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Title: INNATE IMMUNITY IN A PYRALID MOTH: FUNCTIONAL EVALUATION OF DOMAINS FROM A B-1,3-GLUCAN RECOGNITION PROTEIN

Author
item FABRICK, JEFFREY - 5430-05-30
item Baker, James
item KANOST, MICHAEL - KANSAS STATE UNIV

Submitted to: Journal of Biological Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/14/2004
Publication Date: 6/30/2004
Citation: Fabrick, J.A., Baker, J.E., Kanost, M.R. 2004. Innate immunity in a pyralid moth: functional evaluation of domains from a b-1,3-glucan recognition protein. Journal of Biological Chemistry. V.279(25): 16605-26611. (online at: www.jbc.org).

Interpretive Summary: Controlling the Indianmeal moth, the most damaging pest of stored products, is difficult because of its close association with both raw and finished foods and its wide ranging distribution. Novel techniques based on disruption of the immune system in this species offer new hope for managing this major insect pest. A protein that circulates in the insect's blood and that activates its immune system to respond to invasions by microorganisms has been characterized. Specific regions of the large protein molecule that have unique biochemical and biophysical properties were demonstrated to be responsible for its biological effects. This pioneering study opens the way for the molecular design and engineering of small proteins that mediate immunological responses to specific microbes.

Technical Abstract: Invertebrates, like vertebrates, utilize pattern recognition proteins for detection of foreign microbes and subsequent activation of innate immunity. We report structural and functional properties of two domains from a beta-1,3-glucan recognition protein present in hemolymph of a pyralid moth, Plodia interpunctella. A recombinant protein corresponding to the first 181 amino terminal residues binds to beta-1,3-glucan, lipopolysaccharide, and lipoteichoic acid, polysaccharides found on cell surfaces of microorganisms, and also activates the prophenoloxidase activating system, an important immune response pathway in insects. The amino-terminal domain consists primarily of alpha-helical secondary structure with minor beta-structure, is thermally stable, and resists proteolytic degradation. The 290 residue carboxyl-terminal domain, which is similar in sequence to glucanases, has less affinity for the polysaccharides, did not activate the prophenoloxidase cascade, has a more complicated CD spectra, and is heat labile and susceptible to proteinase digestion. The carboxyl-terminal domain did bind to laminarin, a beta-1,3-glucan with beta-1,6 branches, but not to curdlan, a beta-1,3-glucan that lacks branching. These results indicate that the two domains of Plodia beta-1,3-glucan recognition protein, separated by a putative linker region, bind microbial polysaccharides with differing specificities and that the amino-terminal domain, which is unique to this class of pattern recognition receptors from invertebrates, is responsible for stimulating prophenoloxidase activation.