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

理解复杂行为的生物学基础是神经科学的一个主要挑战， 复杂的大脑功能紊乱造成了巨大的社会和经济负担。解决这个问题 需要理解信息处理如何在分子、细胞和电路水平上整合， 影响行为，以及疾病相关的风险因素如何影响这种信息处理。许多 研究表明，KIBRA的常见变体（富含KIdney和BRAin）与人类 内存性能KIBRA多态性和基因表达也与复杂的疾病有关。 大脑功能包括精神分裂症（SCZ）和自闭症谱系障碍（ASD），以及一个惊人的大 神经元KIBRA结合配偶体的比例与SCZ、双相情感障碍和/或ASD相关。因此，在本发明中， KIBRA是揭示控制突触可塑性的分子机制的理想候选者， 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KIdney和BRAin）是AMPAR运输、突触 可塑性，学习和记忆的啮齿动物，但机制，KIBRA影响这些 过程和对电路动态的影响仍然不清楚。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）确定分子机制， KIBRA蛋白复合物响应神经元活动并调节AMPAR运输，2）确定 KIBRA在双向突触可塑性中的分子和发育要求，以及3）建立 KIBRA在调节电路动态中的作用。有趣的是，尽管KIBRA在两个组织中都有强表达， 青少年和成年人的大脑中，突触可塑性的缺陷不会出现，直到年轻的成年期，在组成性 KIBRA基因敲除（KO）小鼠，时间过程与神经发育障碍的发作一致， SCZ和BPD。因此，我们的实验也将评估发育成熟度作为影响发育的因素。 KIBRA蛋白复合物的功能和对KIBRA扰动的神经反应。完成这些 目标，我们将使用结构域突变体，以确定KIBRA相互作用所需的内源性 AMPAR采用生物化学和先进的成像方法（荧光波动光谱法）， 确定KIBRA复合物活性调节动力学和化学计量，检查功能和结构 在来自组成型和条件性KIBRA KO小鼠急性脑切片中的突触可塑性，并在体内进行 在自由行为的小鼠中进行电生理学研究，以评估KIBRA在行为驱动的电路动力学中的作用。 这些拟议中的研究将揭示人类记忆和神经发育功能的关键见解 疾病相关的KIBRA复合体在多个层次的信息处理，具有广泛的影响， 理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.