G protein-coupled receptor kinase 2 (GRK2) as a multifunctional signaling hub (original) (raw)
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British Journal of Pharmacology, 2010
GRK2 is a ubiquitous member of the G protein-coupled receptor kinase (GRK) family that appears to play a central, integrative role in signal transduction cascades. GRKs participate together with arrestins in the regulation of G protein-coupled receptors (GPCR), a family of hundreds of membrane proteins of key physiological and pharmacological importance, by triggering receptor desensitization from G proteins and GPCR internalization, and also by helping assemble macromolecular signalosomes in the receptor environment acting as agonist-regulated adaptor scaffolds, thus contributing to signal propagation. In addition, emerging evidence indicates that GRK2 can phosphorylate a growing number of non-GPCR substrates and associate with a variety of proteins related to signal transduction, thus suggesting that this kinase could also have diverse 'effector' functions. We discuss herein the increasing complexity of such GRK2 'interactome', with emphasis on the recently reported roles of this kinase in cell migration and cell cycle progression and on the functional impact of the altered GRK2 levels observed in several relevant cardiovascular, inflammatory or tumour pathologies. Deciphering how the different networks of potential GRK2 functional interactions are orchestrated in a stimulus, cell type or context-specific way is critical to unveil the contribution of GRK2 to basic cellular processes, to understand how alterations in GRK2 levels or functionality may participate in the onset or development of several cardiovascular, tumour or inflammatory diseases, and to assess the feasibility of new therapeutic strategies based on the modulation of the activity, levels or specific interactions of GRK2. GRK2 interactome and novel cellular functions 822 P Penela et al British Journal of Pharmacology (2010) 160 821-832 GRK2 interactome and novel cellular functions 832 P Penela et al British Journal of Pharmacology (2010) 160 821-832
Biochimica Et Biophysica Acta-biomembranes, 2007
G protein-coupled receptor kinases (GRKs) and arrestins are key participants in the canonical pathways leading to phosphorylation-dependent GPCR desensitization, endocytosis, intracellular trafficking and resensitization as well as in the modulation of important intracellular signaling cascades by GPCR. Novel studies have revealed a phosphorylation-independent desensitization mechanism operating through their RGShomology (RH) domain and the recent determination of the crystal structures of GRK2 and GRK6 has uncovered interesting details on the structure-function relationships of these kinases. Emerging evidence indicates that the activity of GRKs is tightly modulated by mechanisms including phosphorylation by different kinases and interaction with several cellular proteins such as calmodulin, caveolin or RKIP. In addition, GRKs are involved in multiple interactions with non-receptor proteins (PI3K, Akt, GIT or MEK) that point to novel GRK cellular roles. In this article, our purpose is to describe the ever increasing map of functional interactions for GRK proteins as a basis to better understand its contribution to cellular processes.
G protein-coupled receptor kinase 2 (GRK2): mechanisms of regulation and physiological functions
FEBS Letters, 1998
G protein-coupled receptor kinase 2 (GRK2) plays a key role in determining the rate and extent of G protein-coupled receptor (GPCR) desensitization and resensitization. Recent data indicate that GRK2 activity, subcellular distribution and expression are tightly regulated. The important physiological function of GRK2 as a modulator of the efficacy of GPCR signal transduction systems is exemplified by its relevance in cardiovascular physiopathology as well as by its emerging role in the regulation of chemokine receptors.
FEBS Letters, 2002
G protein-coupled receptor kinase 2 (GRK2) phosphorylates G protein-coupled receptors resulting in uncoupling from G proteins. Receptors modulate GRK2 expression, however the mechanistic basis for this effect is largely unknown. Here we report a novel mechanism by which receptors use the extracellular signal-regulated kinase (ERK) cascade to regulate GRK2 cellular levels. ERK activation by receptor stimulation elevated endogenous GRK2 while antagonist treatment decreased cellular GRK2. Activating ERK by overexpressing constitutive active MEK-1 or Ras elevated GRK2 protein levels while blocking ERK using PD98059 or dominant negative Ras abolished this effect. These data suggest ERK is a critical regulator of GRK2 levels. ß 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.
