Extracellular ATP is required for Serratia ShlA toxin-mediated induction of early autophagy and subsequent bacterial exit of host cells

MARISEL TUTTOBENE; JULIETA SCHACHTER; CORA E ALVAREZ; NICOLAS SAFFIOTTI; HELMUT KESSLER; ELEONORA GARCIA VESCOVI; PABLO J SCHWARZBAUM

JOURNAL OF BIOLOGICAL CHEMISTRY

AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Lugar: Bethesda, Maryland; Año: 2023

0021-9258

: Serratia marcescens is an opportunistic human pathogen involved in antibiotic-resistant hospital acquired infections. Upon contact with the host epithelial cell and previous to internalization, Serratia induces an early autophagic response that is entirely dependent on the ShlA toxin. Once Serratia invades the eukaryotic cell and multiples inside an intracellular vacuole, ShlA expression also promotes an exocytic event that allows bacteria egress from the host cell without compromising its integrity. Several toxins, including ShlA, were shown to induce ATP efflux from eukaryotic cells. We demonstrate that ShlA triggered a non-lytic release of ATP from CHO cells. Enzymatic removal of accumulated extracellular ATP (eATP) or pharmacological blockage of eATP-P2Y2 purinergic receptor inhibited the ShlA-promoted autophagic response in CHO cells. Despite the intrinsic ecto-ATPase activity of CHO cells, the effective concentration and kinetic profile of eATP was consistent with the established affinity of the P2Y2 receptor and the known kinetics of autophagy induction. Moreover, eATP removal or P2Y2 receptor inhibition also suppressed the ShlA-induced exocytic expulsion of the bacteria from the host cell. Blocking α5β1 integrin highly inhibited ShlA-dependent autophagy, a result consistent with α5β1 transactivation by the P2Y2 receptor. In sum, eATP operates as the key signaling molecule that allows the eukaryotic cell to detect the challenge imposed by the contact with the ShlA toxin. Stimulation of P2Y2-dependent pathways evokes the activation of a defensive response to counteract cell damage and promotes the non-lytic clearance of the pathogen from the infected cell.