TY - JOUR
T1 - Phosphatidylinositol 3-kinase functionally compartmentalizes the concurrent Gs signaling during β2-adrenergic stimulation
AU - Jo, Su Hyun
AU - Leblais, Veronique
AU - Wang, Ping H.
AU - Crow, Michael T.
AU - Xiao, Rui Ping
N1 - Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2002/7/12
Y1 - 2002/7/12
N2 - 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 β2-adrenoceptor (β2-AR), a prototypical GPCR, activates a tightly localized protein kinase A (PKA) signaling, which regulates substrates at cell surface membranes, bypassing cytosolic target proteins (eg, phospholamban). Although a concurrent activation of β2-AR-coupled Gi proteins has been implicated in the functional compartmentation of PKA signaling, the exact mechanism underlying the restriction of the β2-AR-PKA pathway remains unclear. In the present study, we demonstrate that phosphatidylinositol 3-kinase (PI3K) plays an essential role in confining the β2-AR-PKA signaling. Inhibition of PI3K with LY294002 or wortmannin enables β2-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 β2-AR-induced CAMP formation. Blocking Gi or Gβγ signaling with pertussis toxin or βARK-ct, a peptide inhibitor of Gβγ, completely prevents the potentiating effects induced by PI3K inhibition, indicating that the pathway responsible for the functional compartmentation of β2-AR-PKA signaling sequentially involves Gi, Gβγ, and PI3K. Thus, PI3K constitutes a key downstream event of β2-AR-Gi signaling, which confines and negates the concurrent β2-AR/Gs-mediated PKA signaling.
AB - 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 β2-adrenoceptor (β2-AR), a prototypical GPCR, activates a tightly localized protein kinase A (PKA) signaling, which regulates substrates at cell surface membranes, bypassing cytosolic target proteins (eg, phospholamban). Although a concurrent activation of β2-AR-coupled Gi proteins has been implicated in the functional compartmentation of PKA signaling, the exact mechanism underlying the restriction of the β2-AR-PKA pathway remains unclear. In the present study, we demonstrate that phosphatidylinositol 3-kinase (PI3K) plays an essential role in confining the β2-AR-PKA signaling. Inhibition of PI3K with LY294002 or wortmannin enables β2-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 β2-AR-induced CAMP formation. Blocking Gi or Gβγ signaling with pertussis toxin or βARK-ct, a peptide inhibitor of Gβγ, completely prevents the potentiating effects induced by PI3K inhibition, indicating that the pathway responsible for the functional compartmentation of β2-AR-PKA signaling sequentially involves Gi, Gβγ, and PI3K. Thus, PI3K constitutes a key downstream event of β2-AR-Gi signaling, which confines and negates the concurrent β2-AR/Gs-mediated PKA signaling.
KW - Cardiac contractility
KW - Phosphatidylinositol 3-kinase
KW - Phospholamban
KW - cAMP signal compartmentation
KW - β-adrenoceptor
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U2 - 10.1161/01.RES.0000024115.67561.54
DO - 10.1161/01.RES.0000024115.67561.54
M3 - Article
C2 - 12114321
AN - SCOPUS:0037067463
VL - 91
SP - 46
EP - 53
JO - Circulation Research
JF - Circulation Research
SN - 0009-7330
IS - 1
ER -