Dynamic regulation of phosphoinositide 3-kinase-γ activity and β-adrenergic receptor trafficking in end-stage human heart failure
Dynamic regulation of phosphoinositide 3-kinase-γ activity and β-adrenergic receptor trafficking in end-stage human heart failure
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DOI：
10.1161/circulationaha.107.706515
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发表时间：
2007-11-27
期刊：
影响因子：
37.8
通讯作者：
Prasad, Sathyamangla V. Naga
中科院分区：
文献类型：
--
作者：
Perrino, Cinzia;Schroder, Jacob N.;Prasad, Sathyamangla V. Naga
背景-心力衰竭条件下β-肾上腺素能受体（β AR）的下调需要受体靶向磷酸肌醇3-激酶（PI3K）-γ并将β AR重新分布到内体区室中。由于左心室辅助装置 (LVAD) 的支持可显着改善人类心脏功能，因此我们研究了机械卸载对 PI3K γ 活性调节和 β AR 细胞内分布的影响。此外，我们还测试了 PI3K γ 从激活的 β AR 中的位移是否会恢复衰竭人类心肌细胞的激动剂反应性。方法和结果 - 为了测试 PI3K 对衰竭人类心脏中 β AR 内吞作用的作用，我们在机械卸载 (LVAD) 之前和之后测定了人类左心室样本中的 PI3K 活性。在 LVAD 之前，衰竭的人类心脏表现出与 β AR 激酶 1 (β ARK1) 相关的 PI3K 活性显着增加，这完全归因于 PI3K γ 亚型的活性增强。与不匹配的非衰竭心脏相比，衰竭心脏中 β ARK1 偶联 PI3K 活性的增加与质膜上 β AR 的下调以及早期和晚期核内体的隔离增强有关。重要的是，LVAD 支持逆转 PI3K γ 激活，使质膜上激动剂反应性 β AR 的水平正常化，并耗尽内体区室中的 β AR，而不改变受体总数（质膜以及早期和晚期内体受体的总和）。为了测试 PI3K 从 β AR 复合物的竞争性置换是否恢复了受体反应性，我们在衰竭的人类心肌细胞的原代培养物中过表达 PI3K 的磷酸肌醇激酶结构域（破坏 β ARK1/PI3K 相互作用）。腺病毒介导的磷酸肌醇激酶过度表达显着增加基础收缩力并快速重建对 β 激动剂的反应性。结论 - 这些结果提出了一种新的范例，其中人类 β AR 经历了细胞内隔离过程，该过程在 LVAD 支持后动态逆转。重要的是，机械卸载导致 PI3K γ 和 β ARK1 相关 PI3K 激活完全逆转。此外，从 beta ARK1 中置换活性 PI3K 可恢复衰竭心肌细胞的 beta AR 反应性。
Background-Downregulation of beta-adrenergic receptors (beta ARs) under conditions of heart failure requires receptor targeting of phosphoinositide 3-kinase (PI3K)-gamma and redistribution of beta ARs into endosomal compartments. Because support with a left ventricular assist device (LVAD) results in significant improvement of cardiac function in humans, we investigated the effects of mechanical unloading on regulation of PI3K gamma activity and intracellular distribution of beta ARs. Additionally, we tested whether displacement of PI3K gamma from activated beta ARs would restore agonist responsiveness in failing human cardiomyocytes.Methods and Results-To test the role of PI3K on beta AR endocytosis in failing human hearts, we assayed for PI3K activity in human left ventricular samples before and after mechanical unloading (LVAD). Before LVAD, failing human hearts displayed a marked increase in beta AR kinase 1 (beta ARK1)-associated PI3K activity that was attributed exclusively to enhanced activity of the PI3K gamma isoform. Increased beta ARK1-coupled PI3K activity in the failing hearts was associated with downregulation of beta ARs from the plasma membrane and enhanced sequestration into early and late endosomes compared with unmatched nonfailing controls. Importantly, LVAD support reversed PI3K gamma activation, normalized the levels of agonist-responsive beta ARs at the plasma membrane, and depleted the beta ARs from the endosomal compartments without changing the total number of receptors (sum of plasma membrane and early and late endosome receptors). To test whether the competitive displacement of PI3K from the beta AR complex restored receptor responsiveness, we overexpressed the phosphoinositide kinase domain of PI3K (which disrupts beta ARK1/PI3K interaction) in primary cultures of failing human cardiomyocytes. Adenoviral-mediated phosphoinositide kinase overexpression significantly increased basal contractility and rapidly reconstituted responsiveness to beta-agonist.Conclusions-These results suggest a novel paradigm in which human beta ARs undergo a process of intracellular sequestration that is dynamically reversed after LVAD support. Importantly, mechanical unloading leads to complete reversal in PI3K gamma and beta ARK1-associated PI3K activation. Furthermore, displacement of active PI3K from beta ARK1 restores beta AR responsiveness in failing myocytes.