Autophagy Facilitates Salmonella Replication in HeLa Cells

ABSTRACT Autophagy is a process whereby a double-membrane structure (autophagosome) engulfs unnecessary cytosolic pro-teins, organelles, and invading pathogens and delivers them to the lysosome for degradation.We examined the fate of cytosolic Salmonella targeted by autophagy and found that autophagy-targeted Salmonella present in the cytosol of HeLa cells correlates with intracellular bacterial replication. Real-time analyses revealed that a subset of cytosolic Salmonella extensively associates with autophagy components p62 and/or LC3 and replicates quickly, whereas intravacuolar Salmonella shows no or very limited association with p62 or LC3 and replicates muchmore slowly. Replication of cytosolic Salmonella in HeLa cells is significantly decreased when autophagy components are depleted. Eventually, hyperreplication of cytosolic Salmonella potentiates cell de-tachment, facilitating the dissemination of Salmonella to neighboring cells. We propose that Salmonella benefits from au-tophagy for its cytosolic replication in HeLa cells. IMPORTANCE As a host defense system, autophagy is known to target a population of Salmonella for degradation and hence re-stricting Salmonella replication. In contrast to this concept, a recent report showed that knockdown of Rab1, a GTPase required for autophagy of Salmonella, decreases Salmonella replication in HeLa cells. Here, we have reexamined the fate of Salmonella targeted by autophagy by various cell biology-based assays. We found that the association of autophagy components with cyto-solic Salmonella increases shortly after initiation of intracellular bacterial replication. Furthermore, through a live-cell imaging method, a subset of cytosolic Salmonellawas found to be extensively associated with autophagy components p62 and/or LC3