Solving the elusive mechanism of rapamycin action in lymphocytes

解决雷帕霉素在淋巴细胞中作用的难以捉摸的机制

• 批准号: 8285697
• 负责人: DAVID Alexander FRUMAN
• 金额: $ 19.19万
• 依托单位: UNIVERSITY OF CALIFORNIA-IRVINE
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-20 至 2014-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8285697
• 关键词: Activated Lymphocyte; Affect; Antigens; B-Lymphocytes; Binding Proteins; CCI-779; Calcineurin; Cell Cycle Progression; Cell Nucleus; Cells; Clinical; Complex; Cyclosporine; Cytokine Gene; Data; Enzymes; Event; Exploratory/Developmental Grant; FDA approved; FK506; Family; Funding; Genes; Genetic; Genetically Engineered Mouse; Goals; Growth Factor; Immune; Immune Cell Activation; Immune system; Immunology; Immunosuppression; Immunosuppressive Agents; Learning; Lymphocyte; Lymphocyte Activation; Mammalian Cell; Mammals; Metabolism; Mitogens; Modeling; Molecular Target; Mouse Strains; Names; Nutrient; Organ; Organ Transplantation; Output; Pharmaceutical Preparations; Phosphorylation; Phosphotransferases; Prevention; Process; Protein-Serine-Threonine Kinases; Proteins; Proto-Oncogene Proteins c-akt; Reagent; Regulation; Reporting; Residual state; Resources; Rewards; Ribosomal Protein S6 Kinase; Risk; Role; S Phase; Signal Transduction; Sirolimus; Skeletal Muscle; Specificity; Stress; System; T-Cell Proliferation; T-Lymphocyte; Testing; Textbooks; Tissues; Work; base; cancer cell; cell type; chemical genetics; expectation; human FRAP1 protein; inhibitor/antagonist; kinase inhibitor; leukemia; lymphocyte proliferation; mouse model; novel; prevent; protein function; response; ribosomal protein S6 kinase, 70kD, polypeptide 2

DESCRIPTION (provided by applicant): mTOR is a serine/threonine kinase that is expressed ubiquitously. The mTOR enzyme is present in two cellular complexes, TORC1 and TORC2. mTOR was discovered and named based on its interaction with the drug rapamycin. This compound is an allosteric inhibitor that partially blocks TORC1 activity and generally does not inhibit TORC2 function. Rapamycin treatment of T and B lymphocytes profoundly blocks proliferation triggered by antigen and other mitogens, and rapamycin (sirolimus; Rapamune(R)) is an FDA-approved immunosuppressant. However, rapamycin and analogs have lesser effects on proliferation in other cellular systems including cancer cells. Although the effects of rapamycin on lymphocytes have been studied for 20 years, it remains unclear why the compound induces a profound block of proliferation selectively in lymphocytes. Paradoxically, a novel class of ATP-competitive mTOR kinase inhibitors (TOR-KIs) causes less immunosuppression than rapamycin despite causing more complete inhibition of both TORC1 and TORC2. The goal of this project is to define mechanisms by which rapamycin selectively blocks proliferation of normal lymphocytes. Based on preliminary data, we propose two hypotheses that form the basis of separate specific aims. Aim 1 will test the hypothesis that rapamycin causes more complete and sustained inhibition of S6 kinases, key substrates of TORC1. There are two S6 kinases, S6K1 and S6K2, but their roles in lymphocyte activation and proliferation have not been reported. We will use a novel mouse model that will allow a chemical genetic approach to specifically inhibit S6K activity in normal T and B cells. We will use this model to compare the effects of S6K inhibition with the effects of rapamycin and TOR-KIs. Aim 2 will test the hypothesis that rapamycin inhibits kinase-independent functions of mTOR. We will generate a novel mouse strain in which kinase-dead mTOR can be expressed in a cell-specific manner. This will allow us to test the prediction that lymphocytes expressing kinase-dead mTOR will retain residual proliferation that remains sensitive to rapamycin. We will also begin a candidate approach to test possible kinase-independent mTOR functions. PUBLIC HEALTH RELEVANCE: A drug called rapamycin is used to suppress the immune system and prevent rejection of organ transplants. However, it is not known why rapamycin selectively blocks the activation of immune cells, compared to other cell types. This proposal seeks to solve this long-standing question.

描述（由申请人提供）：mTOR 是一种普遍表达的丝氨酸/苏氨酸激酶。 mTOR 酶存在于两种细胞复合物中：TORC1 和 TORC2。 mTOR 是根据其与药物雷帕霉素的相互作用而被发现并命名的。该化合物是一种变构抑制剂，可部分阻断 TORC1 活性，但通常不抑制 TORC2 功能。雷帕霉素治疗 T 和 B 淋巴细胞可显着阻断由抗原和其他有丝分裂原引发的增殖，雷帕霉素（西罗莫司；Rapamune(R)）是 FDA 批准的免疫抑制剂。然而，雷帕霉素和类似物对包括癌细胞在内的其他细胞系统的增殖影响较小。尽管人们已经研究了雷帕霉素对淋巴细胞的影响 20 年，但仍不清楚为什么该化合物会选择性地深度抑制淋巴细胞的增殖。矛盾的是，尽管一类新型 ATP 竞争性 mTOR 激酶抑制剂 (TOR-KI) 对 TORC1 和 TORC2 具有更完全的抑制作用，但其免疫抑制作用却比雷帕霉素要少。该项目的目标是确定雷帕霉素选择性阻止正常淋巴细胞增殖的机制。根据初步数据，我们提出了两个假设，这些假设构成了单独的具体目标的基础。目标 1 将检验雷帕霉素对 S6 激酶（TORC1 的关键底物）产生更完全和持续的抑制这一假设。 S6激酶有两种，S6K1和S6K2，但它们在淋巴细胞活化和增殖中的作用尚未见报道。我们将使用一种新型小鼠模型，该模型将允许化学遗传方法特异性抑制正常 T 和 B 细胞中的 S6K 活性。我们将使用该模型来比较 S6K 抑制的效果与雷帕霉素和 TOR-KI 的效果。目标 2 将检验雷帕霉素抑制 mTOR 激酶独立功能的假设。我们将产生一种新的小鼠品系，其中激酶死亡的 mTOR 可以以细胞特异性方式表达。这将使我们能够测试表达激酶死亡 mTOR 的淋巴细胞将保留对雷帕霉素敏感的残余增殖的预测。我们还将开始一种候选方法来测试可能的激酶独立性 mTOR 功能。 公众健康相关性：一种名为雷帕霉素的药物用于抑制免疫系统并防止器官移植的排斥反应。然而，与其他细胞类型相比，尚不清楚为什么雷帕霉素选择性地阻止免疫细胞的激活。该提案旨在解决这个长期存在的问题。