Cited by 260Autophagy in Disease and TherapyNeuroinflammation and Neurodegeneration MechanismsImmune Response and Inflammation

TLR4 (toll-like receptor 4) activation suppresses autophagy through inhibition of FOXO3 and impairs phagocytic capacity of microglia

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Lee, Ji-Won, Nam, Hyeri, Kim, Leah Eunjung, Jeon, Yoonjeong, Min, Hyunjung, Ha, Shinwon, Lee, Younghwan, Kim, Seon-Young +3 more·2019·Autophagy

Abstract

Macroautophagy/autophagy is a lysosome-dependent catabolic process for the turnover of proteins and organelles in eukaryotes. Autophagy plays an important role in immunity and inflammation, as well as metabolism and cell survival. Diverse immune and inflammatory signals induce autophagy in macrophages through pattern recognition receptors, such as toll-like receptors (TLRs). However, the physiological role of autophagy and its signaling mechanisms in microglia remain poorly understood. Microglia are phagocytic immune cells that are resident in the central nervous system and share many characteristics with macrophages. Here, we show that autophagic flux and expression of autophagy-related (Atg) genes in microglia are significantly suppressed upon TLR4 activation by lipopolysaccharide (LPS), in contrast to their stimulation by LPS in macrophages. Metabolomics analysis of the levels of phosphatidylinositol (PtdIns) and its 3-phosphorylated form, PtdIns3P, in combination with bioinformatics prediction, revealed an LPS-induced reduction in the synthesis of PtdIns and PtdIns3P in microglia but not macrophages. Interestingly, inhibition of PI3K, but not MTOR or MAPK1/3, restored autophagic flux with concomitant dephosphorylation and nuclear translocation of FOXO3. A constitutively active form of FOXO3 also induced autophagy, suggesting FOXO3 as a downstream target of the PI3K pathway for autophagy inhibition. LPS treatment impaired phagocytic capacity of microglia, including MAP1LC3B/LC3-associated phagocytosis (LAP) and amyloid β (Aβ) clearance. PI3K inhibition restored LAP and degradation capacity of microglia against Aβ. These findings suggest a unique mechanism for the regulation of microglial autophagy and point to the PI3K-FOXO3 pathway as a potential therapeutic target to regulate microglial function in brain disorders.Abbreviations: Atg: autophagy-related gene; Aβ: amyloid-β; BafA1: bafilomycin A1; BECN1: beclin 1, autophagy related; BMDM: bone marrow-derived macrophage; CA: constitutively active; CNS: central nervous system; ZFYVE1/DFCP1: zinc finger, FYVE domain containing 1; FOXO: forkhead box O; ELISA:enzyme-linked immunosorbent assay; HBSS: Hanks balanced salt solution; LAP: LC3-associated phagocytosis; MAP1LC3B: microtubule-associated protein 1 light chain 3; LPS: lipopolysaccharide; LY: LY294002; MTOR: mechanistic target of rapamycin kinase; Pam3CSK4: N-palmitoyl-S-dipalmitoylglyceryl Cys-Ser-(Lys)4; PtdIns: phosphatidylinositol; PtdIns3P: phosphatidylinositol-3-phosphate; PLA: proximity ligation assay; Poly(I:C): polyinosinic-polycytidylic acid; qRT-PCR: quantitative real-time polymerase chain reaction; RPS6KB1: ribosomal protein S6 kinase, polypeptide 1; TLR: Toll-like receptor; TNF: tumor necrosis factor; TFEB: transcription factor EB; TSPO: translocator protein.

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Crossref · 10.1080/15548627.2018.1556946

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  • Activation of innate immune receptors such as TLR4 in microglia suppresses autophagy.

    “Activation of innate immune receptors such as TLR4 in microglia suppresses autophagy39”
  • Among PRRs, TLRs play a crucial role in the inflammatory responses to pathogenic infection and have been a target for many studies exploring phagocytosis.

    “Among the mentioned PRRs, TLRs play crucial role in the inflammatory responses to pathogenic infection and have been a target for many studies exploring phagocytosis course [201,202,203].”

    From MicroRNAs as Regulators of Phagocytosis (2022) · cites this paper as [203]

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Authors
Lee, J.-W., Nam, H., Kim, L. E., Jeon, Y., Min, H., Ha, S., Lee, Y., Kim, S.-Y., Lee, S. J., Kim, E.-K., & Yu, S.-W.
Affiliations
  • Daegu Gyeongbuk Institute of Science and Technology (KR)
  • Seoul National University (KR)
  • Korea Research Institute of Bioscience and Biotechnology (KR)
Corresponding author
Yu, Seong-Woon
Venue
Autophagy
Published
2018-12-13
Volume
15
Issue
5
Pages
753-770
ISSN
  • 1554-8627 (ISSN-L)
  • 1554-8635
OpenAlex
W2903610594
Cited by
260
References
85
Citations by year
2026: 30 · 2025: 34 · 2024: 38 · 2023: 48 · 2022: 40 · 2021: 45 · 2020: 15 · 2019: 9
FWCI
13.47
Type
journal article
Language
en
Open access
Locations
  • Autophagy (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
  • KRIBB Repository (submittedVersion)
Funders
National Research Foundation of Korea (2013M3C7A1056099)
Topics
  • Health Sciences › Medicine › Epidemiology › Autophagy in Disease and Therapy
  • Life Sciences › Neuroscience › Neurology › Neuroinflammation and Neurodegeneration Mechanisms
  • Life Sciences › Immunology and Microbiology › Immunology › Immune Response and Inflammation
Keywords
TLR4, microglia, FOXO3, PI3K signaling, lipopolysaccharide, phagocytosis, amyloid-beta clearance, phosphatidylinositol 3-phosphate, autophagic flux, LC3-associated phagocytosis, neuroinflammation, macrophages, brain disorders, therapeutic target
MeSH terms
RAW 264.7 Cells, Forkhead Box Protein O3, Animals, Animals, Newborn, Autophagy, Cells, Cultured, Lipopolysaccharides, Macrophages, Mice, Inbred C57BL, Phagocytosis, Signal Transduction, Down-Regulation, Amyloid beta-Peptides, Microglia, Mice, Knockout, Phosphatidylinositol 3-Kinases, Toll-Like Receptor 4, Mice

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