An ML protein from the silkworm Bombyx mori may function as a key accessory protein for lipopolysaccharide signaling. (November 2018)

• Record Type: Journal Article
• Authors: Zhang, Ruo-Nan; Ren, Fei-fei; Zhou, Cheng-Bo; Xu, Jun-Feng; Yi, Hui-Yu; Ye, Ming-Qiang; Deng, Xiao-Juan; Cao, Yang; Yu, Xiao-Qiang; Yang, Wan-Ying
• Is Part Of: Developmental and comparative immunology. Volume 88(2018)
• Page Start: 94
• Page End: 103
• Publication Date: 2018-11
• Subjects: BmEsr16 -- Lipopolysaccharide -- Antibacterial -- MD-2 -- Bombyx mori; Immunology -- Periodicals; Developmental immunology -- Periodicals; 616.079
• DOI: 10.1016/j.dci.2018.07.012
• Languages: English
• ISSNs: 0145-305X

Abstract

Abstract: Lipopolysaccharide (LPS) is a common component of the outermost cell wall in Gram-negative bacteria. In mammals, LPS serves as an endotoxin that can be recognized by a receptor complex of TLR4 (Toll-like receptor 4) and MD-2 (myeloid differentiation-2) and subsequently induce a strong immune response to signal the release of tumor necrosis factor (TNF). In Drosophila melanogaster, no receptors for LPS have been identified, and LPS cannot activate immune responses. Here, we report a protein, BmEsr16, which contains an ML (MD-2-related lipid-recognition) domain, may function as an LPS receptor in the silkworm Bombyx mori . We showed that antibacterial activity in the hemolymph of B. mori larvae was induced by Escherichia coli, peptidoglycan (PGN) and LPS and that the expression of antimicrobial peptide genes was also induced by LPS. Furthermore, both the expression of BmEsr16 mRNA in the fat body and the expression of BmEsr16 protein in the hemolymph were induced by LPS. Recombinant BmEsr16 bound to LPS and lipid A, as well as to PGN, lipoteichoic acid, but not to laminarin or mannan. More importantly, LPS-induced immune responses in the hemolymph of B. mori larvae were blocked when the endogenous BmEsr16 protein was neutralized by polyclonal antibody specific to BmEsr16. Our results suggest that BmEsr16 may function as a key accessory protein for LPS signaling in B. mori . Graphical abstract: LPS is a common component of the outermost cell wall in Gram-negative bacteria. For mammals, LPS serves as an endotoxin to induce a strong immune response. In Drosophila melanogaster, no receptors for LPS have been identified and LPS can't activate immune responses. In this paper, we report a protein, BmEsr16, which contains an ML domain, may function as a receptor for LPS in the silkworm. Our results showed that LPS-induced immune responses in the hemolymph of B. mori larvae were blocked when endogenous BmEsr16 protein was neutralized by polyclonal antibody specific to BmEsr16. Image 1 Highlights: Highly purified LPS could induce the expression of antibacterial peptide in B. mori larvae at mRNA and protein level. BmEsr16 could bound to LPS and was induced expression by LPS in the fat body of B. mori larvae. Neutralization of BmEsr16 by antibody could block the LPS-induced antibacterial activity in B. mori larvae.