Neutrophils use selective autophagy receptor p62 to target Staphylococcus aureus for degradation in the zebrafish model

Autophagy leads to degradation of cellular components, and has an important role in destroying intracellular pathogens. Autophagy receptors, including p62, target invading intracellular pathogens to the autophagy pathway for degradation. p62 is able to co-localise with intracellular Staphylococcus aureus, previously shown in vitro, however, whether p62 is beneficial or detrimental in host defence against S. aureus had not been determined. The intracellular fate of S. aureus over time following phagocytosis by neutrophils had not previously been analysed in vivo, and is not readily possible in other in vivo models. Here we use the excellent imaging and genetic capabilities of the zebrafish to analyse the fate and location S. aureus within neutrophils throughout infection. This information adds context to the dynamic temporal recruitment of autophagy proteins Lc3 and p62, accomplished using transgenic reporter lines. We demonstrate, using a new p62 zebrafish mutant to block host p62 function, that p62 is required for a favourable host outcome in the zebrafish S. aureus infection model. We examine the fate of S. aureus throughout the time-course of infection, including bacterial degradation and cellular location, and establish that Lc3 and p62 recruitment to S. aureus within the neutrophil is altered depending on bacterial location within the neutrophil. We suggest that in vivo Lc3 marking of bacterial phagosomes within neutrophils may lead to bacterial degradation and that p62 is important for controlling cytoplasmic bacteria.