AKT2 Oncogene and Human Oncogenesis

描述（由申请人提供）：我们最近克隆了AKT2启动子和AKT2相关蛋白NGB，该蛋白具有GTPase和gtp结合活性。AKT2启动子包含许多转录因子结合位点，由v-src和MyoD诱导。NGB在肿瘤细胞中的异位表达具有抑瘤活性。AKT2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个胶质瘤中有5个检测到NGB突变，但在匹配的正常DNA中未检测到NGB突变。此外，我们已经证明AKT2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，并下调TSC1和TSC2蛋白。cDNA微阵列分析显示，从多西环素诱导的组成活性（myr-AKT2）和显性阴性AKT2转染细胞中制备的RNA显示，在检测的12,000个基因中，68个基因改变超过5倍。在myr-AKT2细胞中增加最多的基因是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异位表达诱导细胞存活、生长和转化，激活AKT2通路，表明hHbl-deltaN在AKT2功能中起重要作用。基于这些数据，我们假设AKT2受致癌转录因子的调控，AKT2及其相关蛋白NGB和TSC2及其转录调控基因在控制细胞增殖和转化中起关键作用。该项目的长期目标是阐明AKT2蛋白的正常细胞功能，并确定AKT2通路扰动在人类肿瘤发生中的重要性。具体目的有：(1)鉴定调控AKT2的DNA应答元件和转录因子。(2)明确AKT2相关蛋白NGB在AKT2信号传导中的作用。(3)检测AKT2磷酸化TSC2对TSC1/TSC2功能的影响。(4)利用cDNA芯片鉴定akt2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.