Fine-tuning of mitochondrial Complex I activity in CD8 cells

总结 代谢是CD 8 T细胞免疫应答的关键因素。线粒体代谢对于 CD 8细胞的功能。因此，增强线粒体呼吸的策略可用于改善 CD 8细胞免疫应答的功效。然而，尽管有许多药理学试剂 抑制电子传递链和/或合成线粒体ATP的不同步骤， 线粒体活动并不容易。我们最近发现了MCJ（甲基化控制的J蛋白，也 称为DnaJC 15）作为复合物I和线粒体呼吸的内源性负调节剂。我们有 显示MCJ的丧失导致复合物I活性、MMP、线粒体呼吸和ATP水平增加 CD 8细胞MCJ缺失引起的线粒体呼吸增加也会增强细胞因子分泌 作为细胞毒活性。因此，发现MCJ如何与复合物I相互作用以及它如何被调节可能会导致新的 破坏这种代谢制动的策略。MCJ的N-末端区域（N-MCJ）与已知的MCJ没有同源性。 真核生物的蛋白质，但它保留了特定的序列，只存在于细菌蛋白质从不同的 α-变形菌门。有趣的是，这些细菌蛋白具有氧化还原酶活性，类似于 复合物I NADH脱氢酶。N-MCJ与NDUFv 1相互作用，NDUFv 1是复合物I的亚基，其含有N-MCJ。 将NADH氧化成NAD+的NADH脱氢酶活性。我们最近的计算分析， 质谱表明N-MCJ可以结合NAD+。我们提出了一个模型，MCJ作为一个动态的 复合物I的负调节物，NAD+作为传感器。当活性物质产生的NAD+水平 复合物I升高，NAD+结合N-MCJ。NAD+与N-MCJ的结合然后引起结构变化 这使得N-MCJ可以与NDUFv 1相互作用，并向复合物I提供负反馈， 减弱其活性并避免过度消耗有限的代谢底物。我们将调查：1） NAD+与N-MCJ的结合及其对N-MCJ构象变化的影响; N-MCJ与NDUFv 1，其微调NAD+和线粒体呼吸的影响。从这些 研究可能会导致新的策略和机制的发展，以安全地增加线粒体 呼吸的CD 8细胞和增强免疫反应。

SUMMARY Metabolism is a key factor for CD8 T cell immune response. Mitochondria metabolism is essential for effector function of CD8 cells. Thus, strategies to enhance mitochondrial respiration could be used to improve efficacy of CD8 cell immune response. However, while there are a number of pharmacological reagents inhibiting different steps of the electron transport chain and/or synthesis mitochondrial ATP, enhancing mitochondrial activity is not easy. We have recently identified MCJ (Methylation-Controlled J protein, also called DnaJC15) as an endogenous negative regulator of Complex I and mitochondrial respiration. We have shown that loss of MCJ results in increased Complex I activity, MMP, mitochondrial respiration and ATP levels in CD8 cells. Increased mitochondrial respiration caused by loss of MCJ enhances cytokine secretion as well as cytotoxic activity. Thus, finding how MCJ interacts with Complex I and how it is regulated could lead to new strategies to disrupt this metabolic brake. The N-terminal region of MCJ (N-MCJ) has no homology to known eukaryotic proteins, but it retains specific sequence present only in bacterial proteins from different Alphaproteobacteria species. Interestingly, those bacterial proteins have an oxidoreductase activity, similarly to Complex I NADH dehydrogenase. N-MCJ interacts with NDUFv1, the subunit of Complex I that contains the NADH dehydrogenase activity to oxidize NADH to NAD+. Our recent computational analysis together with mass spectrometry suggest that N-MCJ can bind NAD+. We propose a model where MCJ acts as a dynamic negative regulator of Complex I with NAD+ as a sensor. When NAD+ levels produced by an active Complex I are elevated, NAD+ binds N-MCJ. Binding of NAD+ to N-MCJ then causes a structural change that makes N-MCJ accessible to interact with NDUFv1, and provide a negative feedback to Complex I to attenuate its activity and avoid overconsumption of limited metabolic substrates. We will investigate: 1) The binding of NAD+ to N-MCJ and its effect on N-MCJ conformational changes; 2) The dynamic interaction of N-MCJ with NDUFv1, its fine-tuning by NAD+ and the impact in mitochondrial respiration. Results from these studies could lead to the development of novel strategies and mechanisms to safely increase mitochondrial respiration in CD8 cells and enhance immune responses.