Mosquito innate immunity: involvement of beta 1,3-glucan recognition protein in melanotic encapsulation immune responses in Armigeres subalbatus.

Wang X, Fuchs JF, Infanger LC, Rocheleau TA, Hillyer JF, Chen CC, Christensen BM
Mol Biochem Parasitol. 2005 139 (1): 65-73

PMID: 15610820 · DOI:10.1016/j.molbiopara.2004.09.009

Beta 1,3-glucan recognition proteins (GRP) have specific affinity for beta 1,3-glucan, a component on the surface of fungi and bacteria. By interacting with beta 1,3-glucan, GRP initiates activation of prophenoloxidase, a key enzyme in the signaling pathway leading to melanotic encapsulation in invertebrates. In this study, we characterize a novel hemocyte-specific GRP from the mosquito, Armigeres subalbatus (AsGRP). The 1.57 kb cDNA clone encodes a 499 deduced amino acid sequence, which contains a region that displays significant similarity to the glucanase-like regions of other GRPs and Gram-negative bacteria binding proteins found in other organisms. AsGRP is constitutively expressed in the hemolymph of adult female mosquitoes, and is upregulated following challenge with Escherichia coli, Micrococcus luteus, and the filarial worm Dirofilaria immitis. AsGRP specifically recognizes curdlan (insoluble beta 1,3-glucan), but not mannose or N-acetyl-D-glucosamine. AsGRP binds a low percentage of E. coli, most M. luteus and D. immitis microfilariae. AsGRP double-stranded RNA interference strongly inhibits melanotic encapsulation of D. immitis in Ar. subalbatus. These results suggest that AsGRP has the capacity to bind to a variety of pathogens, functions as a pattern recognition receptor, and is required for effective melanotic encapsulation immune responses in Ar. subalbatus.

MeSH Terms (20)

Acetylglucosamine Animals Carrier Proteins Cloning, Molecular Culicidae Dirofilaria immitis DNA, Complementary Escherichia coli Female Gene Expression Regulation Immunity, Innate Insect Proteins Melanins Micrococcus luteus Molecular Sequence Data Open Reading Frames Protein Binding RNA Interference Sequence Analysis, DNA Sequence Homology, Amino Acid

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