The Role of STEP in Schizophrenia

描述（由申请人提供）：纹状体富集酪氨酸磷酸酶61 （STEP61）靶向突触隔室并诱导谷氨酸受体内化。我们最近发现，在精神分裂症（SZ）患者的扣带皮层中，STEP61表达升高。我们的初步研究结果表明，STEP61的增加导致谷氨酸受体的内化，这一模型与SZ的谷氨酸假说一致。我们还提出抗精神病药物的有益作用是通过STEP61介导的。本提案的总体目标是确定STEP61介导SZ中谷氨酸受体丢失的机制，以及它在抗精神病药的有益作用中的作用。在Aim 1中，我们将增加SZ扣带皮层的样本，包括背外侧pfc。我们预测STEP61将再次升高。我们将确定发生这种情况的分子机制。STEP61通常被蛋白酶体泛素化和降解。我们认为这个过程在SZ被打乱了。PKA磷酸化的STEP61是STEP61泛素化的一个必要信号。在pka磷酸化缺失的情况下，STEP61不再泛素化和降解。然而，我们假设需要额外的激酶，并将在STEP61中鉴定这些激酶及其磷酸化位点。目的1还将验证神经抑制剂的有益作用是通过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向神经元膜的运输。目的1是重要的，因为它解释了SZ的谷氨酸假说的各个方面，以及抗精神病药如何改善症状。目的2将在SZ （NRG1小鼠）动物模型中验证我们的假设。NRG1小鼠神经元表面功能性NMDARs减少。我们的假设是这些受体的丢失是通过激活STEP61介导的。我们将首先通过用NRG1刺激WT和STEP KO小鼠的神经元培养物和切片来验证我们的假设。我们的预测是，STEP61的缺失将阻止nrg1诱导的NMDARs内化。我们还将通过将NRG1与STEP KO小鼠杂交来验证我们的假设。我们预测，STEP的后代缺失将挽救神经元膜上NMDARs的缺失。STEP KO小鼠神经元膜上的NMDARs和AMPARs水平升高。目的3将验证这些小鼠对拟精神药物的影响不太敏感的假设。初步数据表明：STEP KO小鼠对PCP对运动活动的急性影响以及对认知的亚慢性影响不太敏感。我们已经开发了一种名为LDN-33960的STEP抑制剂，并表明这种化合物可以减少PCP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PCP引起的认知缺陷。最终，我们的工作有可能发现一个新的SZ治疗药物家族。

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.