Culex quinquefasciatus alpha-glucosidase serves as a putative receptor of the Cry48Aa toxin from Lysinibacillus sphaericus. (August 2022)

• Record Type: Journal Article
• Authors: Guo, Qingyun; Gao, Yuan; Xing, Chong; Niu, Yingchao; Ding, Lu; Dai, Xiaohua
• Is Part Of: Insect biochemistry and molecular biology. Volume 147(2022)
• Publication Date: 2022-08
• Subjects: Lysinibacillus sphaericus -- Culex quinquefasciatus -- Cry48Aa/Cry49Aa toxin -- Alpha-glucosidase -- Receptors; 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.2022.103799
• Languages: English
• ISSNs: 0965-1748

Abstract

Abstract: The Cry48Aa/Cry49Aa toxin of Lysinibacillus sphaericus shows specific toxicity towards larvae of Culex spp. Individual Cry48Aa and Cry49Aa subunits interact with distinct target sites in the larval midgut and overcome the resistance of Culex to the Bin toxin. However, the toxin-binding proteins have not yet been identified. The present study aimed to identify Cry48Aa-binding proteins in Culex quinquefasciatus . Pulldown assays using C. quinquefasciatus midgut brush-border membrane fractions (BBMFs) identified a class of proteins, including aminopeptidases (APNs), protease m1 zinc metalloproteases, alkaline phosphatases (ALPs), and maltases, that could be potentially involved in the mode of action of this toxin. RNA interference analysis showed that silenced larvae treated with dsRNA of the alpha-glucosidase (named Glu71) gene were more tolerant of the Cry48Aa/Cry49Aa toxin, which induced less than 20% mortality. The amino acid sequence of Glu71 exhibited 42% identity with Cqm1/Cpm1, which acted as a Bin toxin receptor. Toxin binding assays showed that Cry48Aa had a high specific binding capacity for the Glu71 protein, whereas Cry49Aa exhibited no specific binding. Overall, our results showed that Glu71 is a Cry48-binding protein involved in Cry48Aa/Cry49Aa toxicity. Graphical abstract: Image 1 Highlights: Putative Cry48Aa-binding proteins, including Glu71, were identified in the midgut of Culex quinquefasciatus. RNAi knockdown of Glu71 increased the tolerance of C. quinquefasciatus larvae to Cry48Aa/Cry49Aa toxin. The Glu71 protein shows homology to the Cqm1/Cpm1 receptor of the Bin toxin. Glu71 binds the Cry48Aa toxin with high specificity.