Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
Identification and molecular characterization of a mucosal lectin (MeML) from the blue mussel Mytilus edulis and its potential role in particle capture
Introduction
In the aquatic environment, communication between organisms is often based on molecular language. In numerous physiological processes (defense, reproduction, and predation) marine organisms interact with each other using thousands of organic metabolites belonging to diverse chemical groups (Faulkner, 2002, Hay, 1996 and references therein). Among molecules known for non-self recognition and cell-to-cell interactions, lectins are a large and diverse group of sugar-binding proteins that specifically and reversibly bind to glycans covering living cells (Sharon and Lis, 2004, Vasta, 2009). Their functions are diverse and they have been described to play a role in the defense mechanism (Kenjo et al., 2001, Tasumi and Vasta, 2007), in reproduction (Springer et al., 2008), in parasitism (Hager and Carruthers, 2008, Stevens et al., 2006), and in symbiosis (Bulgheresi et al., 2006, Nyholm and McFall-Ngai, 2004, Wood-Charlson et al., 2006). They can assist the organism by immobilizing particles through agglutination (Fisher and Dinuzzo, 1991, Pales Espinosa et al., 2009) and encapsulation (Koizumi et al., 1999) or can initiate a cascade of events leading, for example, to host colonization (Nyholm and McFall-Ngai, 2004) or to limit pathogen infection (Holmskov et al., 2003).
Lectins are ubiquitously distributed in nature as they are found in viruses, bacteria, fungi, plants, invertebrates and vertebrates (Sharon and Lis, 2004, Vasta and Ahmed, 2008). In bivalves, lectins have been mostly described in hemolymph (Zhang et al., 2009), associated or not with hemocyte membranes (Tasumi and Vasta, 2007), and linked to the defense mechanism (Fisher and Dinuzzo, 1991, Minamikawa et al., 2004, Tripp, 1992, Zhang et al., 2009). In some rare cases, bivalve lectins have been found to be potentially involved in other functions. For example, in Codakia orbicularis, a clam known for its symbiotic relationship with a sulfide-oxidizing chemoautotrophic bacteria (Frenkiel and Moueza, 1995), the lectin “codakine” has been found to be the predominant protein in the gill (Gourdine and Smith-Ravin, 2002) leading Gourdine et al. (2007) to propose its involvement in the mediation of symbiosis. Additionally, the presence of lectins have been suspected (Fisher, 1992) and recently demonstrated (Pales Espinosa et al., 2008) in mucus covering pallial organs (gills, labial palps) in the oyster Crassostrea virginica (Pales Espinosa et al., 2009, Pales Espinosa et al., 2010) and the mussel Mytilus edulis (Pales Espinosa et al., submitted).
Suspension feeding bivalves are well known to be able to select among particles (Cognie et al., 2003, Newell and Jordan, 1983, Pales Espinosa et al., 2008, Ward and Shumway, 2004). Although some aspects of the selection process have been elucidated, the actual mechanism(s) by which particles of poor quality are rejected into pseudofeces while those of higher quality are ingested remain unclear. Among theories advanced in the literature, some studies support the idea that bivalves use chemical cues to discriminate among particles (Beninger and Decottignies, 2005, Beninger et al., 2004, Kiorboe and Mohlenberg, 1981, Newell and Jordan, 1983, Pales Espinosa et al., 2007, Shumway et al., 1985, Ward and Targett, 1989). More recently, our results in oysters (Pales Espinosa et al., 2009, Pales Espinosa et al., 2010) and mussels (Pales Espinosa et al., submitted) showed that particle selection in bivalves is mediated by interactions between lectins present in mucus covering feeding organs and carbohydrates associated with the surface of suspended food particles. Although our previous studies represent, to the best of our knowledge, the first indications for the involvement of lectins in the feeding mechanism of metazoans, carbohydrate–lectin interactions have already been shown to be involved in the feeding mechanisms of predatory protozoans. For example, previous studies have demonstrated the involvement of mannose-binding lectins as a feeding receptor for recognizing preys in the marine dinoflagellate Oxyrrhis marina (Wootton et al., 2007) and in the amoeba Acanthamoebe castellanii (Allen and Dawidowicz, 1990).
In this study, we screened public EST (Expressed Sequence Tag) databases and used a diverse set of molecular techniques to identify lectin candidates that are produced in the feeding organs of the blue mussel, M. edulis. These investigations allowed the identification of a secretory lectin (hereby designated MeML for M. edulis mucocyte lectin) that is specifically produced in mucocytes lining mussel feeding organs (gills, labial palps). The full lectin sequence is presented and the expression of this molecule in response to starvation was investigated. Results highlight the potential involvement of this lectin in particle capture processes.
Section snippets
Animals
Adult (60 to 70 mm in length) blue mussels, M. edulis, were collected from Long Island Sound (Port Jefferson, NY, USA). Their external shell surface was scrubbed to remove mud and marine life. Mussels were then randomly subdivided into 3 different groups. The first 2 groups were immediately used for RNA extraction/cDNA amplification or in situ hybridization analysis. The last group was acclimated in the lab before being used in the starvation study (see below).
