Perinuclear Ryanodine Receptors and Cardiac Remodeling

病理性心肌肥大的发展需要刺激基因转录， Ca 2+依赖的信号通路。然而，特异性靶向这些Ca 2+依赖性途径是困难的 这是由于Ca 2+在心肌细胞生理学中的多种功能。最近的证据表明， Ca 2+微结构域提供了允许Ca 2+信号传导特异性的分子机制。因此，我们认为， 了解每个微区的组成和调控是开发新的微区的关键。 用于预防和治疗病理性肥大的治疗剂。之前我们已经证实 Ca 2 +/钙调蛋白依赖性蛋白磷酸酶钙调神经磷酸酶（CaN）与肌肉特异性A 激酶激活蛋白mAKAPβ介导心肌细胞肥大的诱导。新数据显示， mAKAPβ信号体也是激活转录所需的核周钙瞬变所必需的 导致肌细胞肥大的因子。我们假设，一个池的核周RyR 2定位于 mAKAPβ信号体负责这种Ca 2+微结构域，重要的是，这些核周RyR 2 与参与兴奋-收缩偶联（E-C偶联）的那些分离。的中心假设 这一建议是，RyR 2定位于mAKAPb信号体诱导核周Ca 2+瞬变， CaN依赖性基因表达，在E-C偶联中不依赖于RyR 2的典型功能。目标1： 与mAKAPβ信号体相关的核周RyR 2在独立的Ca 2+信号转导中 调节肌细胞肥大的隔室。目的1的目标是证明mAKAPb- 信号体相关的RyR 2负责bAR刺激的核周Ca 2+瞬变， 肥大，并且该RyR 2库独立于参与E-C偶联的RyR 2调节。使用 新的，有针对性的激活剂和抑制剂的核周RyR 2，我们将证明的重要性， 核周RyR 2对病理基因转录的调节，并显示核周RyR 2的调节 RyR 2不影响收缩性。此外，PKA介导的RyR 2磷酸化的重要性， 将对几个地点进行调查。目的2：mAKAPβ Ca 2 +/CaN隔室的尺寸。目标2将 绘制由mAKAPb信号体指定的核周Ca 2+结构域，并证明这一点。 核周区室不影响胞浆CaN活性，但维持核周CaN活性 活动目的3：需要核周RyR 2信号传导用于体内病理性重塑。治疗 目的3将研究在心脏肥大小鼠模型中靶向核周RyR 2的潜力。 通过这些目标，该提案将定义由mAKAPb编排的新的信号传导隔室， 这是病理基因转录和诱导心脏病所必需的，但不影响E-C偶联。 此外，该项目的完成将揭示靶向mAKAPb信号体如何在治疗上 有益于预防心脏重塑和心力衰竭。

The development of pathological cardiac hypertrophy requires the stimulation of gene transcription activated by Ca2+-dependent signaling pathways. However, targeting specifically these Ca2+-dependent pathways is difficult due to the multiple functions of Ca2+ in myocyte physiology. Recent evidence suggests that formation of distinct Ca2+ microdomains provide the molecular mechanism that allows for specificity in Ca2+ signaling. Therefore, understanding the components and regulation of each microdomain is key for the development of novel therapeutics for the prevention and treatment of pathological hypertrophy. We have previously demonstrated that binding of the Ca2+/calmodulin-dependent protein phosphatase calcineurin (CaN) to the muscle-specific A Kinase Anchoring Protein mAKAPβ mediates the induction of myocyte hypertrophy. New data show that the mAKAPβ signalosome is also required for a perinuclear Ca2+ transient required for the activation of transcription factors responsible for myocyte hypertrophy. We hypothesize that a pool of perinuclear RyR2 localized to the mAKAPβ signalosome is responsible for this Ca2+ microdomain, and importantly, that these perinuclear RyR2 are segregated from those involved in excitation-contraction coupling (E-C coupling). The central hypothesis of this proposal is that RyR2 localized to mAKAPb signalosomes induces perinuclear Ca2+ transients required for CaN-dependent gene expression that are independent of the canonical function of RyR2 in E-C coupling. Aim 1: Perinuclear RyR2 associated with mAKAPβ signalosomes are within an independent Ca2+ signaling compartment that regulates myocyte hypertrophy. The goal of Aim 1 is to demonstrate that mAKAPb- signalosome associated RyR2 is responsible for bAR-stimulated perinuclear Ca2+ transients that induce myocyte hypertrophy and that this pool of RyR2 is regulated independently from RyR2 involved in E-C coupling. Using novel, targeted activators and inhibitors of the perinuclear RyR2, we will demonstrate the importance of perinuclear RyR2 for the regulation of pathological gene transcription, and show that modulation of perinuclear RyR2 does not impact contractility. Furthermore, the importance of PKA-mediated phosphorylation of RyR2 at several sites will be investigated. Aim 2: The dimensions of the mAKAPβ Ca2+/CaN compartment. Aim 2 will map the perinuclear Ca2+ domain that is specified by the mAKAPb signalosome and demonstrate that this perinuclear compartment does not affect cytosolic CaN activity, but functions to maintain perinuclear CaN activity. Aim 3: Requirement of perinuclear RyR2 signaling for pathological remodeling in vivo. The therapeutic potential of targeting perinuclear RyR2 in mouse models of cardiac hypertrophy will be investigated in Aim 3. Through these Aims, this proposal will define a novel signaling compartment orchestrated by mAKAPb that is required for pathological gene transcription and induction of cardiac disease, but does not affect E-C coupling. Furthermore, completion of this project will reveal how targeting mAKAPb signalosomes can be therapeutically beneficial in the prevention of cardiac remodeling and heart failure.