Mdm2 regulates cardiac contractility by inhibiting GRK2-mediated desensitization of β-adrenergic receptor signaling
Mdm2 regulates cardiac contractility by inhibiting GRK2-mediated desensitization of β-adrenergic receptor signaling
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DOI：
10.1172/jci.insight.95998
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发表时间：
2017-09-07
期刊：
影响因子：
8
通讯作者：
Shenoy, Sudha K.
中科院分区：
文献类型：
--
作者：
Jean-Charles, Pierre-Yves;Yu, Samuel Mon-Wei;Shenoy, Sudha K.
癌蛋白Mdm 2是一种含有RING结构域的E3泛素连接酶，其泛素化G蛋白偶联受体激酶2（GRK 2）和β-抑制蛋白2，从而调节β-肾上腺素能受体（β AR）信号传导和内吞作用。以前的研究表明，心脏Mdm 2的表达是控制早期胚胎发育过程中p53依赖性细胞凋亡的关键，但Mdm 2在发达的成人心脏的作用是未知的。我们的目的是确定Mdm 2是否影响成年小鼠的β AR信号传导和心脏功能。使用存活9-12个月的Mdm 2/p53-KO小鼠，我们确定了Mdm 2在成年小鼠心脏中通过调节心脏β 1AR信号传导的关键和潜在的新作用。虽然Mdm 2/p53-KO和野生型（WT）小鼠的基线心脏功能基本相似，但与WT小鼠相比，Mdm 2/p53-KO中异丙肾上腺素诱导的心脏收缩力显著减弱。异丙肾上腺素增加WT小鼠左心室cAMP，但Mdm 2/p53-KO小鼠无此作用。此外，虽然在分离的Mdm 2/p53-KO和WT心肌细胞中基础和毛喉素诱导的钙处理是等效的，但在Mdm 2/p53-KO中异丙肾上腺素诱导的钙处理受损。Mdm 2/p53-KO心脏表达的GRK 2比WT多2倍。在Mdm 2/p53-KO心脏中，通过赖氨酸-48键的GRK 2多聚泛素化显著减少。在成年小鼠中，他莫昔芬诱导的心肌细胞特异性Mdm 2缺失也导致GRK 2显著增加，并导致心脏功能严重受损，死亡率高，且检测不到β AR反应性。使用腺相关病毒9（AAV 9）体内Mdm 2或GRK 2-CT的基因递送有效地挽救了Mdm 2/p53-KO中β 1AR诱导的心肌收缩力。这些发现揭示了Mdm 2在成人心脏中的关键p53非依赖性生理作用，即调节GRK 2介导的β AR信号脱敏。
The oncoprotein Mdm2 is a RING domain-containing E3 ubiquitin ligase that ubiquitinates G protein-coupled receptor kinase 2 (GRK2) and beta-arrestin2, thereby regulating beta-adrenergic receptor (beta AR) signaling and endocytosis. Previous studies showed that cardiac Mdm2 expression is critical for controlling p53-dependent apoptosis during early embryonic development, but the role of Mdm2 in the developed adult heart is unknown. We aimed to identify if Mdm2 affects beta AR signaling and cardiac function in adult mice. Using Mdm2/p53-KO mice, which survive for 9-12 months, we identified a critical and potentially novel role for Mdm2 in the adult mouse heart through its regulation of cardiac beta 1AR signaling. While baseline cardiac function was mostly similar in both Mdm2/p53-KO and wild-type (WT) mice, isoproterenol-induced cardiac contractility in Mdm2/p53-KO was significantly blunted compared with WT mice. Isoproterenol increased cAMP in left ventricles of WT but not of Mdm2/p53-KO mice. Additionally, while basal and forskolin-induced calcium handling in isolated Mdm2/p53-KO and WT cardiomyocytes were equivalent, isoproterenol-induced calcium handling in Mdm2/p53-KO was impaired. Mdm2/p53-KO hearts expressed 2-fold more GRK2 than WT. GRK2 polyubiquitination via lysine-48 linkages was significantly reduced in Mdm2/p53-KO hearts. Tamoxifen-inducible cardiomyocyte-specific deletion of Mdm2 in adult mice also led to a significant increase in GRK2, and resulted in severely impaired cardiac function, high mortality, and no detectable beta AR responsiveness. Gene delivery of either Mdm2 or GRK2-CT in vivo using adeno-associated virus 9 (AAV9) effectively rescued beta 1AR-induced cardiac contractility in Mdm2/p53-KO. These findings reveal a critical p53-independent physiological role of Mdm2 in adult hearts, namely, regulation of GRK2-mediated desensitization of beta AR signaling.