Perinuclear Signaling and Cardiac Hypertrophy

在飞行或战斗反应中刺激b-肾上腺素能受体(BAR)可通过 蛋白激酶A(PKA)刺激肌浆网(SR)的钙离子流动。然而，长期的压力对 心脏通过增加循环中的儿茶酚胺而导致长期刺激酒吧，导致 钙离子介导的基因转录导致的病理性重塑。这些对BAR激活的不同反应 Ca~(2+)信号转导表明，心肌细胞中存在多个由bar调节的PKA活性池。我们 提示核膜内条激活PKA刺激的核周钙信号， 诱导病理性基因转录而不影响心脏收缩能力。因此，可以阻断的试剂 核棒和减弱的核周钙瞬变应防止疾病的发生和/或进展 而不影响伸缩性。我们的初步数据发现，结合在核膜上的PKA位于 支架蛋白肌肉A-激酶锚定蛋白b(MAKAPb)响应内杆启动 核周钙瞬变刺激病理性基因转录。这项提议的核心假设是 靶向mAKAPb信号体将调节b-AR介导的核PKA和钙反应，从而 诱发病理疾病，而不抑制，事实上，维持心脏的收缩能力。具体目标1： 心肌肥厚的诱导需要钙核池的刺激。为了实现这一目标，我们将 利用特定定位的钙结合蛋白依次缓冲mAKAPb刺激的核周钙池 目的：确定该心肌池在诱导成年大鼠心肌肥厚中的重要性。 使用腺相关病毒将mAKAPb靶向的Ca~(2+)“缓冲液”运送到活体心肌细胞，我们 将确定对压力超负荷和儿茶酚胺输注儿茶酚胺引起的病理重塑的影响。 重要的是，缓冲核周钙离子对收缩的影响将被研究。具体目标2： 抑制mAKAPb结合的PKA可阻断心肌肥厚的诱导。这一目标将使用工具 选择性地仅调制mAKAPb结合的PKA以证明相关的激酶既是必需的，也是必要的 足以在体外和体内诱导心肌肥大，但不调节收缩能力。特定目标 3：核棒受体与心肌肥大有关。使用药物抑制剂， MAKAP靶向纳米体，特异性抑制核b-AR激活，以及针对特定b-AR的siRNA 亚型，我们将检验这一假设，即内部的、位于核的杆状结构负责诱导心脏 肥大。然而，调节这些受体不应该影响收缩能力。通过这些目标，这 提案将定义一个由mAKAPb编排的新的信号隔间，这是病理所需的 基因转录和诱导心脏病，但不影响收缩能力。此外，完成 该项目将揭示靶向mAKAPb信号小体如何在预防 心脏重塑和心力衰竭。

Stimulation of the b-adrenergic receptor (bAR) during the flight-or-fight response increases contractility through protein kinase A (PKA)-stimulated Ca2+ fluxes at the sarcoplasmic reticulum (SR). However, chronic stress on the heart leads to long-term stimulation of the bAR by increased circulating catecholamines, resulting in pathological remodeling due to Ca2+-mediated gene transcription. These divergent responses to bAR activation and Ca2+ signaling suggests that multiples pools of bAR-regulated PKA activity exist in the cardiac myocyte. We suggest that internal bARs at the nuclear envelope activate a PKA-stimulated perinuclear Ca2+ signals that induce pathological gene transcription without affecting cardiac contractility. Therefore, reagents that can block nuclear bAR and attenuate perinuclear Ca2+ transients should prevent disease initiation and/or progression without affecting contractility. Our preliminary data finds that PKA bound to the nuclear envelope located scaffolding protein muscle A-kinase anchoring protein b (mAKAPb) responds to internal bARs to initiate perinuclear Ca2+ transients that stimulate pathological gene transcription. The central hypothesis of this proposal is that targeting mAKAPb signalosomes will modulate nuclear b-AR-mediated PKA and Ca2+ responses that induce pathological disease, without inhibiting, and in fact, maintaining cardiac contractility. Specific Aim 1: Stimulation of a nuclear pool of Ca2+ is required for induction of cardiac hypertrophy. In this Aim, we will buffer the mAKAPb-stimulated perinuclear Ca2+ pool using a specifically localized Ca2+ binging protein in order to determine the importance of this pool for induction of cardiac hypertrophy in adult rat ventricular myoytes. Using adeno-associated virus to deliver the mAKAPb-targeted Ca2+ “buffer” to the cardiac myocytes in vivo, we will determine the effect on pathological remodeling induced by pressure overload and catecholamine infusion. Importantly, the effect of buffering perinuclear Ca2+ on contractility will be investigated. Specific Aim 2: Inhibition of mAKAPb-bound PKA blocks induction of cardiac hypertrophy. This Aim will use tools that selectively modulate only mAKAPb-bound PKA to demonstrate that the associated kinase is both necessary and sufficient for induction of cardiac hypertrophy in vitro and in vivo, while not regulating contractility. Specific Aim 3: A nuclear bAR receptor is responsible for cardiac hypertrophy. Using pharmacological inhibitors, mAKAP-targeted nanobodies that inhibit specifically nuclear b-AR activation, and siRNA against specific b-AR subtypes, we will test the hypothesis that internal, nuclear located bARs are responsible for induction of cardiac hypertrophy. However, modulating these receptors should not affect contractility. 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 contractility. Furthermore, completion of this project will reveal how targeting mAKAPb signalosomes can be therapeutically beneficial in the prevention of cardiac remodeling and heart failure.