Department of Biology, University of Texas, Arlington, Texas, USA.
Department of Chemistry and Biochemistry, University of Texas, Arlington, Texas, USA.
J Bacteriol. 2024 Oct 24;206(10):e0020424. doi: 10.1128/jb.00204-24. Epub 2024 Sep 25.
Cell growth in mycobacteria involves cell wall expansion that is restricted to the cell poles. The DivIVA homolog Wag31 is required for this process, but the molecular mechanism and protein partners of Wag31 have not been described. In this study of , we identify a connection between and trehalose monomycolate (TMM) transporter in a suppressor screen and show that Wag31 and polar regulator PlrA are required for MmpL3's polar localization. In addition, the localization of PlrA and MmpL3 is responsive to nutrient and energy deprivation and inhibition of peptidoglycan metabolism. We show that inhibition of MmpL3 causes delocalized cell wall metabolism but does not delocalize MmpL3 itself. We found that cells with an MmpL3 C-terminal truncation, which is defective for localization, have only minor defects in polar growth but are impaired in their ability to downregulate cell wall metabolism under stress. Our work suggests that, in addition to its established function in TMM transport, MmpL3 has a second function in regulating global cell wall metabolism in response to stress. Our data are consistent with a model in which the presence of TMMs in the periplasm stimulates polar elongation and in which the connection between Wag31, PlrA, and the C-terminus of MmpL3 is involved in detecting and responding to stress in order to coordinate the synthesis of the different layers of the mycobacterial cell wall in changing conditions.
This study is performed in , which is used as a model to understand the basic physiology of pathogenic mycobacteria such as . In this work, we examine the function and regulation of three proteins involved in regulating cell wall elongation in mycobacterial cells, which occurs at the cell tips or poles. We find that Wag31, a regulator of polar elongation, works partly through the regulation of MmpL3, a transporter of cell wall constituents and an important drug target. Our work suggests that, beyond its transport function, MmpL3 has another function in controlling cell wall synthesis broadly in response to stress.
分枝杆菌中的细胞生长涉及细胞壁的扩展，而细胞壁的扩展仅限于细胞极。DivIVA 同源物 Wag31 是该过程所必需的，但 Wag31 的分子机制和蛋白伴侣尚未被描述。在这项对 的研究中，我们在一个抑制筛选中确定了 和海藻糖单胞壁酸（TMM）转运蛋白 的连接，并表明 Wag31 和极性调节因子 PlrA 是 MmpL3 极性定位所必需的。此外，PlrA 和 MmpL3 的定位对营养和能量剥夺以及肽聚糖代谢的抑制有反应。我们表明，MmpL3 的抑制会导致细胞壁代谢的去定位，但不会使 MmpL3 本身去定位。我们发现，MmpL3 C 端截断的细胞，其定位有缺陷，只有在极性生长方面的轻微缺陷，但在应激下下调细胞壁代谢的能力受损。我们的工作表明，除了其在 TMM 转运中的既定功能外，MmpL3 在响应应激时还具有调节全局细胞壁代谢的第二个功能。我们的数据与以下模型一致：周质中 TMM 的存在刺激极伸长，而 Wag31、PlrA 和 MmpL3 的 C 末端之间的连接参与检测和响应应激，以协调不同条件下分枝杆菌细胞壁的不同层的合成。
这项研究是在 中进行的，它被用作模型来理解致病性分枝杆菌（如 ）的基本生理学。在这项工作中，我们研究了三个参与调节分枝杆菌细胞细胞壁伸长的蛋白的功能和调节，细胞壁伸长发生在细胞尖端或极。我们发现，Wag31 是极伸长的调节剂，部分通过调节 MmpL3 发挥作用，MmpL3 是细胞壁成分的转运蛋白，也是一个重要的药物靶点。我们的工作表明，除了其转运功能外，MmpL3 在响应应激时还具有控制细胞壁合成的另一种功能。
