Imaging of Rab5 activity identifies essential regulators for phagosome maturation
Imaging of Rab5 activity identifies essential regulators for phagosome maturation
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DOI：
10.1038/nature06857
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发表时间：
2008-05-08
期刊：
影响因子：
64.8
通讯作者：
Matsuda, Michiyuki
中科院分区：
文献类型：
--
作者：
Kitano, Masahiro;Nakaya, Michio;Matsuda, Michiyuki
凋亡细胞的有效吞噬作用对于组织稳态和免疫应答至关重要（1，2）。已知Rab 5是早期内吞途径的关键调节剂（3），并且我们最近已经表明Rab 5也涉及凋亡细胞吞噬（4）;然而，Rab 5活性的精确时空动力学仍然未知。在这里，使用一种新开发的荧光共振能量转移生物传感器，我们描述了Rab 5活性的变化，在吞噬凋亡的胸腺细胞。Rab 5在吞噬体膜上的活性开始增加，在包裹吞噬体的肌动蛋白外壳解体时。Rab 5的激活是连续的或重复的长达10分钟，但它结束之前的崩溃吞噬凋亡细胞。Rab 5显性负突变体的表达延迟了凋亡胸腺细胞的崩溃，显示Rab 5在吞噬体成熟中的作用。用诺考达唑破坏微管抑制吞噬体膜上的Rab 5活化，而不干扰凋亡细胞的吞噬。此外，我们发现，Gapex-5是鸟嘌呤核苷酸交换因子Rab 5激活凋亡细胞的吞噬过程中必不可少的。Gapex- 5与微管尖端相关蛋白EB 1结合，EB 1的耗尽抑制了Rab 5在吞噬过程中的激活.因此，我们提出了一个机制模型，其中通过微管网络的Gapex- 5吞噬体的招聘诱导的短暂Rab 5激活。
Efficient phagocytosis of apoptotic cells is crucial for tissue homeostasis and the immune response(1,2). Rab5 is known as a key regulator of the early endocytic pathway(3) and we have recently shown that Rab5 is also implicated in apoptotic cell engulfment(4); however, the precise spatio- temporal dynamics of Rab5 activity remain unknown. Here, using a newly developed fluorescence resonance energy transfer biosensor, we describe a change in Rab5 activity during the engulfment of apoptotic thymocytes. Rab5 activity on phagosome membranes began to increase on disassembly of the actin coat encapsulating phagosomes. Rab5 activation was either continuous or repetitive for up to 10 min, but it ended before the collapse of engulfed apoptotic cells. Expression of a dominant-negative mutant of Rab5 delayed this collapse of apoptotic thymocytes, showing a role for Rab5 in phagosome maturation. Disruption of microtubules with nocodazole inhibited Rab5 activation on the phagosome membrane without perturbing the engulfment of apoptotic cells. Furthermore, we found that Gapex-5 is the guanine nucleotide exchange factor essential for Rab5 activation during the engulfment of apoptotic cells. Gapex- 5 was bound to a microtubule- tip- associating protein, EB1, whose depletion inhibited Rab5 activation during phagocytosis. We therefore propose a mechanistic model in which the recruitment of Gapex- 5 to phagosomes through the microtubule network induces the transient Rab5 activation.