Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Heart failure (HF) remains a significant and increasing cause of worldwide morbidity and mortality. HF is less a disease than a common clinical endpoint resulting from diverse, but often co-existing etiologies-including hypertension, coronary artery disease, and viral cardiomyopathy. Regardless of the pathologic trigger, HF can be characterized by a series of specific, molecular changes in the diseased myocardium. Noteworthy among these changes are alterations in the beta-adrenergic receptor (betaAR) signaling cascade. betaARs belong to the larger family of G-protein-coupled receptors (GPCRs) and modulate cardiac function by controlling the inotropic and chronotropic response to catecholamines. betaARs, in turn, are regulated by GPCR kinases (GRKs). GRKs phosphorylate betaARs, blocking downstream-signaling cascades and ultimately desensitizing the receptor to further catecholamine stimuli. Recent advances in transgenic mouse and gene therapy techniques have led to therapeutic strategies by manipulating betaAR signaling, specifically through the inhibition of the beta-adrenergic receptor kinase (betaARK1 or GRK2), the predominant myocardial GRK. The purpose of this manuscript, then, is to review (1). the changes that occur to betaAR-signaling pathways in HF, (2). the evidence from transgenic murine studies examining the consequences of betaARK1 manipulation in the failing heart, and (3). the effectiveness of in vivo applications of betaARK1-targeted gene therapy at ameliorating HF.
J Mol Cell Cardiol 2003 Oct
PMID:The beta-adrenergic receptor kinase in heart failure. 1451 24

Agonist-stimulated desensitization of the beta2-adrenergic receptor (beta2AR) is caused by both a potent cAMP-dependent protein kinase (PKA)-mediated phosphorylation and a less potent, occupancy-dependent, G protein-coupled receptor kinase (GRK)-mediated phosphorylation that leads to beta-arrestin binding and internalization. In this study the kinetics of phosphorylation of the third intracellular loop PKA site Ser262 and the putative C-tail GRK sites Ser355, Ser356 of the human beta2AR overexpressed in human embryonic kidney (HEK) 293 cells were characterized using phosphoserine-specific antibodies. Specificity of the antibodies was shown by their lack of reactivity with mutant beta2ARs lacking the respective sites. In addition, overexpression of GRK2 and GRK5 increased basal levels of phosphorylation of the GRK sites Ser355, Ser356 in both COS-7 and HEK 293 cells. Epinephrine, prostaglandin E1, and forskolin at maximum concentrations stimulated phosphorylation of the beta2AR PKA site (Ser262) by 4-fold, whereas PMA stimulated it by 2-fold. Epinephrine stimulated PKA site phosphorylation with an EC50 of 20 to 40 pM. In contrast, epinephrine stimulated GRK site phosphorylation (Ser355,Ser356) with an EC50 of 200 nM (1-min treatments), which is more than 4000-fold higher relative to PKA site phosphorylation, consistent with an occupancy-driven process. After 10 to 30 min, the EC50 for epinephrine stimulation of GRK site phosphorylation was reduced to 10 to 20 nM but was still approximately 200-fold greater than for the PKA site. The EC50 for internalization correlated with GRK site phosphorylation and showed a similar shift with time of epinephrine stimulation. The kinetics of epinephrine-stimulated GRK site phosphorylation were not altered in a mutant of the beta2AR lacking the PKA consensus sites. The initial levels (2 min) of a range of agonist-stimulated GRK site phosphorylations were correlated with their efficacy for activation of adenylyl cyclase, namely epinephrine > or = formoterol = fenoterol > terbutaline = zinterol = albuterol > salmeterol > dobutamine > or = ephedrine. However, after 20 to 30 min of treatment, agonists with intermediate strengths, such as albuterol and salmeterol, stimulate GRK site phosphorylations that are approximately equal to that produced by epinephrine, and the correlation breaks down. The GRK and PKA site antibodies were also effective in detecting phosphorylation of the endogenous beta2AR expressed in A431 human epidermoid carcinoma cells. To summarize, our results show a remarkable amplification of PKA site phosphorylation relative to the putative GRK site phosphorylation, heterologous stimulation of the PKA site phosphorylation, no dependence of GRK site phosphorylation on PKA sites, and a reasonable correlation of initial levels of GRK site phosphorylation with the strength of a range of agonists.
Mol Pharmacol 2004 Jan
PMID:Characterization of agonist stimulation of cAMP-dependent protein kinase and G protein-coupled receptor kinase phosphorylation of the beta2-adrenergic receptor using phosphoserine-specific antibodies. 1472 51

