title: Scophthalmus maximus cystatin B enhances head kidney macrophage-mediated bacterial killing.
abstract: Cystatins form a large family of cysteine protease inhibitors found in a wide arrange of organisms. Studies have indicated that mammalian cystatins play important roles under both physiological and pathological conditions. However, much less is known about fish cystatins. In this report, we described the identification and analysis of a cystatin B homologue, SmCytB, from turbot Scophthalmus maximus. The open reading frame of SmCytB is 300bp, which encodes a 99-residue protein that shares high levels of sequence identities with the cystatin B of a number of fish species and contains the conserved cysteine protease inhibitor motif of cystatin B. Constitutive expression of SmCytB is high in muscle, brain, heart and liver, and low in spleen, blood, gill and kidney. Bacterial infection upregulates SmCytB expression in kidney, spleen, liver and brain but not in muscle or heart. Functional analysis showed that recombinant SmCytB purified from Escherichia coli exhibits apparent cysteine protease inhibitor activity. Transient overexpression of SmCytB in head kidney macrophages enhances macrophage bactericidal activity probably through a nitric oxide-independent mechanism. These results indicate that SmCytB is involved in the immune defense of turbot against bacterial infection.
authors.affiliation: Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, PR China.
authors.forename: Ping-ping
authors.initials: PP
authors.lastname: Xiao
authors.forename: Yong-hua
authors.initials: YH
authors.lastname: Hu
authors.forename: Li
authors.initials: L
authors.lastname: Sun
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D055313:Cystatin B / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D020609:Edwardsiella tarda / Q000276:immunology*; D004756:Enterobacteriaceae Infections / Q000276:immunology / Q000662:veterinary*; D005393:Fish Diseases / Q000276:immunology*; D005412:Flatfishes / Q000235:genetics; D015870:Gene Expression; D007113:Immunity, Innate; D007668:Kidney / Q000276:immunology; D008264:Macrophages / Q000276:immunology*; D016366:Open Reading Frames; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000494:pharmacology; D016415:Sequence Alignment
chemical_list: D015853:Cysteine Proteinase Inhibitors; D011994:Recombinant Proteins; D055313:Cystatin B