Role of brain specific tyrosine phophatase, STEP in neuroprotection and death

描述（由申请人提供）：本研究的长期目标是确定酪氨酸磷酸酶和双特异性磷酸酶在基底神经节和相关结构的神经系统疾病中的作用。我们最近的研究结果表明，纹状体富集酪氨酸磷酸酶，STEP，特别是在皮质，海马和纹状体的神经元中表达可能参与细胞存活后兴奋性毒性损伤。STEP的活性本身由神经递质多巴胺和谷氨酸通过激酶相互作用基序或KIM结构域内的关键丝氨酸残基的磷酸化和去磷酸化来调节。谷氨酸/NMDA受体介导的Ca 2+内流激活STEP，而多巴胺/D1受体介导的PKA激活导致STEP失活。这项拟议的研究现在将测试STEP是否通过NR 2B-NMDA受体激活，NR 2B-NMDA受体是一种与谷氨酸兴奋性毒性相关的NMDA受体。它还将研究活性STEP是否反过来可以下调或抑制参与谷氨酸/NMDA受体介导的细胞死亡的多个相互关联的通路。我们预期活性STEP作为反馈环的一部分，可以通过NR 2B亚基的酪氨酸去磷酸化下调NR 2B-NMDA受体通道活性，从而抑制Ca 2+超载和随后的细胞损伤。它还可以抑制p38 MAP激酶信号通路的激活，该通路已被归因于多种神经退行性疾病中的细胞死亡。以这种方式，STEP可以促进初始损伤后的细胞存活。然而，根据损伤的严重程度，STEP可能被蛋白水解裂解并最终降解，从而促进细胞死亡途径的激活。该研究将进一步研究不能被蛋白水解切割并且可以在体内递送的STEP的组成型活性形式是否能够减轻缺血性脑损伤，其中谷氨酸兴奋性毒性的参与是充分确定的。这些研究将涉及谷氨酸毒性的神经元培养实验和缺血性中风的动物模型，并将利用生物化学、免疫细胞化学和分子生物学技术。这些发现将帮助我们确定酪氨酸磷酸酶STEP是否可能在治疗上有益，并可被考虑用于治疗缺血性中风和相关神经系统疾病。 公共卫生相关性：这项研究的目的是了解脑富集和神经元特异性酪氨酸磷酸酶，STEP，在神经元细胞死亡后兴奋性毒性损伤的作用。这些发现将有助于我们确定STEP是否可以减弱兴奋毒性神经元细胞死亡，并可被视为治疗缺血性卒中和相关神经系统疾病的潜在治疗靶点。

DESCRIPTION (provided by applicant): The long-term goal of this research is to determine the role of tyrosine phosphatases and dual-specificity phosphatases in neurological disorders of the basal ganglia and related structures. Our recent findings indicate that a striatal enriched tyrosine phosphatase, STEP, specifically expressed in the neurons of the cortex, hippocampus and striatum may participate in cell survival following an excitotoxic insult. The activity of STEP is itself regulated by the neurotransmitters dopamine and glutamate through phosphorylation and dephosphorylation of a critical serine residue within the kinase interacting motif or KIM domain. Glutamate/NMDA receptor mediated influx of Ca2+ activates STEP, whereas dopamine/D1 receptor mediated PKA activation leads to inactivation of STEP. The proposed study will now test whether STEP is activated through NR2B-NMDA receptors, a pool of NMDA receptor that is associated with glutamate excitotoxicity. It will also investigate whether active STEP in turn can down regulate or inhibit multiple interrelated pathways that are involved in glutamate/NMDA receptor-mediated cell death. We anticipate that active STEP, as part of a feed-back loop, can down regulate NR2B-NMDA receptor channel activity through tyrosine dephosphorylation of NR2B subunit, thereby inhibiting Ca2+ overload and subsequent cell damage. It can also inhibit the activation of the p38 MAP kinase signaling pathway that has been attributed to cell death in multiple neurodegenerative disorders. In this way STEP may promote cell survival following an initial insult. However depending upon the severity of the insult STEP may be proteolytically cleaved and eventually degraded, thereby facilitating activation of cell death pathways. The study will further investigate if a constitutively active form of STEP that cannot be proteolytically cleaved and can be delivered in vivo will be able to attenuate ischemic brain damage, where the involvement of glutamate excitotoxicity is well established. These studies will involve neuron culture experiments of glutamate toxicity and an animal model of ischemic stroke and will utilize biochemical, immunocytochemical and molecular biology techniques. The findings will help us to determine whether the tyrosine phosphatase STEP may be therapeutically beneficial and can be considered for the treatment of ischemic stroke and related neurological disorders. PUBLIC HEALTH RELEVANCE: The goal of the proposed study is to understand the role of a brain-enriched and neuron-specific tyrosine phosphatase, STEP, in neuronal cell death following an excitotoxic insult. The findings will help us to determine whether STEP can attenuate excitotoxic neuronal cell death and can be considered as a potential therapeutic target for the treatment of ischemic stroke and related neurological disorders.