Disease relevance of ADRBK1

• The absence of relapses in GRK2(+/-) mice was associated with a marked reduction in inflammatory infiltrates in the CNS [1].
• We have shown that MC1R desensitization is mediated by two GRKs expressed in melanocytes and melanoma cells, GRK2 and GRK6 [2].
• G protein-coupled receptor kinase 2 in multiple sclerosis and experimental autoimmune encephalomyelitis [1].
• Here we describe that in leukocytes from patients with active relapsing-remitting multiple sclerosis (MS) or with secondary progressive MS, GRK2 levels are significantly reduced [1].
• This response was blocked by pertussis toxin, and by the Gbetagamma scavengers transducin and beta-adrenergic receptor kinase 1 carboxyl-terminal fragment [3].

Psychiatry related information on ADRBK1

• Dysregulation in Gs protein function is postulated and, agonist-mediated regulation of betaAR expression and/or betaAR kinase activity in PTSD should be investigated in future studies [4].
• The results indicate that opiate addiction in humans (tolerant state) is associated with down-regulation of brain micro-opioid receptors and regulatory GRK 2/6 and beta-arrestin-2 proteins [5].
• Lymphocyte G-protein-coupled receptor kinase-2 is upregulated in patients with Alzheimer's disease [6].

High impact information on ADRBK1

• Rhodopsin kinase and beta-adrenergic receptor kinase (beta ARK) are related members of a serine/threonine kinase family that specifically initiate deactivation of G-protein-coupled receptors [7].
• Highly specific receptor kinases, such as rhodopsin kinase and beta-adrenergic receptor kinase, which show stimulus-dependent phosphorylation of receptors have been described [8].
• Analysis of the ability of these mutants to regulate the activity of calcium and potassium channels, adenylyl cyclase 2, phospholipase C-beta2, and beta-adrenergic receptor kinase revealed the Gbeta residues required for activation of each effector and provides evidence for partially overlapping domains on Gbeta for regulation of these effectors [9].
• Overexpression of beta-arrestins in human embryonic kidney cells rescued the sequestration of beta 2-adrenergic receptor (beta 2AR) mutants defective in their ability to sequester, an effect enhanced by simultaneous overexpression of beta-adrenergic receptor kinase 1 [10].
• Moreover, GRK-5 but not GRK-2 inhibits KSHV-GPCR-stimulated proliferation of rodent fibroblasts [11].

Chemical compound and disease context of ADRBK1

• The full-length, cytoplasmic C-terminus of the beta 2-adrenergic receptor expressed in E. coli acts as a substrate for phosphorylation by protein kinase A, insulin receptor tyrosine kinase, GRK2, but not protein kinase C and suppresses desensitization when expressed in vivo [12].
• We report here that hydrogen peroxide downregulates GRK2 expression in C6 rat glioma cells [13].
• Cardiac-specific GRK2 knockout mice exhibited enhanced inotropic sensitivity to the beta-adrenergic receptor agonist isoproterenol, with impairment of normal inotropic and lusitropic tachyphylaxis, and exhibited accelerated development of catecholamine toxicity with chronic isoproterenol treatment [14].

Biological context of ADRBK1

• In this report, we find that beta-arrestin function and Src-mediated phosphorylation of GRK2 are critically involved in GRK2 proteolysis [15].
• This finding suggested the presence of a second Gbetagamma binding site in GRK2 [16].
• We found that Gbetagamma-activated GRK2 and GRK3 were inhibited by CaM to similar extents (IC50 approximately 2 microM), while a 50-fold more potent inhibitory effect was observed on GRK5 (IC50 = 40 nM) [17].
• Overexpression of GRK2 enhanced agonist-induced GIPR phosphorylation, but receptor endocytosis was not affected by cotransfection with GRKs or beta-arrestin-1 [18].
• The gene for beta ARK1 has been localized to human chromosome 11q13 [19].

Anatomical context of ADRBK1

• Regulation of G protein-coupled receptor kinase subtypes in activated T lymphocytes. Selective increase of beta-adrenergic receptor kinase 1 and 2 [20].
• The modulation of the CCR2B receptor by GRK2 suggests an important role for this kinase in the regulation of monocyte and lymphocyte response to chemokines [21].
• Microinjection of GRK2/3-specific mAbs into chicken sensory neurons, which have been shown to express a GRK3-like protein, abolishes desensitization of the alpha2AR-mediated calcium current inhibition [22].
• In an effort to identify proteins that regulate GRK2 function, we searched for interacting proteins by immunoprecipitation of endogenous GRK2 from HL60 cells [23].
• G protein-coupled receptor kinase 2-mediated phosphorylation of ezrin is required for G protein-coupled receptor-dependent reorganization of the actin cytoskeleton [24].

Associations of ADRBK1 with chemical compounds

• G protein-coupled receptor kinase 2 (GRK2) is a serine/threonine-specific protein kinase that mediates agonist-dependent phosphorylation of numerous G protein-coupled receptors [23].
• And indeed, the amino terminus of GRK2 (GRK2(1-185)) inhibited a Gbetagamma-stimulated inositol phosphate signal in cells, purified GRK2(1-185) suppressed the Gbetagamma-stimulated phosphorylation of rhodopsin, and GRK2(1-185) bound directly to purified Gbetagamma subunits [16].
• Bimodal regulation of the human H1 histamine receptor by G protein-coupled receptor kinase 2 [25].
• The use of various protease inhibitors suggested that GRK2 degradation induced by geldanamycin was predominantly through the proteasome pathway [23].
• Coexpression of beta-adrenergic receptor kinase (betaARK) 1 (GRK2) or 2 (GRK3) could increase epinephrine-induced phosphorylation of the wild type alpha1BAR above basal as compared to that of the receptor expressed alone [26].

