Department of Oral Biology, School of Dental Medicine, University at Buffalo, Buffalo, New York, USA.
Department of Oral Biology, School of Dental Medicine, University at Buffalo, Buffalo, New York, USA
Infect Immun. 2018 Nov 20;86(12). doi: 10.1128/IAI.00685-18. Print 2018 Dec.
Host phagocytic cells are crucial players in initial defense against infection. utilizes MAP kinases and Ras1 stress response signaling pathways to protect itself from killing by immune cells. In this study, we tested the importance of these pathways in phagocytosis by neutrophils and subsequent phagosomal survival. Phagocytosis was influenced by morphology, so hyphal length of >10 μm reduced the phagocytic index (PI) 2- to 3-fold in human neutrophils. Primary human neutrophils killed 81% of phagocytosed , while primary mouse neutrophils killed 63% of yeasts. We found that both the Cek1 and Hog1 pathways were required for survival of phagocytosed yeast, whereas deletion of resulted in an 84% increase in survival within neutrophils compared to that of the wild type (WT). The absence of Ras1 did not alter reactive oxygen species (ROS) production by ; however, phagocytosed Δ/Δ cells reduced ROS release by neutrophils by 86%. Moreover, Δ/Δ cells had increased resistance to hydrogen peroxide as a result of high levels of catalase activity. This phenotype was specific to Ras1, since these effects were not observed in the absence of its partner Cyr1 or with its downstream target Efg1. In addition, Δ/Δ cells had a significantly increased resistance to nonoxidative killing by human neutrophil peptide 1 (HNP-1) that was reversed by restoring cellular cAMP levels. These data show that Ras1 inactivation leads to fungal resistance to both oxidative and nonoxidative mechanisms of neutrophil phagosomal killing.
宿主吞噬细胞是抵御感染的初始防御的关键参与者。利用 MAP 激酶和 Ras1 应激反应信号通路来保护自己免受免疫细胞的杀伤。在这项研究中，我们测试了这些途径在中性粒细胞吞噬作用和随后的吞噬体存活中的重要性。吞噬作用受形态的影响，因此 >10μm 的菌丝长度使人类中性粒细胞的吞噬指数 (PI)降低 2-3 倍。原代人类中性粒细胞杀死 81%吞噬的 ，而原代小鼠中性粒细胞杀死 63%的酵母。我们发现，Cek1 和 Hog1 途径都需要吞噬的酵母存活，而缺失导致与野生型相比，吞噬细胞内的存活率增加 84%。Ras1 的缺失并未改变 产生的活性氧 (ROS)；然而，吞噬的 Δ/Δ细胞使中性粒细胞释放的 ROS 减少 86%。此外，由于过氧化氢酶活性水平高，吞噬的 Δ/Δ细胞对过氧化氢的抵抗力增加。这种表型是 Ras1 特异性的，因为在没有其伴侣 Cyr1 或下游靶标 Efg1 的情况下，没有观察到这些效应。此外， Δ/Δ细胞对人中性粒细胞肽 1 (HNP-1)的非氧化杀伤具有显著增加的抗性，而通过恢复细胞 cAMP 水平可逆转这种抗性。这些数据表明，Ras1 失活导致真菌对中性粒细胞吞噬体杀伤的氧化和非氧化机制均具有抗性。
