AKT2 Oncogene and Human Oncogenesis

描述（由申请人提供）：我们最近克隆了AKT 2启动子和AKT 2相关蛋白NGB，其具有GTP酶和GTP结合活性。AKT 2启动子包含许多转录因子结合位点，并由v-src和MyoD诱导。NGB在肿瘤细胞中的异位表达表现出肿瘤抑制活性。AKT 2与NGB相互作用，磷酸化NGB并消除NGB抑制的细胞增殖。此外，在27例胶质瘤中检测到5例NGB突变，但在匹配的正常DNA中未检测到。此外，我们已经证明AKT 2与结节性硬化症（TSC）2肿瘤抑制因子相互作用并使其磷酸化，以及下调TSC 1和TSC 2蛋白，用从多西环素诱导的组成型活性（myr-AKT 2）和显性阴性AKT 2转染细胞制备的RNA进行的cDNA微阵列分析显示，在检测的12，000个基因中，有68个基因改变超过5倍。在myr-AKT 2细胞中显示最大增加的基因是hHbl-deltaN基因。我们已经在人类癌细胞系和原发性肿瘤中检测到该基因的频繁上调。此外，hHbl-deltaN的异位表达诱导细胞存活、生长和转化，并激活AKT 2途径，表明hHbl-deltaN在AKT 2功能中起重要作用。基于这些数据，我们假设AKT 2受致癌转录因子调节，并且AKT 2及其相关蛋白NGB和TSC 2以及其转录调节基因在控制细胞增殖和转化中起关键作用。该项目的广泛，长期的目标是阐明AKT 2蛋白的正常细胞功能，并确定AKT 2途径在人类肿瘤发生中的扰动的重要性。具体目标是：（1）鉴定调控AKT 2的DNA反应元件和转录因子。(2)定义AKT 2相关蛋白NGB在AKT 2信号传导中的作用。(3)检查TSC 2的AKT 2磷酸化对TSC 1/TSC 2功能的影响。(4)用基因芯片鉴定AKT 2转录调控基因hHbl-AN。

DESCRIPTION (provided by applicant): We recently cloned the AKT2 promoter and an AKT2-associated protein, NGB, which possesses GTPase and GTP-binding activities. The AKT2 promoter contains a number of transcription factor-binding sites and is induced by v-src and MyoD. Ectopic expression of NGB in tumor cells exhibits tumor suppressor activity. AKT2 interacts with, phosphorylates NGB and abrogates NGB-inhibited cell proliferation. Moreover, mutations of NGB were detected in 5 of 27 gliomas examined but not in matched normal DNA. In addition, we have demonstrated that AKT2 interacts with and phosphorylates tuberous sclerosis (TSC) 2 tumor suppressor as well as down-regulates TSC1 and TSC2 proteins, cDNA microarray analyses with RNA prepared from doxycycline-inducible constitutively active (myr-AKT2) and dominant negative AKT2- transfected cells revealed that of 12,000 genes examined, 68 genes were changed more than 5 folds. The gene that showed the largest increase in myr-AKT2 cells is the hHbl-deltaN gene. We have detected frequent upregulation of this gene in human cancer cell lines and primary tumors. Moreover, ectopic expression of the hHbl-deltaN induces cell survival, growth and transformation and activates AKT2 pathway, indicating that hHbl- deltaN plays an important role in AKT2 function. Based on these data, we hypothesize that the AKT2 is regulated by oncogenic transcription factors and that AKT2 and its associated proteins, NGB and TSC2, as well as its transcriptionally regulated gene(s) play a pivotal role in the control of cell proliferation and transformation. The broad, long-term objective of this project is to elucidate the normal cellular function of the AKT2 protein and determine the importance of perturbations of the AKT2 pathway in human oncogenesis. The specific aims are: (1) Identify the DNA response elements and transcription factors that regulate AKT2. (2) Define the role of the AKT2-associated protein NGB in AKT2 signaling. (3) Examine the effects of AKT2 phosphorylation of TSC2 on TSC1/TSC2 function. (4) Characterize the AKT2-transcriptionally regulated gene hHbl-AN identified by cDNA microarray.