title: A cysteine-rich protein from an arthropod stabilizes clotting mesh and immobilizes bacteria at injury sites.
abstract: Hemolymph coagulation in arthropods plays key roles in host defense, including sealing wounds to staunch bleeding and immobilizing invading microorganisms. We have previously reported that horseshoe crab transglutaminase (TGase) promotes cross-linking of a clotting protein (coagulin) with hemocyte-derived proteins (proxins), resulting in the formation of stable coagulin fibrils. Here we show that TGase also cross-links proxins to another hemocyte-derived protein named stablin. Stablin is a cysteine-rich protein of 131 residues. Surface plasmon resonance analysis revealed the specific interaction of stablin with proxin-1 at K(d) = 4.0 x 10(-9) m. Stablin was predominantly localized in the large granules of hemocytes and secreted by lipopolysaccharide-induced exocytosis. Interestingly, stablin bound to chitin at K(d) = 1.5 x 10(-8) m, as determined by using a quartz-crystal microbalance. Stablin also interacted with lipopolysaccharides and lipoteichoic acids and exhibited bacterial agglutinating activity against Gram-positive and -negative bacteria. Immunostaining showed that stablin is co-localized with coagulin in the clotting fibrils that effectively trap bacteria. Moreover, an anti-stablin antibody strongly inhibited the proper formation of the clotting fibrils. These data suggest that stablin promotes the formation of the clotting mesh and the immobilization of invading microbes at injury sites. In arthropods, the TGase-mediated cross-linking may play an important role in the initial stage of host defense, wound closure, and healing, as in the case of mammals.
authors.affiliation: Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Matsuda
authors.affiliation: Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan.
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Osaki
authors.affiliation: Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Hashii
authors.affiliation: Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan.
authors.forename: Takumi
authors.initials: T
authors.lastname: Koshiba
authors.affiliation: Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan. Electronic address: skawascb@mbox.nc.kyushu-u.ac.jp.
authors.forename: Shun-Ichiro
authors.initials: SI
authors.lastname: Kawabata
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003545:Cysteine / Q000737:chemistry*; D006434:Hemocytes / Q000378:metabolism; D006458:Hemolymph / Q000378:metabolism; D006737:Horseshoe Crabs; D007700:Kinetics; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D020349:Surface Plasmon Resonance; D013682:Teichoic Acids / Q000737:chemistry; D011503:Transglutaminases / Q000378:metabolism; D014945:Wound Healing
chemical_list: D003432:Cross-Linking Reagents; D008070:Lipopolysaccharides; D013682:Teichoic Acids; C009900:lipoteichoic acid; D011503:Transglutaminases; D003545:Cysteine