A Fish Galectin-8 Possesses Direct Bactericidal Activity

Abstract

Galectins are a family of animal lectins with high affinity for β-galactosides. Galectins are able to bind to bacteria, and a few mammalian galectins are known to kill the bound bacteria. In fish, no galectins with direct bactericidal effect have been reported. In the present study, we identified and characterized a tandem repeat galectin-8 from tongue sole Cynoglossus semilaevis (designated CsGal-8). CsGal-8 possesses conserved carbohydrate recognition domains (CRDs), as well as the conserved HXNPR and WGXEE motifs that are critical for carbohydrate binding. CsGal-8 was constitutively expressed in nine tissues of tongue sole and up-regulated in kidney, spleen, and blood by bacterial challenge. When expressed in HeLa cells, CsGal-8 protein was detected both in the cytoplasm and in the micro-vesicles secreted from the cells. Recombinant CsGal-8 (rCsGal-8) bound to lactose and other carbohydrates in a dose dependent manner. rCsGal-8 bound to a wide range of gram-positive and gram-negative bacteria and was co-localized with the bound bacteria in animal cells. Lactose, fructose, galactose, and trehalose effectively blocked the interactions between rCsGal-8 and different bacteria. Furthermore, rCsGal-8 exerted potent bactericidal activity against some gram-negative bacterial pathogens by directly damaging the membrane and structure of the pathogens. Taken together, these results indicate that CsGal-8 likely plays an important role in the immune defense against some bacterial pathogens by direct bacterial interaction and killing.

Complement C3 and Activated Fragment C3a Are Involved in Complement Activation and Anti-Bacterial Immunity

“…These results indicate that, as observed in higher vertebrates, rPoC3a may have a pro-inflammatory effect in the immune response of Japanese flounder by enhancing the activity of immune cells. Previous studies have shown that various immune molecules could bind to different glycoconjugates on bacterial cell surfaces (80). In mammals, C3a can bind to C3aR on the cell membrane (17,79).…”

GSDMEa-mediated pyroptosis is bi-directionally regulated by caspase and required for effective bacterial clearance in teleost

“…To prepare recombinant turbot IL-1β (rSmIL-1β), pET30a expressing SmIL-1β was introduced into E. coli , and the expression of the recombinant protein was induced by IPTG as above. The cells were ultrasonically lysed, and the pellet of the cells was used to purify the protein under denaturing condition as reported previously [ 41 ]. All purified proteins were dialyzed three times for 24 h in PBS at 4 °C and concentrated using Ultra free centrifugal filters (Millipore, MA, USA).…”

An Update of Lectins from Marine Organisms: Characterization, Extraction Methodology, and Potential Biofunctional Applications

“…Recombinant tongue sole Cynoglossus semilaevis galectin-8 bound to various Gram-positive and Gram-negative bacteria and the binding was inhibitable by fructose, galactose, lactose, and trehalose. The galectin killed some Gram-negative bacteria by disrupting the membrane [ 181 ]. The recombinant form of tandem-repeat galectin-9 from the Japanese flounder ( Paralichthys olivaceus ) bound to peptidoglycan and lipopolysaccharide, and agglutinated Gram-positive as well as Gram-negative bacteria [ 182 ].…”