Mechanisms of GPCR hijacking byStaphylococcus aureus

Abstract

Atypical chemokine receptor 1 (ACKR1) is a G protein-coupled receptor (GPCR) targeted by Staphylococcus aureus (SA) bi-component pore-forming leukotoxins to promote bacterial growth and immune evasion. Here we have developed an integrative molecular pharmacology and structural biology approach in order to characterize the effect of leukotoxins HlgA and HlgB on ACKR1 structure and function. Interestingly, we found that both components HlgA and HlgB compete with endogenous chemokines through a direct binding to ACKR1 captured by native mass spectrometry (MS). Unexpectedly, Hydrogen/Deuterium exchange-MS revealed that toxin binding allosterically modulates the intracellular G protein-binding domain of the receptor, resulting in dissociation of ACKR1-G protein complexes in living cells. Altogether, our study brings important molecular insights into the initial steps of leukotoxins targeting a host GPCR. Our findings may open the way to develop antibiotics inhibiting host receptors binding, a mechanism of action less prone to resistance.

Structural insights into recognition of chemokine receptors by Staphylococcus aureus leukotoxins

“…LukS-PV binding to C5aR1 was shown to require tyrosine sulfation as well, with a measured affinity of 127 nM (SD ±17 nM) between lukS-PV and the receptor N-terminal peptide by ITC (Spaan, Henry et al 2013). Interestingly, a bound sulfate ion is also visible at LukS-PV site 1 in the PVL crystal structure reported in (Liu, Kozhaya et al 2020 and HlgB (Grison, Leyrat et al 2021), it is tempting to speculate that these residues might play a role in receptor recognition, although further experiments will be necessary to (in)validate this hypothesis. Intriguingly, the Arg residue sitting at the bottom of site 1 pocket (LukE Arg263) is conserved in all toxins, including the more distantly related lukGH.…”

“…Consistent with these observations, the post-translational modification pathways involved in the sulfation of the leukocidin receptors were recently found to impact on HlgAB, HlgCB, LukED, and PVL induced cytotoxicity, most likely through reduced S component binding (Tromp, Van Gent et al 2020). In addition, ACKR1 Tyr41 to Ala mutation was shown to nearly abolish LukED-and HlgAB-induced hemolysis in HEK cells (Spaan, Reyes-Robles et al 2015), while ACKR1 Tyr41 to Phe mutation caused a 10 fold increase in HlgAB EC50 required to dissociate ACKR1-bound Gαi subunit, as measured by BRET (Grison, Leyrat et al 2021). LukS-PV binding to C5aR1 was shown to require tyrosine sulfation as well, with a measured affinity of 127 nM (SD ±17 nM) between lukS-PV and the receptor N-terminal peptide by ITC (Spaan, Henry et al 2013).…”

“…All of the identified receptors belong to the chemokine or complement receptor families of class A G-protein-coupled receptors (GPCRs), except for the divergent lukGH toxin which binds CD11b (aka complement receptor 3) expressed on phagocytic cells (DuMont, Yoong et al 2013). Recently, F-component-specific receptors have been identified as well: human CD45 was shown to act as a receptor for lukF-PV (Tromp, Van Gent et al 2018), while HlgB was found to interact with ACKR1 (Grison, Leyrat et al 2021).…”

Membrane binding of pore-forming γ-hemolysin components studied at different lipid compositions

“…For several leukocidins it was shown that the S components recognize and bind specific receptors on the cell surface of leukocytes; in the case of Hlg2, these receptors are CXCR1, CXCR2 and the CC-chemokine receptor 2 (CCR2) [8]. Recently, a proteinaceous receptor targeted by both LukF and Hlg2 components has also been identified, namely the atypical chemokine receptor 1 ACKR1 [9]. However, it was also experimentally observed that LukF can bind purely lipidic bilayers in the presence of phosphatidylcholine (PC) and that γ-HL possesses permeabilizing activity on model membranes in the absence of additional proteins [10,11].…”