Oxidation inhibits autophagy protein deconjugation from phagosomes to sustain MHC class II restricted antigen presentation

Abstract

LC3-associated phagocytosis (LAP) contributes to a wide range of cellular processes and notably to immunity. The stabilization of phagosomes by the macroautophagy machinery in human macrophages can maintain antigen presentation on MHC class II molecules. However, the molecular mechanisms involved in the formation and maturation of the resulting LAPosomes are not completely understood. Here, we show that reactive oxygen species (ROS) produced by NADPH oxidase 2 (NOX2) stabilize LAPosomes by inhibiting LC3 deconjugation from the LAPosome cytosolic surface. NOX2 residing in the LAPosome membrane generates ROS to cause oxidative inactivation of the protease ATG4B, which otherwise releases LC3B from LAPosomes. An oxidation-insensitive ATG4B mutant compromises LAP and thereby impedes sustained MHC class II presentation of exogenous Candida albicans antigens. Redox regulation of ATG4B is thereby an important mechanism for maintaining LC3 decoration of LAPosomes to support antigen processing for MHC class II presentation.

V-ATPase is a universal regulator of LC3 associated phagocytosis and non-canonical autophagy

“…By linking together NADPH Oxidase, ROS and V-ATPase, these findings reveal direct connections between some of the key players in LAP, thus building towards a unifying mechanism. We note that phagosomal ROS have also been linked to the inhibition of ATG4 deconjugation activity during LAP (Ligeon et al, 2021), which may perhaps be related more to prolonging ATG8 lipidation at phagosomes than to its induction. Further work will be required to assess the triggers for enhanced V0-V1 association in other contexts.…”

Reactive Oxygen Species: Not Omnipresent but Important in Many Locations

“…In recent years, more and more studies supported the model-and highlighted the importance-of localized cellular ROS production in direct vicinity of the redox target (Meinhard and Grill, 2001;Veal et al, 2007;Go and Jones, 2008;Craig and Slauch, 2009;West et al, 2011a;Wink et al, 2011;Zhou et al, 2011;Al-Mehdi et al, 2012;Naviaux, 2012;Allan et al, 2014;Romero et al, 2014;Geng et al, 2015;Gluschko et al, 2018;Herb et al, 2019b;Acin-Perez et al, 2020;Beretta et al, 2020;Chanin et al, 2020;Miller et al, 2020;Sies and Jones, 2020;Herb and Schramm, 2021;Ligeon et al, 2021b;Sies, 2021;Wong et al, 2021). Therefore, the model of ROS molecules as "omnipresent and freely diffusing throughout the cell" should always be interpreted carefully in the context of research and highly depends on the proper use of ROS probes, scavengers and inhibitors.…”

“…Another precise approach for compartment-specific ROS measurements is the coupling of ROS probes to cargo/particles, which can be engulfed by cells. This technique is especially useful in phagocytes like macrophages, to determine ROS levels in the phagosome ( Geng et al, 2015 ; Ligeon et al, 2021a , b ). For further reading on topics regarding ROS detection methods we want to point out to other reviews ( Ermakova et al, 2014 ; Herb and Schramm, 2021 ).…”

“…Both also inhibit Nox-derived ROS production in vitro and in vivo ( Carnesecchi et al, 2009 , 2011 ; Aoyama et al, 2012 ; Green et al, 2012 ; Bettaieb et al, 2015 ; Gorin et al, 2015 ). In sharp contrast to VAS2870 and GKT 137831, the substances apocynin and DPI are still used and falsely addressed as specific Nox inhibitors in many otherwise convincing and excellent studies ( Barbieri et al, 2003 ; Kiritoshi et al, 2003 ; Dostert et al, 2008 ; Choi et al, 2011 ; Abuaita et al, 2015 ; Gatliff et al, 2017 ; Alonso et al, 2019 ; Fan et al, 2019 ; Damiano et al, 2020 ; Geng et al, 2020 ; Inomata et al, 2020 ; Prestes et al, 2020 ; Ahmad et al, 2021 ; Ligeon et al, 2021b ; Martinez et al, 2021 #1039; Troia et al, 2021 ). Several studies have shown that apocynin directly scavenges ROS due to its antioxidant capacities ( Aldieri et al, 2008 ; Heumuller et al, 2008 ; Mora-Pale et al, 2009 ; Wingler et al, 2011 ; Trevelin et al, 2016 ), while DPI inhibits flavoproteins in general ( O’Donnell et al, 1993 ; Wind et al, 2010 ; Altenhofer et al, 2015 ) including Nox2 ( Reis et al, 2020 ), but also various other targets, such as complex I of the mitochondrial electron transport chain ( Bloxham, 1979 ; Lambeth et al, 2008 ; Bulua et al, 2011 ), iNOS ( Stuehr et al, 1991 ; Geyer et al, 1997 ) or xanthine oxidase ( O’Donnell et al, 1993 ; Wind et al, 2010 ) as well as calcium transporters ( Tazzeo et al, 2009 ).…”

Molecular Insights into Tumor Targeted Therapy by Carrier-Free Lycorine Nanoparticles in Vitro and in Vivo

“…Carrier-free nanomedicine could provide perfect drug loading and avoid undesired side effects from nonactive excipients or materials [17]. It is also helpful to minimize the interference of carrier materials to study the effects of nanoparticles on the key proteins of apoptosis [18], autophagy [19] and EMT [20].…”