Selenoprotein K modulates calcium-dependent signaling in immune cells

 描述（由申请人提供）：硒（Se）是一种对人类健康的许多方面都很重要的必需微量营养素，包括最佳免疫反应。硒的生物学效应主要是通过其作为氨基酸硒代半胱氨酸（Sec）掺入硒蛋白而发挥的。在人类中已经鉴定出25种硒蛋白，其中除了一种之外，所有的硒蛋白也以含Sec蛋白的形式存在于小鼠和大鼠中。我们已经证明对最佳免疫应答重要的一种硒蛋白是内质网（ER）跨膜硒蛋白K（Selk）。Selk表达在免疫细胞中表达最高，并且对硒摄入水平敏感。我们第一个资助期的主要目标是了解Selk如何调节免疫细胞功能，并使用我们的新型Selk-/-小鼠模型来确定Selk在体内免疫中的作用。我们成功地揭示了Selk在产生钙（Ca 2+）流中的作用，所述钙流发生在免疫细胞（包括T和B细胞、中性粒细胞和巨噬细胞）中受体介导的活化期间。我们的新数据表明，Selk缺陷导致受损的Ca 2+流量，由于在免疫细胞的ER膜中的Ca 2+通道蛋白，肌醇-1，4，5-三磷酸受体（IP 3R）的棕榈酰化缺陷。IP 3R驱动的Ca 2+通量在免疫细胞活化中起着核心作用，我们的研究表明Selk缺陷会影响各种免疫应答，包括抗病毒免疫、腹膜炎和动脉粥样硬化。这些发现导致了我们的中心假设，即Selk作为棕榈酰酰基转移酶DHHC 6的辅因子发挥作用，从而促进IP 3R和其他细胞蛋白的棕榈酰化，这是膳食硒水平调节免疫力的机制。我们的创新研究将明确确定Selk在IP 3R和其他蛋白质棕榈酰化中的作用，以及这如何影响免疫细胞功能。我们还将通过调查膳食硒和遗传多态性如何与人类的Selk表达和免疫细胞功能相关，向将我们的发现转化为人类健康迈出重要一步。我们将实现以下具体目标：具体目标1.确定Selk调节IP 3R棕榈酰化的机制。具体目标2。识别需要Selk进行棕榈酰化的细胞蛋白质，并确定棕榈酰化如何调节其功能。具体目标3。确定Selk表达如何在人T细胞中调节，以及这如何影响IP 3R表达和T细胞功能。

 DESCRIPTION (provided by applicant): Selenium (Se) is an essential micronutrient important for many aspects of human health, including optimal immune responses. The biological effects of Se are exerted mainly through its incorporation into selenoproteins as the amino acid, selenocysteine (Sec). Twenty-five selenoproteins have been identified in humans, all but one of which also exist as Sec-containing proteins in mice and rats. One selenoprotein that we have shown to be important for optimal immune responses is the endoplasmic reticulum (ER) transmembrane selenoprotein K (Selk). Selk expression is expressed highest in immune cells and is sensitive to levels of Se intake. The main goal of our first funding period was to understand how Selk regulates immune cell function and to use our novel Selk-/- mouse model to determine the role of Selk for in vivo immunity. We were successful in uncovering a role for Selk in generating the calcium (Ca2+) flux that occurs during receptor-mediated activation in immune cells including T and B cells, neutrophils, and macrophages. Our new data have revealed that Selk deficiency leads to impaired Ca2+ flux due to a defect in palmitoylation of the Ca2+ channel protein, inositol-1,4,5-triphosphate receptor (IP3R), in the ER membrane of immune cells. IP3R-driven Ca2+ flux plays a central role in immune cell activation and Selk deficiency was shown in our studies to influence a wide variety of immune responses including anti-viral immunity, peritonitis, and atheroschlerosis. These findings have led to our central hypothesis that Selk functions as a cofactor for the palmitoyl acyl transferase, DHHC6, thereby promoting the palmitoyation of IP3R and other cellular proteins and this serves as a mechanism by which levels of dietary Se regulate immunity. Our innovative studies will definitively determine the role of Selk in the palmitoylation of the IP3R and other proteins and how this affects immune cell function. We also will take an important step toward translating our findings to human health by investigating how dietary Se and genetic polymorphisms are related to Selk expression and immune cell function in humans. We will accomplishment of the following specific aims: Specific Aim 1. Determine the mechanisms by which Selk regulates palmitoylation of the IP3R. Specific Aim 2. Identify cellular proteins that require Selk for palmitoylation and determine how palmitoylation regulates their function. Specific Aim 3. To determine how Selk expression is regulated in human T cells and how this affects IP3R expression and T cell function.