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

基本信息

批准号：
10553204
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
项目类别：
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/10553204
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 Promotion Tumor Tissue Valine Withdrawal Xenograft Model alpha ketoglutarate amino acid metabolism cancer cell glycosylation improved in vivo insight lipid biosynthesis lipid metabolism novel prevent programs promoter rapid growth synergism trafficking transcription factor tumor growth uptake

项目摘要

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，其预后在20世纪90年代至今没有明显改善。过去二十年。迫切需要找到治疗 GBM 的有效策略，但我们的认识还很片面 GBM 生物学的研究极大地阻碍了这一进展。我们实验室长期致力于了解GBM 生物学，最近证明 GBM 重新编程脂质代谢以支持其快速生长。我们确定了甾醇调节元件结合蛋白-1 (SREBP-1)，一种主转录因子调节脂质合成在 GBM 中高度激活，对于肿瘤生长至关重要。然而，分子激活癌细胞中 SREBP-1 和脂肪生成的机制仍不清楚。此外，无论是高度激活的SREBP-1在恶性肿瘤中发挥的新作用尚不清楚。在正常细胞中，SREBP 激活是受到胰岛素诱导基因 (Insig)（一种内质网 (ER) 锚定蛋白）的强烈抑制。它绑定到 SREBP 转运蛋白、SREBP 裂解蛋白 (SCAP)，防止 SREBP ER 至高尔基体易位，后续激活。因此，SREBP-1 激活的第一个关键步骤是 SCAP 从 Insig 解离。如何癌细胞能够释放 Insig 对 SCAP 的严格抑制，从而促进高水平的 SREBP- 1 个激活仍未得到答复。我们最近发现葡萄糖介导的 N-糖基化可以稳定 SCAP。有趣的是，我们新的初步数据表明，在没有谷氨酰胺的情况下，SREBP-1 无法被裂解，尽管SCAP仍然是糖基化的。抑制谷氨酰胺转化为谷氨酸和氨抑制谷氨酰胺酶 (GLS) 显着减少 SREBP-1 裂解。这些数据强烈表明谷氨酰胺在 SREBP-1 激活中发挥着关键作用。有趣的是，表达活性 N 端形式 GBM 细胞中的 SREBP-1 显着增强谷氨酰胺的摄取。 GBM 患者样本分析表明谷氨酰胺转运蛋白 SLC1A5 在肿瘤组织中高表达，与患者的病情呈负相关生存。启动子分析显示 SLC1A5 启动子区域有多个假定的 SREBP-1 结合位点。根据这些新的初步数据和我们发表的研究，我们假设 SCAP 与 Insig 被谷氨酰胺衍生的代谢物激活，导致 SREBP-1 激活；依次激活 SREBP-1 转录上调 SLC1A5 的表达，从而形成前馈循环增加谷氨酰胺摄取和脂质合成，促进 GBM 生长。在本研究中，我们将确定目标 1 中的 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在目标2中调节谷氨酰胺代谢中的作用。我们将进一步检查是否结合抑制 SREBP-1 与 SLC1A5 或 GLS 抑制一起提供强大的协同作用来抑制 GBM 生长（目标 2）。这项研究的完成将显着增进我们对 GBM 生物学和代谢的理解重新布线，并为 GBM 治疗提供有前景的方法。