Although the oxytocin receptor (OTR) mediates many important functions including uterine contractions, milk ejection, and maternal behavior, the mechanisms controlling agonist-induced OTR desensitization have remained unclear, and attempts to demonstrate involvement of a G protein-coupled receptor kinase (GRK) have so far failed. Using the OTR as a model, we demonstrate here directly for the first time the dynamics of agonist-induced interactions of a GRK with a G protein-coupled receptor in real time, using time-resolved bioluminescence resonance energy transfer. GRK2/receptor interactions started within 4 sec, peaked at 10 sec, and decreased to less than 40% within 8 min. By contrast, beta-arrestin/OTR interactions initiated only at 10 sec, reached plateau levels at 120 sec, but remained stable with little decrease thereafter. Physical GRK2/OTR association was further demonstrated by coimmunoprecipitation of endogenous GRK2 with activated OTR. In COS-7 cells, which express low levels of GRK2 and beta-arrestin, overexpression of GRK2 and beta-arrestin increased receptor phosphorylation, desensitization, and internalization to the high levels observed in human embryonic kidney 293 cells. By contrast, specific inhibition of endogenous GRK2 by dominant-negative mutants robustly inhibited OTR phosphorylation and internalization as well as arrestin/OTR interactions. These data characterize the temporal and causal relationship of GRK-2/OTR and beta-arrestin/OTR interactions and establish GRK/OTR interaction as a prerequisite for beta-arrestin-mediated OTR desensitization.
Mol Endocrinol 2004 May
PMID:Real-time detection of interactions between the human oxytocin receptor and G protein-coupled receptor kinase-2. 1497 24

In the heart, beta -adrenergic receptors (beta ARs), members of the superfamily of G protein-coupled receptors (GPCRs), modulate cardiac responses to catecholamines. beta AR signaling, which is compromised in many cardiac diseases (e.g., congestive heart failure), is regulated by GPCR kinases (GRKs). Levels of the most abundant cardiac GRK, known as GRK2 or beta AR kinase 1 (beta ARK1), are increased in both animal and human heart failure. Transgenic mouse models have demonstrated that beta ARK1 plays a vital role in cardiac function and development, as well as in the regulation of myocardial signaling, and pharmacological studies have further implicated GRKs in the impairment of cardiac GPCR signaling. Gene therapy, along with the development of small-molecule modulators of GRK activity, has indicated in multiple animal models that the manipulation of GRK activity may elicit therapeutic benefits in many forms of cardiac disease.
Mol Interv 2003 Aug
PMID:Phosphorylation of G protein-coupled receptors: GPCR kinases in heart disease. 1499 40

In this study, we characterized the effects of activation of cyclic AMP-dependent protein kinase (PKA) on the internalization and functional coupling of the metabotropic glutamate receptor (mGluR1) splice variants mGluR1a and mGluR1b. Using an enzyme-linked immunosorbent assay technique to assess receptor internalization, we found that the glutamate-induced internalization of mGluR1a or mGluR1b transiently expressed in human embryonic kidney (HEK) 293 cells was inhibited by coactivation of endogenous beta2-adrenoceptors with isoprenaline or by direct activation of adenylyl cyclase with forskolin. The PKA inhibitor N-(2-[p-bromocinnamylamino]ethyl)-5-isoquinolinesulfonamide hydrochloride (H89) blocked the effects of both isoprenaline and forskolin. The heterologous internalization of the mGluR1 splice variants triggered by carbachol was also inhibited by isoprenaline and forskolin in a PKA-sensitive fashion, whereas the constitutive (agonist-independent) internalization of mGluR1a was inhibited only modestly by PKA activation. Using inositol phosphate (IP) accumulation in cells prelabeled with [3H]inositol to assess receptor coupling, PKA activation increased basal IP accumulation in mGluR1a receptor-expressing cells and also increased glutamate-stimulated IP accumulation in both mGluR1a- and mGluR1b-expressing cells, but only at short times of glutamate addition. Furthermore, PKA activation completely blocked the carbachol-induced heterologous desensitization of glutamate-stimulated IP accumulation in both mGluR1a- and mGluR1b-expressing cells. In coimmunoprecipitation experiments, the ability of glutamate to increase association of GRK2 and arrestin-2 with mGluR1a and mGluR1b was inhibited by PKA activation with forskolin. Together, these results indicate that PKA activation inhibits the agonist-induced internalization and desensitization of mGluR1a and mGluR1b, probably by reducing their interaction with GRK2 and nonvisual arrestins.
Mol Pharmacol 2004 Jun
PMID:Activation of cyclic AMP-dependent protein kinase inhibits the desensitization and internalization of metabotropic glutamate receptors 1a and 1b. 1515 43

