PGRP-SD, an Extracellular Pattern-Recognition Receptor, Enhances Peptidoglycan-Mediated Activation of the Drosophila Imd Pathway.

Activation of the innate immune response in Metazoans is initiated through the recognition of microbes by host pattern-recognition receptors. In Drosophila, diaminopimelic acid (DAP)-containing peptidoglycan from Gram-negative bacteria is detected by the transmembrane receptor PGRP-LC and by the intracellular receptor PGRP-LE. Here, we show that PGRP-SD acted upstream of PGRP-LC ...
as an extracellular receptor to enhance peptidoglycan-mediated activation of Imd signaling. Consistent with this, PGRP-SD mutants exhibited impaired activation of the Imd pathway and increased susceptibility to DAP-type bacteria. PGRP-SD enhanced the localization of peptidoglycans to the cell surface and hence promoted signaling. Moreover, PGRP-SD antagonized the action of PGRP-LB, an extracellular negative regulator, to fine-tune the intensity of the immune response. These data reveal that Drosophila PGRP-SD functions as an extracellular receptor similar to mammalian CD14 and demonstrate that, comparable to lipopolysaccharide sensing in mammals, Drosophila relies on both intra- and extracellular receptors for the detection of bacteria.
Mesh Terms:
Amino Acid Sequence, Animals, Carrier Proteins, Drosophila Proteins, Drosophila melanogaster, Enterobacter cloacae, Genes, Insect, Molecular Sequence Data, NF-kappa B, Oligonucleotide Array Sequence Analysis, RNA Interference, Sequence Alignment, Signal Transduction
Immunity
Date: Nov. 15, 2016
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