An essential periplasmic protein coordinates lipid trafficking and is required for asymmetric polar growth in mycobacteria.
An essential periplasmic protein coordinates lipid trafficking and is required for asymmetric polar growth in mycobacteria.
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DOI：
10.7554/elife.80395
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发表时间：
2022-11-08
期刊：
影响因子：
7.7
通讯作者：
Rego EH
中科院分区：
文献类型：
--
作者：
Gupta KR;Gwin CM;Rahlwes KC;Biegas KJ;Wang C;Park JH;Liu J;Swarts BM;Morita YS;Rego EH
分枝杆菌，包括人类病原体结核分枝杆菌，通过在其两极插入新的细胞壁材料来生长。这个过程和分裂过程是不对称的，产生表型异质的细胞群，对压力的反应不一致（Aldridge et al., 2012; Rego et al., 2017）。令人惊讶的是，删除单个基因 - lamA - 会导致更加对称，并使细胞群更均匀地被抗生素杀死（Rego et al., 2017）。 LamA 如何造成不对称？在这里，结合定量延时成像、细菌遗传学和脂质分析，我们发现 LamA 将参与细胞壁合成的必需蛋白质招募到细胞的一侧（旧极）。其中一种蛋白质 MSMEG_0317（此处更名为 PgfA）的功能未知。我们发现 PgfA 是一种与 MmpL3 相互作用的周质蛋白，MmpL3 是一种重要的转运蛋白，可将分枝菌酸以海藻糖单分枝菌酸酯 (TMM) 的形式翻转穿过质膜。 PgfA 与 TMM 类似物相互作用，表明 PgfA 在 TMM 转运中发挥直接作用。然而，我们的数据也表明了更广泛的功能，因为 PgfA 水平改变的细胞在其他脂质的丰度方面存在差异，并且对这些脂质的生存依赖程度不同。 PgfA（而非 MmpL3）的过表达可以恢复缺失 lamA 的细胞旧两极的生长。总之，我们的结果表明，PgfA 是分枝杆菌极性生长和细胞包膜组成的关键决定因素，并且 LamA 介导的将该蛋白质募集到细胞一侧是建立细胞不对称性的必要步骤。
Mycobacteria, including the human pathogen Mycobacterium tuberculosis, grow by inserting new cell wall material at their poles. This process and that of division are asymmetric, producing a phenotypically heterogeneous population of cells that respond non-uniformly to stress (Aldridge et al., 2012; Rego et al., 2017). Surprisingly, deletion of a single gene – lamA – leads to more symmetry, and to a population of cells that is more uniformly killed by antibiotics (Rego et al., 2017). How does LamA create asymmetry? Here, using a combination of quantitative time-lapse imaging, bacterial genetics, and lipid profiling, we find that LamA recruits essential proteins involved in cell wall synthesis to one side of the cell – the old pole. One of these proteins, MSMEG_0317, here renamed PgfA, was of unknown function. We show that PgfA is a periplasmic protein that interacts with MmpL3, an essential transporter that flips mycolic acids in the form of trehalose monomycolate (TMM), across the plasma membrane. PgfA interacts with a TMM analog suggesting a direct role in TMM transport. Yet our data point to a broader function as well, as cells with altered PgfA levels have differences in the abundance of other lipids and are differentially reliant on those lipids for survival. Overexpression of PgfA, but not MmpL3, restores growth at the old poles in cells missing lamA. Together, our results suggest that PgfA is a key determinant of polar growth and cell envelope composition in mycobacteria, and that the LamA-mediated recruitment of this protein to one side of the cell is a required step in the establishment of cellular asymmetry.