title: 93-kDa twin-domain serine protease inhibitor (Serpin) has a regulatory function on the beetle Toll proteolytic signaling cascade.
abstract: Serpins are protease inhibitors that play essential roles in the down-regulation of extracellular proteolytic cascades. The core serpin domain is highly conserved, and typical serpins are encoded with a molecular size of 35-50 kDa. Here, we describe a novel 93-kDa protein that contains two complete, tandemly arrayed serpin domains. This twin serpin, SPN93, was isolated from the larval hemolymph of the large beetle Tenebrio molitor. The N-terminal serpin domain of SPN93 forms a covalent complex with the Spätzle-processing enzyme, a terminal serine protease of the Toll signaling cascade, whereas the C-terminal serpin domain of SPN93 forms complexes with a modular serine protease and the Spätzle-processing enzyme-activating enzyme, which are two different enzymes of the cascade. Consequently, SPN93 inhibited β-1,3-glucan-mediated Toll proteolytic cascade activation in an in vitro system. Site-specific proteolysis of SPN93 at the N-terminal serpin domain was observed after activation of the Toll proteolytic cascade in vivo, and down-regulation of SPN93 by RNAi sensitized β-1,3-glucan-mediated larval death. Therefore, SPN93 is the first serpin that contains twin tandemly arrayed and functionally active serpin domains that have a regulatory role in the larval Toll proteolytic signaling cascade.
authors.affiliation: Global Research Laboratory of Insect Symbiosis, College of Pharmacy, Pusan National University, Geumjeong-Gu, Busan 609-735, Korea.
authors.forename: Rui
authors.initials: R
authors.lastname: Jiang
authors.forename: Bing
authors.initials: B
authors.lastname: Zhang
authors.forename: Kenji
authors.initials: K
authors.lastname: Kurokawa
authors.forename: Young-In
authors.initials: YI
authors.lastname: So
authors.forename: Eun-Hye
authors.initials: EH
authors.lastname: Kim
authors.forename: Hyun Ok
authors.initials: HO
authors.lastname: Hwang
authors.forename: Joon-Hee
authors.initials: JH
authors.lastname: Lee
authors.forename: Akiko
authors.initials: A
authors.lastname: Shiratsuchi
authors.forename: Jinghai
authors.initials: J
authors.lastname: Zhang
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Nakanishi
authors.forename: Hee-Seung
authors.initials: HS
authors.lastname: Lee
authors.forename: Bok Luel
authors.initials: BL
authors.lastname: Lee
mesh_terms: D000818:Animals; D002845:Chromatography / Q000379:methods; D003001:Cloning, Molecular; D001517:Coleoptera; D006801:Humans; D008543:Melanins / Q000737:chemistry; D008954:Models, Biological; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D015842:Serine Proteinase Inhibitors / Q000737:chemistry*; D015843:Serpins / Q000737:chemistry* / Q000378:metabolism*; D015398:Signal Transduction; D051193:Toll-Like Receptors / Q000378:metabolism*
chemical_list: D008543:Melanins; D015842:Serine Proteinase Inhibitors; D015843:Serpins; D051193:Toll-Like Receptors