Bacterial detection by Drosophila peptidoglycan recognition proteins.

The mechanisms and molecular effectors of pathogen recognition systems in diverse hosts are highly conserved. Both plant and animal recognition of pathogens relies on sensing of Pathogen-Associated Molecular Patterns (PAMPs) by Pattern Recognition Molecules (PRMs). To detect bacteria, these sensor molecules can recognize a wide array of molecules ranging from lipopolysaccharides (LPS) to peptidoglycan (PGN) or proteins. In contrast to that of mammals, the repertoire of bacterial motifs recognized by the immune system of the fruit fly seems to be much narrower. Works published so far indicate that it is limited to bacterial PGN and its derivatives. The mode of detection of PGN by host proteins is also simpler in the fly immune system than it is in the mammalian counterpart. Although PGN can be detected by Toll-like receptors, Nucleotide-binding oligomerization domain proteins and Peptidoglycan Recognition proteins (PGRPs) in vertebrates, PGRP family members are, so far, the only PGN sensors identified in Drosophila. Interactions between PGN and PGRPs induce multiple processes required to mount a specific and is implicated in multiple processes require to induce a specific and fine-tuned bacterial immune response in fly. Here, we present an overview of our current knowledge of PGRP and their bacterial detection in Drosophila.