Unique position of ATG5 in the atg8ylation cascade provides a switch between autophagy and secretion

ATG5 is a part of the E3 ligase directing lipidation of ATG8 proteins (mATG8s), a process central to membrane atg8ylation and its downstream homeostatic manifestations, including canonical autophagy. Genetic ablation of ATG5 in myeloid cells causes mortality in murine models of tuberculosis. Paradoxically, this in vivo phenotype is specific to ATG5 and does not apply to other ATGs. Here we show that absence of ATG5 but not of other components of canonical autophagy, promotes lysosomal exocytosis, secretion of extracellular vesicles, and in neutrophils their excessive degranulation. This is due to lysosomal disrepair in ATG5 knockout cells and sequestration of ESCRT proteins by an alternative ATG conjugation complex. These findings explain the unique nature of ATG5 in host-protective role in murine experimental models of tuberculosis, and emphasize the significance of the branching aspects of the atg8ylation conjugation cascade beyond the canonical autophagy.