Perinuclear Ryanodine Receptors and Cardiac Remodeling

病理性心肌肥厚的发生需要基因转录的刺激。 依赖于钙离子的信号通路。然而，特别针对这些钙依赖途径是困难的。 由于Ca~(2+)在心肌细胞生理中具有多种功能。最近的证据表明，截然不同的 Ca~(2+)微域提供了在Ca~(2+)信号转导中实现特异性的分子机制。因此， 了解每个微域的组成和调节是小说发展的关键 防治病理性肥厚的治疗学。我们之前已经演示过 钙/钙调蛋白依赖性蛋白磷酸酶钙调神经磷酸酶(CaN)与肌特异性A的结合 激酶锚定蛋白mAKAPβ介导诱导心肌细胞肥大。新数据显示， 转录激活所需的核周钙瞬变也需要mAKAPβ信号体 导致心肌细胞肥大的因素。我们假设一个核周RyR2池定位于 MAKAPβ信号小体负责这个钙微域，更重要的是，这些核周RyR2 与参与兴奋-收缩耦合(E-C耦合)的那些是分开的。的中心假说 这一假设是RyR2定位于mAKAPb信号体诱导核周钙瞬变所需的 依赖于CaN的基因表达不依赖于RyR2在E-C偶联中的典型功能。目标1： 与β信号小体相关的核周RyR2是一个独立的钙信号转导系统 调节心肌细胞肥大的隔室。目标1的目标是证明mAKAPb- 信号小体相关的RyR2负责bar刺激的核周钙瞬变，从而诱导心肌细胞 肥大和RyR2池的调节独立于参与E-C偶联的RyR2。vbl.使用 新的、靶向的核周RyR2激活剂和抑制剂，我们将论证 核周RyR2用于调控病理基因转录，并显示核周的调控 RyR2不影响收缩能力。此外，PKA介导的RyR2磷酸化的重要性在 将对几个地点进行调查。目的2：mAKAPβ钙/钙离子间隔膜的大小。目标2将 绘制由mAKAPb信号体指定的核周围钙结构域，并证明这 核周隔区不影响胞浆CaN活性，但维持核周CaN的功能 活动。目的3：体内病理重塑需要核周RyR2信号。治疗性 靶向核周RyR2在小鼠心肌肥厚模型中的可能性将在Aim 3中进行研究。 通过这些目标，该提案将定义一个由mAKAPb编排的新的信令间隔，即 病理基因转录和心脏病诱导所需的，但不影响E-C偶联。 此外，该项目的完成将揭示靶向mAKAPb信号体的治疗方法。 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.