Group A Streptococcus Prevents Lysosomal Acidification in THP‐1 Macrophages By Inhibiting V‐ATPase Complex Fformation

Abstract

Group A Streptococcus (GAS) is a Gram‐positive bacterial pathogen responsible for approximately 750 million human‐specific infections worldwide every year, ranging in severity from mild pharyngitis to necrotizing fasciitis. To defend against invasive pathogens such as GAS, the innate immune system deploys macrophages to phagocytose and eradicate the bacterial pathogen via engulfment into the phagosome, fusion with lysosomes, phagosomal acidification, and activation of hydrolytic enzymes. We have demonstrated that GAS persists within macrophages despite trafficking normally through the phagocytic pathway. Because GAS is not capable of surviving highly acidic conditions, the data suggest that GAS instead prevents lysosomal acidification. Vacuolar‐ATPase (V‐ATPase), the proton pump on lysosomes responsible for generation of the proton gradient, is a complex of several proteins that must be properly assembled. Here, we investigated disruption of the formation of the V‐ATPase as a possible mechanism employed by GAS to promote intracellular survival. Immunofluorescence data suggest that membrane subunits fundamental to V‐ATPase assembly and function do not localize to the phagolysosomal membrane in GAS‐infected macrophages. Preliminary cell fractionation and mass spectrometry data also indicate that cytosolic components of the V‐ATPase are present in lower quantities in GAS‐infected phagosomes. We are in the process of immunoprecipitating the V‐ATPase complex from GAS‐infected macrophages to further confirm complex formation. The information gained through our investigations provide important insights on the specific mechanisms GAS has evolved to evade the innate immune response, which may contribute toward the development of more effective therapies.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.