Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
Department of Parasitology, National Institute of Infectious Diseases, Tokyo, Japan.
PLoS Pathog. 2024 Nov 13;20(11):e1012364. doi: 10.1371/journal.ppat.1012364. eCollection 2024 Nov.
Macropinocytosis is an evolutionarily conserved endocytic process that plays a vital role in internalizing extracellular fluids and particles in cells. This non-selective endocytic pathway is crucial for various physiological functions such as nutrient uptake, sensing, signaling, antigen presentation, and cell migration. While macropinocytosis has been extensively studied in macrophages and cancer cells, the molecular mechanisms of macropinocytosis in pathogens are less understood. It has been known that Entamoeba histolytica, the causative agent of amebiasis, exploits macropinocytosis for survival and pathogenesis. Since macropinocytosis is initiated by actin polymerization, leading to the formation of membrane ruffles and the subsequent trapping of solutes in macropinosomes, actin cytoskeleton regulation is crucial. Thus, this study focuses on unraveling the role of well-conserved actin cytoskeleton regulators, Rho small GTPase family proteins, in macropinocytosis in E. histolytica. Through gene silencing of highly transcribed Ehrho/Ehrac genes and following flow cytometry analysis, we identified that silencing EhracM enhances dextran macropinocytosis and affects cellular migration persistence. Live imaging and interactome analysis unveiled the cytosolic and vesicular localization of EhRacM, along with its interaction with signaling and membrane traffic-related proteins, shedding light on EhRacM's multiple roles. Our findings provide insights into the specific regulatory mechanisms of macropinocytosis among endocytic pathways in E. histolytica, highlighting the significance of EhRacM in both macropinocytosis and cellular migration.
巨胞饮作用是一种进化上保守的内吞过程，在细胞内吞细胞外液体和颗粒方面发挥着至关重要的作用。这种非选择性的内吞途径对于各种生理功能至关重要，如营养物质摄取、感应、信号转导、抗原呈递和细胞迁移。尽管巨胞饮作用在巨噬细胞和癌细胞中得到了广泛研究，但病原体中巨胞饮作用的分子机制还不太清楚。已知溶组织内阿米巴，即阿米巴病的病原体，利用巨胞饮作用来生存和致病。由于巨胞饮作用是由肌动蛋白聚合引发的，导致形成膜皱襞，并随后将溶质捕获在巨胞饮体中，因此肌动蛋白细胞骨架的调节至关重要。因此，本研究旨在揭示保守的肌动蛋白细胞骨架调节剂、Rho 小 GTPase 家族蛋白在溶组织内阿米巴中的巨胞饮作用中的作用。通过对高转录的 Ehrho/Ehrac 基因进行基因沉默，并进行流式细胞术分析，我们发现沉默 EhracM 增强了葡聚糖巨胞饮作用，并影响细胞迁移的持久性。实时成像和相互作用分析揭示了 EhRacM 的细胞质和囊泡定位，以及它与信号和膜运输相关蛋白的相互作用，揭示了 EhRacM 的多种作用。我们的研究结果提供了关于溶组织内阿米巴中各种内吞途径中巨胞饮作用的特定调节机制的见解，强调了 EhRacM 在巨胞饮作用和细胞迁移中的重要性。
