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Work done by Jonas King, Ken Vernick and Julián Hillyer was published today in the November 25 issue of The Journal of Biological Chemistry.Ìý This work characterizes the biology of two members of the salivary gland specific (SGS) protein family in the malaria mosquito, Anopheles gambiae, and demonstrates their involvement in blood feeding.Ìý Major findings include:

1. 1)Anopheles gambiae SGS4 and SGS5 are expressed exclusively in female salivary glands, expression is upregulated following blood feeding, and protein levels fluctuate in a circadian manner.
   

2. 2)Within the salivary glands, SGS4 and SGS5 are present in the acinar cells of the distal lateral lobes and in the salivary ducts of the proximal lateral lobes.
   

3. 3)SGS4 and SGS5 are major components of mosquito saliva and are highly immunogenic following blood feeding.
   

CITATION:

King, J.G., K.D. Vernick, and J.F. Hillyer. 2011. Members of the salivary gland surface protein family (SGS) are major immunogenic components of mosquito saliva. Journal of Biological Chemistry. 286(47): 40824-40834.

DOI: 10.1074/jbc.M111.280552

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ARTICLE 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 SGS proteins 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. Lastly, 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.