A Truncated Galectin-3 Isolated from Skin Mucus of Atlantic Salmon Salmo salar Binds to and Modulates the Proteome of the Gram-Negative Bacteria Moritella viscosa

Abstract

The mucus of fish skin plays a vital role in innate immune defense. Some mucus proteins have the potential to incapacitate pathogens and/or inhibit their passage through the skin. In this study the aim was to isolate and characterize galectin(s), β-galactosides binding proteins, present in skin mucus. A novel short form of galectin-3 was isolated from Atlantic salmon skin mucus by α-lactose agarose based affinity chromatography followed by Sephadex G-15 gel filtration. Mass spectrometric analysis showed that the isolated protein was the C-terminal half of galectin-3 (galectin-3C). Galectin-3C showed calcium independent and lactose inhabitable hemagglutination, and agglutinated the Gram-negative pathogenic bacteria Moritella viscosa. Galectin-3 mRNA was highly expressed in skin and gill, followed by muscle, hindgut, spleen, stomach, foregut, head kidney, and liver. Moritella viscosa incubated with galectin-3C had a modified proteome. Proteins with changed abundance included multidrug transporter and three ribosomal proteins L7/12, S2, and S13. Overall, this study shows the isolation and characterization of a novel galectin-3 short form involved in pathogen recognition and modulation, and hence in immune defense of Atlantic salmon.

Dietary Inclusion of Black Soldier Fly (Hermetia Illucens) Larvae Meal and Paste Improved Gut Health but Had Minor Effects on Skin Mucus Proteome and Immune Response in Atlantic Salmon (Salmo Salar)

“…Besides, the fish were in the freshwater phase, which has been shown to have lower mucus viscosity than in seawater, meaning a different protein and glycosylation pattern ( 106 ). It is important to note that in the present study, trypsinized peptides were used in the mass spectrometry analysis, that might affect the protein conformation ( 107 ). It is possible that BSFL might have an effect on the conformation or glycosylation of skin mucus protein, which was not assessed in the present study.…”

Immune and proteomic responses to the soybean meal diet in skin and intestine mucus of Atlantic salmon ( Salmo salar L.)

“…In salmon, galectins have been involved with a variety of roles in innate immune defence. As reported by Patel et al (2020), galectin‐3 is highly expressed in skin and gills and can agglutinate the Gram‐negative bacterium Moritella viscosa . Further analysis is needed to elucidate the role of galectins on intestinal inflammation.…”

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

“…The structure also depicted a Ca 2+ ions binding at the bottom of the funnel-shaped tunnel at the center of the propeller. Several CTLs have previously been isolated from the eggs [ 68 ], intestine, gills [ 72 ], serum, and skin mucus [ 73 , 74 ] of fish. Typically, CTLs contain a double loop, where two highly conserved disulphide bridges, hydrophobic and polar interactions, occur.…”

“…Elevated expression of galectin-3 mRNA was noted in the gills and skin, followed by muscle, hindgut, spleen, stomach, foregut, head kidney, and the liver. Galectin-3C treatment altered the amount of three ribosomal proteins L7/12, S2, and S13 and multidrug transporter in M. viscosa [ 74 ]. The mannose-binding skin mucus pufflectin of the pufferfish Takifugu rubripes , which manifested sequence resemblance to monocot mannose-binding lectins but not to animal lectins, showed binding activity to the trematode parasite Heterobothrium okamotoi .…”