The dual phosphatase activity of synaptojanin1 is required for both efficient synaptic vesicle endocytosis and reavailability at nerve terminals
The dual phosphatase activity of synaptojanin1 is required for both efficient synaptic vesicle endocytosis and reavailability at nerve terminals
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DOI：
10.1016/j.neuron.2007.10.032
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发表时间：
2007-12-20
期刊：
影响因子：
16.2
通讯作者：
Ryan, Timothy A.
中科院分区：
文献类型：
--
作者：
Mani, Meera;Lee, Sang Yoon;Ryan, Timothy A.
磷酸肌醇与突触囊泡循环有关，这主要是基于对调节磷酸肌醇合成和水解的酶的研究。一种这样的酶是synaptojanin 1，一种从酵母到人类都保守的多功能蛋白质，它含有两个磷酸肌醇磷酸酶结构域和一个富含脯氨酸的结构域。synaptojanin 1的基因消融导致突触前功能的多效性缺陷，包括游离网格蛋白包被的囊泡的积累和延迟的囊泡可再利用性，暗示这种酶在胞内后囊泡的脱壳中。为了进一步阐明synaptojanin 1在神经末梢中的作用，我们在synj 1（-/-）神经元中进行了定量突触囊泡再循环测定。我们的研究表明，synaptojanin 1也需要正常的囊泡内吞作用。内吞和胞内后囊泡再利用的缺陷可以完全恢复后重新引入synaptojanin 1。然而，表达的synaptojanin 1突变废除催化活性的每个磷酸酶域揭示了这两个域的双重作用是正常的突触囊泡内化和再利用所需的。
Phosphoinositides have been implicated in synaptic vesicle recycling largely based on studies of enzymes that regulate phosphoinositide synthesis and hydrolysis. One such enzyme is synaptojanin1, a multifunctional protein conserved from yeast to humans, which contains two phosphoinositol phosphatase domains and a proline-rich domain. Genetic ablation of synaptojanin1 leads to pleiotropic defects in presynaptic function, including accumulation of free clathrin-coated vesicles and delayed vesicle reavailability, implicating this enzyme in postendocytic uncoating of vesicles. To further elucidate the role of synaptojanin1 at nerve terminals, we performed quantitative synaptic vesicle recycling assays in synj1(-/-) neurons. Our studies show that synaptojanin1 is also required for normal vesicle endocytosis. Defects in both endocytosis and postendocytic vesicle reavailability can be fully restored upon reintroduction of synaptojanin1. However, expression of synaptojanin1 with mutations abolishing catalytic activity of each phosphatase domain reveals that the dual action of both domains is required for normal synaptic vesicle internalization and reavailability.