Schwarz Lisa, Sharma Karan, Dodi Lorenzo D, Rieder Lara-Sophie, Fallier-Becker Petra, Casadei Nicolas, Fitzgerald Julia C
Department of Neurodegenerative Diseases, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.
Institute of Pathology and Neuropathology, University of Tübingen, Tübingen, Germany.
Front Mol Neurosci. 2022 Dec 2;15:966209. doi: 10.3389/fnmol.2022.966209. eCollection 2022.
The Rho GTPase Miro1, located at the mitochondrial outer membrane is known to properly distribute mitochondria to synapses, aid calcium buffering and initiate PINK1-Parkin mediated mitophagy. Several heterozygous /Miro1 variants were identified in sporadic Parkinson's disease patients. Miro1 R272Q is located within a calcium binding domain, but the functional outcome of this point mutation and its contribution to the development of disease are unclear. To address this, we introduced a heterozygous /Miro1 R272Q point mutation in healthy induced pluripotent stem cells. In dopaminergic neurons, Miro1 R272Q does not affect Miro1 protein levels, CCCP-induced mitophagy, nor mitochondrial movement yet causes the fragmentation of mitochondria with reduction of cristae and ATP5A. Inhibition of the mitochondrial calcium uniporter phenocopied Miro1 R272Q cytosolic calcium response to Thapsigargin in active neurons, a similar effect was observed during the calcium buffering phase in Miro1 knockdown neuroblastoma cells. Altered mitochondrial calcium regulation is associated with reduced mitochondrial respiration and reduced catecholamine neurotransmitter uptake. Synaptic changes are not coupled to dopamine distribution or dopamine transporters but are linked to Miro1 R272Q-related calcium handling the mitochondria concomitant with defective dopamine regulation at the mitochondrial surface by monoamine oxidase. We conclude that the Miro1 R272Q heterozygous point mutation dampens mitochondrial-calcium regulation and mitochondrial capacity events at the outer membrane that are sufficient to disrupt dopaminergic function.
位于线粒体外膜的Rho GTP酶Miro1已知可将线粒体正确分布到突触，协助钙缓冲并启动PINK1-帕金介导的线粒体自噬。在散发性帕金森病患者中鉴定出几种杂合的/Miro1变体。Miro1 R272Q位于钙结合域内，但这种点突变的功能结果及其对疾病发展的贡献尚不清楚。为了解决这个问题，我们在健康的诱导多能干细胞中引入了杂合的/Miro1 R272Q点突变。在多巴胺能神经元中，Miro1 R272Q不影响Miro1蛋白水平、CCCP诱导的线粒体自噬，也不影响线粒体运动，但会导致线粒体碎片化，同时嵴和ATP5A减少。抑制线粒体钙单向转运体可模拟Miro1 R272Q在活跃神经元中对毒胡萝卜素的胞质钙反应，在Miro1基因敲低的神经母细胞瘤细胞的钙缓冲阶段也观察到了类似的效果。线粒体钙调节的改变与线粒体呼吸减少和儿茶酚胺神经递质摄取减少有关。突触变化与多巴胺分布或多巴胺转运体无关，但与Miro1 R272Q相关的线粒体钙处理有关，同时单胺氧化酶在线粒体表面对多巴胺的调节存在缺陷。我们得出结论，Miro1 R272Q杂合点突变会削弱线粒体钙调节和线粒体功能，这些线粒体外膜事件足以破坏多巴胺能功能。
