RSV is the leading cause of infant hospitalizations and a significant cause of paediatric and geriatric morbidity worldwide. Recently, we reported that insulin-like growth factor 1 receptor (IGF1R) was a receptor for respiratory syncytial virus (RSV) in airway epithelial cells and that activation of IGF1R recruited the coreceptor, nucleolin (NCL), to the cell surface. Cilia and mucus that line the airways pose a significant barrier to viral and bacterial infection. The cortical actin cytoskeleton has been shown by others to mediate RSV entry, so we studied the roles of the RSV receptors and actin remodelling during virus entry. We found that IGF1R expression and phosphorylation were associated with the ability of RSV to infect cells. Confocal immunofluorescence imaging showed that actin projections, a hallmark of macropinocytosis, formed around viral particles 30 min after infection. Consistent with prior reports we also found that virus particles were internalized into early endosome antigen-1 positive endosomes within 90 min. Inhibiting actin polymerization significantly reduced viral titre by approximately ten-fold. Inhibiting PI3 kinase and PKCζ in stratified air-liquid interface (ALI) models of the airway epithelium had similar effects on reducing the actin remodelling observed during infection and attenuating viral entry. Actin projections were associated with NCL interacting with RSV particles resting on apical cilia of the ALIs. We conclude that macropinocytosis-like actin projections protrude through normally protective cilia and mucus layers of stratified airway epithelium that helps present the IGF1R receptor and the NCL coreceptor to RSV particles waiting at the surface.

中文翻译：

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肌动蛋白细胞骨架重塑破坏了感染的物理屏障，并为呼吸道合胞病毒提供了进入受体

RSV 是导致婴儿住院的主要原因，也是全世界儿科和老年人发病的重要原因。最近，我们报道胰岛素样生长因子 1 受体 (IGF1R) 是气道上皮细胞中呼吸道合胞病毒 (RSV) 的受体，IGF1R 的激活将辅助受体核仁素 (NCL) 募集到细胞表面。呼吸道内的纤毛和粘液对病毒和细菌感染构成了重要屏障。其他人已证明皮质肌动蛋白细胞骨架介导 RSV 进入，因此我们研究了 RSV 受体和肌动蛋白重塑在病毒进入过程中的作用。我们发现 IGF1R 表达和磷酸化与 RSV 感染细胞的能力相关。共聚焦免疫荧光成像显示，感染后 30 分钟，在病毒颗粒周围形成肌动蛋白投射（巨胞饮作用的标志）。与之前的报道一致，我们还发现病毒颗粒在 90 分钟内内化到早期内体抗原 1 阳性内体中。抑制肌动蛋白聚合可显着降低病毒滴度约十倍。在气道上皮分层气液界面 (ALI) 模型中抑制 PI3 激酶和 PKC z 对于减少感染期间观察到的肌动蛋白重塑和减弱病毒进入具有类似的作用。肌动蛋白投射与 NCL 与位于 ALI 顶端纤毛上的 RSV 颗粒相互作用有关。我们得出的结论是，巨胞饮作用样肌动蛋白突出物穿过正常保护性的纤毛和复层气道上皮的粘液层，有助于将 IGF1R 受体和 NCL 辅助受体呈现给等待在表面的 RSV 颗粒。