Charroux, B., Capo, F., Kurz, C.L., Peslier, S., Chaduli, D., Viallat-Lieutaud, A., Royet, J. (2018). Cytosolic and Secreted Peptidoglycan-Degrading Enzymes in Drosophila Respectively Control Local and Systemic Immune Responses to Microbiota.  Cell Host Microbe 23(2): 215--228.e4.

FBrf0238078

Research paper

Gut-associated bacteria produce metabolites that both have a local influence on the intestinal tract and act at a distance on remote organs. In Drosophila, bacteria-derived peptidoglycan (PGN) displays such a dual role. PGN triggers local antimicrobial peptide production by enterocytes; it also activates systemic immune responses in fat-body cells and modulates fly behavior by acting on neurons. How these responses to a single microbiota-derived compound are simultaneously coordinated is not understood. We show here that the PGRP-LB locus generates both cytosolic and secreted PGN-cleaving enzymes. Through genetic analysis, we demonstrate that the cytosolic PGRP-LB isoforms cell-autonomously control the intensity of NF-κB activation in enterocytes, whereas the secreted isoform prevents massive and detrimental gut-derived PGN dissemination throughout the organism. This study explains how Drosophila are able to uncouple the modulation of local versus systemic responses to a single gut-bacteria-derived product by using isoform-specific enzymes.