Cohen Henry M, Gottschalk Benjamin, Choya-Foces Carmen, Chathoff Adam, Wilkinson Anya, Garbincius Joanne F, Johnson Adyson, Stevens Tyler L, Howe Jordan E, Megill Emily, Ngo Jennyfer, Tomar Dhanendra, Snyder Nathaniel W, Graier Wolfgang F, Elrod John W
Aging + Cardiovascular Discovery Center, Lewis Katz School of Medicine at Temple University, Philadelphia, PA.
Gottfried Schatz Research Center, Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria.
Res Sq. 2025 Jun 26:rs.3.rs-6346822. doi: 10.21203/rs.3.rs-6346822/v1.
Mitochondrial matrix Ca concentration ([Ca]) is theorized to be an essential regulator of mitochondrial metabolism by positively regulating key mitochondrial dehydrogenases. However, ablation or functional inhibition of the mitochondrial calcium uniporter channel (mtCU) fails to significantly perturb basal metabolism and is largely phenotypically silent in the absence of stress. This begs the question, what are the primary molecular mechanisms regulating calcium-dependent changes in metabolism? The primary function of MICU proteins (MICU1, MICU2, and MICU3) is reported to be gatekeeping of the mtCU and regulating mitochondrial Ca uptake. Here, we demonstrate that MICU proteins function in coordination to impart Cadependent regulation to FADH-dependent mitochondrial dehydrogenases through metabolon formation independent of the mtCU and [Ca]. Our results demonstrate that MICU proteins differentially localize to mitochondrial microdomains and form heterodimers and interactomes in response to intermembrane space Ca binding their respective EF-hand domains. Utilizing an equimolar expression platform coupled with unbiased proteomics we reveal unique interactomes for MICU1/2 versus MICU1/3 heterodimers and demonstrate that MICU proteins control coupling of Mitochondrial Glycerol-3-Phosphate Dehydrogenase with Succinate Dehydrogenase/Complex II and impart Cadependent changes in activity. We propose that MICU-mediated mitochondrial metabolons are a fundamental system facilitating matching of mitochondrial energy production with cellular demand and is the primary physiological Ca signaling mechanism regulating homeostatic energetics - not mtCU-dependent changes in [Ca].
线粒体基质钙浓度（[Ca]）被认为是线粒体代谢的重要调节因子，它通过正向调节关键的线粒体脱氢酶来实现这一功能。然而，线粒体钙单向转运通道（mtCU）的缺失或功能抑制并不会显著干扰基础代谢，并且在没有应激的情况下，其表型在很大程度上是沉默的。这就引出了一个问题，调节代谢中钙依赖性变化的主要分子机制是什么？据报道，MICU蛋白（MICU1、MICU2和MICU3）的主要功能是作为mtCU的守门人并调节线粒体对钙的摄取。在这里，我们证明MICU蛋白协同发挥作用，通过独立于mtCU和[Ca]的代谢体形成，对依赖FADH的线粒体脱氢酶赋予钙依赖性调节。我们的结果表明，MICU蛋白差异定位于线粒体微区，并响应膜间隙钙结合其各自的EF手结构域而形成异二聚体和相互作用组。利用等摩尔表达平台结合无偏蛋白质组学，我们揭示了MICU1/2与MICU1/3异二聚体的独特相互作用组，并证明MICU蛋白控制线粒体甘油-3-磷酸脱氢酶与琥珀酸脱氢酶/复合体II的偶联，并赋予活性的钙依赖性变化。我们提出，MICU介导的线粒体代谢体是一个基本系统，有助于使线粒体能量产生与细胞需求相匹配，并且是调节稳态能量学的主要生理钙信号传导机制——而不是mtCU依赖性的[Ca]变化。
