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

描述（由申请人提供）：Ca2+激活的K+通道KCa3.1是Ca2+内流和随后的B细胞和T细胞激活所必需的。KCa3.1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，这强调了了解这些通道如何被调节的重要性。我们对KCa3.1调控的研究发现了一个全新的人CD4 T细胞再激活所需的信号通路。该途径包括一种潜在的新型磷脂酰肌醇3激酶（PI3K）异构体磷脂酰肌醇3-磷酸（PI(3)P）和一种哺乳动物组氨酸激酶核苷二磷酸激酶B (NDPK-B)，它们是KCa3.1通道激活所必需的。我们发现NDPK-B在PI(3)P下游通过磷酸化KCa3.1羧基末端（CT）尾部的H358来激活KCa3.1。此外，我们还发现了两种新的T细胞激活负调节因子，分别是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)，它们通过分别使PI(3)P和KCa3.1去磷酸化来抑制KCa3.1。本研究的主要目标是进一步探索这些分子调控KCa3.1的机制及其与T细胞活化和疾病的生物学相关性。Specific Aim (SA) 1将确定CD4 T细胞中对于产生介导KCa3.1通道激活的PI(3)P池至关重要的信号通路，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和在SA1中鉴定的PI3K亚型向免疫突触（IS）的再分配，以及这在调节KCa3.1通道活性中的作用。SA3将鉴定负调控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。我们最近的数据表明，组氨酸磷酸酶PHPT-1和磷酸赖氨酸磷酸组氨酸无机焦磷酸盐磷酸酶（LHPP）是KCa3.1的负调控因子，并通过去磷酸化KCa3.1 CT中的组氨酸358 （H358）来逆转NDPK-B对KCa3.1的激活。Ca2+激活的K+通道KCa3.1是Ca2+内流和随后的B细胞和T细胞激活所必需的。KCa3.1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，这强调了了解这些通道如何被调节的重要性。

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.