Peptidoglycan induces loss of a nuclear peptidoglycan recognition protein during host tissue development in a beneficial animal-bacterial symbiosis.
Peptidoglycan recognition proteins (PGRPs) are mediators of innate immunity and recently have been implicated in developmental regulation. To explore the interplay between these two roles, we characterized a PGRP in the host squid Euprymna scolopes (EsPGRP1) during colonization by the mutualistic bacterium Vibrio fischeri. Previous research on the squid-vibrio symbiosis had shown that, upon colonization of deep epithelium-lined crypts of the host light organ, symbiont-derived peptidoglycan monomers induce apoptosis-mediated regression of remote epithelial fields involved in the inoculation process. In this study, immunofluorescence microscopy revealed that EsPGRP1 localizes to the nuclei of epithelial cells, and symbiont colonization induces the loss of EsPGRP1 from apoptotic nuclei. The loss of nuclear EsPGRP1 occurred prior to DNA cleavage and breakdown of the nuclear membrane, but followed chromatin condensation, suggesting that it occurs during late-stage apoptosis. Experiments with purified peptidoglycan monomers and with V. fischeri mutants defective in peptidoglycan-monomer release provided evidence that these molecules trigger nuclear loss of EsPGRP1 and apoptosis. The demonstration of a nuclear PGRP is unprecedented, and the dynamics of EsPGRP1 during apoptosis provide a striking example of a connection between microbial recognition and developmental responses in the establishment of symbiosis.
Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, 53706, USA.
Joshua V
JV
Troll
Dawn M
DM
Adin
Andrew M
AM
Wier
Nicholas
N
Paquette
Neal
N
Silverman
William E
WE
Goldman
Frank J
FJ
Stadermann
Eric V
EV
Stabb
Margaret J
MJ
McFall-Ngai
D048908:Aliivibrio fischeri / Q000235:genetics / Q000276:immunology* / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D002352:Carrier Proteins / Q000276:immunology* / Q000378:metabolism; D002467:Cell Nucleus / Q000737:chemistry; D049832:Decapodiformes / Q000276:immunology* / Q000382:microbiology*; D004847:Epithelial Cells / Q000737:chemistry / Q000382:microbiology; D017353:Gene Deletion; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010457:Peptidoglycan / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D013559:Symbiosis
D002352:Carrier Proteins; D010457:Peptidoglycan; C118897:peptidoglycan recognition protein