Physical interactions of ADRBK1

• Cytosolic GRK activity in mononuclear cells decreased by 39 +/- 29%; cytosolic GRK2 and membrane-bound GRK6 decreased by 90 +/- 15 and 65 +/- 43%, respectively [27].
• In this study, we identify the protein G-coupled receptor kinase 2 (GRK2), a kinase involved in the desensitization of G protein-coupled receptors (GPCR), as a downstream target and regulator of the TGFbeta-signaling cascade [28].
• Our data suggest that the D3R, filamin A, and beta-arrestin form a signaling complex that is destabilized by agonist- or expression-mediated increases in GRK2/3 activity [29].
• In vitro binding assays show that the residues 498-502 of GRK2 bind the amino-terminal domain of clathrin heavy chain to almost the same extent as beta-arrestin1 [30].
• However, these mGluR1a/Galphaq/11 interactions are not antagonized by the overexpression of either GRK2 mutants defective in Galphaq/11 binding or RGS4 [31].

Enzymatic interactions of ADRBK1

• Using a mixed micelle assay, GRK2 (beta ARK1) was found to require phospholipid in order to phosphorylate the beta 2-adrenergic receptor [32].
• Mutants of AKAP79 that do not bind PKA or target to the beta2AR markedly inhibit phosphorylation of beta2AR/PKA-. We show that PKA directly phosphorylates GRK2 on serine 685 [33].
• Ser(670) is located in a peptide sequence that conforms to an ERK consensus phosphorylation sequence, and in vitro, in the presence of heparin, ERK1 phosphorylates GRK2 [34].
• We demonstrate that c-Src can directly phosphorylate GRK2 on tyrosine residues, as shown by in vitro experiments with purified proteins [35].
• Thus, the agonist-occupied PTH receptor is phosphorylated by a kinase similar or identical to GRK2 in HEK-293 cells, but this phosphorylation is not requisite for efficient receptor endocytosis [36].

Co-localisations of ADRBK1

• The beta(1)AR/GRK2 fusion protein internalizes via clathrin-coated pits and is found to co-localize with the endosome that contains transferrin [30].

Regulatory relationships of ADRBK1

• The antibody-mediated inhibition was released by purified Gbetagamma subunits, strongly suggesting that Gbetagamma binding to the amino terminus of GRK2 enhances the kinase activity toward rhodopsin [16].
• As assessed by ligand binding, the FSH-R was found expressed in the fractions where GRK 2 and beta-arrestins were recruited upon FSH treatment [37].
• Coexpression of GRK2 strongly enhanced agonist-stimulated phosphorylation of the wild-type DOR (WT), but Delta15 or mutant DOR (T358A/T361A/S363G) failed to show any detectable phosphorylation under these conditions [38].
• PDE4-selective inhibition also enhances the ability of isoprenaline to trigger the PKA phosphorylation of GRK2 in cardiac myocytes [39].
• Here we show that AKAP79 also regulates the ability of GRK2 to phosphorylate agonist-occupied receptors [33].

Other interactions of ADRBK1

• In contrast, whereas GRK2 and -3 efficiently phosphorylate alpha 2-C2-AR, GRK5 is quite weak [40].
• Overexpression of GRK2 promoted H1HR phosphorylation in intact HEK293 cells and completely inhibited inositol phosphate production stimulated by H1HR, whereas GRK5 and GRK6 had lesser effects on H1HR phosphorylation and signaling [25].
• Both cell types also express beta ARK1 and the associated inhibitory proteins beta-arrestin-1 and beta-arrestin-2, as assessed by immunoblotting [41].
• This agonist-induced beta 1AR phosphorylation derives approximately equally from PKA and GRK activity, as judged by intact cell studies with kinase inhibitors or dominant negative beta ARK1 (K220R) mutant overexpression [41].
• Our data show that the site of phosducin phosphorylation by GRK2 is different and independent from that previously reported for the cAMP-dependent protein kinase [42].
• We find that activation of the PI3K/Akt pathway by insulin-like growth factor-1 alters Mdm2-mediated GRK2 degradation, leading to enhanced GRK2 stability and increased kinase levels [43].

Analytical, diagnostic and therapeutic context of ADRBK1

• GRK2 and beta-arrestin-1 messenger RNAs were identified by Northern blot analysis to be expressed endogenously in betaTC3 and L293 cells [18].
• To identify novel nonreceptor substrates of GRK2, we used two-dimensional gel electrophoresis to find cellular proteins that were phosphorylated upon agonist-stimulation of the beta2AR in a GRK2-dependent manner [44].
• Here, molecular modeling of the Galpha(q).GRK2 complex and site-directed mutagenesis of Galpha(q) were used to identify residues in Galpha(q) that interact with GRK2 [45].
• Two-dimensional peptide mapping of PKCalpha-phosphorylated GRK2 showed a single site of phosphorylation, which was identified as serine 29 by HPLC-MS [46].
• The expression of GRK2 protein was strong in the human bladder detrusor, but was significantly weakened by western blotting in obstructed bladder in comparison with control bladder [47].

References