The University of Maryland Baltimore, Baltimore, MD, USA.
Harvard Medical School, Boston, MA, USA.
Parasit Vectors. 2024 Feb 9;17(1):57. doi: 10.1186/s13071-024-06150-7.
The blacklegged tick, Ixodes scapularis, transmits most vector-borne diseases in the US. It vectors seven pathogens of public health relevance, including the emerging human pathogen Anaplasma phagocytophilum. Nevertheless, it remains critically understudied compared to other arthropod vectors. Ixodes scapularis releases a variety of molecules that assist in the modulation of host responses. Recently, it was found that extracellular vesicles (EVs) carry several of these molecules and may impact microbial transmission to the mammalian host. EV biogenesis has been studied in mammalian systems and is relatively well understood, but the molecular players important for the formation and secretion of EVs in arthropods of public health relevance remain elusive. RabGTPases are among the major molecular players in mammalian EV biogenesis. They influence membrane identity and vesicle budding, uncoating, and motility.
Using BLAST, an in silico pathway for EV biogenesis in ticks was re-constructed. We identified Rab27 for further study. EVs were collected from ISE6 tick cells after knocking down rab27 to examine its role in tick EV biogenesis. Ixodes scapularis nymphs were injected with small interfering RNAs to knock down rab27 and then fed on naïve and A. phagocytophilum-infected mice to explore the importance of rab27 in tick feeding and bacterial acquisition.
Our BLAST analysis identified several of the proteins involved in EV biogenesis in ticks, including Rab27. We show that silencing rab27 in I. scapularis impacts tick fitness. Additionally, ticks acquire less A. phagocytophilum after rab27 silencing. Experiments in the tick ISE6 cell line show that silencing of rab27 causes a distinct range profile of tick EVs, indicating that Rab27 is needed to regulate EV biogenesis.
Rab27 is needed for successful tick feeding and may be important for acquiring A. phagocytophilum during a blood meal. Additionally, silencing rab27 in tick cells results in a shift of extracellular vesicle size. Overall, we have observed that Rab27 plays a key role in tick EV biogenesis and the tripartite interactions among the vector, the mammalian host, and a microbe it encounters.
黑腿蜱，Ixodes scapularis，在美国传播大多数媒介传播疾病。它传播七种具有公共卫生相关性的病原体，包括新兴的人类病原体嗜吞噬细胞无形体。尽管如此，与其他节肢动物媒介相比，它的研究仍然严重不足。Ixodes scapularis 释放多种分子，有助于调节宿主反应。最近发现，细胞外囊泡（EVs）携带其中几种分子，可能影响微生物向哺乳动物宿主的传播。EV 的生物发生已在哺乳动物系统中进行研究，并且相对了解，但对于公共卫生相关节肢动物中 EV 形成和分泌的重要分子参与者仍不清楚。RabGTPases 是哺乳动物 EV 生物发生的主要分子参与者之一。它们影响膜身份和囊泡出芽、脱壳和运动。
使用 BLAST，重新构建了蜱虫 EV 生物发生的计算机途径。我们鉴定了 Rab27 进行进一步研究。在敲低 rab27 后从 ISE6 蜱细胞中收集 EV，以检查其在蜱 EV 生物发生中的作用。用小干扰 RNA 注射Ixodes scapularis 若虫以敲低 rab27，然后让其吸食 naive 和 A. phagocytophilum 感染的小鼠，以探索 rab27 在蜱吸食和细菌获取中的重要性。
我们的 BLAST 分析鉴定了蜱虫 EV 生物发生中的几种蛋白质，包括 Rab27。我们表明，rab27 在 I. scapularis 中的沉默会影响蜱的适应性。此外，在 rab27 沉默后，蜱虫获取的 A. phagocytophilum 较少。在 ISE6 蜱细胞系中的实验表明，rab27 的沉默会导致蜱 EV 的明显范围谱，表明 Rab27 是调节 EV 生物发生所必需的。
Rab27 是成功的蜱吸食所必需的，并且在血液餐期间获取 A. phagocytophilum 可能很重要。此外，在蜱细胞中沉默 rab27 会导致细胞外囊泡大小的转移。总体而言，我们观察到 Rab27 在蜱 EV 生物发生以及媒介、哺乳动物宿主和它遇到的微生物之间的三重相互作用中发挥关键作用。
