Modulation of Mitofusin Activity to Treat Heart Disease

线粒体“连接性”和线粒体-内质网/肌浆网（ER/SR）“接近性” 通过多种机制增强尿道介导的代谢和坏死。线粒体融合素（MFN） 1和2是在线粒体连接和线粒体-ER/SR中起关键作用的大GTP酶 接近MFN 1和MFN 2存在于线粒体外膜，在那里它们介导线粒体内的 核聚变MFN 2，而不是MFN 1，也存在于ER/SR膜上，在那里它将ER/SR束缚到线粒体上 通过与脑内定位的MFN 1或MFN 2的相互作用。MFN 1或MFN 2的缺失降低了心肌 在缺血/再灌注（I/R）期间的梗塞（MI）大小。相反，MFN 1和MFN 2过表达增加了 新陈代谢.鉴于这一信息，治疗性抑制MFN有望减少梗死面积 而治疗性激活MFN可能通过增强代谢来减轻心力衰竭（HF）。 面临的挑战是找到一种手段来操纵内源性最惠国的活动。协同 其他人，我们创造了第一个肽和小分子，调节MFN 1和MFN 2的构象， 描绘了这些影响的潜在结构基础。我们以前报道过，最惠国激活剂增加， 而MFN抑制剂减少，线粒体融合。这些都是需要这些代理绑定的直接影响 MFN 1或MFN 2。我们在这里提出的新数据表明，MFN激活剂增加，而MFN抑制剂， 减少，线粒体-ER/SR接近和Ca ~（2+）向线粒体转移。此外，我们注意到， 心肌I/R期间，激活剂加重梗死面积，而MFN抑制剂减少两个心脏的梗死面积 和脑I/R模型有趣的是，激活剂的这些作用依赖于MFN 2，而不是MFN 1， 这表明MFN-ER/SR接近的重要性，但不排除MFN 2- 线粒体连接性和形状的依赖性变化也有贡献。此外，MFN活化剂 促进心肌细胞代谢。本项目的目标是了解最惠国待遇 调节剂影响心肌细胞死亡和代谢，并测试这些药物是否可能提供新的 MI和HF的治疗策略。我们建议：1.将MFN激活/抑制的变化与 成年人线粒体连接性、线粒体-ER/SR邻近性、Ca 2+转移、细胞死亡和代谢 心肌细胞2.为了描述线粒体连接和线粒体- ER/SR接近体内心肌细胞的细胞死亡和代谢。3.评估米托融合素 调节剂为MI和HF提供了新的治疗策略。该项目在定义 MFN调节剂影响心肌细胞死亡和代谢的机制以及MFN是否提供 一种针对MI和HF的新型疗法的可操作靶标。

Mitochondrial “connectivity” and mitochondrial-endoplasmic/sarcoplasmic reticulum (ER/SR) “proximity” each potentiate mitochondrial-mediated metabolism and necrosis through a variety of mechanisms. Mitofusins (MFN) 1 and 2 are large GTPases that play critical roles in mitochondrial connectivity and mitochondrial-ER/SR proximity. MFN1 and MFN2 reside in the outer mitochondrial membrane where they mediate mitochondrial fusion. MFN2, but not MFN1, also resides in the ER/SR membrane, where it tethers ER/SR to mitochondria through interactions with mitochondrial-localized MFN1 or MFN2. Deletion of MFN1 or MFN2 reduces myocardial infarct (MI) size during ischemia/reperfusion (I/R). Conversely, MFN1 and MFN2 overexpression augment metabolism. Given this information, therapeutic inhibition of MFNs would be expected to reduce infarct size during MI, while therapeutic activation of MFNs might attenuate heart failure (HF) by augmenting metabolism. The challenge has been to find a means to manipulate the activities of endogenous MFNs. In collaboration with others, we created the first peptides and small molecules that modulate conformations of MFN1 and MFN2 and delineated the underlying structural basis for these effects. We reported previously that MFN activators increase, while MFN inhibitors decrease, mitochondrial fusion. These are direct effects that require binding of these agents to either MFN1 or MFN2. We present here new data showing that MFN activators increase, while MFN inhibitors decrease, mitochondrial-ER/SR proximity and Ca2+ transfer to mitochondria. Moreover, we observed that MFN activators exacerbate infarct size during myocardial I/R, while MFN inhibitors reduce infarct size in both heart and brain I/R models. Interestingly, these effects of the activators are dependent on MFN2, but not MFN1, suggesting the importance of mitochondrial-ER/SR proximity but not excluding the possibility that MFN2- dependent changes in mitochondrial connectivity and shape also contribute. Additionally, MFN activators promote cardiomyocyte metabolism. The goals of this project are to understand the mechanisms by which MFN modulators impact cardiomyocyte death and metabolism and to test whether these agents might provide novel therapeutic strategies for MI and HF. We propose: 1. To correlate changes in MFN activation/inhibition with mitochondrial connectivity, mitochondrial-ER/SR proximity, Ca2+ transfer, cell death, and metabolism in adult cardiomyocytes. 2. To delineate the individual contributions of mitochondrial connectivity and mitochondrial- ER/SR proximity to cell death and metabolism in cardiomyocytes in vivo. 3. To assess whether mitofusin modulators provide novel therapeutic strategies for MI and HF. This project breaks new ground in defining the mechanisms by which MFN modulators impact cardiomyocyte death and metabolism and whether MFNs provide an actionable target for novel therapies directed against MI and HF.