Reverting the mode of action of the mitochondrial F_OF₁-ATPase by <i>Legionella pneumophila</i> preserves its replication niche.

Abstract

<i>Legionella pneumophila,</i> the causative agent of Legionnaires' disease, a severe pneumonia, injects via a type 4 secretion system (T4SS) more than 300 proteins into macrophages, its main host cell in humans. Certain of these proteins are implicated in reprogramming the metabolism of infected cells by reducing mitochondrial oxidative phosphorylation (OXPHOS) early after infection. Here. we show that despite reduced OXPHOS, the mitochondrial membrane potential (Δ<i>ψ</i>_m) is maintained during infection of primary human monocyte-derived macrophages (hMDMs). We reveal that <i>L. pneumophila</i> reverses the ATP-synthase activity of the mitochondrial F_OF₁-ATPase to ATP-hydrolase activity in a T4SS-dependent manner, which leads to a conservation of the Δ<i>ψ</i>_m, preserves mitochondrial polarization, and prevents macrophage cell death. Analyses of T4SS effectors known to target mitochondrial functions revealed that <i>Lp</i>Spl is partially involved in conserving the Δ<i>ψ</i>_m, but not LncP and MitF. The inhibition of the <i>L. pneumophila</i>-induced 'reverse mode' of the F_OF₁-ATPase collapsed the Δ<i>ψ</i>_m and caused cell death in infected cells. Single-cell analyses suggested that bacterial replication occurs preferentially in hMDMs that conserved the Δ<i>ψ</i>_m and showed delayed cell death. This direct manipulation of the mode of activity of the F_OF₁-ATPase is a newly identified feature of <i>L. pneumophila</i> allowing to delay host cell death and thereby to preserve the bacterial replication niche during infection.