Role of Glutathione in Buffering Excess Intracellular Copper in Streptococcus pyogenes.
Role of Glutathione in Buffering Excess Intracellular Copper in Streptococcus pyogenes.
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DOI：
10.1128/mbio.02804-20
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发表时间：
2020-12-01
期刊：
影响因子：
6.4
通讯作者：
Djoko KY
中科院分区：
文献类型：
--
作者：
Stewart LJ;Ong CY;Zhang MM;Brouwer S;McIntyre L;Davies MR;Walker MJ;McEwan AG;Waldron KJ;Djoko KY
胞内金属可用性的控制是细菌生理学的基础。在铜（Cu）的情况下，已经确定细胞内Cu水平的上升最终填充内源性Cu感应转录调控因子的金属感应位点，这反过来诱导铜输出泵的转录。这种反应将细胞内的铜可用性限制在一个明确的阈值以下，并防止铜毒性。谷胱甘肽在许多细菌中含量丰富，已知与铜结合，长期以来被认为有助于细菌对铜的处理。然而，由于其生物合成和吸收都不受cu的调节，因此存在一些不确定性。此外，除了测量谷胱甘肽缺乏突变体在Cu存在下的生长外，几乎没有实验支持谷胱甘肽的这种生理作用。我们对A群链球菌的研究提供了新的证据，证明谷胱甘肽增加了细菌耐受的细胞内铜可用性的阈值，从而促进了对细菌铜处理的基本理解。铜（Cu）是细菌生理必需的金属，但过量的铜是细菌毒性的。为了限制铜在细胞质中的水平，大多数细菌都有一个铜输出的转录反应系统。在革兰氏阳性人类病原体化脓性链球菌（A群链球菌[GAS]）中，该系统由copYAZ操纵子编码。本研究表明，尽管GAS感染部位代表了一个富铜环境，但在侵袭性疾病小鼠模型中，copA铜外排基因的失活并不会降低毒力。在体外，Cu处理导致多种可观察到的表型，包括生长和活力缺陷，发酵降低，甘油醛-3-磷酸脱氢酶（GapA）活性抑制，以及金属稳态失调，这可能是Cu错金属化非同源金属结合位点的结果。令人惊讶的是，尽管暴露于Cu后copZ的表达立即上调，但这些效应的发生延迟了约4小时。进一步的生化研究表明，所有表型的发生都与细胞内谷胱甘肽（GSH）的消耗一致。补充细胞外谷胱甘肽可以补充细胞内硫醇池，并抑制Cu处理的所有可观察到的影响。这些结果表明，当转录反应的铜输出系统不堪重负时，谷胱甘肽可以缓冲细胞内过量的铜。因此，虽然copYAZ操纵子负责Cu稳态，但谷胱甘肽在Cu耐受性中起作用，并允许细菌在过量存在这种金属离子的情况下维持代谢。
The control of intracellular metal availability is fundamental to bacterial physiology. In the case of copper (Cu), it has been established that rising intracellular Cu levels eventually fill the metal-sensing site of the endogenous Cu-sensing transcriptional regulator, which in turn induces transcription of a copper export pump. This response caps intracellular Cu availability below a well-defined threshold and prevents Cu toxicity. Glutathione, abundant in many bacteria, is known to bind Cu and has long been assumed to contribute to bacterial Cu handling. However, there is some ambiguity since neither its biosynthesis nor uptake is Cu-regulated. Furthermore, there is little experimental support for this physiological role of glutathione beyond measuring growth of glutathione-deficient mutants in the presence of Cu. Our work with group A Streptococcus provides new evidence that glutathione increases the threshold of intracellular Cu availability that can be tolerated by bacteria and thus advances fundamental understanding of bacterial Cu handling. Copper (Cu) is an essential metal for bacterial physiology but in excess it is bacteriotoxic. To limit Cu levels in the cytoplasm, most bacteria possess a transcriptionally responsive system for Cu export. In the Gram-positive human pathogen Streptococcus pyogenes (group A Streptococcus [GAS]), this system is encoded by the copYAZ operon. This study demonstrates that although the site of GAS infection represents a Cu-rich environment, inactivation of the copA Cu efflux gene does not reduce virulence in a mouse model of invasive disease. In vitro, Cu treatment leads to multiple observable phenotypes, including defects in growth and viability, decreased fermentation, inhibition of glyceraldehyde-3-phosphate dehydrogenase (GapA) activity, and misregulation of metal homeostasis, likely as a consequence of mismetalation of noncognate metal-binding sites by Cu. Surprisingly, the onset of these effects is delayed by ∼4 h even though expression of copZ is upregulated immediately upon exposure to Cu. Further biochemical investigations show that the onset of all phenotypes coincides with depletion of intracellular glutathione (GSH). Supplementation with extracellular GSH replenishes the intracellular pool of this thiol and suppresses all the observable effects of Cu treatment. These results indicate that GSH buffers excess intracellular Cu when the transcriptionally responsive Cu export system is overwhelmed. Thus, while the copYAZ operon is responsible for Cu homeostasis, GSH has a role in Cu tolerance and allows bacteria to maintain metabolism even in the presence of an excess of this metal ion.
影响因子：
3.6
作者：
Foster AW;Pernil R;Patterson CJ;Robinson NJ
通讯作者：
Robinson NJ