Two Unique Phosphorylation-Driven Signaling Pathways Crosstalk in Staphylococcus aureus to Modulate the Cell-Wall Charge: Stk1/Stp1 Meets GraSR
Two Unique Phosphorylation-Driven Signaling Pathways Crosstalk in Staphylococcus aureus to Modulate the Cell-Wall Charge: Stk1/Stp1 Meets GraSR
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DOI：
10.1021/bi401177n
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发表时间：
2013-11-12
期刊：
影响因子：
2.9
通讯作者：
Golemi-Kotra, Dasantila
中科院分区：
文献类型：
--
作者：
Fridman, Michael;Williams, G. Declan;Golemi-Kotra, Dasantila
Stk1/Stp1 和 GraSR 信号转导途径是金黄色葡萄球菌中的两条不同途径，它们依赖于细胞内转导外部刺激的可逆磷酸化过程。 Stk1/Stp1 是真核生物样 Ser/Thr 激酶磷酸酶对，参与嘌呤生物合成、细胞壁代谢和自溶。 GraSR 是一种双组分系统，参与对阳离子抗菌肽的耐药性。这两个系统都与金黄色葡萄球菌毒力和对细胞壁抑制剂的抗性有关。我们的研究表明，反应调节蛋白 GraR 在 DNA 结合域的三个苏氨酸残基处被 Stk1 磷酸化。 Stk1 的磷酸化取决于 GraR 的结构完整性以及磷酸化位点侧翼的氨基酸序列。其在枯草芽孢杆菌中的同源物 BceR 具有 GraR 三个磷酸化位点中的两个，不会发生 Stk1 依赖性磷酸化。 GraR 参与 dltABCD 操纵子的调节，其基因产物在壁磷壁酸 (WTA) 上添加 D-Ala。通过 NMR 光谱对从金黄色葡萄球菌 RN6390 Delta graR 菌株中分离出的 WTA 进行研究，结果表明 graR 缺失对 WTA 的 D-Ala 含量产生明显的负面影响。此外，Delta graR 突变体与缺乏 Stk1 磷酸化位点的 graR 的互补反映了这种效应。这些发现提供了 GraR 是 Stk1 体内靶标的证据，并表明 D-Ala 对 WTA 的修饰受到 Stk1 的调节。这两条原本独立的信号通路之间的串扰可能促进金黄色葡萄球菌与其环境的相互作用，从而调节细胞生长、分裂和毒力等过程。
The Stk1/Stp1 and GraSR signal-transduction pathways are two distinct pathways in Staphylococcus aureus that rely on a reversible phosphorylation process in transducing external stimuli intracellularly. Stk1/Stp1 is an eukaryote-like Ser/Thr kinase phosphatase pair involved in purine biosynthesis, cell-wall metabolism, and autolysis. GraSR is a two-component system involved in resistance to cationic antimicrobial peptides. Both systems are implicated in S. aureus virulence and resistance to cell-wall inhibitors. Our study shows that the response regulator protein GraR undergoes phosphorylation by Stk1 at three threonine residues in the DNA-binding domain. Phosphorylation by Stk1 depends on the structural integrity of GraR as well as the amino acid sequences flanking the phosphorylation sites. Its homologue in Bacillus subtilis, BceR, which harbors two of the three phosphorylation sites in GraR, does not undergo Stk1-dependent phosphorylation. GraR is involved in regulation of the dltABCD operon, the gene products of which add the D-Ala on wall teichoic acid (WTA). Investigation of WTA isolated from the S. aureus RN6390 Delta graR strain by NMR spectroscopy showed a clear negative effect that graR deletion has on the D-Ala content of WTA. Moreover, complementation of Delta graR mutant with graR lacking the Stk1 phosphorylation sites mirrors this effect. These findings provide evidence that GraR is a target of Stk1 in vivo and suggest that modification of WTA by D-Ala is modulated by Stk1. The crosstalk between these two otherwise independent signaling pathways may facilitate S. aureus interaction with its environment to modulate processes such as cell growth and division and virulence.