Neural function of the human memory-associated protein KIBRA: bridging molecular to circuit-level function

了解复杂行为的生物学基础是神经科学的一大挑战，而且 复杂的大脑功能障碍造成了巨大的社会和经济负担。解决这个问题 需要了解跨分子、细胞和电路级别的信息处理如何集成 影响行为，以及与疾病相关的风险因素如何影响此类信息处理。数不胜数 研究表明，Kibra的常见变体(富含肾脏和大脑)与人类 内存性能。Kibra基因多态和基因表达也与复合体疾病相关 大脑功能包括精神分裂症(SCZ)和自闭症谱系障碍(ASD)，而且 神经性Kibra结合伙伴的比例与SCZ、双相情感障碍和/或ASD有关。因此， Kibra是揭示控制突触可塑性和 负责正常认知过程的回路功能，在精神疾病中受损。 我们最近发现Kibra(富含肾脏和大脑)是AMPAR运输、突触的调节者 啮齿动物的可塑性、学习和记忆，但Kibra影响这些的机制 这一过程及其对电路动力学的影响尚不清楚。本项目旨在阐明Kibra的功能 通过三个目标跨越多个层次的信息处理：1)确定通过 Kibra蛋白复合体对神经元活动作出反应并调节AMPAR转运，2)决定 Kibra在双向突触可塑性中的分子和发育要求；3)建立 Kibra在调节电路动态中的作用。耐人寻味的是，尽管Kibra在 青少年和成年人的大脑，突触可塑性的缺陷直到成年后才会出现 Kibra基因敲除(KO)小鼠，这一时间过程与神经发育障碍的发病过程一致，如 SCZ和BPD。因此，我们的实验也将评估发育成熟度作为影响 Kibra蛋白复合体的功能及其对Kibra扰动的神经反应。要实现这些目标 目标，我们将使用结构域突变来确定运输内源蛋白所需的Kibra相互作用因子 AMPAR，使用生化和先进的成像方法(荧光波动光谱)来 确定Kibra络合物的活性调节动力学和化学计量，检查功能和结构 组件性和条件性Kibra KO小鼠急性脑片突触可塑性的研究 自由行为小鼠的电生理学以评估Kibra在行为驱动的电路动力学中的作用。 这些拟议的研究将揭示对人类记忆和神经发育功能的关键洞察力 与无序相关的Kibra复合体在多个信息处理水平，具有广泛的意义 了解复杂行为背后的机制和神经发育脆弱性。

Understanding the biological basis of complex behavior is a major challenge in neuroscience, and disorders of complex brain function exact an enormous social and financial burden. Solving this problem requires understanding how information processing integrates across molecular, cellular, and circuit levels to influence behavior, and how disease-associated risk factors impact such information processing. Numerous studies demonstrate that common variants of KIBRA (enriched in KIdney and BRAin) associate with human memory performance. KIBRA polymorphisms and gene expression also associate with disorders of complex brain function including schizophrenia (SCZ) and autism spectrum disorder (ASD), and a strikingly large proportion of neuronal KIBRA binding partners associate with SCZ, bipolar disorder, and/or ASD. Thus, KIBRA represents an ideal candidate to reveal molecular mechanisms that control synaptic plasticity and circuit function responsible for normal cognitive processes that are impaired in mental illness. We recently identified KIBRA (enriched in KIdney and BRAin) as a regulator of AMPAR trafficking, synaptic plasticity, and learning and memory in rodents, but the mechanisms by which KIBRA influences these processes and the impact on circuit dynamics remain unclear. This project aims to elucidate KIBRA function across multiple levels of information processing via three aims: 1) identify molecular mechanisms by which KIBRA protein complexes respond to neuronal activity and regulate AMPAR trafficking, 2) determine the molecular and developmental requirements for KIBRA in bidirectional synaptic plasticity, and 3) establish the role of KIBRA in regulating circuit dynamics. Intriguingly, despite robust expression of KIBRA in both the juvenile and adult brain, deficits in synaptic plasticity do not emerge until young adulthood in constitutive KIBRA knockout (KO) mice, a time course consistent with the onset of neurodevelopmental disorders such as SCZ and BPD. Thus, our experiments will also evaluate developmental maturity as a factor impacting the function of KIBRA protein complexes and the neural response to perturbation of KIBRA. To accomplish these goals, we will use domain mutants to identify KIBRA interactors required for trafficking of endogenous AMPARs, employ biochemical and advanced imaging methods (Fluorescence Fluctuation Spectroscopy) to identify activity-regulated dynamics and stoichiometry of KIBRA complexes, examine functional and structural synaptic plasticity in acute brain slices from constitutive and conditional KIBRA KO mice, and perform in vivo electrophysiology in freely behaving mice to evaluate the role of KIBRA in behaviorally-driven circuit dynamics. These proposed studies will reveal critical insight into the function of human-memory- and neurodevelopmental disorder-associated KIBRA complexes at multiple levels of information processing, with broad implications for understanding the mechanisms and neurodevelopmental vulnerabilities underlying complex behavior.