Role of Kalirin 7 in Estrogen-Mediated Spine Plasticity in the Hippocampus

描述（由申请人提供）：雌激素在体外和体内引起海马神经元中棘和兴奋性突触的形成，但其潜在机制尚未完全了解。Kalirin（Kal）7仅定位于海马神经元中兴奋性突触的突触后侧。在体外海马神经元中，外源性Kal 7的表达增加棘密度，而内源性Kal 7的减少降低棘密度。Kal 7是Kal 7敲除（Kal 7 KO）小鼠中CA 1神经元中突触结构和功能所必需的。我的初步数据表明，海马神经元中的Kal 7免疫反应性在体内和体外受雌激素的调节，这一结果得到了Western blot的证实。雌激素不再能够增加突触的形成时，内源性Kal 7表达减少。这些数据导致了这样的假设，即Kal 7在雌激素调节突触可塑性的机制中起着关键作用。目标1.确定雌激素如何增加海马中Kal 7的表达。雌激素可以直接作用于锥体神经元和/或通过中间神经元增加CA 1锥体神经元中的棘/突触密度。目前尚不清楚雌激素是否在转录（mRNA）或转录后水平调节Kal 7表达。目标1是确定：（1）雌激素影响Kal 7 mRNA水平的时间过程;（2）Kal 7表达在发情周期中是否发生变化;（3）内源性雌激素是否影响Kal 7表达;（4）哪种雌激素受体（1或2）在此过程中起关键作用。目标2.确定Kal 7是否是雌激素介导的海马神经元棘形成和突触功能所必需的。了解雌激素调节Kal 7表达的机制将有助于雌激素介导的突触可塑性的操纵。如果Kal 7对于雌激素介导的棘形成和突触功能是必需的，那么与OVX野生型对照相比，卵巢切除（Ovx）Kal 7 KO小鼠中雌激素介导的棘形成和突触功能可能减弱或消除。目标2是确定：（1）Kal 7是否在体外雌激素介导的突触功能中起重要作用;（2）Kal 7是否在体内雌激素介导的棘形成中必不可少;（3）Kal 7是否在雌激素介导的LTP诱导中必不可少;（4）雌激素调节Kal 7表达的途径。 公共卫生相关性：雌激素在体外和体内均可引起海马神经元树突棘和兴奋性突触的形成，但其机制尚不完全清楚。本研究的目的是确定Kal 7对雌激素介导的海马神经元脊髓可塑性的影响。

DESCRIPTION (provided by applicant): Estrogen causes the formation of spines and excitatory synapses in hippocampal neurons in vitro and in vivo, but the underlying mechanisms are not fully understood. Kalirin (Kal) 7 is exclusively localized to the postsynaptic side of excitatory synapses in hippocampal neurons. Expression of exogenous Kal7 increases spine density whereas reduced endogenous Kal7 decreases spine density in hippocampal neurons in vitro. Kal7 is required for synaptic structure and function in CA1 neurons in Kal7 knockout (Kal7KO) mice. My preliminary data show that Kal7 immunoreactivity in hippocampal neurons is regulated by estrogen in vivo and in vitro; this result was confirmed by Western blot. Estrogen was no longer able to increase synapse formation when endogenous Kal7 expression was reduced. These data led to the hypothesis that Kal7 plays a key role in the mechanisms by which estrogen regulates synaptic plasticity. Aim1. To determine how estrogen increases Kal7 expression in the hippocampus. Estrogen may act directly on pyramidal neurons and/or through interneurons to increase spine/synaptic density in CA1 pyramidal neurons. It is not yet clear whether estrogen regulates Kal7 expression at the transcriptional (mRNA) or post-transcriptional level. Aim1 is to determine: (1) the time course over which estrogen affects Kal7 mRNA levels; (2) whether Kal7 expression changes during the estrous cycle; (3) whether endogenous estrogen affects Kal7 expression; (4) which estrogen receptor (1 or 2) plays a key role in this process. Aim 2. To determine whether Kal7 is essential for estrogen-mediated spine formation and synaptic functions in hippocampal neurons. Understanding the mechanisms through which estrogen regulates Kal7 expression will facilitate manipulation of estrogen-mediated synaptic plasticity. If Kal7 is essential for estrogen-mediated spine formation and synaptic functions, estrogen replacement-mediated spine formation and synaptic functions in ovariectomized (Ovx) Kal7KO mice are likely attenuated or abolished compared to OVX wildtype controls. Aim 2 is to determine: (1) whether Kal7 plays an essential role in estrogen-mediated synaptic function in vitro; (2) whether Kal7 is essential for estrogen-mediated spine formation in vivo; (3) whether Kal7 is essential for estrogen-mediated LTP induction; (4) the pathway through which estrogen regulates Kal7 expression. PUBLIC HEALTH RELEVANCE: Estrogen causes the formation of dendritic spines and excitatory synapses in hippocampal neurons in vitro and in vivo, but the underlying mechanisms are not fully understood. The aim of this research is to determine the effects of Kal7 on estrogen-mediated spine plasticity in hippocampal neurons.