Fleurie Aurore, Manuse Sylvie, Zhao Chao, Campo Nathalie, Cluzel Caroline, Lavergne Jean-Pierre, Freton Céline, Combet Christophe, Guiral Sébastien, Soufi Boumediene, Macek Boris, Kuru Erkin, VanNieuwenhze Michael S, Brun Yves V, Di Guilmi Anne-Marie, Claverys Jean-Pierre, Galinier Anne, Grangeasse Christophe
Bases Moléculaires et Structurales des Systèmes Infectieux, IBCP, Université Lyon 1, CNRS, UMR 5086, Lyon, France.
Bases Moléculaires et Structurales des Systèmes Infectieux, IBCP, Université Lyon 1, CNRS, UMR 5086, Lyon, France; Key laboratory of Medical Molecular Virology, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, China.
PLoS Genet. 2014 Apr 10;10(4):e1004275. doi: 10.1371/journal.pgen.1004275. eCollection 2014 Apr.
Despite years of intensive research, much remains to be discovered to understand the regulatory networks coordinating bacterial cell growth and division. The mechanisms by which Streptococcus pneumoniae achieves its characteristic ellipsoid-cell shape remain largely unknown. In this study, we analyzed the interplay of the cell division paralogs DivIVA and GpsB with the ser/thr kinase StkP. We observed that the deletion of divIVA hindered cell elongation and resulted in cell shortening and rounding. By contrast, the absence of GpsB resulted in hampered cell division and triggered cell elongation. Remarkably, ΔgpsB elongated cells exhibited a helical FtsZ pattern instead of a Z-ring, accompanied by helical patterns for DivIVA and peptidoglycan synthesis. Strikingly, divIVA deletion suppressed the elongated phenotype of ΔgpsB cells. These data suggest that DivIVA promotes cell elongation and that GpsB counteracts it. Analysis of protein-protein interactions revealed that GpsB and DivIVA do not interact with FtsZ but with the cell division protein EzrA, which itself interacts with FtsZ. In addition, GpsB interacts directly with DivIVA. These results are consistent with DivIVA and GpsB acting as a molecular switch to orchestrate peripheral and septal PG synthesis and connecting them with the Z-ring via EzrA. The cellular co-localization of the transpeptidases PBP2x and PBP2b as well as the lipid-flippases FtsW and RodA in ΔgpsB cells further suggest the existence of a single large PG assembly complex. Finally, we show that GpsB is required for septal localization and kinase activity of StkP, and therefore for StkP-dependent phosphorylation of DivIVA. Altogether, we propose that the StkP/DivIVA/GpsB triad finely tunes the two modes of peptidoglycan (peripheral and septal) synthesis responsible for the pneumococcal ellipsoid cell shape.
尽管经过多年深入研究，但要理解协调细菌细胞生长和分裂的调控网络，仍有许多有待发现之处。肺炎链球菌形成其特征性椭圆形细胞形状的机制在很大程度上仍不清楚。在本研究中，我们分析了细胞分裂旁系同源物DivIVA和GpsB与丝氨酸/苏氨酸激酶StkP之间的相互作用。我们观察到，divIVA缺失阻碍细胞伸长，导致细胞缩短和变圆。相比之下，GpsB缺失导致细胞分裂受阻并引发细胞伸长。值得注意的是，ΔgpsB伸长的细胞呈现螺旋状FtsZ模式而非Z环，同时DivIVA和肽聚糖合成也呈现螺旋状模式。令人惊讶的是，divIVA缺失抑制了ΔgpsB细胞的伸长表型。这些数据表明DivIVA促进细胞伸长，而GpsB则起到相反作用。蛋白质-蛋白质相互作用分析表明，GpsB和DivIVA不与FtsZ相互作用，而是与细胞分裂蛋白EzrA相互作用，而EzrA本身与FtsZ相互作用。此外，GpsB直接与DivIVA相互作用。这些结果与DivIVA和GpsB作为分子开关协调外周和隔膜肽聚糖合成并通过EzrA将它们与Z环相连相一致。转肽酶PBP2x和PBP2b以及脂质翻转酶FtsW和RodA在ΔgpsB细胞中的细胞共定位进一步表明存在一个单一的大型肽聚糖组装复合体。最后，我们表明GpsB是StkP隔膜定位和激酶活性所必需的，因此也是DivIVA依赖StkP磷酸化所必需的。总之，我们提出StkP/DivIVA/GpsB三联体精细调节负责肺炎球菌椭圆形细胞形状的两种肽聚糖（外周和隔膜）合成模式。
