N-glycosylated proteins and distinct lipooligosaccharide glycoforms ofCampylobacter jejunitarget the human C-type lectin receptor MGL

Abstract

SummaryAn increasing number of bacterial pathogens produce an array of glycoproteins of unknown function. Here we report that Campylobacter jejuni proteins that are modified by the N-linked glycosylation machinery encoded by the pgl locus bind the human Macrophage Galactose-type lectin (MGL). MGL receptor binding was abrogated by EDTA and N-acetylgalactosamine (GalNAc) and was successfully transferred to Escherichia coli by introducing the C. jejuni pgl locus together with a glycan acceptor protein. In addition to glycoproteins, C. jejuni lipooligosaccharide with a terminal GalNAc residue was recognized by MGL. Recombinant E. coli expressing the C. jejuni pgl locus in the absence of a suitable glycan acceptor protein produced altered lipopolysaccharide glycoforms that gained MGL reactivity. Infection assays demonstrated high levels of GalNAc-dependent interaction of the recombinant E. coli with MGL-transfected mammalian cells. In addition, interleukin-6 production by human dendritic cells was enhanced by C. jejuni lacking N-linked glycans compared with wild-type bacteria. Collectively, our results provide evidence that both N-linked glycoproteins and distinct lipooligosaccharide glycoforms of C. jejuni are ligands for the human C-type lectin MGL and that the C. jejuni N-glycosylation machinery can be exploited to target recombinant bacteria to MGL-expressing eukaryotic cells.

Modification of the Campylobacter jejuni N-Linked Glycan by EptC Protein-mediated Addition of Phosphoethanolamine

“…Although no clear differences in reactivity to patient sera were observed, this does not preclude a role for the pEtN-glycan in innate immunity or in modifying host cell interactions. For example, previous studies have shown that C. jejuni N-linked glycoproteins and LOS displaying terminal GalNAc can bind the human macrophage galactose-type lectin (MGL) (64). Although speculative, the addition of pEtN to the N-glycan may block interactions between the previously terminal GalNAc of the canonical glycan and MGL, thus disrupting adherence between C. jejuni and MGL-expressing dendritic and macrophage cells.…”

Targeting of macrophage galactose‐type C‐type lectin (MGL) induces DC signaling and activation

“…hMGL is equipped with a partial dileucine zipper and with YENF internalization motifs [11]. This receptor is involved in the recognition of a large plethora of pathogens by DCs [12][13][14][15] and in the maintenance of T-cell homeostasis [16]. Moreover, in vivo, MGL appears to play a crucial role in close proximity of the endothelial structures of lymph nodes and thymus, where iDCs are hampered in their migration activity until maturation [6].…”

Molecular mechanisms and biological role ofCampylobacter jejuniattachment to host cells

“…Inactivation of N-linked glycosylation machinery leads to decreased colonisation ability of bacteria, as well as to a reduction of adherence to and invasion of human epithelial cells suggesting that some of these glycoproteins may play a role of adhesins [57][58][59][60]. Although it remains unknown whether Campylobacter N-glycosylation is required for adhesion there is some evidence that it might influence host immune response [61,62].…”

“…Excessive production of IL-10 also inhibited maturation of dendritic cells, thus, further assisting bacteria to evade host immune response [64]. In the study by van Sorge et al [61] it was shown that N-linked glycoproteins of C. jejuni interact with Ctype lectins of macrophage galactose-type lectins (MGL). These findings suggest a possible role of Campylobacter N-lined glycosylation system for modulation of host immune responses.…”

“…In addition to galactose-specific C-type lectins described above, other C-type lectins as well as sialic acidbinding immunoglobulin-like lectins (siglecs) may be involved in host-pathogen interaction [61,62]. Siglecs are a family of type I membrane proteins widely expressed on immune cells that have specificity for sialic acid-containing glycans present in some types of Campylobacter lipo-oligosaccharides (LOSs).…”