Abstract
SummaryMacrophages represent the first line of immune defense against pathogens, and phagosome acidification is a necessary step in pathogen clearance. Here, we identified the bicarbonate transporter SLC4A7, which is strongly induced upon macrophage differentiation, as critical for phagosome acidification. Loss of SLC4A7 reduced acidification of phagocytosed beads or bacteria and impaired the intracellular microbicidal capacity in human macrophage cell lines. The phenotype was rescued by wild-type SLC4A7, but not by SLC4A7 mutants, affecting transport capacity or cell surface localization. Loss of SLC4A7 resulted in increased cytoplasmic acidification during phagocytosis, suggesting that SLC4A7-mediated, bicarbonate-driven maintenance of cytoplasmic pH is necessary for phagosome acidification. Altogether, we identify SLC4A7 and bicarbonate-driven cytoplasmic pH homeostasis as an important element of phagocytosis and the associated microbicidal functions in macrophages.
Highlights
We hypothesized that SLCs could be essential for macrophages to undergo the metabolic changes associated with phagocytosis, and aimed for an appropriate model system suitable for CRISPR/Cas9-based genetic screens (Figure 1A)
Killing of the S. aureus USA300 strain was increased in the knockout cells compared with control (Figure 2C, right panel), suggesting impaired intracellular survival due to reduced acidification
Reduced phagosome acidification accompanied by more acidic cytoplasmic pH upon SLC4A7 knockout was consistently observed across different cell lines (THP-1 and U937) and phagosomal cargos (Figures 2F and S2C)
Summary
Sedlyarov, Ruth Eichner, Enrico Girardi, ..., Pavel Kovarik, Nicolas Demaurex, Giulio Superti-Furga. Highlights d CRISPR screen identifies SLC4A7 to be required for phagosome acidification. Phagosome acidification is a necessary step in pathogen clearance by macrophages. Sedlyarov et al identify the bicarbonate transporter SLC4A7 as essential for phagosome acidification. SLC4A7-mediated bicarbonate import ensures homeostatic regulation of cytoplasmic pH. In the absence of SLC4A7, the macrophage cytoplasm acidifies, which perturbs phagosome maturation and impairs bacterial killing by macrophages. D Intracellular bacterial killing by macrophages is impaired in absence of SLC4A7 d Bicarbonate transport activity of SLC4A7 is required for phagosome acidification d SLC4A7 regulates phagosome acidification via homeostatic control of cytoplasmic pH. 2018, Cell Host & Microbe 23, 766–774 June 13, 2018 a 2018 The Author(s).
Published Version (Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have