Regulation of oxidative stress-induced autophagy by ATG9A ubiquitination

Abstract

High levels of reactive oxygen species (ROS) result in oxidative stress, which damages cells and leads to the development of many diseases. Macroautophagy/autophagy plays an important role in protecting cells from diverse stress stimuli including oxidative stress. However, the molecular mechanisms of autophagy activation in response to oxidative stress remain largely unclear. In this study, we showed that TRAF6 mediates oxidative stress-induced ATG9A ubiquitination at two C-terminal lysine residues (K581 and K838). ATG9A ubiquitination promotes its association with BECN1, BECN1-PIK3C3/VPS34-UVRAG complex assembly and PIK3C3/VPS34 activation, thereby activating autophagy and endocytic trafficking. We also identified TNFAIP3/A20 as a negative regulator of oxidative-induced autophagy by counteracting TRAF6-mediated ATG9A ubiquitination. Moreover, ATG9A depletion attenuates LPS-induced autophagy and causes aberrant TLR4 signaling and inflammatory responses. Our findings revealed a critical role of ATG9A ubiquitination in oxidative stress-induced autophagy, endocytic trafficking and innate immunity.

Keywords: ATG9A; BECN1; PIK3C3/VPS34; TNFAIP3/A20; TRAF6; UVRAG; autophagy; endocytic trafficking; oxidative stress; ubiquitination.

Figure 1.

Scheme depicting the mechanisms of ATG9A ubiquitination in oxidative stress induced-autophagy. TNFAIP3/A20 interacts with ATG9A under normal conditions. Upon oxidative stress, TRAF6 mediates ATG9A ubiquitination, thereby enhancing ATG9A-BECN1 interaction, BECN1-PIK3C3/VPS34-UVRAG complex assembly, PIK3C3/VPS34 activation, autophagosome formation, and endocytic trafficking. Ablation of TRAF6 or ATG9A, or expression of TNFAIP3/A20 or ATG9A ubiquitination mutant impairs BECN1-PIK3C3/VPS34-UVRAG complex assembly and PIK3C3/VPS34 activity.