TSC1-mTOR signaling and T cell tolerance

描述（由申请人提供）：T细胞耐受性不仅在预防自身免疫性疾病中至关重要，而且还有助于肿瘤耐受性。T细胞能量和调节性T细胞（Treg）是外周T细胞耐受的两种主要形式。然而，控制T细胞能量和Treg的具体机制仍然没有得到很好的理解。雷帕霉素作为免疫抑制剂已经使用了几十年。它的靶点，哺乳动物雷帕霉素靶点（mTOR），是一种丝氨酸苏氨酸激酶，通过调节营养摄取、转录、翻译、自噬和细胞存活，在多种细胞过程中起着至关重要的作用。mTOR形成两个信号复合物（mTORC1和mTORC2），具有不同的信号特性和对雷帕霉素的敏感性。最近的证据表明，mTOR是效应T细胞分化、T细胞能量、诱导调节性T细胞分化和记忆T细胞对病毒病原体反应的关键调节因子。然而，导致T细胞中mTOR激活的途径以及严格控制mTOR活性的重要性仍然知之甚少。本提案的目的是提高对mTOR信号传导的理解，以及肿瘤抑制结节复合体1 （TSC1）作为mTOR在控制T细胞耐受性中的关键调节因子的重要性。通过基因操作小鼠和细胞系模型，我们最近发现，在T细胞受体（TCR）刺激后，RasGRP1-Ras- Mek1/2-Erk1/2通路对mTORC1和mTORC2的激活至关重要。我们和其他人也证明了TSC1抑制mTORC1，但促进T细胞中的mTORC2信号传导，对正常T细胞稳态很重要。我们的主要假设是：1)TCR下游的多个信号级联控制mTOR的激活；2)TSC1是通过严格控制mTORC1和mTORC2信号传导来诱导Treg和T细胞能量的关键调节剂。有了强有力的初步数据，我们计划通过追求三个具体目标来检验我们的假设。在目的1中，我们将研究控制T细胞中mTOR激活的机制。我们将验证Erk1/2磷酸化多种底物以促进mTORC1和mTORC2激活的假设。在目标2中，我们将确定TSC1如何控制T细胞能量。在目标3中，我们将确定TSC1如何控制诱导Treg和辅助T细胞分化。这些研究将为理解mTOR信号、TSC1在T细胞中的重要性以及调节T细胞耐受性的机制提供新的见解。

DESCRIPTION (provided by applicant): T cell tolerance not only is critical in preventing autoimmune diseases but also contributes to tumor tolerance. T cell anergy and regulatory T cells (Treg) are two major forms of peripheral T cell tolerance. However, the specific mechanisms that control T cell anergy and Treg are still not well understood. Rapamycin has been utilized as an immunosuppressant for decades. Its target, the mammalian target of rapamycin (mTOR), is a serine threonine kinase that plays crucial roles in multiple cellular processes by regulating nutrient uptake, transcription, translation, autophagy, and cell survival. mTOR forms two signaling complexes (mTORC1 and mTORC2) with distinct signaling properties and sensitivities to rapamycin. Recent evidence has established mTOR as a crucial regulator for effector T cell differentiation, T cell anergy, inducible regulatory T cell differentiation, and memory T cell responses to viral pathogens. However, the pathways leading to mTOR activation in T cells and the importance of tight control of mTOR activity remain poorly understood. The objective of this proposal is to improve the understanding of mTOR signaling and the importance of the tumor suppressor tuberous complex 1 (TSC1) as a critical regulator for mTOR in the control of T cell tolerance. Using genetically manipulated mice and cell line models, we have recently revealed that the RasGRP1-Ras- Mek1/2-Erk1/2 pathway is critical for both mTORC1 and mTORC2 activation in T cells following T cell receptor (TCR) stimulation. We and others have also demonstrated that TSC1 inhibits mTORC1 but promotes mTORC2 signaling in T cells and is important for normal T cell homeostasis. Our central hypotheses for this proposal are 1) multiple signaling cascades downstream of the TCR control mTOR activation and 2) TSC1 is a critical regulator for inducible Treg and T cell anergy by tight contro of mTORC1 and mTORC2 signaling. With strong preliminary data, we plan to test our hypotheses by pursuing three specific aims. In aim 1, we will investigate the mechanisms that control mTOR activation in T cells. We will test the hypothesis that Erk1/2 phosphorylate multiple substrates to promote mTORC1 and mTORC2 activation. In aim 2, we will determine how TSC1 controls T cell anergy. In aim 3, we will determine how TSC1 controls inducible Treg and helper T cell differentiation. The proposed studies will provide new insight into the understanding of mTOR signaling, the importance of TSC1 in T cells, and the mechanisms modulating T cell tolerance.