A novel tumor suppressor protein encoded by circular AKT3 RNA inhibits glioblastoma tumorigenicity by competing with active phosphoinositide-dependent Kinase-1
A novel tumor suppressor protein encoded by circular AKT3 RNA inhibits glioblastoma tumorigenicity by competing with active phosphoinositide-dependent Kinase-1
复制标题
由环状 AKT3 RNA 编码的新型肿瘤抑制蛋白通过与活性磷酸肌醇依赖性激酶 1 竞争来抑制胶质母细胞瘤致瘤性
DOI：
10.1186/s12943-019-1056-5
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发表时间：
2019-08-30
期刊：
影响因子：
37.3
通讯作者：
Zhang, Nu
中科院分区：
文献类型：
--
作者：
Xia, Xin;Li, Xixi;Zhang, Nu
RTK/PI3K/AKT通路在许多肿瘤的发生发展中起着关键作用，包括基底膜。作为一种调节分子和潜在的药物靶点，AKT的致癌作用已经得到了实质性的研究。AKT的三种亚型已被鉴定，包括AKT1、AKT2和AKT3，但它们在GBM中的单独功能仍存在争议。方法采用高通量RNA测序和定量逆转录-聚合酶链式反应(QRT-PCR)的方法，对GBM组织和配对的正常组织中差异表达的CircRNA进行鉴定。高通量RNA测序用于鉴定CIRC-AKT3调控的信号通路。用质谱仪、免疫印迹和免疫荧光染色等方法验证AKT3-174aa的表达。体外和体内实验验证了AKT3-174aa的抑瘤作用。结果Circ-AKT3是一个未鉴定的AKT转录本突变体。与配对的相邻正常脑组织相比，CIRC-AKT3在GBM组织中的表达水平较低。CIRC-AKT3利用重叠的起始-终止密码子编码174个氨基酸(AA)的新蛋白，我们将其命名为AKT3-174aa。AKT3-174aa过表达降低了GBM细胞的增殖、辐射抗性和体内致瘤性，而CIRC-AKT3基因敲除则增强了星形细胞瘤细胞的恶性表型。AKT3-174aa竞争性地与磷酸化的PDK1相互作用，减少AKT-Thr308的磷酸化，并在调节PI3K/AKT信号强度方面起到负性调节作用。结论我们的数据表明AKT3基因CircRNA的表达受损参与了GBM的发生，我们的数据支持了这样的假设，即在抑制激活的AKT的同时恢复AKT3-174aa可能会为某些GBM患者提供更多的好处。
BackgroundThe RTK/PI3K/AKT pathway plays key roles in the development and progression of many cancers, including GBM. As a regulatory molecule and a potential drug target, the oncogenic role of AKT has been substantially studied. Three isoforms of AKT have been identified, including AKT1, AKT2 and AKT3, but their individual functions in GBM remain controversial. Moreover, it is not known if there are moreAKTalternative splicing variants.MethodsHigh-throughput RNA sequencing and quantitative reverse transcription-PCR were used to identify the differentially expressed circRNAs in GBM samples and in paired normal tissues. High throughput RNA sequencing was used to identify circ-AKT3 regulated signaling pathways. Mass spectrometry, western blotting and immunofluorescence staining analyses were used to validate AKT3-174aa expression. The tumor suppressive role of AKT3-174aa was validated in vitro and in vivo. The competing interaction between AKT3-174aa and p-PDK1 was investigated by mass spectrometry and immunoprecipitation analyses.ResultsCirc-AKT3 is a previously uncharacterizedAKTtranscript variant. Circ-AKT3 is expressed at low levels in GBM tissues compared with the expression in paired adjacent normal brain tissues. Circ-AKT3 encodes a 174 amino acid (aa) novel protein, which we named AKT3-174aa, by utilizing overlapping start-stop codons. AKT3-174aa overexpression decreased the cell proliferation, radiation resistance and in vivo tumorigenicity of GBM cells, while the knockdown of circ-AKT3 enhanced the malignant phenotypes of astrocytoma cells. AKT3-174aa competitively interacts with phosphorylated PDK1, reduces AKT-thr308 phosphorylation, and plays a negative regulatory role in modulating the PI3K/AKT signal intensity.ConclusionsOur data indicate that the impaired circRNA expression of theAKT3gene contributes to GBM tumorigenesis, and our data corroborate the hypothesis that restoring AKT3-174aa while inhibiting activated AKT may provide more benefits for certain GBM patients.