TOR Complex 2 and sphingolipid biosynthesis.

我们的长期目标是了解细胞 真核细胞中的生长受控制，特别是受雷帕霉素敏感的 Tor激酶。最近在几个实验室进行的研究，包括我自己的，已经 证明了TOR作为两种不同蛋白质复合体的一部分发挥作用， TORC1和TORC2，其中TORC1唯一地被雷帕霉素抑制。 雷帕霉素被证明有许多有益的治疗应用，包括 作为一种潜在的抗癌治疗方法，人们对此非常感兴趣 更多地了解TOR的细胞作用。因为它不是直接的 然而，作为雷帕霉素的靶点，TORC2的细胞作用仍然很大 没有TORC1那么好的特征。相应地，替代方法有 需要研究TORC2。为此，我们最近发现，一个 TORC2特定成分中的突变会显著影响最早的 鞘磷脂途径的步骤，特别是新形成的 发芽酵母中的神经酰胺。最近，我们扩大了这一观察范围 到哺乳动物细胞，我们已经证明抑制mTORC2在 HEK393T细胞还导致神经酰胺酶活性降低 合成酶。神经酰胺及其直接前体，长脂肪酸 链碱基(LCB)，代表越来越多人认识的脂类 在恶性细胞生长、肿瘤形成以及衰老过程中起着至关重要的作用。 因此，TOR和神经酰胺的生物合成都是重要的重要领域 对于生物医学研究，我们的发现第一次表明，他们是 紧密联系在一起。 在这里提出的实验中，我们将确定 神经酰胺的合成受到TORC2的调节，包括对 神经酰胺合成酶，并将开始描绘参与的信号通路 这项规定。为此，我们将使用酵母和哺乳动物细胞作为 互补的实验系统。我们还将解决以下角色 MTORC2信号在某些癌细胞对 化疗药物，已知的增加从头合成 神经酰胺，并通过诱导这些药物的细胞杀伤作用 神经酰胺介导的细胞凋亡。

Our long-term goal is to understand the molecular mechanisms by which cell growth is controlled in eukaryotic cells, in particular by the rapamycin-sensitive TOR kinase. Recent studies in several laboratories, including my own, have demonstrated that TOR functions as part of two distinct protein complexes, TORC1 and TORC2, where TORC1 is uniquely inhibited by rapamycin. Rapamycin is proving to have many beneficial therapeutic applications, including as a potential anti-cancer treatment, and so there is great interest in understanding more about the cellular role of TOR. Because it is not a direct target for rapamycin, however, the cellular role of TORC2 has remained much less well characterized than TORC1. Accordingly, alternative approaches are needed to study TORC2. To this end, we have discovered recently that a mutation within a TORC2-specific component affects dramatically the earliest steps of the sphingolipid pathway, in particular the de novo formation of ceramides, in budding yeast. More recently, we have extended this observation to mammalian cells, where we have shown that inhibiting mTORC2 function in HEK393T cells also leads to a reduction in the activity of the enzyme ceramide synthase. Ceramides, as well as their immediate precursors, the fatty acid long chain bases (LCBs), represent classes of lipids that are increasingly recognized as playing crucial roles in malignant cell growth, tumorigenesis, as well as aging. Thus, both TOR and ceramide biosynthesis represent important areas important for biomedical research, and our findings indicate for the first time that they are intimately linked. In the experiments proposed here, we will identify the mechanism by which ceramide synthesis is regulated by TORC2, including a detailed analysis of the ceramide synthase, and will begin to delineate the signaling pathway involved in this regulation. For this purpose, we will use both yeast and mammalian cells as complementary experimental systems. We will also address the role that mTORC2 signaling plays in the response of certain cancer cells to chemotherapeutic drugs, which are known to increase the de novo synthesis of ceramides and contribute to the cell killing action of these drugs by inducing ceramide-mediated apoptosis.