The Helicobacter pylori adhesin protein HopQ exploits the dimer interface of human CEACAMs to facilitate translocation of the oncoprotein CagA

Abstract

infects half of the world's population, and strains that encode the type IV secretion system for injection of the oncoprotein CagA into host gastric epithelial cells are associated with elevated levels of cancer. CagA translocation into host cells is dependent on interactions between the adhesin protein HopQ and human CEACAMs. Here, we present high-resolution structures of several HopQ-CEACAM complexes and CEACAMs in their monomeric and dimeric forms establishing that HopQ uses a coupled folding and binding mechanism to engage the canonical CEACAM dimerization interface for CEACAM recognition. By combining mutagenesis with biophysical and functional analyses, we show that the modes of CEACAM recognition by HopQ and CEACAMs themselves are starkly different. Our data describe precise molecular mechanisms by which microbes exploit host CEACAMs for infection and enable future development of novel oncoprotein translocation inhibitors and -specific antimicrobial agents.

Genomic features of the Helicobacter pylori strain PMSS1 and its virulence attributes as deduced from its in vivo colonisation patterns

“…5B,C). Although it has been suggested that HopQ affects the adherence to human cells (Bonsor et al, 2018), we observed no difference in the adhesion to AGS cells with any of the strains (Fig. 5E).…”

CEACAM1 structure and function in immunity and its therapeutic implications

“…Recently, the first high resolution structures (2.68-2.8 Å) of the hCEACAM1 IgV domain in complex with a bacterial receptor were solved with the H. pylori outer membrane adhesin HopQ (PDB ID 6AW2, 6GBG) [62,63]. Although HopQ adopts an alpha-beta folded structure that diverges significantly from Opa CEA , its mode of binding to the GFCC'C" surface on CEACAM1 is conserved with other microbial ligands.…”

“…Four loops (α3-β1, β2-α4, α5-α6, α7-α8) form a binding surface that allows for the β2-α4 loop to participate in an extensive van der Waals and hydrogen bonding network with the CEACAM1 IgV GFCC'C" surface. This specifically involves interactions with CEACAM1 residues on the CC' loop (F29, V39, Q44) and FG loop (Q89, I91, V96) [63]. HopQ binds to CEACAM1 through a distinct coupled folding and binding mechanism [63] that exhibits high affinity for CEACAM1 IgV with a binding constant that exceeds CEACAM1 homodimerization (K D =23-279 nM) [43,63].…”

“…This specifically involves interactions with CEACAM1 residues on the CC' loop (F29, V39, Q44) and FG loop (Q89, I91, V96) [63]. HopQ binds to CEACAM1 through a distinct coupled folding and binding mechanism [63] that exhibits high affinity for CEACAM1 IgV with a binding constant that exceeds CEACAM1 homodimerization (K D =23-279 nM) [43,63]. Importantly, small-angle X-ray scattering (SAXS) studies demonstrated that HopQ is able is disassociate CEACAM1 IgV homodimers into monomeric species that allow for heterophilic interactions with HopQ.…”

Expression of CEACAM1 or CEACAM5 in AZ-521 cells restores the type IV secretion deficiency for translocation of CagA byHelicobacter pylori

“…Once this first contact is achieved, the T4SS can establish binding to numerous host cell surface factors such as integrin receptors and phosphatidylserine to assist the delivery of CagA, possibly in lipid rafts (cholesterol-rich microdomains) in the focal adhesions (Backert et al, 2015;Hayashi et al, 2012;Kwok et al, 2007;Lai et al, 2008;Posselt, Backert, & Wessler, 2013;Tegtmeyer, Wessler, et al, 2017). A fourth group of factors, the CEACAM receptors and their bacterial ligand HopQ, came into play just recently and are also required for full T4SS function (Bonsor et al, 2018;Javaheri et al, 2016;Koniger et al, 2016;Moonens et al, 2018). A fourth group of factors, the CEACAM receptors and their bacterial ligand HopQ, came into play just recently and are also required for full T4SS function (Bonsor et al, 2018;Javaheri et al, 2016;Koniger et al, 2016;Moonens et al, 2018).…”