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Cuticle proteins (CPs) are the vital components of the cuticle and chitin lining covering the digestive tract of crustaceans. In this study, four new CP genes (designated as EsCP3 , EsCP4 , EsCP5 , and EsCP8) were initially cloned and identified from the Chinese mitten crab Eriocheir sinensis. EsCP3/4/5/8 included 375, 411, 381, and 570 bp open reading frame encoding 124, 136, 126, and 189 amino acid proteins, respectively. Except for EsCP8, EsCP3/4/5 all contained a Chitin_bind_4 domain. EsCP3/4/5/8 were clustered into different groups in the phylogenetic tree. Quantitative real-time PCR results indicated that four EsCP genes have different patterns of tissue distribution. Changes in the expression levels of these four EsCP genes were observed in the intestine of crabs under Vibrio parahaemolyticus challenge. RNA interference assay showed that the knockdown of EsCPs in the intestine could inhibit the expression of antimicrobial peptides (AMPs), including crustins and anti-lipopolysaccharide factors. In addition, the knockdown of EsRelish in the intestine decreased the expression levels of these four EsCP genes. These results indicated that EsCPs were involved in regulating the expression of AMPs , and EsCPs were regulated by EsRelish. • Four new cuticle proteins were initially identified from Eriocheir sinensis. • The expression of four EsCPs showed apparent changes after bacterial challenge. • EsCPs suppressed the expression of several antimicrobial peptides. • EsCPs were regulated by EsRelish. [ABSTRACT FROM AUTHOR]

Pseudomonas plecoglossicida , the causative agent of Visceral White Spot Disease, poses substantial risks to large yellow croaker (Larimichthys crocea) aquaculture. Previous genome-wide association studies (GWAS), directed towards elucidating the resistance mechanisms of large yellow croaker against this affliction, suggested that the transmembrane protein 208 (named Lctmem208) may confer a potential advantage. TMEM proteins, particularly TMEM208 located in the endoplasmic reticulum, plays significant roles in autophagy, ER stress, and dynamics of cancer cell. However, research on TMEM's function in teleost fish immunity remains sparse, highlighting a need for further study. This study embarks on a comprehensive examination of LcTmem208 , encompassing cloning, molecular characterization, and its dynamics in immune function in response to Pseudomonas plecoglossicida infection. Our findings reveal that LcTmem208 is highly conserved across teleost species, exhibiting pronounced expression in immune-relevant tissues, which escalates significantly upon pathogenic challenge. Transcriptome analysis subsequent to LcTmem208 overexpression in kidney cells unveiled its pivotal role in modulating immune-responsive processes, notably the p53 signaling pathway and cytokine-mediated interactions. Enhanced phagocytic activity in macrophages overexpressing LcTmem208 underscores its importance in innate immunity. Taken together, this is the first time reported the critical involvement of LcTmem208 in regulating innate immune responses of defensing P. plecoglossicida , thereby offering valuable insights into teleost fish immunity and potential strategies for the selective breeding of disease-resistant strains of large yellow croaker in aquaculture practices. • Tmem208 was reported on the role in the immune response of teleost fish for the first time. • LcTmem208 was identified as crucial for large yellow croaker's defense against Visceral White Spot Disease. • Heightened LcTmem208 expression in immune tissues upon Pseudomonas plecoglossicida induced, significantly enhancing macrophage phagocytic activity, highlighting its role in innate immunity. • Overexpression studies indicate LcTmem208's vital role in activating immune pathways, particularly the p53 signaling pathway and cytokine-mediated interactions, providing insights into immune response mechanisms. [ABSTRACT FROM AUTHOR]

L-type lectins (LTLs) contain a carbohydrate recognition domain homologous to leguminous lectins, and have functions in selective protein trafficking, sorting and targeting in the secretory pathway of animals. In this study, a novel LTL, designated as ToERGIC-53 , was cloned and identified from obscure puffer Takifugu obscurus. The open reading frame of ToERGIC-53 contained 1554 nucleotides encoding 517 amino acid residues. The deduced ToERGIC-53 protein consisted of a signal peptide, a leguminous lectin domain (LTLD), a coiled-coil region, and a transmembrane region. Quantitative real-time PCR showed that ToERGIC-53 was expressed in all examined tissues, with the highest expression level in the liver. The expression of ToERGIC-53 was significantly upregulated after infection with Vibrio harveyi and Staphylococcus aureus. Recombinant ToERGIC-53-LTLD (rToERGIC-53-LTLD) protein could not only agglutinate and bind to one Gram-positive bacterium (S. aureus) and three Gram-negative bacteria (V. harveyi , V. parahaemolyticus and Aeromonas hydrophila), but also bind to glycoconjugates on the surface of bacteria such as lipopolysaccharide, peptidoglycan, mannose and galactose. In addition, rToERGIC-53-LTLD inhibited the growth of bacteria in vitro. All these results suggested that ToERGIC-53 might be a pattern recognition receptor involved in antibacterial immune response of T. obscurus. • ToERGIC-53 was first identified from Takifugu obscurus. • ToERGIC-53 was significantly regulated after stimulation with V. harveyi and S. aureus. • rToERGIC-53-LTLD could agglutinate several Gram-positive and Gram-negative bacteria. • rToERGIC-53-LTLD could bind to a variety of bacteria and saccharides. • rToERGIC-53-LTLD could inhibit the growth of V. harveyi and S. aureus. [ABSTRACT FROM AUTHOR]