突触结合蛋白I的c(2)b结构域中的离散残基分别决定内吞速率和突触小泡大小。

Discrete residues in the c(2)b domain of synaptotagmin I independently specify endocytic rate and synaptic vesicle size.

作者信息

Poskanzer Kira E, Fetter Richard D, Davis Graeme W

机构信息

Department of Biochemistry and Biophysics, University of California, San Francisco, Rock Hall, 1550 Fourth Street, Box 2822, San Francisco, California 94158, USA.

出版信息

Neuron. 2006 Apr 6;50(1):49-62. doi: 10.1016/j.neuron.2006.02.021.

DOI:10.1016/j.neuron.2006.02.021

PMID:16600855

Abstract

It has been demonstrated that synapses lacking functional synaptotagmin I (Syt I) have a decreased rate of synaptic vesicle endocytosis. Beyond this, the function of Syt I during endocytosis remains undefined. Here, we demonstrate that a decreased rate of endocytosis in syt(null) mutants correlates with a stimulus-dependent perturbation of membrane internalization, assayed ultrastructurally. We then separate the mechanisms that control endocytic rate and vesicle size by mapping these processes to discrete residues in the Syt I C(2)B domain. Mutation of a poly-lysine motif alters vesicle size but not endocytic rate, whereas the mutation of calcium-coordinating aspartate residues (syt-D3,4N) alters endocytic rate but not vesicle size. Finally, slowed endocytic rate in the syt-D3,4N animals, but not syt(null) animals, can be rescued by elevating extracellular calcium concentration, supporting the conclusion that calcium coordination within the C(2)B domain contributes to the control of endocytic rate.

摘要

已经证明，缺乏功能性突触结合蛋白I（Syt I）的突触具有降低的突触小泡内吞速率。除此之外，Syt I在内吞过程中的功能仍不明确。在这里，我们证明，通过超微结构分析，syt（缺失）突变体中内吞速率的降低与膜内化的刺激依赖性扰动相关。然后，我们通过将这些过程映射到Syt I C（2）B结构域中的离散残基来分离控制内吞速率和小泡大小的机制。多聚赖氨酸基序的突变改变了小泡大小，但没有改变内吞速率，而钙配位天冬氨酸残基的突变（syt-D3,4N）改变了内吞速率，但没有改变小泡大小。最后，通过提高细胞外钙浓度，可以挽救syt-D3,4N动物而非syt（缺失）动物中减慢的内吞速率，这支持了C（2）B结构域内的钙配位有助于控制内吞速率的结论。