PICK1 knockout mice: role for D-serine in neonatal forebrains

描述（由申请人提供）：与c -激酶相互作用的蛋白（PICK1）是一种多功能支架蛋白，可与神经元和胶质细胞中的许多蛋白相互作用。我们最近报道PICK1直接结合d -丝氨酸合成酶丝氨酸消旋酶（SR）。在细胞培养中，敲低PICK1的表达降低了SR中d -丝氨酸的水平。我们发表了一篇文章，在PICK1基因敲除（PICK1 KO）的新生儿前脑中观察到d -丝氨酸水平下降，这与细胞生物学的观察结果一致。最近的几项研究表明，d -丝氨酸在包括精神分裂症在内的与皮质回路相关的精神障碍中发挥着作用。然而，据我们所知，PICK1的作用主要是在突触可塑性的背景下研究的，主要是通过使用小脑和海马体的切片。因此，在这项拟议的研究中，我们将在行为分析和电生理方法中检查PICK1敲除小鼠，并关注该蛋白对D-丝氨酸配置和脑功能的影响，特别是与皮质回路相关的影响。在我们的初步研究中，我们得到：(1)新生儿时期前脑d -丝氨酸水平下降，但在成年期没有；(2)成年期的多种行为缺陷，包括空间工作记忆和脉冲前抑制；(3) PICK1 KO小鼠成年期皮质锥体神经元对NMDA的反应降低。根据初步数据，我们的总体假设是，新生儿d -丝氨酸的缺陷可能与谷氨酸功能异常有关，影响前额皮质回路的成熟，导致锥体神经元和中间神经元突触和nmda依赖性反应的缺陷，而此时d -丝氨酸水平是正常的。在Aim 1中，我们将检测发育过程中前脑中d -丝氨酸的水平，特别是在PICK1 KO小鼠的新生儿阶段。在Aim 2中，我们将通过一组行为分析来描述成年PICK1 KO小鼠的特征，特别是那些用于测量皮质功能的分析，以及电生理方法。在Aim 3中，我们将通过在新生儿阶段给予d -丝氨酸（如有必要）与DAAO抑制剂联合，使PICK1 KO小鼠的d -丝氨酸水平正常化。然后，我们将研究在新生儿期d -丝氨酸治疗是否会影响成年PICK1 KO小鼠可能的异常行为和生理表型。通过这些实验，我们将研究PICK1与d -丝氨酸在新生儿前脑中的作用，希望通过本研究获得的信息将成为理解精神障碍和大脑发育的重要基础。

DESCRIPTION (provided by applicant): Protein Interacting with C-Kinase (PICK1) is a multifunctional scaffold protein that interacts with many proteins in neurons and glial cells. We recently reported that PICK1 binds directly to the D-serine synthesizing enzyme, serine racemase (SR). Knockdown expression of PICK1 decreased levels of D-serine from SR in cell cultures. We published that decreased levels of D-serine were observed in neonatal forebrains in PICK1 knockout (PICK1 KO), consistent with the observation from cell biology. Several recent studies have suggested roles for D-serine in mental disturbances associated with cortical circuitry, including schizophrenia. To our knowledge, however, roles for PICK1 have largely been studied in the context of synaptic plasticity, mainly by using slices from the cerebellum and hippocampus. Therefore, in this proposed study, we will examine PICK1 knockout mice in behavioral assays and electrophysiological approaches and focus on the impact of the protein on D- serine disposition and brain functions, especially those associated with cortical circuitry. In our preliminary studies, we obtained (1) decreased levels of D-serine in the forebrain during the neonatal period, but not in the adulthood; (2) several behavioral deficits in adulthood, which includes those in spatial working memory and prepulse inhibition; and (3) decreased response of the cortical pyramidal neurons to NMDA in adulthood, in PICK1 KO mice. Based on preliminary data, our overall hypothesis is that neonatal deficits in D-serine, which is likely to associate with abnormal glutamate function, affect the maturation of prefrontal cortical circuits and result in deficits in synaptic and NMDA-dependent responses in pyramidal neurons and interneurons in adulthood, whereas at this time the levels of D-serine are normal. In Aim 1, we will examine levels of D-serine in the forebrain during development, especially in neonatal stages in PICK1 KO mice. In Aim 2, we will characterize adult PICK1 KO mice by a set of behavioral assays, in particular those for measuring cortical functions, and also by electrophysiological approaches. In Aim 3, we will normalize the levels of D-serine in PICK1 KO mice by administering D-serine, if necessary, combined with a DAAO inhibitor during the neonatal stage. We will then examine whether the D-serine treatment during neonatal periods influences possible abnormal behaviors and physiological phenotypes in adult PICK1 KO mice. Through these experiments, we will study a role for PICK1 in the neonatal forebrain in conjunction with D-serine, hoping that the information obtained from this study will be an important basis in understanding mental disorders and brain development. PUBLIC HEALTH RELEVANCE: PICK1 knockout mice Recent evidence has suggested that PICK1 may regulate glutamate neurotransmission via regulating D-serine metabolism in the neonatal forebrain. Formation of neuronal circuitry during neonatal stages is crucial for proper brain development and functions of adult brain. We will study role for PICK1 in the neonatal forebrain in conjunction with D- serine by characterizing PICK1 knockout mice, hoping that the information obtained from this study will be an important basis in understanding mental disorders and brain development.