A multi-CRD C-type lectin with broad recognition spectrum and cellular adhesion from Argopectenirradians

Area of Science:

• Immunology
• Marine Biology
• Biochemistry

Background:

• C-type lectins are crucial Ca(2+)-dependent carbohydrate-binding proteins involved in innate immunity as pattern recognition receptors (PRRs).
• Understanding novel PRRs in invertebrates like scallops is vital for deciphering immune mechanisms against pathogens.

Purpose of the Study:

• To identify and characterize a novel C-type lectin from Argopecten irradians (scallop).
• To investigate the immune response role of this novel C-type lectin, designated AiCTL-9, in scallops.

Main Methods:

• Identification and sequencing of the full-length cDNA for AiCTL-9.
• Analysis of its carbohydrate-recognition domains (CRDs) and tertiary structure.
• Expression analysis in different scallop tissues and hemocytes upon microbial challenge.
• Binding assays with various pathogen-associated molecular patterns (PAMPs) and agglutination tests.
• In vitro assays assessing hemocyte adhesion and encapsulation.

Main Results:

• A novel C-type lectin, AiCTL-9, with four distinct CRDs was identified in Argopecten irradians.
• AiCTL-9 mRNA was predominantly found in hepatopancreas and gonads, with significant upregulation in hemocytes after exposure to fungi and bacteria.
• Recombinant AiCTL-9 (rAiCTL-9) demonstrated Ca(2+)-dependent binding to PAMPs (LPS, PGN, mannan, glucan) and agglutinated various microbes.
• rAiCTL-9 promoted hemocyte adhesion and enhanced in vitro hemocyte encapsulation.

Conclusions:

• AiCTL-9 functions as a novel pattern recognition receptor (PRR) in scallops.
• It plays a significant role in innate immunity by recognizing diverse PAMPs and enhancing hemocyte-mediated immune responses.
• AiCTL-9 contributes to scallop defense against a broad spectrum of pathogens.