Membrane Insertion of Mycobacterium tuberculosis EsxA in Cultured Lung Epithelial Cells

Abstract

EsxA has long been recognized as an important virulence factor of Mycobacterium tuberculosis (Mtb) that plays an essential role in Mtb virulence. However, current data regarding to its role in Mtb virulence are controversial. Here, we have obtained evidence showing that the cytolytic activity of EsxA at neutral pH is due to contamination of ASB-14, a detergent used in EsxA preparation. Moreover, it is for the first time we have found that EsxA protein is endocytosed into lung epithelial cells and inserts into the host membranes within acidic subcellular compartments, implicating an important role of the acidic pH-dependent membrane permeabilizing activity of EsxA in Mtb virulence.