Department for Hospital Infection Control and Research, Institute of Disease Control and Prevention of PLA, Academy of Military Medical Sciences, Beijing, China.
PLoS One. 2011;6(7):e21468. doi: 10.1371/journal.pone.0021468. Epub 2011 Jul 8.
The internalization of Aspergillus fumigatus into lung epithelial cells is a process that depends on host cell actin dynamics. The host membrane phosphatidylcholine cleavage driven by phospholipase D (PLD) is closely related to cellular actin dynamics. However, little is known about the impact of PLD on A. fumigatus internalization into lung epithelial cells. Here, we report that once germinated, A. fumigatus conidia were able to stimulate host PLD activity and internalize more efficiently in A549 cells without altering PLD expression. The internalization of A. fumigatus in A549 cells was suppressed by the downregulation of host cell PLD using chemical inhibitors or siRNA interference. The heat-killed swollen conidia, but not the resting conidia, were able to activate host PLD. Further, β-1,3-glucan, the core component of the conidial cell wall, stimulated host PLD activity. This PLD activation and conidia internalization were inhibited by anti-dectin-1 antibody. Indeed, dectin-1, a β-1,3-glucan receptor, was expressed in A549 cells, and its expression profile was not altered by conidial stimulation. Finally, host cell PLD1 and PLD2 accompanied A. fumigatus conidia during internalization. Our data indicate that host cell PLD activity induced by β-1,3-glucan on the surface of germinated conidia is important for the efficient internalization of A. fumigatus into A549 lung epithelial cells.
烟曲霉内化到肺上皮细胞是一个依赖宿主细胞肌动蛋白动力学的过程。由磷脂酶 D（PLD）驱动的宿主膜磷脂酰胆碱裂解与细胞肌动蛋白动力学密切相关。然而，关于 PLD 对烟曲霉内化到肺上皮细胞的影响知之甚少。在这里，我们报告一旦发芽，烟曲霉分生孢子能够刺激宿主 PLD 活性，并在不改变 PLD 表达的情况下更有效地内化到 A549 细胞中。使用化学抑制剂或 siRNA 干扰下调宿主细胞 PLD 可抑制烟曲霉在 A549 细胞中的内化。热灭活肿胀的分生孢子，但不是静止的分生孢子，能够激活宿主 PLD。此外，β-1,3-葡聚糖，分生孢子细胞壁的核心成分，刺激宿主 PLD 活性。这种 PLD 激活和分生孢子内化被抗 dectin-1 抗体抑制。事实上，dectin-1，一种β-1,3-葡聚糖受体，在 A549 细胞中表达，并且其表达谱不受分生孢子刺激的影响。最后，宿主细胞 PLD1 和 PLD2 在烟曲霉分生孢子内化过程中伴随。我们的数据表明，由发芽分生孢子表面的β-1,3-葡聚糖诱导的宿主细胞 PLD 活性对于烟曲霉有效内化到 A549 肺上皮细胞中是重要的。
