An essential nonredundant role for mycobacterial DnaK in native protein folding.
An essential nonredundant role for mycobacterial DnaK in native protein folding.
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DOI：
10.1371/journal.pgen.1004516
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发表时间：
2014-07
期刊：
影响因子：
4.5
通讯作者：
Glickman MS
中科院分区：
文献类型：
--
作者：
Fay A;Glickman MS
蛋白质伴侣在生命的各个领域都是必不可少的，以防止和解决蛋白质在翻译和蛋白毒性应激过程中的错误折叠。HSP70家族分子伴侣包括E. coli DnaK，在应激诱导的蛋白质重折叠和降解中起作用，但由于冗余的分子伴侣系统阻止了全局新生肽的不溶性，因此对细胞活力不利。然而，HSP70分子伴侣在分枝杆菌（包括多种人类病原体的属）中的功能尚未被研究。我们发现，分枝杆菌DnaK是必不可少的细胞生长和所需的天然蛋白质折叠在耻垢分枝杆菌。DnaK的丧失伴随着蛋白毒性崩溃，其特征在于不溶性新合成蛋白质的积累。DnaK是大的多模块脂质脱氢酶（包括必需的脂质合成酶FASI）的溶解性所必需的，并且DnaK损失伴随着膜结构的破坏和细胞渗透性的增加。触发因子是非必需的，并且在天然蛋白质折叠中具有次要作用，其仅在不存在DnaK的情况下明显。在未应激的细胞中，DnaK定位于多个动态焦点，但在稳定期或聚集肽表达后重新定位于焦点蛋白聚集体。分枝杆菌细胞在蛋白毒性应激后通过将含有蛋白质聚集体的持久性DnaK与子细胞分离来重新开始细胞生长。这些结果揭示了分枝杆菌DnaK在分枝杆菌中不可预见的重要非冗余作用，并表明DnaK在分枝杆菌蛋白质稳态网络中定义了一个独特的易感点。所有生物体都使用蛋白质伴侣来防止蛋白质自发地或在可能损害蛋白质的细胞应激期间变得不溶。HSP70分子伴侣DnaK已在E.且对于细菌抵抗蛋白质热变性是重要，但是由于与其它分子伴侣系统的冗余，在没有应激的情况下不利于细胞生长。然而，伴侣蛋白在细菌病原体中的功能，暴露于宿主内的蛋白质应激，受到较少的关注。在这里，我们研究了DnaK在分枝杆菌中的功能，分枝杆菌是一个包括多种人类病原体的属，并发现DnaK是细胞生长所必需的。这种基本功能是由于缺乏冗余与其他分子伴侣系统的蛋白质折叠，即使在没有压力。这些发现扩展了DnaK功能的范例，并将DnaK确定为分枝杆菌抗生素开发的有希望的靶点。
Protein chaperones are essential in all domains of life to prevent and resolve protein misfolding during translation and proteotoxic stress. HSP70 family chaperones, including E. coli DnaK, function in stress induced protein refolding and degradation, but are dispensable for cellular viability due to redundant chaperone systems that prevent global nascent peptide insolubility. However, the function of HSP70 chaperones in mycobacteria, a genus that includes multiple human pathogens, has not been examined. We find that mycobacterial DnaK is essential for cell growth and required for native protein folding in Mycobacterium smegmatis. Loss of DnaK is accompanied by proteotoxic collapse characterized by the accumulation of insoluble newly synthesized proteins. DnaK is required for solubility of large multimodular lipid synthases, including the essential lipid synthase FASI, and DnaK loss is accompanied by disruption of membrane structure and increased cell permeability. Trigger Factor is nonessential and has a minor role in native protein folding that is only evident in the absence of DnaK. In unstressed cells, DnaK localizes to multiple, dynamic foci, but relocalizes to focal protein aggregates during stationary phase or upon expression of aggregating peptides. Mycobacterial cells restart cell growth after proteotoxic stress by isolating persistent DnaK containing protein aggregates away from daughter cells. These results reveal unanticipated essential nonredunant roles for mycobacterial DnaK in mycobacteria and indicate that DnaK defines a unique susceptibility point in the mycobacterial proteostasis network. All living organisms use protein chaperones to prevent proteins from becoming insoluble either spontaneously or during cellular stress that can damage proteins. The HSP70 chaperone DnaK has been well characterized in E. coli and is important for that bacterium to resist protein denaturation from heat, but is dispensable for cell growth in the absence of stress due to redundancy with other chaperone systems. However, the function of chaperones in bacterial pathogens, which are exposed to protein stress within the host, has received less attention. Here we examine the function of DnaK in mycobacteria, a genus that includes multiple human pathogens, and find that DnaK is required for cell growth. This essential function is due to a lack of redundancy with other chaperone systems for the folding of proteins, even in the absence of stress. These findings expand the paradigm of DnaK function and identify DnaK as a promising target for antibiotic development for mycobacteria.
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影响因子：
3.6
作者：
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通讯作者：
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影响因子：
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DOI：
10.1152/ajpendo.00409.2012
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Mendonça-Lima L