Molecular Mechanisms of Dendritic Abnormalities Related to D-Serine Deficiency

描述(由申请人提供)： 有重要证据表明，N-甲基-D-天冬氨酸受体(NMDAR)功能低下是精神分裂症的核心病因成分。丝氨酸消旋酶零突变(SRKO)小鼠的NMDAR信号转导功能低下，皮质树突状细胞形态减少，类似于精神分裂症中观察到的情况。拟议的实验将检验依赖NMDAR的分子机制，这些分子机制负责在SRKO小鼠中产生树突状改变。钙(Ca~(2+))通过NMDAR激活钙/钙调蛋白(CaM)激酶(CaMK)和丝裂原活化蛋白激酶(MAPK)信号通路。这些途径调节cAMP/钙反应元件结合蛋白(CREB)依赖的转录，并参与NMDAR活性依赖的树突状可塑性的变化。目的1确定NMDAR功能低下是否对前额叶皮质(PFC)CaMK和MAPK信号的活性产生负面影响。MicroRNAs(MiRs)与精神分裂症的病理生理学有关。它们通过控制靶mRNAs的翻译来调节神经可塑性。MIR-132富含在神经元中，调节基础和活动诱导的轴突生长，其表达受CREB调控。转录抑制因子甲基CpG结合蛋白2(MeCP2)是miR-132调控的靶标，调节依赖活性的树突状细胞构型。目的2将确定NMDAR功能低下是否降低了CREB介导的PFC中miR-132的转录，以及MeCP2的mRNA和蛋白水平。原代皮质培养将用于直接测试miR-132过度表达是否增强树突形态并降低MeCP2水平。认知障碍是精神分裂症的一个明确的组成部分，并与前额叶功能的改变相结合，前额叶是大脑中与树突异常最相关的区域。临床证据表明，典型的抗精神病药物是无效的，而非典型的抗精神病药物与一些认知方面的好处有关。D-丝氨酸和N[3-(4‘-氟苯基)-3-(4’苯基苯氧基)丙基]肌氨酸(NFPS)是通过甘氨酸调节位点(GMS)增强NMDAR信号的药物，在精神分裂症的药理动物模型中具有前认知作用。然而，关于抗精神病药物和GMS调节剂如何调控树突状细胞的形态发生，人们知之甚少。因此，Aim 3将使用来自WT和SRKO小鼠的培养的皮质神经元来比较典型和非典型抗精神病药物以及D-丝氨酸和NFPS影响树突状细胞可塑性的能力。 公共卫生相关性： 临床上治疗精神分裂症的药物在治疗认知缺陷方面并不有效。目前的研究旨在发现这种疾病的新的潜在原因，希望开发出能够更彻底地治疗这种疾病的新的作用疗法。

DESCRIPTION (provided by applicant): There is significant evidence that N-methyl-D-aspartate receptor (NMDAR) hypofunction is a core etiological component of schizophrenia. Serine racemase null mutant (SRKO) mice have hypofunctional NMDAR signaling and exhibit reductions in cortical dendritic morphology, similar to what is observed in schizophrenia. The proposed experiments will examine NMDAR-dependent molecular mechanisms responsible for producing the dendritic alterations in SRKO mice. Calcium (Ca2+) influx through NMDARs activates Ca2+/calmodulin (CaM) kinase (CaMK) and mitogen-activated protein kinase (MAPK) signaling. These pathways modulate cAMP/Ca2+ response element binding protein (CREB)-dependent transcription and are involved in NMDAR activity-dependent changes in dendritic plasticity. Aim 1 will determine whether NMDAR hypofunction negatively impacts the activity of CaMK and MAPK signaling in the prefrontal cortex (PFC). microRNAs (miRs) have been implicated in the pathophysiology of schizophrenia. They regulate neural plasticity by controlling the translation of target mRNAs. miR-132 is enriched in neurons, regulates basal and activity-induced neurite outgrowth, and its expression is regulated by CREB. The transcriptional repressor methyl-CpG-binding protein 2 (MeCP2) is a target of miR-132 regulation and modulates activity-dependent dendritic patterning. Aim 2 will determine if NMDAR hypofunction reduces the CREB-mediated transcription of miR-132 in the PFC, and the mRNA and protein levels of MeCP2. Primary cortical cultures will be used to directly test whether miR-132 over-expression enhances dendritic morphology and reduces MeCP2 levels. Cognitive disturbances are a well-defined component of schizophrenia and are coupled with altered functioning of the PFC, the brain region most associated with dendritic abnormalities. Clinical evidence suggests that typical antipsychotics are not effective, while atypical antipsychotics are associated with some cognitive benefit. D-serine and N[3-(4'-fluorophenyl)-3-(4' phenylphenoxy) propyl] sarcosine (NFPS), drugs that enhance NMDAR signaling via the glycine modulatory site (GMS), have pro-cognitive effects in pharmacological animal models of schizophrenia. However, little is known about how antipsychotics and GMS modulators regulate dendritic morphogenesis. Therefore, Aim 3 will use cultured cortical neurons from WT and SRKO mice to compare the ability of typical and atypical antipsychotics, as well as D-serine and NFPS, to affect dendritic plasticity. PUBLIC HEALTH RELEVANCE: Clinically available drugs for schizophrenia are not effective at treating the cognitive deficits. The current research aims to discover new underlying causes of the disease in the hopes of developing novel acting therapeutics that will more completely treat the illness.