Heart failure (HF) represents one of the leading causes of morbidity and mortality in developed nations today. Although this disease process represents a final common endpoint for several entities, including hypertension, coronary artery disease, and cardiomyopathy, a predominant characteristic of end-stage HF is an altered beta-adrenergic receptor signaling cascade. In the heart, beta-adrenergic receptors (beta ARs), members of the superfamily of G-protein-coupled receptors (GPCRs), modulate cardiac function by controlling chronotropic, inotropic, and lusitropic responses to catecholamines of the sympathetic nervous system. In HF, beta ARs are desensitized and downregulated in a maladaptive response to chronic stimulation. This process is largely mediated by G-protein-coupled receptor kinases (GRKs), which phosphorylate GPCRs leading to functional uncoupling. The most abundant cardiac GRK, known as GRK2 or beta AR kinase 1 (beta ARK1), is increased in human HF, and has been implicated in the pathogenesis of dysfunctional cardiac beta AR signaling. The association of beta ARs and GRKs with impaired cardiac function has been extensively studied using transgenic mouse models, which have demonstrated that beta ARK1 plays a vital role in the regulation of myocardial beta AR signaling. These findings have caused beta ARs and GRKs to be regarded as potential therapeutic targets, and gene therapy strategies have been used to manipulate the beta AR signaling pathway in myocardium, leading to improved function in the compromised heart. Ultimately, these genetic modifications of the heart may represent new potential therapies for human HF.
J Mol Cell Cardiol 2004 Jul
PMID:Genetic manipulation of myocardial beta-adrenergic receptor activation and desensitization. 1524 31

Attenuation of CRH receptor type 1 (CRH-R1) signaling activity might involve desensitization and uncoupling of CRH-R1 from intracellular effectors. We investigated the desensitization of native CRH-R in human myometrial cells from pregnant women and recombinant CRH-R1alpha stably overexpressed in human embryonic kidney (HEK) 293 cells. In both cell types, CRH-R1-mediated adenylyl cyclase activation was susceptible to homologous desensitization induced by pretreatment with high concentrations of CRH. Time course studies showed half-maximal desensitization occurring after approximately 40 min of pretreatment and full recovery of CRH-R1alpha functional response within 2 h of removal of CRH pretreatment. In HEK 293 cells, desensitization of CRH-R1alpha was associated with receptor phosphorylation and subsequent endocytosis. To analyze the mechanism leading to CRH-R1alpha desensitization, we overexpressed a truncated beta-arrestin (319-418) and performed coimmunoprecipitation and G protein-coupled receptor kinase (GRK) translocation studies. We found that GRK3 and GRK6 are the main isoforms that interact with CRH-R1alpha, and that recruitment of GRK3 requires Gbetagamma-subunits as well as beta-arrestin. Site-directed mutagenesis of Ser and Thr residues in the CRH-R1alpha C terminus, identified Thr399 as important for GRK-induced receptor phosphorylation and desensitization.We conclude that homologous desensitization of CRH-R1alpha involves the coordinated action of multiple GRK isoforms, Gbeta gamma dimers and beta-arrestin. Based on our identification of key amino acid(s) for GRK-dependent phosphorylation, we demonstrate the importance of the CRH-R1alpha carboxyl tail for regulation of receptor activity.
Mol Endocrinol 2005 Feb
PMID:Regulation of corticotropin-releasing hormone receptor type 1alpha signaling: structural determinants for G protein-coupled receptor kinase-mediated phosphorylation and agonist-mediated desensitization. 1549 32

