The Role of STEP in Schizophrenia

描述(申请人提供)：纹状体富含酪氨酸磷酸酶61(STEP61)针对突触间隔，诱导谷氨酸受体内化。我们最近发现STEP61在精神分裂症(SZ)患者的扣带回皮质中升高。我们的初步发现表明，STEP61的增加导致谷氨酸受体内化，这一模型与SZ的谷氨酸假说一致。我们还认为抗精神病药物的有益作用是通过STEP61介导的。这项提案的总体目标是确定STEP61介导SZ谷氨酸受体丢失的机制，以及它在抗精神病药物有益效果中的作用。在目标1中，我们将增加SZ扣带回皮质的样本，并包括背外侧PFC。我们的预测是STEP61将再次上升。我们将确定这种情况发生的分子机制。正常情况下，STEP61被蛋白酶体泛素化和降解。我们认为这一过程在深圳被打乱了。STEP61的PKA磷酸化是STEP61泛素化所必需的信号之一。在没有PKA磷酸化的情况下，STEP61不再泛素化和降解。然而，我们假设，需要更多的激酶，并将在STEP61中确定这些激酶及其磷酸化位点。目的1还将检验神经抗精神病药的有益作用是通过STEP61介导的假设。我们预测，多巴胺D2R拮抗剂激活PKA，导致STEP61的磷酸化和失活。STEP61的失活促进NMDAR向神经细胞膜的转运。目的1是有意义的，因为它解释了SZ的谷氨酸假说的各个方面，以及神经抗精神病药物如何发挥改善症状的作用。目的2将在SZ(NRG1小鼠)的动物模型上验证我们的假设。NRG1小鼠神经细胞表面功能性NMDAR减少。我们的假设是，这些受体的丢失是通过激活STEP61介导的。我们将首先通过刺激来自WT和STEP KO小鼠的神经元培养和切片来检验我们的假设。我们的预测是，STEP61的缺失将阻止NRG1诱导的NMDAR的内化。我们还将通过将NRG1与STEP KO小鼠杂交来检验我们的假设。我们预测，子代Null for Step将挽救神经细胞膜上NMDAR的丢失。Step KO小鼠神经细胞膜上的NMDAR和AMPAR水平升高。目标3将验证这样的假设，即这些小鼠对精神分裂药物的影响不那么敏感。初步数据表明，情况是这样的：STEP KO小鼠对PCP对运动活动的急性影响以及PCP对认知的亚慢性影响不那么敏感。我们已经开发了一种名为LDN-33960的步进抑制剂，并表明这种化合物可以减少五氯苯酚对运动活动的急性影响。我们将测试这种化合物是否也能减少五氯苯酚引起的认知缺陷。最终，我们的工作有可能发现一系列新的治疗SZ的药物。 公共卫生相关性：这份R01在精神分裂症研究领域提出了一个新的假设：它通过STEP促进NMDAR内化的能力，在这种毁灭性疾病的病理生理学中牵涉到纹状体富含酪氨酸磷酸酶(STEP)。STEP KO小鼠对非竞争性NMDAR拮抗剂PCP的拟精神效应不那么敏感，概念验证研究表明，我们开发的一种STEP抑制剂减少了PCP对WT小鼠的影响。拟议的研究有可能在该领域取得重大进展，因为我们将澄清神经抗精神病药物是如何发挥作用的，我们还将确定神经调节蛋白/ErbB4途径是如何通过STEP发挥作用的，在精神分裂症的遗传学研究中，神经调节蛋白/ErbB4途径与疾病有关。

DESCRIPTION (provided by applicant): Striatal-Enriched tyrosine Phosphatase 61 (STEP61) is targeted to synaptic compartments and induces glutamate receptor internalization. We recently discovered that STEP61 is elevated in cingulate cortex of persons with schizophrenia (SZ). Our preliminary findings suggest that the increase of STEP61 results in internalization of glutamate receptors, a model consistent with the glutamate hypothesis of SZ. We also propose that the beneficial effects of antipsychotic medications are mediated through STEP61. The overall goals of this proposal are to define the mechanisms by which STEP61 mediates the loss of glutamate receptors in SZ, as well as its role in the beneficial effects of neuroleptics. In Aim 1, we will increase our samples of SZ cingulate cortex and include dorsolateral PFC. Our prediction is that STEP61 will again be elevated. We will determine the molecular mechanism by which this occurs. STEP61 is normally ubiquitinated and degraded by the proteasome. We propose that this process is disrupted in SZ. PKA phosphorylation of STEP61 is one signal that is necessary for the ubiquitination of STEP61. In the absence of PKA-phosphorylation, STEP61 is no longer ubiquitinated and degraded. We hypothesize, however, that additional kinases are required, and will identify these kinases and their phosphorylation sites in STEP61. Aim 1 will also test the hypothesis that the beneficial effects of neuroleptics are mediated through STEP61. We predict that dopamine D2R antagonists activate PKA, leading to the phosphorylation and inactivation of STEP61. Inactivation of STEP61 promotes trafficking of NMDAR to neuronal membranes. Aim 1 is significant as it explains aspects of the glutamate hypothesis of SZ as well as how neuroleptics function to ameliorate symptoms. Aim 2 will test our hypothesis in an animal model of SZ (NRG1 mice). NRG1 mice have decreased functional NMDARs on neuronal surfaces. Our hypothesis is that the loss of these receptors is mediated by activation of STEP61. We will first test our hypothesis by stimulating neuronal cultures and slices derived from WT and STEP KO mice with NRG1. Our prediction is that the absence of STEP61 will prevent NRG1-induced internalization of NMDARs. We will also test our hypothesis by crossing NRG1 with STEP KO mice. We predict that progeny null for STEP will rescue the loss of NMDARs from neuronal membranes. STEP KO mice have elevated levels of NMDARs and AMPARs on neuronal membranes. Aim 3 will test the hypothesis that these mice are less sensitive to the effects of psychotomimetic agents. Preliminary data indicate that this is the case: STEP KO mice are less sensitive to the acute effects of PCP on locomotor activity, as well as the subchronic effects of PCP on cognition. We have developed a STEP inhibitor called LDN-33960, and have shown that this compound reduces the acute effects of PCP on locomotor activity. We will test if this compound also reduces the cognitive deficits induced by PCP. Ultimately, our work has the potential of discovering a new family of therapeutic agents for SZ. PUBLIC HEALTH RELEVANCE: This R01 proposes a new hypothesis in the field of Schizophrenia Research: it implicates STriatal-Enriched tyrosine Phosphatase (STEP) in the pathophysiology of this devastating disease through STEP's ability to promote NMDAR internalization. STEP KO mice are less sensitive to the psychotomimetic effects of the noncompetitive NMDAR antagonist, PCP, and proof-of-concept studies demonstrate that a STEP inhibitor we have developed reduces the effects of PCP in WT mice. The proposed studies have the potential of making a major advance in the field as we will clarify how neuroleptics function, and we will also determine how the neuregulin/ErbB4 pathway, which has been implicated in the disease in genetic studies of schizophrenia, exerts its effects through STEP.