title: Members of the salivary gland surface protein (SGS) family are major immunogenic components of mosquito saliva.
abstract: Mosquitoes transmit Plasmodium and certain arboviruses during blood feeding, when they are injected along with saliva. Mosquito saliva interferes with the host's hemostasis and inflammation response and influences the transmission success of some pathogens. One family of mosquito salivary gland proteins, named SGS, is composed of large bacterial-type proteins that in Aedes aegypti were implicated as receptors for Plasmodium on the basal salivary gland surface. Here, we characterize the biology of two SGSs in the malaria mosquito, Anopheles gambiae, and demonstrate their involvement in blood feeding. Western blots and RT-PCR showed that Sgs4 and Sgs5 are produced exclusively in female salivary glands, that expression increases with age and after blood feeding, and that protein levels fluctuate in a circadian manner. Immunohistochemistry showed that SGSs are present in the acinar cells of the distal lateral lobes and in the salivary ducts of the proximal lobes. SDS-PAGE, Western blots, bite blots, and immunization via mosquito bites showed that SGSs are highly immunogenic and form major components of mosquito saliva. Last, Western and bioinformatic analyses suggest that SGSs are secreted via a non-classical pathway that involves cleavage into a 300-kDa soluble fragment and a smaller membrane-bound fragment. Combined, these data strongly suggest that SGSs play an important role in blood feeding. Together with their role in malaria transmission, we propose that SGSs could be used as markers of human exposure to mosquito bites and in the development of disease control strategies.
authors.affiliation: Department of Biological Sciences and Institute for Global Health, Vanderbilt University, Nashville, Tennessee 37235, USA.
authors.forename: Jonas G
authors.initials: JG
authors.lastname: King
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Vernick
authors.forename: Julián F
authors.initials: JF
authors.lastname: Hillyer
mesh_terms: D000818:Animals; D000852:Anopheles / Q000276:immunology* / Q000378:metabolism*; D019295:Computational Biology; D029721:Drosophila Proteins; D005260:Female; D005786:Gene Expression Regulation; D005967:Glue Proteins, Drosophila / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007155:Immunologic Factors / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D059748:Proteolysis; D012463:Saliva / Q000276:immunology* / Q000378:metabolism*; D012469:Salivary Glands / Q000378:metabolism*; D013997:Time Factors
chemical_list: D029721:Drosophila Proteins; D005967:Glue Proteins, Drosophila; D007155:Immunologic Factors; C424382:Sgs4 protein, Drosophila