Equipe Communication Intercellulaire et Infections Microbiennes. Centre de Recherche Interdisciplinaire en Biologie (CIRB). Collège de France, 11, Place Marcelin Berthelot, 75005, Paris, France.
Institut National de la Santé et de la Recherche Médicale (Inserm) U1050, Paris, Cedex 15, France.
Nat Commun. 2018 May 23;9(1):2027. doi: 10.1038/s41467-018-04414-2.
Many bacterial proteins require specific subcellular localization for function. How Escherichia coli proteins localize at one pole, however, is still not understood. Here, we show that the DnaK (HSP70) chaperone controls unipolar localization of the Shigella IpaC type III secretion substrate. While preventing the formation of lethal IpaC aggregates, DnaK promoted the incorporation of IpaC into large and dynamic complexes (LDCs) restricted at the bacterial pole through nucleoid occlusion. Unlike stable polymers and aggregates, LDCs show dynamic behavior indicating that nucleoid occlusion also applies to complexes formed through transient interactions. Fluorescence recovery after photobleaching analysis shows DnaK-IpaC exchanges between opposite poles and DnaKJE-mediated incorporation of immature substrates in LDCs. These findings reveal a key role for LDCs as reservoirs of functional DnaK-substrates that can be rapidly mobilized for secretion triggered upon bacterial contact with host cells.
许多细菌蛋白的功能需要特定的细胞内定位。然而，大肠杆菌蛋白如何在一个极定位仍然不清楚。在这里，我们表明 DnaK（HSP70）伴侣蛋白控制志贺氏菌 IpaC 型 III 分泌底物的单极定位。虽然防止形成致命的 IpaC 聚集体，但 DnaK 促进 IpaC 掺入到通过核区排除限制在细菌极的大型和动态复合物（LDC）中。与稳定的聚合物和聚集体不同，LDC 表现出动态行为，表明核区排除也适用于通过瞬时相互作用形成的复合物。光漂白后荧光恢复分析显示 DnaK-IpaC 在相反的两极之间交换，以及 DnaKJE 介导的 LDC 中未成熟底物的掺入。这些发现揭示了 LDC 作为功能性 DnaK-底物的储存库的关键作用，这些底物可以在细菌与宿主细胞接触时迅速被动员用于分泌。
