Lectin in Innate Immunity of Crustacea

Review Article

Austin Biol. 2016; 1(1): 1001.

Lectin in Innate Immunity of Crustacea

Maghil Denis*, Karthigayani Thayappan, Sivakumar Mullaivanam Ramasamy, Arumugam Munusamy

Department of Zoology, University of Madras, India

*Corresponding author: Maghil Denis, University of Madras, Kotturpuram Road, Guindy Campus, Chennai, Tamilnadu, India

Received: February 17, 2016; Accepted: March 25, 2016; Published: March 29, 2016

Abstract

Lectins are protein or glycoprotein with binding specificity to sugars and as pattern recognition molecule recognize glycosylated surface of pathogens. In crustacea, lectins are diverse and species specific and the mechanism of recognition by the lectin have an impact on immune response and immune regulation. The present review explains the evolutionary success of innate immunity based on the diversity of these recognition molecules.

Keywords: Crustacea; Lectins; Opsonin; Innate Immunity; Receptor

Introduction

The innate immunity of invertebrate appears to have evolved to a complex adaptive immune mechanism in vertebrates. The simple process of antigen or nonself recognition of innate immune response are transformed from a single step process to pathways or cascades involving receptor selection and regulatory process that target and attenuate adaptive immune responses [1]. The recognition and distinguishing of the nonself are based on recognition of cell surface glycoconjugate [2]. The modulations in carbohydrate molecules appear to be specific for species and are the basis of pathogen recognition. The glycosylated Pathogen Associated Molecular Pattern (PAMP) include, Lipopolysaccharide (LPS), Peptidoglycan (PGN), and diverse sugars including β1-3 glucan and sialic acid, recognized by Pattern Recognition Receptors (PRR) that activate an immune response to eliminate the pathogen [3]. Lectins are molecules of ubiquitous occurrence and distinguish the nonself by binding specifically to the glycan of cell surface [4]. The report on the roles of lectins in enhancement of cellular immune responses also elaborates the function of lectin not only as recognition molecules but also as an opsonin [5]. The ability of lectin to bind to microbial glycosylated surface and induce a cascade of response leading to its elimination of invading pathogen was found to vary among the organisms [6]. The diverse ligand specificity and cell-cell interactions are the basis of multiple functions and pathways of immune response. In crustacea the structural and functional diversity of the lectins based on its sugar specificity appear to display diverse innate immune responses. The present review attempts to summarize the reported role of lectins in immunological functions in crustacea.

Carbohydrate Recognition Domain (CRD) in lectins

The Ca2+-dependent carbohydrate-binding lectin are termed the C-type lectins are mediated by a compact module known as the ‘Carbohydrate Recognition Domain” (CRD) present in all Ca2+- dependent lectins but not in other types of animal lectins [7]. This domain, shows specific, but weak calcium-dependent binding to a variety of monosaccharides [8]. C-type lectin CRDs are found as building blocks in a variety of multi-domain proteins involved in organizing the extracellular matrix, endocytosis, the primary immune system and interactions of blood cells [9]. The CRD from various species of crustacea are summarized in (Table 1). The CRD with sequence QPD (Gln-Pro-Asp) motif was predicted with binding specificity for galactose and the CRD comprised of EPN (Glu-Pro- Asn) motif for mannose [10]. The C-type lectins of the shrimps PmLT, Penaeus monodon [11], Fc-Lec2 Fenneropenaeus chinensis [12] and LvLT Litopenaeus vannamei, [13], had the two CRD with binding specificity for galactose and mannose. The lectins from shrimps possessed CRD with binding specificity for either one of the two sugars, the CRD for galactose QPD in Fc-Lec5 lectin from F. chinensis [14] and LvLectin 2 from L. vannamei, [15] and EPN CRD for mannose in, LvCTL of L. vannamei [16] and Fc-hsL of F. chinensis [16]. The phylogeny of the CRD for mannose and galactose from different species of shrimps appear conserved and despite the similarity in sugar binding specificity the amino acid sequence of the lectins appear divergent [13,18,19]. The evolutionary relationship of these CRDs in shrimp imply that the motif of amino acid sequence of the lectin protein though appear conserved differ with the binding glycan cluster [20]. The C-type lectin PtLP from the swimming crab Portunus trituberculatus contains a single CRD domain with six conserved cysteine residues does not contain a typical EPN or QPD motif in phylogenetic analysis was found in the a large cluster together with black tiger shrimp lectin PmAV [18]. The report of C-type lectins EsLecA and EsLecG from Chinese mitten crab, Eriocheir sinensis showed conserved CRD of QPD (Gln-Pro-Asp) motif for galactose in EsLecA, whereas the EsLecG had a key “EPE” (Glu-Pro-Glu) motif a mutated expression of mannose [21]. This clearly demonstrated the diversification of CRD by mutations and also explains convergence by retaining the conserved CRD. The CRD in lectin from different species of crustacea fail to explain the ligand specificity which appears to be determined either by multivalency of CRD developed within the primary structure of the protein or by clustering in cell surface glycans [22]. This amply describes the diversity in PAMP that enables the evolution under selection pressure of CRD in lectins.

Citation: Chiu W-Y, Su T-H and Lo Y-H. A Near Miss: Cervical Spine Fracture in a Young Adult. J Fam Med. 2016; 3(9): 1090.