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》杂志上发表文章说，肌醇（1，4，5）三磷酸3-激酶B（Itpk B）通过产生新的可溶性“第三”信使分子肌醇四磷酸（IP 4），对胸腺细胞的正选择至关重要。在ItpkB-/-胸腺细胞中不能产生足够的IP 4损害了T细胞受体（TCR）信号传导和阳性选择，导致T细胞免疫缺陷。目前还不清楚ItpkB是如何被TCR激活的。在非淋巴组织培养细胞中，ItpkB可通过与钙调蛋白的Ca 2+依赖性相互作用而被激活。有限的证据表明，这种相互作用的蛋白激酶C同工酶（PKC）的调制。根据Sauer博士的初步数据，我假设，钙离子/钙调素结合是必要的TCR诱导的ItpkB活化胸腺细胞，这种相互作用是负调控PKC磷酸化的钙调素结合域ItpkB。在这个项目中，我将确定钙/钙调素结合的作用和它的调节PKCs在调节ItpkB活性和功能的胸腺细胞。这项研究的结果将揭示通过ItpkB调节正选择的分子电路的新组成部分，并有助于阐明胸腺细胞发育中PKC的功能尚不清楚。此外，他们将提供重要的见解调节可溶性肌醇-多磷酸信号在体内的机制-一个非常令人兴奋的，高度创新的，新兴的研究领域。

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.