Dual pili post-translational modifications synergize to mediate meningococcal adherence to platelet activating factor receptor on human airway cells.

Pili of pathogenic Neisseria are major virulence factors associated with adhesion, twitching motility, auto-aggregation, and DNA transformation. Pili of N. meningitidis are subject to several different post-translational modifications. Among these pilin modifications, the presence of phosphorylcholine (ChoP) and a glycan on the pilin protein are phase-variable (subject to high frequency, reversible on/off switching of expression). In this study we report the location of two ChoP modifications on the C-terminus of N. meningitidis pilin. We show that the surface accessibility of ChoP on pili is affected by phase variable changes to the structure of the pilin-linked glycan. We identify for the first time that the platelet activating factor receptor (PAFr) is a key, early event receptor for meningococcal adherence to human bronchial epithelial cells and tissue, and that synergy between the pilin-linked glycan and ChoP post-translational modifications is required for pili to optimally engage PAFr to mediate adherence to human airway cells. Neisseria meningitidis is an important human pathogen that can cause rapidly progressing, life threatening meningitis and sepsis in humans. There is no fully protective vaccine against this pathogen in current use and the key processes that dictate the transition from harmless carriage of the bacterium in the airway (the case for the vast majority of colonised hosts) to invasive disease are largely undefined. A key missing link in this organism's interaction with the human host is the identity of the receptor that is the first point of contact for the organism within the airway. In this study, we report that the receptor for this important human pathogen on airway epithelial cells is the platelet activating factor receptor (PAFr), an immunomodulatory molecule shown by others to play a role in promoting bacterial sepsis. We also show that two post-translational modifications, glycosylation and phosphorylcholine, are subject to phase-variation (high frequency, reversible switching of gene expression). They are closely associated on adjacent pilin subunits, and synergy between both are required for the efficient engagement with the PAFr. These data define a new role for these post-translational modifications in meningococcal adherence and also provide an insight into the selective pressures that underlie their phase variable expression.

致病性奈瑟菌的菌毛是与黏附、颤搐运动、自身聚集和DNA转化相关的主要毒力因子。脑膜炎奈瑟菌的菌毛会经历几种不同的翻译后修饰。在这些菌毛蛋白修饰中，菌毛蛋白上磷酸胆碱（ChoP）和聚糖的存在是相位可变的（表达会发生高频率、可逆的开/关转换）。在这项研究中，我们报道了脑膜炎奈瑟菌菌毛蛋白C末端的两种ChoP修饰的位置。我们表明菌毛上ChoP的表面可及性受菌毛蛋白连接聚糖结构的相位可变变化的影响。我们首次确定血小板活化因子受体（PAFr）是脑膜炎球菌黏附于人支气管上皮细胞和组织的关键早期事件受体，并且菌毛蛋白连接聚糖和ChoP翻译后修饰之间的协同作用是菌毛最佳地结合PAFr以介导对人呼吸道细胞的黏附所必需的。 脑膜炎奈瑟菌是一种重要的人类病原体，可在人体内引起快速进展的、危及生命的脑膜炎和败血症。目前使用的针对这种病原体的疫苗没有完全的保护作用，决定细菌从在呼吸道无害携带（绝大多数定植宿主的情况）转变为侵袭性疾病的关键过程在很大程度上尚未明确。这种生物体与人类宿主相互作用中缺失的一个关键环节是作为生物体在呼吸道内第一个接触点的受体的身份。在这项研究中，我们报道呼吸道上皮细胞上这种重要的人类病原体的受体是血小板活化因子受体（PAFr），这是一种已被他人证明在促进细菌性败血症中起作用的免疫调节分子。我们还表明两种翻译后修饰，糖基化和磷酸胆碱，是相位可变的（基因表达的高频率、可逆转换）。它们在相邻的菌毛蛋白亚基上紧密相关，并且两者之间的协同作用对于与PAFr的有效结合是必需的。这些数据确定了这些翻译后修饰在脑膜炎球菌黏附中的新作用，并且也提供了对其相位可变表达背后的选择压力的深入了解。