Phosphodiesterases coordinate cAMP propagation induced by two stimulatory G protein-coupled receptors in hearts

Abstract

Inflammation is a significant player in the progression of heart failure and has detrimental effects on cardiac function. Prostaglandin (PG)E2, a major proinflammatory prostanoid in the cardiovascular system, is a potent stimulus in inducing intracellular cAMP but minimally affects cardiac contractile function. Here, we show that the PGE2 stimulation attenuates the adrenergic-induced cardiac contractile response in animal hearts. Stimulation with PGE2 leads to stimulatory G protein (Gs)-dependent production of cAMP. However, the induced cAMP is spatially restricted because of its degradation by phosphodiesterase (PDE)4 and cannot access the intracellular sarcoplasmic reticulum (SR) for increasing calcium signaling and myocyte contraction. Moreover, pretreatment with PGE2 significantly inhibits PKA activities at the SR induced by a β-adrenergic agonist, isoproterenol, and subsequently blocks isoproterenol-induced PKA phosphorylation of phospholamban and contractile responses in myocytes. Further analysis reveals that the PGE2-induced cAMP/PKA is sufficient to phosphorylate and activate PDE4D isoforms, which, in turn, spatially inhibits the diffusion of adrenergic-induced cAMP from the plasma membrane to the SR. Inhibition of PDE4 rescues the adrenergic-induced increase in cAMP/PKA activities at the SR, PKA phosphorylation of phospholamban, and contractile responses in PGE2-pretreated myocytes. Thus, this offers an example that one Gs-coupled receptor is able to inhibit the intracellular signaling transduction initiated by another Gs-coupled receptor via controlling the diffusion of cAMP, presenting a paradigm for G protein-coupled receptor (GPCR) signal transduction. It also provides a mechanism for the integration of signaling initiated by different neurohormonal stimuli, as well as long-term effects of chronically circulating proinflammatory factors in myocardium.FRET | subcellular diffusion | cross-talk

Culture and adenoviral infection of sinoatrial node myocytes from adult mice

“…GECIs can be targeted to subcellular microdomains and have yielded much important information about localized Ca 2ϩ signaling in other types of cardiac myocytes (10,11,22,27,36). In a similar manner, tethered FRET-based cAMP sensors could be used to characterize spatio-temporal cAMP signaling associated with different GPCRs and phosphodiesterase isoforms, as has been done in other cardiac myocytes (20,23,30,37,43). cAMP sensors are of particular interest in SAMs, given the fundamental importance of cAMP signaling to sinoatrial myocyte function (15,16,41).…”

Prostaglandin E2 does not attenuate adrenergic-induced cardiac contractile response

“…In order to rule out possible agonist specific peculiarities, we used isoprenaline, the same agonist as Liu et al (2012) used in their experiments. When comparing five right ventricular trabeculae from two patients, pretreated with PGE 2 , with six ventricular trabeculae without PGE treatment, −logEC 50 values for isoprenaline did not differ (−logEC 50 PGE 2 (n=5/2) 7.06±0.35 vs. TMC (n=6/2) 7.21±0.41; p=0.81).…”

“…It showed in mice that stimulation with PGE 2 did not lead to hyperphosphorylation of the classical PKA substrate PLB but of PDE4D. As a result, not only the potency, but also the efficacy of catecholamines to stimulate force of contraction was dramatically reduced: a 2 log unit shift of the concentration-response-curve and reduction of maximum force to about 50 % of control (Liu et al 2012). From a more general view, the results were interpreted as an elegant mechanistic link between chronic inflammation and desensitization of adrenergic pathways as seen in heart failure.…”

A Long Lasting β1 Adrenergic Receptor Stimulation of cAMP/Protein Kinase A (PKA) Signal in Cardiac Myocytes

“…All procedures were approved by the Institutional Animal Care and Use Committee at the University of California at Davis. The isolated heart perfusion technique has been described previously (13). Hearts were excised from mice under anesthesia (sodium pentobarbital, 120 mg/kg body weight, intraperitoneally) and transferred rapidly to the Langendorff apparatus.…”

“…Cardiac Myocyte and Prefrontal Cortical Neuron Isolation and Adenovirus Infection-Neonatal cardiac myocytes and prefrontal cortical neurons were isolated from newborn pups lacking the ␤ 2 AR gene (␤ 2 AR-KO), the ␤ 1 AR gene (␤ 1 AR-KO), or lacking both the ␤ 1 and ␤ 2 AR genes (␤ 1 ␤ 2 AR-KO), as described previously (13,14). Cells were cultured in coverslip chambers precoated with laminin for live cell imaging.…”