Autophagy targeting of Listeria monocytogenes and the bacterial countermeasure

Autophagy acts as an intrinsic defense system against intracellular bacterial survival. Recently, multiple cellular pathways that target intracellular bacterial pathogens to autophagy have been described. These include the Atg5/LC3 pathway, which targets Shigella, the ubiquitin (Ub)-NDP52LC3 pathway, which targets Group A Streptococcus (GAS) and Salmonella typhimurium, the Ub-p62-LC3 pathway, which targets Mycobacterium tuberculosis, Listeria monocytogenes and S. typhimurium, and the diacylglycerol-dependent pathway, which targets S. typhimurium. In addition, the bacterial invasion process is targeted by the NOD1 or NOD2-Atg16L-LC3 pathway. Bacterial pathogens with an intracytosolic lifestyle, i.e., those capable of inducing actin polymerization and cell-to-cell spreading, also employ diverse tactics to evade autophagic recognition. Thus, Shigella, L. monocytogenes and Burkholderia pseudomallei deploy highly evolved systems to evade autophagic recognition and growth restriction. Here, we briefly review current knowledge of host recognition of L. monocytogenes by the innate immune system, and highlight how autophagic recognition by the host is overcome by bacterial countermeasures.