Phagocytosis Enhances Lysosomal and Bactericidal Properties by Activating the Transcription Factor TFEB

Abstract

Summary 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 respectively internalize immunoglobulin G (IgG)-opsonized particles and polyvalent IgG immune complexes. We report that Fcγ receptor activation in macrophages enhanced lysosome-based proteolysis and killing of subsequently phagocytosed E. coli compared to naïve macrophages. Importantly, we show that Fcγ receptor activation caused nuclear translocation of TFEB, a transcription factor that boosts expression of lysosome genes. Indeed, Fc receptor activation was accompanied by increased expression of specific lysosomal proteins. Remarkably, TFEB silencing repressed the Fcγ receptor-mediated enhancements in degradation and bacterial killing. In addition, nuclear translocation of TFEB required phagosome completion and failed to occur in cells silenced for MCOLN1, a lysosomal Ca2+ channel, suggesting that lysosomal Ca2+ released during phagosome maturation activates TFEB. Finally, we demonstrated that non-opsonic phagocytosis of E. coli also enhanced 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.

Evaluation of dietary chitosan effects on growth performance, immunity, body composition and histopathology of Nile tilapia (Oreochromis niloticus) as well as the resistance toStreptococcus agalactiaeinfection

“…Swain, Behura, Dash, and Nayak (2007) reported chitosan plays a vital role in the stimulation of bactericidal activity and phagocytic cells that stem particularly from its stimulation of the generation of reactive oxygen species such as O 2 by the affected cells. Therefore, chitosan proved to be an effective immunostimulant preventing the organization of bacterial infection in common carp (Mustafa et al, 2014 results of the immune response in the control group after experimental infection, there was a significant increase in the immune response, which attributed to experimental infection that was confirmed by the result of Gray et al (2016).…”

The complex relationship between TFEB transcription factor phosphorylation and subcellular localization

“…These include infection (Visvikis et al, 2014;Campbell et al, 2015;Pastore et al, 2016), bacterial phagocytosis (Gray et al, 2016), inflammation (i.e., LPS treatment; Pastore et al, 2016), physical exercise (in muscle; Mansueto et al, 2017), mitochondrial damage (Nezich et al, 2015), PIKfyve inhibition (Gayle et al, 2017), and ER stress . These include infection (Visvikis et al, 2014;Campbell et al, 2015;Pastore et al, 2016), bacterial phagocytosis (Gray et al, 2016), inflammation (i.e., LPS treatment; Pastore et al, 2016), physical exercise (in muscle; Mansueto et al, 2017), mitochondrial damage (Nezich et al, 2015), PIKfyve inhibition (Gayle et al, 2017), and ER stress .…”

The big and intricate dreams of little organelles: Embracing complexity in the study of membrane traffic

“…Similarly, in mammalian macrophages, bacteria and bacterial products such as lipopolysaccharides activate TFEB and TFE3 leading to upregulation of immuno‐modulating cytokines and chemokines in vitro and in vivo . Lastly, phagocytosis by macrophages activates TFEB to stimulate lysosomal activity and improve bactericidal activity against subsequent rounds of phagocytosed bacteria, indicating that lysosomal adaptation within the innate immune system controls pathogenic clearance . Strikingly, and speaking to the intense interest to better understand TFEB and related transcription factors, several additional modulators were recently discovered including the kinases glycogen synthase kinase 3β (GSK3β), protein kinase Cβ (PKCβ) and the microRNAs miR33 and miR33* .…”

“…134,135 Lastly, phagocytosis by macrophages activates TFEB to stimulate lysosomal activity and improve bactericidal activity against subsequent rounds of phagocytosed bacteria, indicating that lysosomal adaptation within the innate immune system controls pathogenic clearance. 136 Strikingly, and speaking to the intense interest to better understand TFEB and related transcription factors, several additional modulators were recently discovered including the kinases glycogen synthase kinase 3β (GSK3β), protein kinase Cβ (PKCβ) and the microRNAs miR33 and miR33*. [137][138][139] Collectively these studies show that cells integrate a diverse range of cellular signals to modulate TFEB, TFE3 and MITF, thus adapting lysosomal content, size, number and function to specific conditions.…”