A novel ML protein functions as a pattern recognition protein in antibacterial responses in Eriocheir sinensis

• Published in: Developmental and comparative immunology Vol. 127; p. 104310
• Main Authors: Song, Yu, Zhou, Kaimin, Nan, Xingyu, Qin, Yukai, Zhao, Ke, Li, Weiwei, Wang, Qun
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 01.02.2022; Elsevier Science Ltd
• Subjects: Amino Acid Sequence; Animals; Anti-Bacterial Agents - metabolism; Antiinfectives and antibacterials; Arthropod Proteins - metabolism; Bacteria; Bacterial diseases; Bacterial infections; Brachyura - metabolism; Clearances; Eriocheir sinensis; GM2-activator protein; Gram-negative bacteria; Gram-positive bacteria; Hemocytes; Immune clearance; Immune response; Immune response (cell-mediated); Immunity, Innate; Infections; Invertebrate immunity; Invertebrates; Lipid metabolism; Lipids; Lipopolysaccharides; Microorganisms; ML proteins; Niemann-Pick disease; Niemann-pick disease type C2 (NPC2); PAMPs; Pattern recognition; Peptidoglycans; Phagocytes; Phagocytosis; Phylogeny; Proteins; Signal transduction; Vertebrates; Vibrio parahaemolyticus; PBS; Eriocheir sinensis; IKK; MAPK; GM2; PRR; BSA; Invertebrate immunity; NPC2; LB; MD-2; PAMPs; ML proteins; Niemann-pick disease type C2 (NPC2); ML
• ISSN: 0145-305X; 1879-0089
• DOI: 10.1016/j.dci.2021.104310

The myeloid differentiation factor 2 (MD-2)-related lipid recognition (ML) domain is present in MD-2, MD-1, GM2-activator protein (GM2A) and Niemann-Pick disease type C2 (NPC2). ML proteins function in antibacterial signal transduction and lipid metabolism in vertebrates, but the mechanism in invertebrates is unknown. In this study, we found that ML proteins were involved in bacterial resistance in Chinese mitten crab (Eriocheir sinensis). One member, EsML3, a soluble, bacterial-induced pattern recognition protein was upregulated in hemocytes following bacterial challenge. Recombinant EsML3 bound to Gram-negative bacteria (Vibrio parahaemolyticus) and Gram-positive bacteria (Staphylococcus aureus) by interaction with peptidoglycan, lipopolysaccharide. EsML3 showed no direct bacteriostatic or bacteriocidal activity. Pre-incubating bacteria with rEsML3 significantly promoted in vivo bacterial clearance. EsML3 also promoted phagocytic activity and plays a role against bacterial infection. In summary, EsML3 mediates cellular immune responses by recognising invasive microorganisms, promoting bacterial clearance and phagocytosis against bacterial infection in crab. •EsML3 may function as a pattern recognition protein in crab antibacterial immunity.•EsML3 is upregulated in crab challenged by bacteria.•EsML3 promotes in vivo bacterial clearance and phagocytosis against bacterial infection in crab.