A GM1b/asialo-GM1 oligosaccharide-binding R-type lectin from purplish bifurcate mussels Mytiliseptavirgata and its effect on MAP kinases.

Yuki Fujii,Sarkar M A Kawsar,Alberto Pallavicini,Kenichi Kamata,Yasuhiro Koide,Francesca Spazzali,Sultana Rajia,Jeremy R H Tame,Masahiro Hosono,Yasuhiro Ozeki,Yukiko Ogawa,Shigeki Sugawara,Imtiaj Hasan,Tatsusada Yoshida,Hideaki Fujita,Marco Gerdol

doi:10.1111/febs.15154

Abstract

A 15‐kDa lectin, termed SeviL, was isolated from Mytilisepta virgata (purplish bifurcate mussel). SeviL forms a noncovalent dimer that binds strongly to ganglio‐series GM1b oligosaccharide (Neu5Acɑ2‐3Galβ1‐3GalNAcβ1‐4Galβ1‐4Glc) and its precursor, asialo‐GM1 (Galβ1‐3GalNAcβ1‐4Galβ1‐4Glc). SeviL also interacts weakly with the glycan moiety of SSEA‐4 hexaose (Neu5Acα2‐3Galβ1‐3GalNAcβ1‐3Galα1‐4Galβ1‐4Glc). A partial protein sequence of the lectin was determined by mass spectrometry, and the complete sequence was identified from transcriptomic analysis. SeviL, consisting of 129 amino acids, was classified as an R(icin B)‐type lectin, based on the presence of the QxW motif characteristic of this fold. SeviL mRNA is highly expressed in gills and, in particular, mantle rim tissues. Orthologue sequences were identified in other species of the family Mytilidae, including Mytilus galloprovincialis, from which lectin MytiLec‐1 was isolated and characterized in our previous studies. Thus, mytilid species contain lectins belonging to at least two distinct families (R‐type lectins and mytilectins) that have a common β‐trefoil fold structure but differing glycan‐binding specificities. SeviL displayed notable cytotoxic (apoptotic) effects against various cultured cell lines (human breast, ovarian, and colonic cancer; dog kidney) that possess asialo‐GM1 oligosaccharide at the cell surface. This cytotoxic effect was inhibited by the presence of anti‐asialo‐GM1 oligosaccharide antibodies. With HeLa ovarian cancer cells, SeviL showed dose‐ and time‐dependent activation of kinase MKK3/6, p38 MAPK, and caspase‐3/9. The transduction pathways activated by SeviL via the glycosphingolipid oligosaccharide were triggered apoptosis.DatabaseNucleotide sequence data have been deposited in the GenBank database under accession numbers MK434191, MK434192, MK434193, MK434194, MK434195, MK434196, MK434197, MK434198, MK434199, MK434200, and MK434201.

Highlights

Many marine invertebrates possess lectins with various glycan-binding properties [1,2,3]
We have demonstrated the presence of an R-type lectin (SeviL) in Mytilisepta virgata, a member of the family Mytilidae
Mytilisepta virgata R-type lectin (SeviL) was assigned to the R-type lectin family on the basis of sequence similarities to the prototypical ricin Bchain domain, but it displays features not found in other members of this family

Summary

Introduction

Many marine invertebrates possess lectins (glycanbinding proteins) with various glycan-binding properties [1,2,3]. In the differentiation of phylogeny, lectinmediated interactions between glycans and proteins were adapted into various kinds of key pathways involved in a variety of fundamental biological processes, including embryonic development, immune responses, and cell growth regulation [4,5,6]. During this functional diversification, marine invertebrates developed an unusually large number of lectins, many having convergent structures that facilitate binding to specific glycan structures exposed on the surface of target cells. The taxonomic distribution of mytilectins known to date is limited to the protostome clade Lophotrochozoa and discontinuous; members of this family have been identified only in the subclass Pteriomorphia (phylum Mollusca) and the order Lingulida (phylum Brachiopoda) [19]

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Results

Conclusion