title: Identification of a serine proteinase homolog (Sp-SPH) involved in immune defense in the mud crab Scylla paramamosain.
abstract: Clip domain serine proteinase homologs are involved in many biological processes including immune response. To identify the immune function of a serine proteinase homolog (Sp-SPH), originally isolated from hemocytes of the mud crab, Scylla paramamosain, the Sp-SPH was expressed recombinantly and purified for further studies. It was found that the Sp-SPH protein could bind to a number of bacteria (including Aeromonas hydrophila, Escherichia coli, Staphylococcus aureus, Vibrio fluvialis, Vibrio harveyi and Vibrio parahemolyticus), bacterial cell wall components such as lipopolysaccharide or peptidoglycan (PGN), and β-1, 3-glucan of fungus. But no direct antibacterial activity of Sp-SPH protein was shown by using minimum inhibitory concentration or minimum bactericidal concentration assays. Nevertheless, the Sp-SPH protein was found to significantly enhance the crab hemocyte adhesion activity (paired t-test, P<0.05), and increase phenoloxidase activity if triggered by PGN in vitro (paired t-test, P<0.05). Importantly, the Sp-SPH protein was demonstrated to promote the survival rate of the animals after challenge with A. hydrophila or V. parahemolyticus which were both recognized by Sp-SPH protein, if pre-incubated with Sp-SPH protein, respectively. Whereas, the crabs died much faster when challenged with Vibrio alginolyiicus, a pathogenic bacterium not recognized by Sp-SPH protein, compared to those of crabs challenged with A. hydrophila or V. parahemolyticus when pre-coated with Sp-SPH protein. Taken together, these data suggested that Sp-SPH molecule might play an important role in immune defense against bacterial infection in the mud crab S. paramamosain.
authors.affiliation: State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, China.
authors.forename: Qiu-xia
authors.initials: QX
authors.lastname: Zhang
authors.forename: Hai-peng
authors.initials: HP
authors.lastname: Liu
authors.forename: Rong-yuan
authors.initials: RY
authors.lastname: Chen
authors.forename: Kai-li
authors.initials: KL
authors.lastname: Shen
authors.forename: Ke-jian
authors.initials: KJ
authors.lastname: Wang
mesh_terms: D000818:Animals; D001419:Bacteria / Q000187:drug effects / Q000378:metabolism; D003386:Brachyura / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology* / Q000382:microbiology; D002448:Cell Adhesion / Q000187:drug effects; D002457:Cell Extracts; D004591:Electrophoresis, Polyacrylamide Gel; D005658:Fungi / Q000187:drug effects / Q000378:metabolism; D006434:Hemocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D007109:Immunity / Q000187:drug effects; D014442:Monophenol Monooxygenase / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D011994:Recombinant Proteins / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D057057:Serine Proteases / Q000378:metabolism*
chemical_list: D002457:Cell Extracts; D011994:Recombinant Proteins; D014442:Monophenol Monooxygenase; D057057:Serine Proteases