Critical roles of sea cucumber C-type lectin in non-self recognition and bacterial clearance

Abstract

a b s t r a c t C-type lectin is one important pattern recognition receptor (PRR) that plays crucial roles in multiple immune responses. A C-type lectin from sea cucumber Apostichopus japonicus (AjCTL-1) was characterized in the present study. The amino acid sequence of AjCTL-1 shared high similarities with other Ctype lectins from invertebrates and vertebrates. The C-type lectin domain (CTLD) of AjCTL-1 contained a Ca 2þ -binding site 2 and four conserved cysteine residues. AjCTL-1 mRNA expression patterns in tissues and after bacterial challenge were then analysed. Quantitative PCR revealed that AjCTL-1 mRNA was widely expressed in the tested tissues of healthy sea cucumber. The highest expression level occurred in gonad followed by body wall, coelomocytes, tentacle, intestinum and longitudinal muscle, and the lowest expression level was in respiratory tree. AjCTL-1 mRNA expression in coelomocytes was significantly induced by gram-negative Listonella anguillarum and gram-positive Micrococcus luteus, with different upregulation patterns post-challenge. Recombinant AjCTL-1 exhibited the ability to bind peptidoglycan directly, agglutinate M. luteus, Staphylococcus aureus and Escherichia coli, in a Ca 2þ -dependant manner, and enhance the phagocytosis of coelomocytes against E. coli in vitro. The results indicated that AjCTL-1 could act as a PRR in Apostichopus japonicus and had critical roles in non-self recognition and bacterial clearance against invading microbes.

Molecular Aspects of Regeneration Mechanisms in Holothurians

“…Lectins are one of the major factors that protect holothurians from bacteria. In intact holothurians, many tissues, as well as coelomocytes, express C-type lectins [128][129][130]. Since transcripts of various lectins are found in transcriptomes of regenerating organs [71,102,116], it is likely that cells of anlagen can also synthesize these substances.…”

“…The major role of lectins in the immune response is to interact with extracellular sugar residues that are part of the bacterial wall. It has been shown that C-lectin from A. japonicus (AjCTL-1) is a pattern recognition receptor [128]. Its expression is induced by gram-positive and gram-negative bacteria.…”

A New C-Type Lectin Homolog SpCTL6 Exerting Immunoprotective Effect and Regulatory Role in Mud Crab Scylla paramamosain

“…Interestingly, SpCTL6 was highly expressed in the testis of adult male crabs (its absolute copy number was the highest compared with other male tissues and all female tissues), which is quite different from reported crustacean CTLs. In other aquatic invertebrates, it was found that two CTLs, AjCTL-1 from sea cucumber Apostichopus japonicus and AiCTL-9 from scallop Argopecten irradians also had the highest expression level in gonad (48,49). Wang et al performed a genome-wide survey on the lectin domain containing proteins (LDCPs) of oyster Crassostrea gigas and found that C-type lectin domain containing proteins (CTLPs) were the most abundant proteins (50).…”

Molecular Characterization and Biological Effects of a C-Type Lectin-Like Receptor in Large Yellow Croaker (Larimichthys crocea)

“…C-type lectins have essential roles in non-self-recognition and clearance of pathogenic microbes by binding to microbial surface carbohydrates [ 24 ]. In ayu, PaCTLRC showed agglutinating activity to all tested bacteria, including four Gram-negative bacteria ( V. parahaemolyticus , V. anguillarum , E. coli , and A. hydrophila ) and three Gram-positive bacteria ( Listeria monocytogenes , S. iniae and S. aureus ), in presence of Ca 2+ [ 17 ].…”