Department of Chemistry, University of Texas at El Paso, 500 West University Avenue, El Paso, TX, 79968, USA.
Department of Biological Sciences, University of Texas at El Paso, 500 West University Avenue, TX, 79968, USA; Border Biomedical Research Center at University of Texas at El Paso, 500 West University Avenue, TX, 79968, USA.
Tuberculosis (Edinb). 2019 Sep;118:101854. doi: 10.1016/j.tube.2019.07.005. Epub 2019 Jul 30.
As a key virulence factor of Mycobacterium tuberculosis, EsxA or 6-kDa early secreted antigenic target (ESAT-6) has been implicated in phagosome rupture and mycobacterial translocation from the phagosome to the cytosol within macrophages. Our previous studies have shown that EsxA permeabilizes liposomal membrane at acidic pH and a membrane-permeabilization defective mutant Q5K attenuates mycobacterial cytosolic translocation and virulence in macrophages. To further probe the mechanism of EsxA membrane permeabilization, here we characterized the effects of various lipid compositions, including biologically relevant phagosome-mimicking lipids and lipid rafts, on the structural stability and membrane insertion of EsxA WT and Q5K. We have found a complex dual play of membrane fluidity and charge in regulating EsxA membrane insertion. Moreover, Q5K affects the membrane insertion through a structure- and lipid composition-independent mechanism. The results of this study provide a novel insights into the mechanism of EsxA membrane interaction.
作为结核分枝杆菌的一个关键毒力因子，EsxA 或 6-kDa 早期分泌抗原靶标（ESAT-6）被认为参与了吞噬体破裂以及分枝杆菌从吞噬体向巨噬细胞胞浆内的易位。我们之前的研究表明，EsxA 在酸性 pH 值下可使脂质体膜穿孔，而膜穿孔缺陷突变体 Q5K 则减弱了分枝杆菌在巨噬细胞胞浆内的易位和毒力。为了进一步探究 EsxA 膜穿孔的机制，我们在这里研究了各种脂质组成，包括与生物学相关的吞噬体模拟脂质和脂筏，对 EsxA WT 和 Q5K 的结构稳定性和膜插入的影响。我们发现了膜流动性和电荷在调节 EsxA 膜插入中的复杂双重作用。此外，Q5K 通过一种结构和脂质组成无关的机制影响膜插入。本研究的结果为 EsxA 与膜相互作用的机制提供了新的见解。