RNA extraction
Eight mussels were bled from the
Identification of MeML
Among the 13 tested ESTs, 3 candidates were not detected in any of the tested organs and 9 were homogenously expressed in all tissues including hemocytes. Only one candidate (EST 11) was expressed in the labial palps, gills and the digestive gland (weak signal) but not in hemocytes (Fig. 1). Further analysis of this EST revealed that it codes for a complete protein, hereby designated MeML [GenBank accession no. HM049926]. The complete sequence consisted of a 459 bp encoding for a predicted
Discussion
Most previously described lectins in marine invertebrates were identified in hemolymph or hemocytes and were suspected or found to be involved in the defense system against pathogens (Tasumi and Vasta, 2007, Vasta et al., 1984, Zheng et al., 2008). Given their diverse molecular structures and their specific interactions with carbohydrate moieties, lectins were also found in organs and tissues other than blood, and have been shown to play roles as diverse as the establishment of symbiosis (
Acknowledgments
This work was funded in part by a grant from the National Science Foundation to EPE and BA (IOS-0718453).
References (68)
- et al.
Specificity of lung surfactant protein Sp-a for both the carbohydrate and the lipid moieties of certain neutral glycolipids
J. Biol. Chem.
(1992) 2 distinct classes of carbohydrate-recognition domains in animal Lectins
J. Biol. Chem.
(1988)Evolution of Ca2+-dependent animal lectins
Prog. Nucleic Acid Res. Mol. Biol.
(1993)Occurrence of agglutinins in the pallial cavity mucus of oysters
J. Exp. Mar. Biol. Ecol.
(1992)- et al.
Agglutination of bacteria and erythrocytes by serum from 6 species of marine mollusks
J. Invertebr. Pathol.
(1991) - et al.
A lectin isolate from mucus of Helix aspersa
Comp. Biochem. Phys. B
(1984) - et al.
The three-dimensional structure of codakine and related marine C-type lectins. Fish
Shellfish Immunol.
(2007) - et al.
MARveling at parasite invasion
Trends Parasitol.
(2008) Marine chemical ecology: what's known and what's next?
J. Exp. Mar. Biol. Ecol.
(1996)- et al.
The surprising complexity of signal sequences
Trends Biochem. Sci.
(2006)
Variability of feeding processes in the cockle Cerastoderma edule (L) in response to changes in seston concentration and composition
J. Exp. Mar. Biol. Ecol.
Cloning and characterization of novel ficolins from the solitary ascidian, Halocynthia roretzi
J. Biol. Chem.
Lipopolysaccharide-binding protein of Bombyx mori participates in a hemocyte-mediated defense reaction against gram-negative bacteria
J. Insect Physiol.
Structural basis of galactose recognition by C-type animal lectins
J. Biol. Chem.
An ancient and variable mannose-binding lectin from the coral Acropora millepora binds both pathogens and symbionts
Dev. Comp. Immunol.
Analysis of relative gene expression data using real-time quantitative PCR and the 2(T)(− Delta Delta C) method
Methods
Isolation and partial characterization of a calcium-dependent lectin (chiletin) from the haemolymph of the flat oyster, Ostrea chilensis. Fish
Shellfish Immunol.
Mechanism of Ca2+ and monosaccharide binding to a C-type carbohydrate-recognition domain of the macrophage mannose receptor
J. Biol. Chem.
Galectin containing cells in the skin and mucosal tissues in Japanese conger eel, Conger myriaster: an immunohistochemical study
Dev. Comp. Immunol.
Tandem repeat L-rhamnose-binding lectin from the skin mucus of ponyfish, Leiognathus nuchalis
Biochem. Bioph. Res. Commun.
Use of encapsulated live microalgae to investigate pre-ingestive selection in the oyster Crassostrea gigas
J. Exp. Mar. Biol. Ecol.
Particle selection, ingestion, and absorption in filter-feeding bivalves
J. Exp. Mar. Biol. Ecol.
Glycan microarray analysis of the hemagglutinins from modern and pandemic influenza viruses reveals different receptor specificities
J. Mol. Biol.
Primary structure and characteristics of a lectin from skin mucus of the Japanese eel Anguilla japonica
J. Biol. Chem.
Agglutinins in the hemolymph of the hard clam, Mercenaria mercenaria
J. Invertebr. Pathol.
Yeast-binding C-type lectin with opsonic activity from conger eel (Conger myriaster) skin mucus
Mol. Immunol.
A lectin on the hemocyte membrane of the oyster (Crassostrea virginica)
Cell. Immunol.
Identification and tissue expression analysis of C-type lectin and galectin in the Pacific oyster, Crassostrea gigas
Comp. Biochem. Phys. B
A novel C-type lectin (Cflec-3) from Chlamys farreri with three carbohydrate-recognition domains. Fish
Shellfish Immunol.
A lectin (CfLec-2) aggregating Staphylococcus haemolyticus from scallop Chlamys farreri. Fish
Shellfish Immunol.
Phagocytosis in Acanthamoeba. 1. A mannose receptor is responsible for the binding and phagocytosis of yeast
J. Cell. Physiol.
Ecophysiological deterministic model for Crassostrea gigas in an estuarine environment
Aquat. Living Resour.
What makes diatoms attractive for suspensivores? The organic casing and associated organic molecules of Coscinodiscus perforatus are quality cues for the bivalve Pecten maximus
J. Plankton Res.
Localization of qualitative particle selection sites in the heterorhabdic filibranch Pecten maximus (Bivalvia: Pectinidae)
Mar. Ecol. Prog. Ser.
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