Abstract
BackgroundVarious proteins that display carbohydrate-binding activity in a Ca2+-dependent manner are classified into the C-type lectin family. They have one or two C-type carbohydrate-recognition domains (CRDs) composed of 110–130 amino acid residues in common. C-type lectins mediate cell adhesion, non-self recognition, and immuno-protection processes in immune responses and thus play significant roles in clearance of invaders, either as cell surface receptors for microbial carbohydrates or as soluble proteins existing in tissue fluids. The lectin of Spodoptera littoralis is still uncharacterized.MethodologyA single orf encoding a deduced polypeptide consisting of an 18-residue signal peptide and a 291-residue mature peptide, termed SpliLec, was isolated from the haemolymph of the cotton leafworm, S. littoralis, after bacterial challenge using RACE-PCR. Sequence analyses of the data revealed that SpliLec consists of two CRDs. Short-form CRD1 and long-form CRD2 are stabilized by two and three highly conserved disulfide bonds, respectively. SpliLec shares homology with some dipteran lectins suggesting possible common ancestor. The purified SpliLec exhibited a 140-kDa molecular mass with a subunit molecular mass of 35 kDa. The hemagglutination assays of the SpliLec confirmed a thermally stable, multisugar-binding C-type lectin that binds different erythrocytes. The purified SpliLec agglutinated microorganisms and exhibited comparable antimicrobial activity against gram (+) and gram (−) bacteria too.ConclusionsOur results suggested an important role of the SpliLec gene in cell adhesion and non-self recognition. It may cooperate with other AMPs in clearance of invaders of Spodoptera littoralis.
Highlights
After pathogens penetrate the insects’ structural barriers, they rely solely on an efficient innate immune system which shares many characteristics with the innate immune system of vertebrates
Our results suggested an important role of the SpliLec gene in cell adhesion and non-self recognition
Lectins are an important class of carbohydrate-binding proteins that have several distinct biological activities. They mediate cell adhesion, non-self recognition and immuno-protection processes in immune responses [6]. They exist in a wide variety of plants, animals, fungi, bacteria and viruses [7] and play significant role in clearance of invaders, either as cell surface receptors for microbial carbohydrates or as soluble proteins existing in tissue fluids [8]
Summary
After pathogens penetrate the insects’ structural barriers, they rely solely on an efficient innate immune system which shares many characteristics with the innate immune system of vertebrates. They mediate cell adhesion (i.e. bind to microbial surface components), non-self recognition and immuno-protection processes in immune responses [6] They exist in a wide variety of plants, animals, fungi, bacteria and viruses [7] and play significant role in clearance of invaders, either as cell surface receptors for microbial carbohydrates or as soluble proteins existing in tissue fluids [8]. Various proteins that display carbohydrate-binding activity in a Ca2+-dependent manner are classified into the C-type lectin family They have one or two C-type carbohydrate-recognition domains (CRDs) composed of 110–130 amino acid residues in common. C-type lectins mediate cell adhesion, non-self recognition, and immuno-protection processes in immune responses and play significant roles in clearance of invaders, either as cell surface receptors for microbial carbohydrates or as soluble proteins existing in tissue fluids.
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