β-Arrestin2-mediated inotropic effects of the angiotensin II type 1A receptor in isolated cardiac myocytes

Nitric oxide (NO) and hydrogen peroxide (H 2 O 2 ) are synthesized within cardiac myocytes and play key roles in modulating cardiovascular signaling. Cardiac myocytes contain both the endothelial (eNOS) and neuronal (nNOS) NO synthases, but the differential roles of these NOS isoforms and the interplay of reactive oxygen species and reactive nitrogen species in cardiac signaling pathways are poorly understood. Using a recently developed NO chemical sensor [Cu 2 ðFL2EÞ] to study adult cardiac myocytes from wild-type, eNOS null , and nNOS null mice, we discovered that physiological concentrations of H 2 O 2 activate eNOS but not nNOS. H 2 O 2 -stimulated eNOS activation depends on phosphorylation of both the AMPactivated protein kinase and kinase Akt, and leads to the robust phosphorylation of eNOS. Cardiac myocytes isolated from mice infected with lentivirus expressing the recently developed H 2 O 2 biosensor HyPer2 show marked H 2 O 2 synthesis when stimulated by angiotensin II, but not following β-adrenergic receptor activation. We discovered that the angiotensin-II-promoted increase in cardiac myocyte contractility is dependent on H 2 O 2 , whereas β-adrenergic contractile responses occur independently of H 2 O 2 signaling. These studies establish differential roles for H 2 O 2 in control of cardiac contractility and receptor-dependent NOS activation in the heart, and they identify new points for modulation of NO signaling responses by oxidant stress.

Section: Resultsmentioning

confidence: 72%

Hydrogen peroxide differentially modulates cardiac myocyte nitric oxide synthesis

Sartoretto

Kalwa

Pluth

et al. 2011

“…Treatment of rVSMCs with either SDF-1α or ITAC did not result in intracellular calcium flux, a response that would be expected for activation of either CXCR4 or CXCR3 (Fig. 3C) (compared to a positive control of angiotensin, a well-characterized G α q-coupled receptor) (23). Thus, we conclude that ITAC binds CXCR7 alone without any activation of G proteins, and SDF-1α binds to both CXCR4 and CXCR7, resulting in G α i activation, albeit with minimal signaling through a typical G α i-coupled pathway.…”

Section: Cxcr7 Recruitment Of β-Arrestin Is Associated With Phosphoerkmentioning

confidence: 78%

β-arrestin- but not G protein-mediated signaling by the “decoy” receptor CXCR7

Rajagopal

Kim

Ahn

et al. 2009

Self Cite

531

561

Ubiquitously expressed seven-transmembrane receptors (7TMRs) classically signal through heterotrimeric G proteins and are commonly referred to as G protein-coupled receptors. It is now recognized that 7TMRs also signal through β-arrestins, which act as versatile adapters controlling receptor signaling, desensitization, and trafficking. Most endogenous receptors appear to signal in a balanced fashion using both β-arrestin and G protein-mediated pathways. Some 7TMRs are thought to be nonsignaling “decoys” because of their inability to activate typical G protein signaling pathways; it has been proposed that these receptors act to scavenge ligands or function as coreceptors. Here we demonstrate that ligand binding to the decoy receptor CXCR7 does not result in activation of signaling pathways typical of G proteins but does activate MAP kinases through β-arrestins in transiently transfected cells. Furthermore, we observe that vascular smooth muscle cells that endogenously express CXCR7 migrate to its ligand interferon-inducible T-cell alpha chemoattractant (ITAC), an effect that is significantly attenuated by treatment with either a CXCR7 antagonist or β-arrestin depletion by siRNA. This example of an endogenous “β-arrestin-biased” 7TMR that signals through β-arrestin in the absence of G protein activation demonstrates that some 7TMRs encoded in the genome have evolved to signal through β-arrestin exclusively and suggests that other receptors that are currently thought to be orphans or decoys may also signal through such nonclassical pathways.

“…Other studies have shown that β-arrestins and GRK6 are overexpressed in mouse and monkey models of PD (43,44), and that lentiviral-mediated overexpression of GRK6 in rodent and monkey models of PD reduces LIDs (30). GRK6, which lies upstream of β-arrestins in the GPCR signaling cascade, presumably promotes β-arrestin-dependent signaling (45)(46)(47). Therefore, we reasoned that βarr2 might play a critical role in the mechanism of L-DOPA therapy in PD.…”

Section: Resultsmentioning

confidence: 95%

Targeting β-arrestin2 in the treatment ofl-DOPA–induced dyskinesia in Parkinson’s disease

Urs¹,

Bido

Peterson³

et al. 2015

100

105

Parkinson's disease (PD) is characterized by severe locomotor deficits and is commonly treated with the dopamine (DA) precursor L-3,4-dihydroxyphenylalanine (L-DOPA), but its prolonged use causes dyskinesias referred to as L-DOPA-induced dyskinesias (LIDs). Recent studies in animal models of PD have suggested that dyskinesias are associated with the overactivation of G proteinmediated signaling through DA receptors. β-Arrestins desensitize G protein signaling at DA receptors (D1R and D2R) in addition to activating their own G protein-independent signaling events, which have been shown to mediate locomotion. Therefore, targeting β-arrestins in PD L-DOPA therapy might prove to be a desirable approach. Here we show in a bilateral DA-depletion mouse model of Parkinson's symptoms that genetic deletion of β-arrestin2 significantly limits the beneficial locomotor effects while markedly enhancing the dyskinesia-like effects of acute or chronic L-DOPA treatment. Viral rescue or overexpression of β-arrestin2 in knockout or control mice either reverses or protects against LIDs and its key biochemical markers. In other more conventional animal models of DA neuron loss and PD, such as 6-hydroxydopamine-treated mice or rats and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated nonhuman primates, β-arrestin2 overexpression significantly reduced dyskinesias while maintaining the therapeutic effect of L-DOPA. Considerable efforts are being spent in the pharmaceutical industry to identify therapeutic approaches to block LIDs in patients with PD. Our results point to a potential therapeutic approach, whereby development of either a genetic or pharmacological intervention to enhance β-arrestin2-or limit G protein-dependent D1/D2R signaling could represent a more mechanistically informed strategy.is a major catecholamine neurotransmitter that is released by midbrain DA neurons. DA activates G protein-coupled receptors (GPCRs), which belong to the dopamine D1 (D1R and D5R) or D2 (D2R, D3R, and D4R) class of DA receptors that are known to signal via G protein-dependent mechanisms (1, 2). However, recent studies have shown that in addition to G protein-mediated signaling, many GPCRs, including DA receptors, signal through beta-arrestin 1 and 2 (βarr1 and βarr2)-dependent mechanisms (3, 4). The two isoforms of β-arrestin, β-arrestin1 (βarr1) and β-arrestin2 (βarr2) are widely coexpressed in the brain (5, 6). β-Arrestins were originally appreciated for their ability to desensitize (i.e., turn off) GPCR signaling in a GPCR kinase (GRK)-dependent manner (7,8). Binding of β-arrestin to the GPCR sterically hinders G protein binding and in most instances initiates receptor endocytosis via interactions with adaptor protein complex-2 (AP-2) and clathrin (9-11). It is now appreciated that β-arrestins regulate physiology and behaviors independently of G protein signaling through their ability to scaffold multiple intracellular signaling molecules such as kinases and phosphatases (3,4,12,13). Studies from our laboratory have shown that through ...