MODULATION OF T CELL RECEPTOR (TCR) SIGNAL TRANSDUCTION BY CAMP

探讨肌醇水解的活化机理 磷脂（InsPL）对鼠T细胞干扰的响应 淋巴细胞Aq受体（TCR），及其调节的激活剂， 腺苷酸环化酶（AC）系统。InsPL的水解，是最重要的 在细胞中观察到的快速反应，被认为具有换能器的作用 在TCR启动的信号。这种代谢途径的中心是 一种酶，InsPL特异性磷脂酶C（PLC）的激活。小 已知这种酶的调节和偶联机制， TCR。T细胞相关性的第二个信号转导机制 淋巴细胞活化由AC/cAMP途径表示。AC激活 在Th细胞中已经清楚地记录了对 淋巴细胞的药理学治疗（即FSK、CTx）或 autocoids（即：前列腺素E2）。 cAMP水平升高， 与几种T细胞反应的下调有关，包括 淋巴因子分泌和增殖。增加的机制 cAMP水平抑制淋巴细胞功能还没有确定，但我们的研究表明， 初步数据表明，它与InsPL的减少有关 水解我们建议研究AC激活剂和cAMP的作用， 对InsPL水解响应TCR扰动的调节， 完整或透化的细胞。这种方法将使我们能够描述 cAMP在抑制TCR介导的InsPL水解中的作用位点。我们 已经能够在透化的T细胞中诱导InsPL水解， 加入GTP的不可水解类似物（如GTP-γ-S）， 否则对完整细胞是不可渗透的。GTP-γ-S激活一种 调节PLC活性的G蛋白，绕过TCR（或其他细胞） 表面结构），支持G蛋白在 TCR信号转导。如果AC/cAMP/PKA通路的激活在 该模型导致INSPL水解的抑制，然后直接影响 在PLC或G蛋白上的环核苷酸是可能的。可选择地， cAMP在这些实验条件下不能抑制， 表明在接近G蛋白活化水平上的作用，可能在 受体的水平。

To study the mechanism of activation of the hydrolysis of inositol phospholipids (InsPL) in response to perturbation of the murine T lymphocyte Aq receptor (TCR), and its regulation by activators of the adenylate cyclase (AC) system. The hydrolysis of InsPL, one of the most rapid responses observed in cells, is deemed to have a role as a transducer of the signal initiated at the TCR. This metabolic pathway is centered on the activation of an enzyme, a InsPL-specific phospholipase C (PLC). Little is known about the regulation and coupling mechanism of this enzyme with the TCR. A second signal transduction mechanism of relevance in T lymphocyte activation is represented by the AC/cAMP pathway. AC activation in Th cells has been clearly documented in response to either-pharmacological treatment (i.e. FSK, CTx) of lymphocytes or to autocoids (i.e.: prostaglandin E2). Increased levels of cAMP are associated with down regulation of several T cell responses, including lymphokine secretion and proliferation. The mechanism by which increased levels of cAMP depress lymphocyte function is not defined, but our preliminary data indicates that it is associated with a decrease in InsPL hydrolysis. we propose to investigate the effect of AC activators and cAMP on the regulation of InsPL hydrolysis in response to TCR perturbation in intact or permeabilized cells. This approach will allow us to characterize the site of action of cAMP in inhibiting TCR-mediated InsPL hydrolysis. We have been able to induce InsPL hydrolysis in permeabilized T cells by the addition of non-hydrolyzable analogs of GTP (such as GTP-gamma-S), which are otherwise non-permeable to intact cells. GTP-gamma-S activates a G-protein that regulates PLC activity, bypassing the TCR (or other cell surface structure), supporting the hypothesis of a role for G-proteins in TCR signal transduction. If the activation of the AC/cAMP/PKA pathway in this model results in inhibition of INSPL hydrolysis, then a direct effect of the cyclic nucleotide on PLC or on G-protein is likely. Alternatively, the failure of cAMP to inhibit under these experimental conditions will suggest an effect at a level proximal to G-protein activation, possibly at the level of the receptor.