Role played by Atg16L1 in maintaining macrophage homeostasis

Zhekova, Aleksandra (2017) Role played by Atg16L1 in maintaining macrophage homeostasis. Doctoral thesis, University of East Anglia.

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Abstract

Autophagy is a membrane trafficking pathway that delivers portions of the cytoplasm to lysosomes for degradation. Degradation of damaged organelles and proteins allows autophagy to play key roles in maintaining cell and tissue homeostasis and reducing inflammation. Autophagy can also degrade intracellular pathogens and expose pathogen components to innate and adaptive immune systems. Recent work has identified LC3-associated phagocytosis (LAP) as a pathway related to autophagy that is activated during the phagocytosis of pathogens and may also facilitate delivery to lysosomes. Autophagy protein Atg16L1 is required for both autophagy and LAP, and also for the suppression of secretion of the pro-inflammatory cytokine IL-1beta from macrophages. The N-terminal region of Atg16L1 contains a short atg5-binding and coiled coil domain (CCD) that binds WIPI2b and is required for autophagy. The large C-terminal domain is made from seven tryptophan-aspartic acid (WD) repeats folded into a -propeller thought to provide a platform for protein interactions important for autophagy. This study has used mice lacking the WD domain of Atg16L1 to investigate the role played by these domains in determining the inflammatory status of macrophages. Mice carrying a stop codon at the end of the CCD were unable to express the WD domain. The inflammatory status of macrophages isolated from these mice was compared with macrophages carrying an additional deletion that removed a glutamate residue at position 230 in the CCD required for WIPI2b binding and autophagy. Bone marrow-derived macrophages from mice lacking both the WD domain and glutamate 230 were unable to induce autophagy. They were also unable to suppress IL-1beta secretion in response to LPS or differentiate into anti-inflammatory M2 macrophages. Mice that lacked the WD domain of Atg16L1, but retained glutamate 230 could activate autophagy, suppress inflammation and differentiate into anti-inflammatory macrophages. These results suggested that the inflammatory status of macrophages is maintained independently of the WD domain, and relies on the short N-terminal coiled coil domain of Atg16L1, which is able to activate autophagy. Parallel studies following the uptake of polystyrene beads by macrophages showed that the WD domain of Atg16L1 was required for LAP. LAP is therefore activated during phagocytosis, but since the inflammatory status of macrophages is independent of the WD domain, LAP does not appear to play a role in suppressing inflammatory responses of macrophages.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Medicine and Health Sciences > Norwich Medical School
Depositing User: Gillian Aldus
Date Deposited: 10 Sep 2018 10:07
Last Modified: 10 Sep 2018 10:07
URI: https://ueaeprints.uea.ac.uk/id/eprint/68210
DOI:

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