POSTTRANSLATIONAL MODIFICATION OF RASGRP1 PROTEIN IN T LYMPHOCYTES

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 T细胞急性淋巴细胞性白血病/淋巴瘤(TALL/L)涉及淋巴细胞或白细胞的异常增殖。ALL/L患者的血液和骨髓细胞中的癌蛋白活性形式RasGTP水平经常升高。与其他癌症相比，这些Tall/L患者中几乎没有典型的RAS蛋白突变来解释这种积累。这一发现提示许多TALL/L患者存在RasGTP上游信号蛋白的异常表达或活性。淋巴细胞表达两种RAS鸟嘌呤核苷酸交换因子(RasGEF)，SOS和RASGRP1，当细胞表面受体受到刺激时，这两种因子共同作用激活RAS。以往的工作表明，在抗原受体刺激后，RASGRP1是淋巴细胞中主要的RasGRP1。过度表达野生型RASGRP1的小鼠会患上胸腺瘤和皮肤癌。因此，非癌症细胞必须有一种限制RASGRP1功能的机制。令人惊讶的是，关闭这种由RASGRP1驱动的强劲增长信号并防止失控扩散的负面监管因素尚不清楚。 通过受体结合接收的信号的控制可以通过信号成分的翻译后修饰发生。T细胞受体(TCR)刺激后RASGRP1蛋白水平的降低先于RASGRP1转录本的降解。这项研究将确定控制淋巴细胞内RASGRP1蛋白水平和活性的翻译后修饰事件。拟议的实验将使用质谱学来检查TCR刺激后RASGRP1蛋白发生的翻译后修饰事件。所发现的修饰位点将使我们深入了解正常淋巴细胞中RASGRP1活性的控制，并为具有RASGRP1突变形式的TALL/L患者样本提供机制线索。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. T cell acute lymphoblastic leukemia/lymphoma (TALL/L) involves abnormal proliferation of lymphocytes, or white blood cells. TALL/L patients often show elevated levels of the active form of the oncoprotein, RasGTP, in blood and bone marrow cells. In contrast to other cancers, few of these TALL/L patients have the typical mutations in Ras protein that would explain this accumulation. This finding suggests that many TALL/L patients have abnormal expression or activity of signaling proteins upstream of RasGTP. Lymphocytes express two Ras guanine nucleotide exchange factors (RasGEFs), SOS and RasGRP1, which work together to activate Ras when cell surface receptors are stimulated. Previous work demostrated that RasGRP1 is the dominant RasGEF in lymphocytes after antigen receptor stimulation. Mice overexpressing wild type RasGRP1 develop thymomas and skin carcinomas. Thus non-cancerous cells must have a mechanism to limit RasGRP1 function. Surprisingly, the negative regulatory factors that turn off this strong, RasGRP1-driven growth signal and prevent uncontrolled proliferation are unknown. Control of signals received via receptor binding can occur through posttranslational modification of signaling components. Decreases in RasGRP1 protein level after T cell receptor (TCR) stimulation precedes RasGRP1 transcript degradation. This study will identify the posttranslational modification events controlling RasGRP1 protein levels and activity within lymphocytes. The proposed experiments will use Mass Spectrometry to examine posttranslational modification events that occur on RasGRP1 protein following TCR stimulation. Modified sites identifed will give us insight into the control of RasGRP1 activity in normal lymphocytes and provide mechanistic clues for TALL/L patient samples with mutated forms of RasGRP1.