Neutrophils use selective autophagy receptor Sqstm1/p62 to target Staphylococcus aureus for degradation in vivo in zebrafish

Macroautophagy/autophagy functions to degrade cellular components and intracellular pathogens. Autophagy receptors, including SQSTM1/p62, target intracellular pathogens. Staphylococcus aureus is a significant pathogen of humans, especially in immunocompromise. S. aureus may use neutrophils as a proliferative niche, but their intracellular fate following phagocytosis has not been analyzed in vivo. In vitro, SQSTM1 can colocalize with intracellular Staphylococcus aureus, but whether SQSTM1 is beneficial or detrimental in host defense against S. aureus in vivo is unknown. Here we determine the fate and location of S. aureus within neutrophils throughout zebrafish infection. We show Lc3 and Sqstm1 recruitment to phagocytosed S. aureus is altered depending on the bacterial location within the neutrophil and that Lc3 marking of bacterial phagosomes within neutrophils may precede bacterial degradation. Finally, we show Sqstm1 is important for controlling cytosolic bacteria, demonstrating for the first time a key role of Sqstm1 in autophagic control of S. aureus in neutrophils.Abbreviations: AR: autophagy receptor; CFU: colony-forming unit; CHT: caudal hematopoietic tissue; GFP: green fluorescent protein; hpf: hours post-fertilization; hpi: hours post-infection; LWT: london wild-type: lyz: lysozyme; Map1lc3/Lc3: microtubule-associated protein 1 light chain 3; RFP: red fluorescent protein; Sqstm1/p62: sequestosome 1; Tg: transgenic; TSA: tyramide signal amplification; UBD: ubiquitin binding domain.