Journal of Biological Chemistry, 2014
Background: Activation of GRK2 requires interaction with agonist-occupied GPCRs. Results: Residues on the GRK2 N terminus and kinase domain extension collaborate to create a GPCR docking site. Conclusion: Three GRK subfamilies use similar determinants to create the putative docking site, but subtle differences may dictate selectivity. Significance: Mapping the GRK-GPCR interface is required to understand the mechanism and specificity of GRK activation, and, therefore, the regulation of GPCRs. G protein-coupled receptor kinases (GRKs) phosphorylate agonist-occupied receptors initiating the processes of desensitization and -arrestin-dependent signaling. Interaction of GRKs with activated receptors serves to stimulate their kinase activity. The extreme N-terminal helix (␣N), the kinase small lobe, and the active site tether (AST) of the AGC kinase domain have previously been implicated in mediating the allosteric activation. Expanded mutagenesis of the ␣N and AST allowed us to further assess the role of these two regions in kinase activation and receptor phosphorylation in vitro and in intact cells. We also developed a bioluminescence resonance energy transfer-based assay to monitor the recruitment of GRK2 to activated ␣ 2A-adrenergic receptors (␣ 2A ARs) in living cells. The bioluminescence resonance energy transfer signal exhibited a biphasic response to norepinephrine concentration, suggesting that GRK2 is recruited to G␥ and ␣ 2A AR with EC 50 values of 15 nM and 8 M, respectively. We show that mutations in ␣N (L4A, V7E, L8E, V11A, S12A, Y13A, and M17A) and AST (G475I, V477D, and I485A) regions impair or potentiate receptor phosphorylation and/or recruitment. We suggest that a surface of GRK2, including Leu 4 , Val 7 , Leu 8 , Val 11 , and Ser 12 , directly interacts with receptors, whereas residues such as Asp 10 , Tyr 13 , Ala 16 , Met 17 , Gly 475 , Val 477 , and Ile 485 are more important for kinase domain closure and activation. Taken together with data on GRK1 and GRK6, our data suggest that all three GRK subfamilies make conserved interactions with G protein-coupled receptors, but there may be unique interactions that influence selectivity.
G-Protein–Coupled Receptor Kinase 2 as a Potential Modulator of the Hallmarks of Cancer
Molecular Pharmacology, 2016
Malignant features-such as sustained proliferation, refractoriness to growth suppressors, resistance to cell death or aberrant motility, and metastasis-can be triggered by a variety of mutations and signaling adaptations. Signaling nodes can act as cancer-associated factors by cooperating with oncogenegoverned pathways or participating in compensatory transduction networks to strengthen tumor properties. G-protein-coupled receptor kinase 2 (GRK2) is arising as one of such nodes. Via its complex network of connections with other cellular proteins, GRK2 contributes to the modulation of basic cellular functionssuch as cell proliferation, survival, or motility-and is involved in metabolic homeostasis, inflammation, or angiogenic processes. Moreover, altered GRK2 levels are starting to be reported in different tumoral contexts and shown to promote breast tumorigenesis or to trigger the tumoral angiogenic switch. The ability to modulate several of the hallmarks of cancer puts forward GRK2 as an oncomodifier, able to modulate carcinogenesis in a cell-type specific way.
