Mechanismen der Inostitol (1,4,5) trisphosphate 3-kinase B (ltpkB) Upstream-Reguation in Thymozyten

Sauer博士的实验室最近在《科学》杂志上发表了一篇文章，指出肌醇(1，4，5)三磷酸3-激酶B(ItpkB)是胸腺细胞阳性选择所必需的，它通过产生新型的、可溶的“第三”信使分子肌醇-四磷酸(IP4)。ItpkB-/-胸腺细胞不能产生足够的IP4会损害T细胞受体(TCR)信号转导和阳性选择，导致T细胞免疫缺陷。目前尚不清楚TCR是如何激活ItpkB的。在非淋巴组织培养细胞中，ItpkB可能通过钙依赖的与钙调蛋白的相互作用而被激活。有限的证据表明这种相互作用受蛋白激酶C同工酶(PKCs)的调节。根据Sauer博士的初步数据，我假设TCR诱导的胸腺细胞中ItpkB的激活需要钙/钙调蛋白结合，这种相互作用受到ItpkB中钙调蛋白结合域的PKC磷酸化的负调控。在这个项目中，我将确定钙/钙调蛋白结合的作用以及PKCs对其在调节胸腺细胞ItpkB活性和功能中的调节作用。这项研究的结果将揭示通过ItpkB调节正选择的分子回路的新组件，并有助于阐明PKCs在胸腺细胞发育中仍不清楚的功能。此外，他们将为体内调节可溶性肌醇-多聚磷酸信号的机制提供重要的见解--这是一个非常令人兴奋的、高度创新的新兴研究领域。

Dr. Sauer's lab recently published in Science that Inositol(1,4,5)trisphosphate 3-kinase B (ItpkB) is essential for thymocyte positive selection by producing the novel, soluble "third" messenger molecule Inositol-tetrakisphosphate (IP4). Inability to produce sufficient IP4 in ItpkB-/- thymocytes impaired T cell receptor (TCR) signaling and positive selection, resulting in T cell immunodeficiency. It is unclear how ItpkB is activated by the TCR. In nonlymphoid tissue culture cells, ItpkB may be activated via Ca2+-dependent interactions with Calmodulin. Limited evidence suggests modulation of this interaction by protein kinase C isoenzymes (PKCs). Based on Dr. Sauer's preliminary data, I hypothesize that Ca2+/Calmodulin binding is required for TCR induced ItpkB activation in thymocytes and that this interaction is negatively regulated by PKC phosphorylation of the Calmodulin binding domain in ItpkB. In this project I will determine the role of Ca2+/Calmodulin binding and its modulation by PKCs in regulating ItpkB activity and function in thymocytes. The results of this study will unveil new components of the molecular circuitry regulating positive selection through ItpkB and help to elucidate the still unclear functions of PKCs in thymocyte development. Moreover, they will provide important insights into the mechanisms regulating soluble inositol-polyphosphate signaling in vivo - a very exciting, highly innovative, emerging field of research.