Heart failure is a leading cause of hospitalization worldwide. No major significant improvements in prognosis have been achieved for heart failure over the last several decades despite advances in disease management. Heart failure itself represents a final common endpoint for several disease entities, including hypertension and coronary artery disease. On a molecular level, certain biochemical features remain common to failing myocardium. Among these are alterations in the beta-adrenergic receptor (beta-AR) signaling cascade. Recent advances in transgenic and gene therapy techniques have presented novel therapeutic strategies for management of heart failure via genetic manipulation of beta-AR signaling including the targeted inhibition of the beta-AR kinase (betaARK1 or GRK2). In this review, we will discuss the beta-AR signaling changes that accompany heart failure as well as corresponding therapeutic strategies. We will then review the evidence from transgenic mouse work supporting the use of beta-AR manipulation in the failing heart and more recent in vivo applications of gene therapy directed at reversing or preventing heart failure.
Mol Cell Biochem 2004 Aug
PMID:Genetic and phenotypic targeting of beta-adrenergic signaling in heart failure. 1552 62

G protein-coupled receptor kinases (GRKs) mediate desensitization of agonist-occupied G protein-coupled receptors (GPCRs). Here we report that GRK5 contains a DNA-binding nuclear localization sequence (NLS) and that its nuclear localization is regulated by GPCR activation, results that suggest potential nuclear functions for GRK5. As assessed by fluorescence confocal microscopy, transfected and endogenous GRK5 is present in the nuclei of HEp2 cells. Mutation of basic residues in the catalytic domain of GRK5 (between amino acids 388 and 395) results in the nuclear exclusion of the mutant enzyme (GRK5(Delta)(NLS)), demonstrating that GRK5 contains a functional NLS. The nuclear localization of GRK5 is subject to dynamic regulation. Calcium ionophore treatment or activation of Gq-coupled muscarinic-M3 receptors promotes the nuclear export of the kinase in a Ca(2+)/calmodulin (Ca(2+)/CaM)-dependent fashion. Ca(2+)/CaM binding to the N-terminal CaM binding site of GRK5 mediates this effect. Furthermore, GRK5, but not GRK5(Delta)(NLS) or GRK2, binds specifically and directly to DNA in vitro. Consistent with their presence in the nuclei of transfected cells, all the GRK4, but not GRK2, subfamily members contain putative NLSs. These results suggest that the GRK4 subfamily of GRKs may play a signaling role in the nucleus and that GRK4 and GRK2 subfamily members perform divergent cellular functions.
Mol Cell Biol 2004 Dec
PMID:G protein-coupled receptor kinase 5 contains a DNA-binding nuclear localization sequence. 1554 28

G-protein-coupled receptor kinases (GRKs) are involved in cardiac hypertrophy and failure. But their temporal expression and cellular localization during the development of hypertrophy and its transition to failure remains to be investigated. In this study, we determined the expression and subcellular distribution of GRK2, GRK3, GRK5, and GRK6 in cardiac myocytes of 2- to 24-month-old spontaneously hypertensive heart failure (SHHF) rats. GRK2 increased in the intercalated disks in 6-, 12-, and 24-month-old SHHF rats, although total expression remained relatively constant from 2 to 24 months in both SHHF and normotensive rats. GRK3 expression progressively increased in 6-, 12-, and 24-month-old SHHF rats and was significantly higher than in age-matched controls. Immunolabeling of GRK3 showed a typical pattern of cross-striations that colocalized with alpha-actinin and G(alphas) at Z-lines in both SHHF and control rats. GRK5 expression showed no change from 2 to 24 months in both SHHF and normotensive rats. Confocal analysis revealed nuclear translocation of GRK5 in myocytes of SHHF rats. GRK6 had a striated pattern colocalized with alpha-actinin at Z-lines in the cytoplasm and was also present in the intercalated disks of cardiac myocytes from both SHHF and control rats. GRK6 expression increased in 12- and 24-month-old SHHF rats and was significantly higher than in age-matched controls. GRK6 labeling was reduced at the intercalated disks, but increased in the cytoplasm of cardiac myocytes from SHHF rats compared to age-matched controls. The increased expression of GRK3 and GRK6 and subcellular redistribution of GRK2, GRK5, and GRK6 in SHHF rats may be involved in abnormal remodeling of cardiac myocytes in hypertensive hypertrophy and failure.
Anat Rec A Discov Mol Cell Evol Biol 2005 Jan
PMID:Myocardial expression and redistribution of GRKs in hypertensive hypertrophy and failure. 1558 34


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