Mitochondria-Derived Vesicles Deliver Antimicrobial Reactive Oxygen Species to Control Phagosome-Localized Staphylococcus aureus

Abstract

Pathogenic bacteria taken up into the macrophage phagosome are the target of many anti-microbial mechanisms. Although mitochondria-derived antimicrobial effectors like reactive oxygen species (mROS) aid in bacterial killing, it is unclear how these effectors reach bacteria within the phagosomal lumen. We show here that endoplasmic reticulum stress triggered upon methicillin-resistant Staphylococcus aureus (MRSA) infection induces mROS that are delivered to bacteria-containing phagosomes via mitochondria-derived vesicles (MDVs). The endoplasmic reticulum stress sensor IRE1α induces mROS, specifically hydrogen peroxide (mH2O2), upon MRSA infection. MRSA infection also stimulates the generation of MDVs, which require the mitochondrial stress response factor Parkin, and contributes to mH2O2 accumulation in bacteria-containing phagosomes. Accumulation of phagosomal H2O2 requires Toll-like receptor signaling and the mitochondrial enzyme superoxide dismutase-2 (Sod2), which is delivered to phagosomes by MDVs. Sod2 depletion compromises mH2O2 production and bacterial killing. Thus, mitochondrial redox capacity enhances macrophage antimicrobial function by delivering mitochondria-derived effector molecules into bacteria-containing phagosomes. Bacterial pathogens can invade the protected intracellular space, potentially evading host immune function. Abuaita et al. show that macrophage infection by methicillin-resistant Staphylococcus aureus activates host stress response pathways that trigger innate intracellular defense mechanisms. Infection stimulates delivery of antimicrobial-containing mitochondria-derived vesicles to phagosomes to participate in bacterial killing.