A predicted DXD-motif glycosyltransferase blocks immune activation.

Pathogens enhance their survival during infections by manipulating host defenses. evades innate immune responses, which we have found to be dependent on an understudied gene (FTL_0883/FTT_0615c). To understand the function of YbeX, we sought protein interactors in subsp. live vaccine strain (LVS). An unstudied protein co-immunoprecipitated with recombinant YbeX, which is a predicted glycosyltransferase with a DXD-motif. There are up to four genomic copies of this gene with identical sequence in strains of pathogenic to humans, despite ongoing genome decay. Disruption mutations were generated by intron insertion into all three copies of this glycosyltransferase domain containing gene in LVS, . The resulting strains stimulated more cytokines from macrophages than wild-type LVS and were attenuated in two infection models. GdcA was released from LVS during culture and was sufficient to block NF-κB activation when expressed in eukaryotic cells. When co-expressed in zebrafish, GdcA and YbeX were synergistically lethal to embryo development. Glycosyltransferases with DXD-motifs are found in a variety of pathogens including NleB, an type-III secretion system effector that inhibits NF-κB by antagonizing death receptor signaling. To our knowledge, GdcA is the first DXD-motif glycosyltransferase that inhibits NF-κB in immune cells. Together, these findings suggest DXD-motif glycosyltransferases may be a conserved virulence mechanism used by pathogenic bacteria to remodel host defenses.