Regulation of Mitochondrial Fission/Fusion by PP2A and PKA in Neurons

描述（由申请人提供）：线粒体提供能量，缓冲钙，并隔离细胞死亡诱导分子，线粒体功能障碍涉及各种神经病理学。特别是在神经元中，线粒体是高度动态的细胞器，不断移动，分裂和融合。该提议研究神经元中线粒体分裂和融合的调节，这是由类似于发动蛋白的大GTP酶进行的拮抗过程。其中两种酶Opal和Mfn 2的突变是遗传性神经系统疾病的原因。虽然线粒体融合和断裂的适当平衡对于神经元存活显然是重要的，但一些断裂对于线粒体的轴突和树突运输是必要的，因此对于突触的发育和功能也是必要的。我们已经发现，线粒体的形状变化是由一个相对的蛋白激酶和磷酸酶，通过特定的靶向/调节亚基定位到线粒体外膜控制。在磷酸酶方面，Bp 2是一种神经元特异性的、出生后诱导的蛋白磷酸酶2A（PP 2A）调节亚基，在脊髓小脑共济失调12型中突变。选择性剪接的Bp 2的N末端介导PP 2A全酶易位到线粒体表面，其中PP 2A加速细胞死亡，显然是通过破碎线粒体。对抗PP 2A/Bp 2对线粒体形态和存活的影响的激酶是通过A激酶锚定蛋白（AKAP）121锚定到OMM的cAMP依赖性蛋白激酶（PKA）。目的1探讨线粒体外PP 2A和PKA调控神经元存活的机制。在目标2中，我们将确定线粒体分裂/融合酶之间的相关底物和磷酸化位点。目的3解决了PP 2A/PKA依赖的线粒体重组的线粒体的交付和树突棘的发展中的作用。最后，目的4描述了PP 2A/Bp 2基因敲除小鼠的线粒体和突触形态以及对缺血性损伤的抗性。这些研究将促进我们对线粒体形状转变如何调节的理解，以及这如何影响神经元的脆弱性和它们之间功能连接的建立。我们的研究可能最终导致更好的治疗中风和神经退行性疾病。

DESCRIPTION (provided by applicant): Mitochondria provide energy, buffer calcium, and sequester cell death-inducing molecules, and mitochondrial dysfunction is implicated in various neuropathologies. Especially in neurons, mitochondria are highly dynamic organelles that constantly move, divide, and fuse. This proposal investigates the regulation of mitochondrial fission and fusion in neurons, which are antagonistic processes carried out by large GTPases similar to dynamin. Mutations in two of these enzymes, Opal and Mfn2, are responsible for hereditary neurological diseases. While a proper balance of mitochondrial fusion and fragmentation is clearly important for neuronal survival, some fragmentation is necessary for axonal and dendritic transport of mitochondria, and consequently for the development and function of synapses. We have found that shape changes of mitochondria are controlled by an opposing protein kinase and phosphatase that are localized to the outer mitochondrial membrane via specific targeting/regulatory subunits. On the phosphatase side, Bp2 is a neuron-specific, postnatally induced protein phosphatase 2A (PP2A) regulatory subunit mutated in spinocerebellar ataxia type 12. The alternatively spliced N terminus of Bp2 mediates translocation of the PP2A holoenzyme to the mitochondrial surface, where PP2A accelerates cell death, apparently by fragmenting mitochondria. The kinase opposing PP2A/Bp2's effect on mitochondrial morphology and survival is cAMP-dependent protein kinase (PKA) anchored to the OMM via A kinase anchoring protein (AKAP)121. Aim 1 investigates the mechanism by which outer-mitochondrial PP2A and PKA control neuronal survival. In Aim 2, we will identify the relevant substrates and phosphorylation sites among mitochondrial fission/fusion enzymes. Aim 3 addresses the role of PP2A/PKA-dependent mitochondrial restructuring in the delivery of mitochondria to and development of dendritic spines. Finally, Aim 4 characterizes PP2A/Bp2 knockout mice in terms of mitochondria and synapse morphology and resistance to ischemic injury. These studies will advance our understanding of how shape transitions of mitochondria are regulated, and how this affects vulnerability of neurons and the establishment of functional connections between them. Our studies may ultimately lead to better therapies for stroke and neurodegenerative disorders.