title: Phagocytosis Enhances Lysosomal and Bactericidal Properties by Activating the Transcription Factor TFEB.
abstract: Macrophages internalize pathogens through phagocytosis, entrapping them into organelles called phagosomes. Phagosomes then fuse with lysosomes to mature into phagolysosomes, acquiring an acidic and hydrolytic lumen that kills the pathogens. During an ongoing infection, macrophages can internalize dozens of bacteria. Thus, we hypothesized that an initial round of phagocytosis might boost lysosome function and bactericidal ability to cope with subsequent rounds of phagocytosis. To test this hypothesis, we employed Fcγ-receptor-mediated phagocytosis and endocytosis, which internalize immunoglobulin G (IgG)-opsonized particles and polyvalent IgG immune complexes, respectively. We report that Fcγ receptor activation in macrophages enhances lysosome-based proteolysis and killing of subsequently phagocytosed E. coli compared to naive macrophages. Importantly, we show that Fcγ receptor activation causes nuclear translocation of TFEB, a transcription factor that boosts expression of lysosome genes. Indeed, Fc receptor activation is accompanied by increased expression of specific lysosomal proteins. Remarkably, TFEB silencing represses the Fcγ-receptor-mediated enhancements in degradation and bacterial killing. In addition, nuclear translocation of TFEB requires phagosome completion and fails to occur in cells silenced for MCOLN1, a lysosomal Ca(2+) channel, suggesting that lysosomal Ca(2+) released during phagosome maturation activates TFEB. Finally, we demonstrate that non-opsonic phagocytosis of E. coli also enhances lysosomal degradation in a TFEB-dependent manner, suggesting that this phenomenon is not limited to Fcγ receptors. Overall, we show that macrophages become better killers after one round of phagocytosis and suggest that phagosomes and lysosomes are capable of bi-directional signaling.
authors.affiliation: Department of Chemistry and Biology, Ryerson University, Toronto, ON M5B2K3, Canada.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Gray
authors.affiliation: Department of Chemistry and Biology, Ryerson University, Toronto, ON M5B2K3, Canada; Program in Molecular Science, Ryerson University, Toronto, ON M5B2K3, Canada.
authors.forename: Christopher H
authors.initials: CH
authors.lastname: Choy
authors.affiliation: Department of Chemistry and Biology, Ryerson University, Toronto, ON M5B2K3, Canada; Program in Molecular Science, Ryerson University, Toronto, ON M5B2K3, Canada.
authors.forename: Roya M
authors.initials: RM
authors.lastname: Dayam
authors.affiliation: Department of Chemistry and Biology, Ryerson University, Toronto, ON M5B2K3, Canada; Program in Molecular Science, Ryerson University, Toronto, ON M5B2K3, Canada.
authors.forename: Erika
authors.initials: E
authors.lastname: Ospina-Escobar
authors.affiliation: Department of Chemistry and Biology, Ryerson University, Toronto, ON M5B2K3, Canada.
authors.forename: Alexander
authors.initials: A
authors.lastname: Somerville
authors.affiliation: Department of Chemistry and Biology, Ryerson University, Toronto, ON M5B2K3, Canada.
authors.forename: Xuan
authors.initials: X
authors.lastname: Xiao
authors.affiliation: Department of Cell Biology and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University, New Haven, CT 06510, USA.
authors.forename: Shawn M
authors.initials: SM
authors.lastname: Ferguson
authors.affiliation: Department of Chemistry and Biology, Ryerson University, Toronto, ON M5B2K3, Canada; Program in Molecular Science, Ryerson University, Toronto, ON M5B2K3, Canada. Electronic address: rbotelho@ryerson.ca.
authors.forename: Roberto J
authors.initials: RJ
authors.lastname: Botelho
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000235:genetics* / Q000276:immunology; D004705:Endocytosis; D004926:Escherichia coli / Q000276:immunology; D008247:Lysosomes / Q000502:physiology*; D051379:Mice; D010587:Phagocytosis / Q000502:physiology*; D021381:Protein Transport; D000067996:RAW 264.7 Cells; D017452:Receptors, IgG / Q000235:genetics / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D017452:Receptors, IgG; C484068:Tcfeb protein, mouse
keywords: Fc receptors; endocytosis; gene expression; lysosomes; macrophages; phagocytosis