) was cloned and functionally characterized. The full-length trx1 cDNA was 834 bp, containing a 324 bp open reading frame encoding a 107-amino-acid protein with the conserved Cys-Gly-Pro-Cys (CGPC) redox-active motif. Phylogenetic and structural analyses demonstrated that Trx1 was highly conserved among vertebrates. The trx1 transcripts were ubiquitously expressed in all tested tissues, with relatively high levels in the spleen and liver, and were significantly induced by lipopolysaccharide (LPS), polyinosinic-polycytidylic acid (poly I:C), and grass carp reovirus (GCRV) infection. Recombinant Trx1 was successfully expressed in Escherichia coli and enhanced bacterial resistance to H2O2-induced oxidative stress. Subcellular localization analysis detected Trx1-GFP signals in the cytoplasm and nucleus of C. idella kidney (CIK) cells, with obvious nuclear enrichment after H2O2 treatment and GCRV infection. Functional analyses demonstrated that trx1 overexpression alleviated oxidative stress, inflammation, and apoptosis, accompanied by reduced GCRV replication, whereas trx1 silencing produced the opposite effects. Collectively, these findings suggest that trx1 acts as an important antiviral regulator that maintains intracellular redox homeostasis and contributes to host protection against GCRV infection by limiting oxidative stress, apoptosis, and excessive inflammatory responses.