Galactoside-binding lectin in Solen grandis as a pattern recognition receptor mediating opsonization

Area of Science:

• Invertebrate immunology
• Molecular biology
• Biochemistry

Background:

• Galectins are key pathogen recognition molecules in invertebrate innate immunity.
• A previous study identified the galectin gene SgGal-1 in the mollusk Solen grandis.
• The precise immune functions of SgGal-1 required further elucidation.

Purpose of the Study:

• To functionally characterize Solen grandis galectin-1 (SgGal-1) in the context of innate immunity.
• To investigate the role of SgGal-1 as a pattern recognition receptor (PRR).
• To determine SgGal-1's involvement in hemocyte-mediated immune responses.

Main Methods:

• Expression analysis of SgGal-1 in various S. grandis tissues.
• In vitro binding assays of recombinant SgGal-1 (rSgGal-1) with microbial components (PGN, β-glucan, LPS).
• Microbial agglutination assays using rSgGal-1.
• Functional assays assessing rSgGal-1's effect on hemocyte recruitment and phagocytosis, including blocking experiments with specific antibodies.

Main Results:

• SgGal-1 protein was detected in gill, mantle, hepatopancreas, and gonad tissues, but not in hemocytes or muscle.
• rSgGal-1 specifically bound to peptidoglycan (PGN) and β-glucan, but not lipopolysaccharide (LPS).
• rSgGal-1 induced significant agglutination of five tested microbial species.
• SgGal-1 facilitated hemocyte recruitment for encapsulation and enhanced hemocyte phagocytosis of Escherichia coli.
• These functions were inhibited by anti-rSgGal-1 serum.

Conclusions:

• SgGal-1 functions as a pattern recognition receptor (PRR) in Solen grandis, recognizing specific microbial patterns.
• SgGal-1 plays a direct role in immune opsonization by promoting hemocyte recruitment and phagocytosis.
• SgGal-1 is a vital component of the innate immune system in S. grandis, contributing to host defense against pathogenic infections.