Phosphatidylinositol 3-kinase functionally compartmentalizes the concurrent Gs signaling during β2-adrenergic stimulation
Phosphatidylinositol 3-kinase functionally compartmentalizes the concurrent Gs signaling during β2-adrenergic stimulation
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DOI：
10.1161/01.res.0000024115.67561.54
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发表时间：
2002-07-12
影响因子：
20.1
通讯作者：
Xiao, RP
中科院分区：
文献类型：
--
作者：
Jo, SH;Leblais, V;Xiao, RP
细胞内信号通路的区隔是赋予G蛋白偶联受体(GPCR)信号特异性的重要机制。在心脏，刺激β(2)-肾上腺素能受体(β(2)-AR)是一种典型的GPCR，它激活了一个紧密定位的蛋白激酶A(PKA)信号，该信号调节细胞表面膜上的底物，绕过胞浆靶蛋白(Ca，磷蛋白)。尽管β(2)-AR偶联G蛋白的同时激活参与了PKA信号的功能区隔，但限制β(2)-AR-PKA通路的确切机制仍不清楚。在本研究中，我们证明了磷脂酰肌醇3-激酶(PI3K)在限制β(2)-AR-PKA信号转导中起着重要作用。用LY294002或Wortmannin抑制PI3K可以使β(2)-AR-PKA信号到达细胞内底物，表现为磷蛋白磷酸化的强劲增加，并显著增强受体介导的心肌细胞正性收缩和舒张反应。PI3K抑制剂的这些增强作用并不伴随着β(2)-AR诱导的cAMP形成的增加。用百日咳毒素或GOT的多肽抑制剂BetaARK-ct阻断G或GOT信号，可完全阻断PI3K抑制所引起的增强效应，表明参与β(2)-AR-PKA信号功能区划的通路依次涉及G(I)、Gbetagamma和PI3K。因此，PI3K构成了β(2)-AR-G信号通路的关键下游事件，限制和否定了同时存在的β(2)-AR/G(S)介导的PKA信号通路。
Compartmentation of intracellular signaling pathways serves as an important mechanism conferring the specificity of G protein-coupled receptor (GPCR) signaling. In the heart, stimulation Of beta(2)-adrenoceptor (beta(2)-AR), a prototypical GPCR, activates a tightly localized protein kinase A (PKA) signaling, which regulates substrates at cell surface membranes, bypassing cytosolic target proteins (ca, phospholamban). Although a concurrent activation of beta(2)-AR-coupled G, proteins has been implicated in the functional compartmentation of PKA signaling, the exact mechanism underlying the restriction of the beta(2)-AR-PKA pathway remains unclear. In the present study, we demonstrate that phosphatidylinositol 3-kinase (PI3K) plays an essential role in confining the beta(2)-AR-PKA signaling. Inhibition of PI3K with LY294002 or wortmannin enables beta(2)-AR-PKA signaling to reach intracellular substrates, as manifested by a robust increase in phosphorylation of phospholamban, and markedly enhances the receptor-mediated positive contractile and relaxant responses in cardiac myocytes. These potentiating effects of PI3K inhibitors are not accompanied by an increase in beta(2)-AR-induced cAMP formation. Blocking G, or GOT signaling with pertussis toxin or betaARK-ct, a peptide inhibitor of GOT, completely prevents the potentiating effects induced by PI3K inhibition, indicating that the pathway responsible for the functional compartmentation Of beta(2)-AR-PKA signaling sequentially involves G(i), Gbetagamma, and PI3K. Thus, PI3K constitutes a key downstream event of beta(2)-AR-G, signaling, which confines and negates the concurrent beta(2)-AR/G(s)-mediated PKA signaling.