Molecular and biochemical characterization of the bed bug salivary gland cholinesterase as an acetylcholine-sequestering enzyme. (November 2018)

• Record Type: Journal Article
• Authors: Kim, Ju Hyeon; Hwang, Chae Eun; Yoon, Kyungjae Andrew; Seong, Keon Mook; Lee, Jonghwa; Kim, Jeong Han; Lee, Si Hyeock
• Is Part Of: Insect biochemistry and molecular biology. Volume 102(2018)
• Page Start: 52
• Page End: 58
• Publication Date: 2018-11
• Subjects: Bed bug -- Cimex lectularius -- Cholinesterase -- Salivary gland -- Sequestration -- Blood feeding; Insect biochemistry -- Periodicals; Insects -- Physiology -- Periodicals; Insects -- Molecular aspects -- Periodicals; Biochemistry -- Periodicals; Insectes -- Biochimie -- Périodiques; Insectes -- Composition -- Périodiques; Insectes -- Physiologie -- Périodiques; Insectes -- Aspect moléculaire -- Périodiques; Biochimie -- Périodiques; Biochemistry; Insect biochemistry; Insects -- Molecular aspects; Insects -- Physiology; Periodicals; 572.8157
• DOI: 10.1016/j.ibmb.2018.09.009
• Languages: English
• ISSNs: 0965-1748

Abstract

Abstract: The common bed bug, Cimex lectularius, possesses a cholinesterase expressed exclusively in the salivary gland (ClSChE). In this study, we investigated the molecular forms, tissue distribution patterns and biochemical properties of ClSChE and showed that ClSChE exists as a soluble monomeric form or a soluble dimeric form connected by a disulfide bridge. Immunohistochemical analysis confirmed that ClSChE was expressed in the epithelial cells of both the salivary gland and the duct. In addition, the secretion of monomeric ClSChE through the proboscis during feeding was confirmed by western blotting using a ClSChE-specific antibody. To predict the role of ClSChE injected into the tissue of an animal host, we analyzed the extent of hydrolysis of acetylcholine (ACh) by ClSChE by ultra-performance liquid chromatography-tandem mass spectrometry. ClSChE binding to ACh was not clearly resolved in the binding assay format used in this study, probably due to the weak but detectable ACh-hydrolytic activity of ClSChE. Nevertheless, kinetic analysis revealed that ClSChE possesses extremely low Km (high affinity to ACh) and Vmax values. These findings suggest that ClSChE functions virtually as an ACh-sequestering protein by having a very strong affinity to ACh but an extremely long turnover time. Given that ACh regulates a wide variety of host physiologies, we discuss the tentative roles of ClSChE in blood vessel constriction and itch/pain regulation in the host. Graphical abstract: Highlights: ClSChE is expressed in the epithelial cells of both salivary gland and duct. Monomeric form of ClSChE is secreted through proboscis during feeding. UPLC-MS/MS-based kinetic analysis reveals extremely low Km and Vmax of ClSChE. ClSChE appears to function virtually as acetylcholine-sequestration protein. Putative roles of ClSChE in blood feeding are discussed.