Mechanisms of regulation of the expression and function of G protein-coupled receptor kinases
Cellular Signalling, 2003
G protein-coupled receptor kinases (GRKs) are key modulators of G protein-coupled receptor signalling. Increasing evidence points to the occurrence of complex mechanisms able to modulate the subcellular localization, activity and expression levels of GRKs, revealing new functional interactions of these kinases with different cellular proteins and transduction cascades. GRK activity and subcellular targeting is tightly regulated by interaction with receptor domains, G protein subunits, lipids, anchoring proteins, caveolin and calcium-sensing proteins. In addition, GRK phosphorylation by several other kinases has recently been shown to modulate its functionality, thus putting forward new feedback mechanisms connecting different signalling pathways to G protein-coupled receptors (GPCR) regulation. On the other hand, the mechanisms governing GRK expression at both transcriptional and protein stability levels are just beginning to be unveiled. Namely, GRK2 has been shown to be rapidly degraded by the proteasome pathway in a process dependent on h-arrestin and c-Src function, and also to be proteolyzed by m-calpain. A better knowledge of GRK regulatory mechanisms would contribute to greater understanding of GRK physiological function and also its reported alterations in different pathological situations, such as congestive heart failure, hypertension or inflammation. D
G protein-coupled receptor kinase 4γ interacts with inactive Gαs and Gα13
Biochemical and Biophysical Research Communications, 2008
G protein-coupled receptors (GPCRs) are regulated by multiple families of kinases including GPCR kinases (GRKs). GRK4 is constitutively active towards GPCRs, and polymorphisms of GRK4γ are linked to hypertension. We examined, through co-immunoprecipitation, the interactions between GRK4γ and the Gα and Gβ subunits of heterotrimeric G proteins. Because GRK4 has been shown to inhibit Gα s -coupled GPCR signaling and lacks a PH domain, we hypothesized that GRK4γ would interact with active Gα s , but not Gβ. Surprisingly, GRK4γ preferentially interacts with inactive Gα s and Gβ to a greater extent than active Gα s . GRK4γ also interacts with inactive Gα 13 and Gβ. Functional studies demonstrate that wild-type GRK4γ, but not kinase-dead GRK4γ, ablates isoproterenol-mediated cAMP production indicating that the kinase domain is responsible for GPCR regulation. This evidence suggests that binding to inactive Gα s and Gβ may explain the constitutive activity of GRK4γ towards Gα s coupled receptors.
Journal of Biological Chemistry, 2012
Background: GRKs phosphorylate activated GPCRs to terminate signaling. Results: Disrupting residues required for GPCR phosphorylation and G␥ and phospholipid binding eliminated Ce-GRK-2 chemosensory function. Conclusion: These interactions are required for Ce-GRK-2 function in vivo and support a recently proposed universal model for GRK activation. Significance: This is the first study to systematically determine the residues required for GRK function in live animals. G protein-coupled receptor kinases (GRKs) are key regulators of signal transduction that specifically phosphorylate activated G protein-coupled receptors (GPCRs) to terminate signaling. Biochemical and crystallographic studies have provided great insight into mammalian GRK2/3 interactions and structure. However, despite extensive in vitro characterization, little is known about the in vivo contribution of these described GRK structural domains and interactions to proper GRK function in signal regulation. We took advantage of the disrupted chemosensory behavior characteristic of Caenorhabditis elegans grk-2 mutants to discern the interactions required for proper in vivo Ce-GRK-2 function. Informed by mammalian crystallographic and biochemical data, we introduced amino acid substitutions into the Ce-grk-2 coding sequence that are predicted to selectively disrupt GPCR phosphorylation, G␣ q/11 binding, G␥ binding, or phospholipid binding. Changing the most aminoterminal residues, which have been shown in mammalian systems to be required specifically for GPCR phosphorylation but not phosphorylation of alternative substrates or recruitment to activated GPCRs, eliminated the ability of Ce-GRK-2 to restore chemosensory signaling. Disrupting interaction between the predicted Ce-GRK-2 amino-terminal ␣-helix and kinase domain, posited to stabilize GRKs in their active ATP-and GPCR-bound conformation, also eliminated Ce-GRK-2 chemosensory function. Finally, although changing residues within the RH domain, predicted to disrupt interaction with G␣ q/11 , did not affect Ce-GRK-2 chemosensory function, disruption of the predicted PH domain-mediated interactions with G␥ and phospholipids revealed that both contribute to Ce-GRK-2 function in vivo. Combined, we have demonstrated functional roles for broadly conserved GRK2/3 structural domains in the in vivo regulation of organismal behavior.