Identifying SREBP-1 activation mechanism in glioblastoma and its new role in regulating glutamine metabolism

鉴定胶质母细胞瘤中SREBP-1的激活机制及其在调节谷氨酰胺代谢中的新作用

• 批准号: 10334514
• 负责人: Deliang Guo
• 金额: $ 35.95万
• 依托单位: OHIO STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-04-01 至 2025-01-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10334514
• 关键词: 18F-Glutamine; Adult; Affect; Affinity; Amino Acid Transporter; Ammonia; Binding; Binding Sites; Biology; Brain; Cells; Cholesterol; Clinical; Data; Dissociation; Endoplasmic Reticulum; Enzymes; Essential Amino Acids; Exhibits; Genes; Genetic Transcription; Glioblastoma; Glucose; Glutamates; Glutaminase; Glutamine; Golgi Apparatus; Growth; In Vitro; Insulin; Isoleucine; Knowledge; Laboratories; Leucine; Link; Lipids; Malignant Neoplasms; Measures; Mediating; Membrane; Metabolic; Metabolism; Modeling; Molecular; Mutate; N-terminal; Normal Cell; Outcome; Pathway interactions; Patients; Play; Positron-Emission Tomography; Primary Brain Neoplasms; Process; Prognosis; Promoter Regions; Protein Conformation; Proteins; Proteolysis; Publishing; Reporting; Repression; Role; SCAP protein; SRE-1 binding protein; Sampling; Site; Therapeutic; Tumor Tissue; Valine; Withdrawal; Xenograft Model; alpha ketoglutarate; amino acid metabolism; base; cancer cell; glycosylation; improved; in vivo; insight; lipid biosynthesis; lipid metabolism; novel; prevent; promoter; rapid growth; synergism; trafficking; transcription factor; tumor growth; uptake

ABSTRACT Glioblastoma (GBM) is the most lethal primary brain tumor, and its prognosis has no significantly improved in the past two decades. It is urgent to identify effective strategies to treat GBM, but our only partial understanding of GBM biology significantly hinders this progress. Our laboratory has long focused on understanding GBM biology and recently demonstrated that GBM reprograms lipid metabolism to support its rapid growth. We identified that sterol regulatory element-binding protein-1 (SREBP-1), a master transcription factor regulating lipid synthesis, is highly activated in GBM and is essential for tumor growth. However, the molecular mechanism activating SREBP-1 and lipogenesis in cancer cells remains unclear. Moreover, whether the highly activated SREBP-1 plays new roles in malignancy is unknown. In normal cells, SREBP activation is strongly repressed by Insulin-induced gene (Insig), an endoplasmic reticulum (ER)-anchored protein. It binds to the SREBP transporter, SREBP-cleavage protein (SCAP), preventing SREBP ER-to-Golgi translocation and subsequent activation. Thus, the first key step for SREBP-1 activation is SCAP dissociation from Insig. How cancer cells are able to release the tight repression of Insig on SCAP to promote high levels of SREBP- 1 activation remains unanswered. We recently found that glucose-mediated N-glycosylation stabilizes SCAP. Interestingly, our new preliminary data showed that in the absence of glutamine, SREBP-1 failed to be cleaved, although SCAP remained glycosylated. Inhibiting glutamine conversion to glutamate and ammonia by suppressing glutaminase (GLS) markedly reduced SREBP-1 cleavage. These data strongly suggest that glutamine plays a critical role in SREBP-1 activation. Interestingly, expressing the active N-terminal form of SREBP-1 in GBM cells significantly enhanced glutamine uptake. Analysis of GBM patient samples showed that the glutamine transporter, SLC1A5, is highly expressed in tumor tissues and is inversely correlated with patient survival. Promoter analysis showed multiple putative SREBP-1 binding sites in the SLC1A5 promoter region. Based on these new preliminary data and our published studies, we hypothesize that SCAP dissociation from Insig is activated by glutamine-derived metabolites, leading to SREBP-1 activation; in turn, activated SREBP-1 transcriptionally upregulate the expression of SLC1A5, resulting in a feedforward loop to increase glutamine uptake and lipid synthesis to promote GBM growth. In this study, we will identify the molecular mechanism activating SREBP-1 and lipogenesis by glutamine in GBM in Aim 1, and reveal the new role of SREBP-1 in regulating glutamine metabolism in Aim 2. We will further examine whether combining inhibition of SREBP-1 together with SLC1A5 or GLS suppression provides strong synergy to inhibit GBM growth (Aim 2). Completion of this study will significantly advance our understanding of GBM biology and metabolism rewiring, and provide promising approaches for GBM therapy.

抽象的 胶质母细胞瘤（GBM）是最致命的原发性脑肿瘤，其预后没有显着改善 过去二十年。迫切需要确定治疗GBM的有效策略，但我们唯一的部分理解 GBM生物学的作用极大地阻碍了这一进展。我们的实验室长期以来一直专注于了解GBM 生物学并最近证明，GBM重编程脂质代谢以支持其快速生长。我们 确定固醇调节元素结合蛋白-1（SREBP-1），一种调节的主转录因子 脂质合成在GBM中高度激活，对于肿瘤生长至关重要。但是，分子 激活SREBP-1的机制和癌细胞中的脂肪生成尚不清楚。而且，是否 高度激活的SREBP-1在恶性肿瘤中扮演新角色是未知的。在正常细胞中，SREBP激活为 受胰岛素诱导的基因（Insig），内质网（ER）锚定蛋白的抑制作用。它与 SREBP转运蛋白，SREBP裂解蛋白（SCAP），防止SREBP ER到GOLGI易位和 随后的激活。因此，SREBP-1激活的第一个关键步骤是与Insig的SCAP解离。如何 癌细胞能够释放出对SCAP的影响的严重抑制，以促进高水平的SREBP- 1激活仍未得到解答。最近，我们发现葡萄糖介导的N-糖基化稳定SCAP。 有趣的是，我们的新初步数据表明，在没有谷氨酰胺的情况下，SREBP-1未能裂解， 尽管SCAP仍然是糖基化的。通过抑制谷氨酰胺转化为谷氨酸和氨 抑制谷氨酰胺酶（GLS）显着降低了SREBP-1裂解。这些数据强烈表明 谷氨酰胺在SREBP-1激活中起关键作用。有趣的是，表达活跃的N末端形式 GBM细胞中的SREBP-1显着增强了谷氨酰胺的摄取。 GBM患者样本的分析表明 谷氨酰胺转运蛋白SLC1A5在肿瘤组织中高度表达，与患者成反比 生存。启动子分析显示SLC1A5启动子区域中的多个推定的SREBP-1结合位点。 基于这些新的初步数据和我们已发表的研究，我们假设SCAP与 Intig被谷氨酰胺衍生的代谢产物激活，导致SREBP-1激活。反过来，激活 SREBP-1在转录上上调SLC1A5的表达，导致前馈环至 增加谷氨酰胺摄取和脂质合成以促进GBM生长。在这项研究中，我们将确定 AIM 1中GBM中谷氨酰胺激活SREBP-1和脂肪生成的分子机制，并揭示了新的 SREBP-1在AIM 2中调节谷氨酰胺代谢中的作用。我们将进一步研究是否合并 抑制SREBP-1与SLC1A5或GLS抑制作用可抑制GBM生长的强大协同作用 （目标2）。这项研究的完成将大大提高我们对GBM生物学和代谢的理解 重新布线，并为GBM治疗提供了有希望的方法。