EptC of Campylobacter jejuni Mediates Phenotypes Involved in Host Interactions and Virulence

Abstract

e Campylobacter jejuni is a natural commensal of the avian intestinal tract. However, the bacterium is also the leading cause of acute bacterial diarrhea worldwide and is implicated in development of Guillain-Barré syndrome. Like many bacterial pathogens, C. jejuni assembles complex surface structures that interface with the surrounding environment and are involved in pathogenesis. Recent work in C. jejuni identified a gene encoding a novel phosphoethanolamine (pEtN) transferase, EptC (Cj0256), that plays a promiscuous role in modifying the flagellar rod protein, FlgG; the lipid A domain of lipooligosaccharide (LOS); and several N-linked glycans. In this work, we report that EptC catalyzes the addition of pEtN to the first heptose sugar of the inner core oligosaccharide of LOS, a fourth enzymatic target. We also examine the role pEtN modification plays in circumventing detection and/or killing by host defenses. Specifically, we show that modification of C. jejuni lipid A with pEtN results in increased recognition by the human Toll-like receptor 4 -myeloid differentiation factor 2 (hTLR4-MD2) complex, along with providing resistance to relevant mammalian and avian antimicrobial peptides (i.e., defensins). We also confirm the inability of aberrant forms of LOS to activate Toll-like receptor 2 (TLR2). Most exciting, we demonstrate that strains lacking eptC show decreased commensal colonization of chick ceca and reduced colonization of BALB/cByJ mice compared to wild-type strains. Our results indicate that modification of surface structures with pEtN by EptC is key to its ability to promote commensalism in an avian host and to survive in the mammalian gastrointestinal environment. Campylobacter jejuni is a major cause of bacterial diarrhea worldwide (1). Infection with the pathogen results in significant acute illness, as well as serious life-threatening consequences, such as Guillain-Barré syndrome (2). Like many bacterial pathogens, C. jejuni assembles complex surface structures critical for long-term commensal colonization of the avian host, as well as pathogenesis in humans. Two major surface structures, the glycolipid lipooligosaccharide (LOS) and flagella, both important for pathogenesis, are often targets for modification and/or phase variation, providing the bacteria with antigenic diversity and adaptability in inhospitable environments. For example, variation of surface-exposed LOS results in a form of molecular mimicry between bacterial surface and host peripheral nerve gangliosides, implicating them in postinfectious neuropathies (2, 3). Another example is posttranslational modification of membrane-and surface-exposed proteins targeted by the C. jejuni Pse and Pgl family of proteins responsible for O-and N-linked glycosylation, respectively. O-linked glycosylation of the flagellar filament proteins, FlaA/B, is thought to provide antigenic diversity but the role Nlinked glycosylation plays in cellular processes is undetermined (4-6). Considering the importance of LOS in host-pathogen interactions, the requ...

LPS modification promotes maintenance of Yersinia pestis in fleas

“…It is possible that expression of this transferase is also affected, which could interfere with LPS modification by phosphoethanolamine (Reynolds et al, 2005). In other species, phosphoethanolamine modifications to the LPS core have been shown to be involved in maintaining outer membrane integrity and may increase resistance to some CAMPs (Cullen et al, 2013;Reynolds et al, 2005;Viau et al, 2011). Lastly, the 5F7 mutant contains an insertion in a predicted transposase gene (y1748).…”

Structure of a lipid A phosphoethanolamine transferase suggests how conformational changes govern substrate binding

“…The structures of the soluble periplasmic domain of EptA from Nm (14), and the homologs, EptC, from Campylobacter jejuni (15) and Mcr-1 in E. coli (16), all of which add PEA to lipid A, have been determined (17)(18)(19)(20). These structures all reveal a hydrolase fold similar to that of phosphonate monoester hydrolase (21) and arylsulfatase (22)(23)(24).…”

Unique Structural Modifications Are Present in the Lipopolysaccharide from Colistin-Resistant Strains of Acinetobacter baumannii

“…In the flagellated bacterium Campylobacter jejuni, lipid A is decorated with pEtN mediated by EptC, which serves a dual role as a pEtN transferase modulating CAMP resistance and as a modifier of the flagellar rod protein FlgG (35,36). Helicobacter pylori modifies its lipid A in a two-step process whereby the removal of the 1-phosphate group by a lipid A phosphatase LpxE is followed by the addition of a pEtN residue catalyzed by EptA, resulting in increased resistance to polymyxin (37).…”