New signaling pathways that positively and negatively regulate CD4 T cells via th

描述(申请人提供)：钙激活的K通道，KCa3.1，是钙内流和随后激活B和T细胞所必需的。KCa3.1的抑制剂正在开发中，用于治疗自身免疫性疾病和移植排斥反应，这突显了了解这些通道是如何调节的重要性。我们对KCa3.1调控的研究揭示了人类CD4T细胞重新激活所需的一个全新的信号通路。该途径包括KCa3.1通道激活所需的新的磷脂酰肌醇3-磷酸酶(PI3K)亚型磷脂酰肌醇3-磷酸(PI(3)P)和哺乳动物组氨酸激酶(NDPK-B)。我们发现，NDPK-B在PI(3)P下游通过磷酸化KCa3.1‘S羧基末端(CT)的H358来激活KCa3.1。此外，我们还发现了两个新的T细胞激活负调控因子，PI(3)P磷酸酶肌管蛋白相关蛋白6(MTMR6)和组氨酸磷酸酶磷酸组氨酸磷酸酶-1(PHPT-1)，它们分别通过去磷酸化PI(3)P和KCa3.1来抑制KCa3.1。这项建议的主要目的是进一步探索这些分子调节KCa3.1的机制及其与T细胞激活和疾病的生物学相关性。特异性靶点(SA)1将确定CD4T细胞中对产生PI(3)P池至关重要的信号通路，PI(3)P池介导KCa3.1通道激活，以及PI(3)P上游调节NDPK-B的机制。SA2将决定T细胞受体(TCR)刺激是否调节NDPK-B、KCa3.1、MTMR6和SA1中确定的PI3K亚型重新分布到免疫突触(IS)，以及这在调节KCa3.1通道活性中所起的作用。SA3将确定负调控KCa3.1通道活性的组氨酸磷酸酶及其在T细胞生物学中的作用。我们最近的研究表明，组氨酸磷酸酶PHPT-1和磷酸化磷酸化组氨酸无机焦磷酸酯酶(LHPP)是KCa3.1的负调节因子，它们通过去磷酸化KCa3.1的CT中的组氨酸358(H358)来逆转NDPK-B激活KCa3.1的作用。KCa3.1的抑制剂正在开发中，用于治疗自身免疫性疾病和移植排斥反应，这突显了了解这些通道是如何调节的重要性。 公共卫生相关性：我们对KCa3.1调控的研究发现了新的信号通路，这些信号通路对KCa3.1通道活动起着积极和消极的调节作用。通过干扰分子的药理作用，我们发现，正向调节KCa3.1可能会发现治疗移植排斥和自身免疫性疾病的新的药物靶点。另一方面，我们发现的负调控KCa3.1分子的异常表达或活性可能为研究自身免疫性疾病提供新的视角。

DESCRIPTION (provided by applicant): The Ca2+-activated K+ channel, KCa3.1, is required for Ca2+ influx and the subsequent activation of B and T cells. Inhibitors of KCa3.1 are in development to treat autoimmune diseases and transplant rejection, underscoring the importance in understanding how these channels are regulated. Our studies on the regulation of KCa3.1 have uncovered a completely new signaling pathway required for the reactivation of human CD4 T cells. This pathway includes a potentially novel phosphatidylinositol 3 Kinase (PI3K) isoform, phosphatidylinositol 3-Phosphate (PI(3)P), and a mammalian histidine kinase, Nucleoside Diphosphate Kinase B (NDPK-B), that are required for KCa3.1 channel activation. We found that NDPK-B functions downstream of PI(3)P to activate KCa3.1 by phosphorylating H358 in KCa3.1's carboxyterminal (CT) tail. Moreover, we have identified 2 new negative regulators of T cell activation, the PI(3)P phosphatase myotubularin related protein 6 (MTMR6) and the histidine phosphatase, phosphohistidine phosphatase-1 (PHPT-1), which inhibit KCa3.1 by dephosphorylating PI(3)P and KCa3.1 respectively. The major goal of this proposal is to further explore the mechanisms whereby these molecules regulate KCa3.1 and their biological relevance to T cell activation and disease. Specific Aim (SA) 1 will identify the signaling pathway in CD4 T cells that is critical for generating the PI(3)P pool that mediates KCa3.1 channel activation and the mechanism whereby PI(3)P functions upstream to regulate NDPK-B. SA2 will determine whether T cell receptor (TCR) stimulation regulates the redistribution of NDPK-B, KCa3.1, MTMR6, and the PI3K isoform identified in SA1 to the immunological synapse (IS), and the consequences this plays in the regulation of KCa3.1 channel activity. SA3 will identify the histidine phosphatase that negatively regulates KCa3.1 channel activity and its role in T cell biology. Our recent data indicates that the histidine phosphatases PHPT-1 and phospholysine phosphohistidine inorganic pyrophosphate phosphatase (LHPP) are negative regulators of KCa3.1 and function to reverse the activation of KCa3.1 by NDPK-B by dephosphorylating histidine 358 (H358) in the CT of KCa3.1.The Ca2+-activated K+ channel, KCa3.1, is required for Ca2+ influx and the subsequent activation of B and T cells. Inhibitors of KCa3.1 are in development to treat autoimmune diseases and transplant rejection, underscoring the importance in understanding how these channels are regulated. Public Health Relevance: Our studies on the regulation of KCa3.1 have uncovered new signaling pathways that functions as both positive and negative regulators of KCa3.1 channel activity. Interfering pharmacologically with molecules we found that positively regulate KCa3.1 may identify novel drug targets to treat transplant rejection and autoimmune disease. On the flip side, abnormal expression or activity of molecules we identified that negative regulate KCa3.1 could provide new insight into autoimmune diseases.