Figure 4.

Functions of insect PGRP proteins. In response to peptidoglycan (PGN) from bacteria or other stimulants (yellow), insect PGRPs activate the (a) Toll and (b) Imd pathways and (c) the prophenol-oxidase cascade, which results in the production of antimicrobial products. (d) The structure of DAP-type peptidoglycan, indicating the positions at which proinflammatory peptidoglycan can be hydrolyzed by some PGRPs, reducing inflammation. Drosophila PGRPs are shown (green) unless otherwise indicated (Bm, Bombyx mori; Hd, Holotrichia diomphalia; Tm, Tenebrio molitor). Multiple arrows signify multiple steps; question marks signify unconfirmed or controversial functions. PGN, peptidoglycan; m-DAP, meso-DAP. See text for more details of the pathways shown.