Regulation of post-synaptic receptor recycling by synaptotagmin 3

在上一个资助期，我们提出研究不同突触塔蛋白（syt）同型异构体在神经元中不同囊泡亚型的定位，使用一种新技术从非常少量的神经元组织中分离囊泡，该技术由实验室博士后开发（现已发表：Ahmed等人）。Nat. Protocols（2013）。上一次资助期的数据（现已公布：Dean et al.）。摩尔。杂志。Cell 2012)表明，syt分子家族的成员在神经元中不同的囊泡亚型中有不同的定位。在对syt4亚型的进一步表征中，我们发现syt4/ bdnf窝藏囊泡具有不同的融合特性，被分类为轴突和树突（现已发表：Dean et al.， J. Neurosci. 2012）。在检查syt亚型的特性时，我们发现，在下面描述的初步数据中，syt3独特地定位于突触后膜，在那里它调节突触后AMPA受体的内吞作用。这是一个特别有趣的发现，因为突触后受体在突触后膜之间的循环是突触强度的长期增强（LTP）和长期抑制（LTD）所必需的——突触强度是神经元的基本特性，对大脑的学习和信息存储至关重要。但是，介导受体进出突触后膜的外吞作用和内吞作用的分子机制尚不清楚。我们建议结合成像、生化和电生理方法来确定syt3是否是突触后钙传感器，在突触可塑性过程中调节受体的再循环。这不仅将揭示这种独特的系统异构体在神经元中的位置和功能，而且还将回答一个长期存在的问题，即如何调节突触后受体再循环以影响突触可塑性。

In the last funding period we proposed to investigate the localization of different synaptotagmin (syt) isoforms to distinct vesicle subtypes in neurons, using a new technique to isolate vesicles from very small amounts of neuronal tissue, developed by a postdoc in the lab (now published: Ahmed et al. Nat. Protocols 2013). Data from the last funding period (now published: Dean et al. Mol. Biol. Cell 2012) suggested that members of the syt family of molecules are differentially localized to distinct vesicle subtypes in neurons. In a further characterization of one isoform, syt4, we found that syt4/ BDNF-harboring vesicles with distinct fusion properties are sorted to axons versus dendrites (now published: Dean et al., J. Neurosci. 2012). While examining the properties of the syt isoforms, we discovered, in preliminary data described below, that syt3 is uniquely localized exclusively to the post-synaptic membrane, where it regulates endocytosis of post-synaptic AMPA receptors. This is a particularly interesting finding because post-synaptic receptor recycling to and from the post-synaptic membrane is essential for long-term potentiation (LTP) and long-term depression (LTD) of synaptic strength - a fundamental property of neurons that is crucial for learning and information storage in the brain. But the molecular machinery mediating the exo- and endocytosis of receptors to and from the post-synaptic membrane is poorly understood. We propose to determine, using a combination of imaging, biochemical, and electrophysiological approaches, if syt3 is the post-synaptic calcium sensor that regulates recycling of receptors during synaptic plasticity. This will not only reveal the location and function of this unique syt isoform in neurons, but will also answer a long-standing question regarding how post-synaptic receptor recycling is regulated to affect synaptic plasticity.