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Octopus sinensis, the species of Cephalopoda, is known as the highest Mollusca and is an economic and new aquaculture species in the coastal waters of southern China. The immune system has been well documented to have a function of resisting the invasion of pathogens in the external environment among mollusca species. As a kind of signaling molecule in the innate immune system, tumor necrosis factor (TNF) receptor-associated factor (TRAF) plays significant roles in TNF receptor (TNFR)/interleukin-1 receptor (IL-1R)/Toll-like receptor (TLR) signaling pathways. Until now, seven TRAF members (TRAF1-7) have been discovered, and they have been reported to participate in regulating signal pathways mediated by pattern recognition receptors and play important roles in the innate immune response of the hosts. In this study, five TRAF genes of O. sinensis (OsTRAF2, OsTRAF3, OsTRAF4, OsTRAF6, and OsTRAF7) were identified, whose full length of the open reading frame is 1473 bp, 1629 bp, 1431 bp, 1353 bp and 2121 bp respectively, encoding 490, 542, 476, 450 and 706 amino acids, respectively. Bioinformatics analysis showed that each OsTRAF has different chromosome locations. In addition to seven consecutive WD40 domains on the C-terminal of OsTRAF7 protein, the C-terminal of OsTRAF proteins all contain a conserved TRAF domain, namely the MATH domain. Phylogenetic analysis showed that OsTRAF proteins were clustered together with TRAF proteins of bivalves. Moreover, TRAF1 and TRAF2, TRAF3 and TRAF5 were clustered together in a large clade, respectively, revealing they have a close genetic relationship. The results of quantitative Real-time PCR showed that OsTRAF genes were highly expressed in the gill, hepatopancreas and white body. After stimulation with PGN, poly I:C and V. parahaemolyticus, the expression levels of OsTRAF genes were up-regulated in the gill, hepatopancreas and white body at different time points. These results indicated that OsTRAF genes play an important role in the antibacterial and antiviral immune response of O. sinensis., (Copyright © 2024. Published by Elsevier Ltd.)

Toll-like receptors (TLRs) are one of the extensively studied pattern recognition receptors (PRRs) and play crucial roles in the immune responses of vertebrates and invertebrates. In this study, 14 TLR genes were identified from the genome-wide data of Octopus sinensis. Protein structural domain analysis showed that most TLR proteins had three main structural domains: extracellular leucine-rich repeats (LRR), transmembrane structural domains, and intracellular Toll/IL-1 receptor domain (TIR). The results of subcellular localization prediction showed that the TLRs of O. sinensis were mainly located on the plasma membrane. The results of quantitative real-time PCR (qPCR) showed that the detected TLR genes were differentially expressed in the hemolymph, white bodies, hepatopancreas, gills, gill heart, intestine, kidney, and salivary gland of O. sinensis. Furthermore, the present study investigated the expression changes of O. sinensis TLR genes in hemolymph, white bodies, gills, and hepatopancreas in different phases (6 h, 12 h, 24 h, 48 h) after stimulation with PGN, poly(I: C) and Vibrio parahaemolyticus. The expression of most of the TLR genes was upregulated at different time points after infection with pathogens or stimulation with PAMPs, a few genes were unchanged or even down-regulated, and many of the TLR genes were much higher after V. parahaemolyticus infection than after PGN and poly(I:C) stimulation. The results of this study contribute to a better understanding of the molecular immune mechanisms of O. sinensis TLRs genes in resistance to pathogen stimulation. • Fourteen TLR genes were identified from the whole genome data of Octopus sinensis. • The 14 TLRs of O. sinensis were expressed to varying degrees in eight tissues. • After Vibrio , PGN, and poly(I: C) stimulation, most of TLR s were up-regulated in examined tissues. • 4.The expression of many TLR s after Vibrio infection was higher than those stimulated by PGN and poly(I: C). [ABSTRACT FROM AUTHOR]

Mitochondrial dysfunction critically contributes to many major human diseases. The impact of specific gut microbial metabolites on mitochondrial functions of animals and the underlying mechanisms remain to be uncovered. Here, we report a profound role of bacterial peptidoglycan muropeptides in promoting mitochondrial functions in multiple mammalian models. Muropeptide addition to human intestinal epithelial cells (IECs) leads to increased oxidative respiration and ATP production and decreased oxidative stress. Strikingly, muropeptide treatment recovers mitochondrial structure and functions and inhibits several pathological phenotypes of fibroblast cells derived from patients with mitochondrial disease. In mice, muropeptides accumulate in mitochondria of IECs and promote small intestinal homeostasis and nutrient absorption by modulating energy metabolism. Muropeptides directly bind to ATP synthase, stabilize the complex, and promote its enzymatic activity in vitro , supporting the hypothesis that muropeptides promote mitochondria homeostasis at least in part by acting as ATP synthase agonists. This study reveals a potential treatment for human mitochondrial diseases. [Display omitted] • Muropeptides accumulate in mitochondria and enhance OXPHOS in human IECs • Muropeptides recover mitochondrial structure and functions in mitochondrial disease cells • Muropeptides promote small intestinal epithelial homeostasis and nutrient uptake in mice • Muropeptides bind and stabilize ATP synthase complex and enhance its activity Tian et al. report a profound role of bacterial peptidoglycan muropeptides in promoting mitochondrial functions and suppressing oxidative stress in cultured human intestinal epithelial cells, fibroblast cells from patients with mitochondrial disease, and mouse intestinal epithelial cells. Muropeptides were shown to bind ATP synthase and enhance its activity in vitro. [ABSTRACT FROM AUTHOR]