The different roles of V-ATPase a subunits in phagocytosis/endocytosis and autophagy.

Autophagy Pub Date : 2024-10-01 Epub Date: 2024-06-25 DOI:10.1080/15548627.2024.2366748
Qi Chen, Hanjing Kou, Doris Lou Demy, Wei Liu, Jianchao Li, Zilong Wen, Philippe Herbomel, Zhibin Huang, Wenqing Zhang, Jin Xu
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Abstract

Microglia are specialized macrophages responsible for the clearance of dead neurons and pathogens by phagocytosis and degradation. The degradation requires phagosome maturation and acidification provided by the vesicular- or vacuolar-type H+-translocating adenosine triphosphatase (V-ATPase), which is composed of the cytoplasmic V1 domain and the membrane-embedded Vo domain. The V-ATPase a subunit, an integral part of the Vo domain, has four isoforms in mammals. The functions of different isoforms on phagosome maturation in different cells/species remain controversial. Here we show that mutations of both the V-ATPase Atp6v0a1 and Tcirg1b/Atp6v0a3 subunits lead to the accumulation of phagosomes in zebrafish microglia. However, their mechanisms are different. The V-ATPase Atp6v0a1 subunit is mainly distributed in early and late phagosomes. Defects of this subunit lead to a defective transition from early phagosomes to late phagosomes. In contrast, The V-ATPase Tcirg1b/Atp6v0a3 subunit is primarily located on lysosomes and regulates late phagosome-lysosomal fusion. Defective Tcirg1b/Atp6v0a3, but not Atp6v0a1 subunit leads to reduced acidification and impaired macroautophagy/autophagy in microglia. We further showed that ATP6V0A1/a1 and TCIRG1/a3 subunits in mouse macrophages preferentially located in endosomes and lysosomes, respectively. Blocking these subunits disrupted early-to-late endosome transition and endosome-to-lysosome fusion, respectively. Taken together, our results highlight the essential and conserved roles played by different V-ATPase subunits in multiple steps of phagocytosis and endocytosis across various species.Abbrevations: Apoe: apolipoprotein E; ANXA5/annexin V: annexin A5; ATP6V0A1/a1: ATPase H+-transporting V0 subunit a1; ATP6V0A2/a2: ATPase H+-transporting V0 subunit a2; ATP6V0A4/a4: ATPase H+-transporting V0 subunit a4; dpf: days post-fertilization; EEA1: early endosome antigen 1; HOPS: homotypic fusion and protein sorting; LAMP1: lysosomal associated membrane protein 1; Lcp1: lymphocyte cytosolic protein 1 (L-plastin); Map1lc3/Lc3: microtubule-associated protein 1 light chain 3; NR: neutral red; PBS: phosphate-buffered saline; PtdIns: phosphatidylinositol; PtdIns3P: phosphatidylinositol-3-phosphate; PtdIns(3,5)P2: phosphatidylinositol (3,5)-bisphosphate; RAB4: RAB4, member RAS oncogene family; RAB5: RAB5, member RAS oncogene family; RAB7: RAB7, member RAS oncogene family; TCIRG1/Atp6v0a3/a3: T cell immune regulator 1, ATPase H+-transporting V0 subunit a3; V-ATPase: vacuolar-type H+-translocating adenosine triphosphatase; Xla.Tubb2b/NBT: tubulin beta 2B class IIb.

V-ATPase a 亚基在吞噬/内吞和自噬中的不同作用。
小胶质细胞是一种特化的巨噬细胞,负责通过吞噬和降解清除死亡的神经元和病原体。降解需要吞噬体的成熟和由囊泡或空泡型 H+-转运腺苷三磷酸酶(V-ATPase)提供的酸化。V-ATPase a 亚基是 Vo 结构域的组成部分,在哺乳动物中有四种同工形式。不同异构体在不同细胞/物种中对吞噬体成熟的功能仍存在争议。在这里,我们发现 V-ATPase Atp6v0a1 和 Tcirg1b/Atp6v0a3 亚基的突变都会导致斑马鱼小胶质细胞中吞噬体的积累。然而,它们的机制不同。V-ATPase Atp6v0a1亚基主要分布在早期和晚期吞噬体中。该亚基缺陷会导致从早期吞噬体向晚期吞噬体过渡的缺陷。相反,V-ATP 酶 Tcirg1b/Atp6v0a3 亚基主要位于溶酶体,调节晚期吞噬体与溶酶体的融合。Tcirg1b/Atp6v0a3亚基而非Atp6v0a1亚基的缺陷会导致小胶质细胞酸化减少和大自噬/自噬功能受损。我们进一步发现,小鼠巨噬细胞中的 ATP6V0A1/a1 和 TCIRG1/a3 亚基分别优先位于内体和溶酶体中。阻断这些亚基分别会破坏早期到晚期的内质体转换以及内质体到溶酶体的融合。综上所述,我们的研究结果突显了不同的 V-ATPase 亚基在不同物种的吞噬和内吞过程的多个步骤中所扮演的重要而保守的角色。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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