Functions of Armigeres subalbatus C-type lectins in innate immunity

• Published in: Insect biochemistry and molecular biology Vol. 52; pp. 102 - 114
• Main Authors: Shi, Xiu-Zhen, Kang, Cui-Jie, Wang, Song-Jie, Zhong, Xue, Beerntsen, Brenda T., Yu, Xiao-Qiang
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.09.2014
• Subjects: Animals; Armigeres subalbatus; C-type lectin; Culicidae - immunology; Culicidae - microbiology; Escherichia coli - immunology; Female; Gram-Negative Bacteria - immunology; Gram-Positive Bacteria - immunology; Hemocytes - immunology; Immunity, Innate; Innate immunity; Lectins, C-Type - immunology; Lectins, C-Type - metabolism; Micrococcus luteus - immunology; Protein Binding; Receptors, Pattern Recognition - immunology; Receptors, Pattern Recognition - metabolism; RNA, Double-Stranded; RNAi; Survival; Innate immunity; RNAi; Survival; C-type lectin; Armigeres subalbatus
• ISSN: 0965-1748; 1879-0240
• DOI: 10.1016/j.ibmb.2014.06.010

C-type lectins (CTLs) are a superfamily of calcium-dependent carbohydrate binding proteins containing at least one carbohydrate-recognition domain (CRD) and they are present in almost all metazoans. Insect CTLs may function as pattern-recognition receptors and play important roles in innate immunity. In this study, we selected five AsCTLs from the mosquito Armigeres subalbatus, a natural vector of filarial nematodes, and performed both in vitro and in vivo studies to elucidate their functions in innate immunity. AsCTLMA15, AsCTLGA5 and AsCTL15 were mainly expressed in hemocytes, AsCTL16 was expressed in fat body, while AsCTLMA11 was expressed in both hemocytes and fat body, and only AsCTLMA11 and AsCTL16 were expressed at high levels in adult females. In vitro binding assays showed that all five recombinant AsCTLs could bind to different microbial cell wall components, including lipopolysaccharide (LPS), lipid A, peptidoglycan (PG), lipoteichoic acid (LTA), zymosan and laminarin (beta-1,3-glucan). Recombinant AsCTLs also bound to several Gram-negative and Gram-positive bacteria, and could agglutinate bacterial cells. Injection of double-stranded RNAs (dsRNAs) could significantly reduce expression of the five AsCTL mRNAs, and the survival of mosquitoes treated with dsRNA to AsCTLGA5 was significantly decreased after Escherichia coli infection, but did not change significantly after Micrococcus luteus infection compared to the control groups, suggesting that Ar. subalbatus AsCTLGA5 may participate in innate immunity against E. coli. Injection of dsRNA to AsCTLGA5 significantly reduced expression of AsCTLGA5 mRNA in female mosquitoes (A), and RNAi knockdown expression of AsCTLGA5 significantly decreased the survival of mosquitoes after Escherichia coli infection (B). [Display omitted] •Armigeres subalbatus C-type lectins (AsCTLs) transcripts were expressed mainly in hemocytes and/or fat body.•Recombinant AsCTLs bound to several microbial components, such as LPS, peptidoglycan and lipoteichoic acid.•AsCTLs directly bound to several Gram-negative and Gram-positive bacteria and agglutinated bacterial cells.•Injection of dsRNAs to AsCTLs into female mosquitoes effectively knocked down expression of AsCTLs transcripts.•RNAi knockdown of AsCTLGA5 significantly decreased the survival of mosquitoes after Escherichia coli infection.