The ALPK1 pathway drives the inflammatory response to Campylobacter jejuni in human intestinal epithelial cells

Abstract

The Gram-negative bacterium Campylobacter jejuni is a major cause of foodborne disease in humans. After infection, C. jejuni rapidly colonizes the mucus layer of the small and large intestine and induces a potent pro-inflammatory response characterized by the production of a large repertoire of cytokines, chemokines, and innate effector molecules, resulting in (bloody) diarrhea. The virulence mechanisms by which C. jejuni causes this intestinal response are still largely unknown. Here we show that C. jejuni releases a potent pro-inflammatory compound into its environment, which activates an NF-κB-mediated pro-inflammatory response including the induction of CXCL8, CXCL2, TNFAIP2 and PTGS2. This response was dependent on a functional ALPK1 receptor and independent of Toll-like Receptor and Nod-like Receptor signaling. Chemical characterization, inactivation of the heptose-biosynthesis pathway by the deletion of the hldE gene and in vitro engineering identified the released factor as the LOS-intermediate ADP-heptose and/or related heptose phosphates. During C. jejuni infection of intestinal cells, the ALPK1-NF-κB axis was potently activated by released heptose metabolites without the need for a type III or type IV injection machinery. Our results classify ADP-heptose and/or related heptose phosphates as a major virulence factor of C. jejuni that may play an important role during Campylobacter infection in humans.

Gain-of-function mutations inALPK1cause an NF-κB-mediated autoinflammatory disease: functional assessment, clinical phenotyping and disease course of patients with ROSAH syndrome

“…1 However, there is increasing evidence that ALPK1 plays a role in innate immune activation. [3][4][5][6][7][8] ALPK1 has been shown to act as an intracellular sensor for metabolites produced by a variety of bacteria including Helicobacter pylori, Shigella flexneri and Burkholderia cenocepacia. Specifically, the N-terminal domain of ALPK1 binds bacterial sugars, including ADP-beta-D-mannoheptose (ADP-heptose).…”

“…However, there is increasing evidence that ALPK1 plays a role in innate immune activation 3–8. ALPK1 has been shown to act as an intracellular sensor for metabolites produced by a variety of bacteria including Helicobacter pylori , Shigella flexneri and Burkholderia cenocepacia .…”

Akkermansia muciniphila upregulates genes involved in maintaining the intestinal barrier function via ADP-heptose-dependent activation of the ALPK1/TIFA pathway

“… 14 We show, for the first time, that the commensal bacterium, A. muciniphila can release in the medium an heptose-related molecules able to activate the ALPK1/TIFA pathway, a feature that has only been reported for N. meningitidis and C. jejuni . 15 , 36 The exact nature of the ALPK1-activating molecules released by A. muciniphila remains to be precisely characterized but our data strongly suggest that it is ADP-H. First, extracellular ADP-H triggers ALPK1-mediated signaling in HEK293 cells whereas the related bacterial metabolite HBP needs to be electroporated. 11 , 12 , 36 Our results show that the ALPK1-activating molecule released by A. muciniphila does not require transfection, electroporation or artificial permeabilization to enter the cells, excluding HBP as a candidate.…”

“…The ALPK1/TIFA axis has also been associated with immune response induction. 13 , 15 We thus assessed the proinflammatory cytokines CXCL8, IL-1β and the anti-inflammatory cytokine TGFβ1 in the same set-up. WT and TIFA −/− HT29 cells were incubated with an A. muciniphila culture supernatant, a non-inoculated control medium or ADP-H for 6 hours.…”

Mass Spectrometry-based Proteomics and Glycoproteomics in COVID-19 Biomarkers Identification: A Mini-review

“…The binding of the S protein to the ACE2 receptor is mainly due to the interaction of polar residues between the RBD and the structural domain of ACE2 [ 11 , 99 , 169 ]. Trimeric, complex glycosylated S proteins give them an advantage over monomeric and immature glycosylated variants for receptor binding [ 171 ]. The hinge-like dynamic movement of the RBD on the S protein occurs intensifies the affinity of the RBD to ACE2 up to 10–20 times, which partly explains the high viral transmissibility [ 98 , 99 , 172 ].…”