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Antioxidants & Redox Signaling May 2022Adaptor proteins control the spatiotemporal dynamics of cellular signaling. Dysregulation of adaptor protein function can cause aberrant cell signaling and promote... (Review)
Review
Adaptor proteins control the spatiotemporal dynamics of cellular signaling. Dysregulation of adaptor protein function can cause aberrant cell signaling and promote cancer. The arrestin family of adaptor proteins are known to regulate signaling by the superfamily of G protein-coupled receptors (GPCRs). The GPCRs are highly druggable and implicated in cancer progression. However, the molecular mechanisms responsible for arrestin dysregulation and the impact on GPCR function in cancer have yet to be fully elucidated. A new family of mammalian arrestins, termed the α-arrestins, was recently discovered. The α-arrestin, arrestin domain-containing protein 3 (ARRDC3), in particular, has been identified as a tumor suppressor and is reported to control cellular signaling of GPCRs in cancer. Compared with the extensively studied mammalian β-arrestins, there is limited information regarding the regulatory mechanisms that control α-arrestin activation and function. Here, we discuss the molecular mechanisms that regulate ARRDC3, which include post-translational modifications such as phosphorylation and ubiquitination. We also provide evidence that ARRDC3 can interact with a wide array of proteins that control diverse biological functions. ARRDC3 interacts with numerous proteins and is likely to display diverse functions in cancer, metabolic disease, and other syndromes. Thus, understanding the regulatory mechanisms of ARRDC3 activity in various cellular contexts is critically important. Recent studies suggest that α-arrestins may be regulated through post-translational modification, which is known to impact adaptor protein function. However, additional studies are needed to determine how these regulatory mechanisms affect ARRDC3 tumor suppressor function. 36, 1066-1079.
Topics: Adaptor Proteins, Signal Transducing; Animals; Arrestin; Arrestins; Mammals; Neoplasms; Receptors, G-Protein-Coupled; Ubiquitination
PubMed: 34465145
DOI: 10.1089/ars.2021.0193 -
Circulation Research Sep 2022An ancient family of arrestin-fold proteins, termed alpha-arrestins, may have conserved roles in regulating nutrient transporter trafficking and cellular metabolism as...
BACKGROUND
An ancient family of arrestin-fold proteins, termed alpha-arrestins, may have conserved roles in regulating nutrient transporter trafficking and cellular metabolism as adaptor proteins. One alpha-arrestin, TXNIP (thioredoxin-interacting protein), is known to regulate myocardial glucose uptake. However, the in vivo role of the related alpha-arrestin, ARRDC4 (arrestin domain-containing protein 4), is unknown.
METHODS
We first tested whether interaction with GLUTs (glucose transporters) is a conserved function of the mammalian alpha-arrestins. To define the in vivo function of ARRDC4, we generated and characterized a novel knockout (KO) mouse model. We then analyzed the molecular interaction between arrestin domains and the basal GLUT1.
RESULTS
ARRDC4 binds to GLUT1, induces its endocytosis, and blocks cellular glucose uptake in cardiomyocytes. Despite the closely shared protein structure, ARRDC4 and its homologue TXNIP operate by distinct molecular pathways. Unlike TXNIP, ARRDC4 does not increase oxidative stress. Instead, ARRDC4 uniquely mediates cardiomyocyte death through its effects on glucose deprivation and endoplasmic reticulum stress. At baseline, -KO mice have mild fasting hypoglycemia. -KO hearts exhibit a robust increase in myocardial glucose uptake and glycogen storage. Accordingly, deletion of improves energy homeostasis during ischemia and protects cardiomyocytes against myocardial infarction. Furthermore, structure-function analyses of the interaction of ARRDC4 with GLUT1 using both scanning mutagenesis and deep-learning identify specific residues in the C-terminal arrestin-fold domain as the interaction interface that regulates GLUT1 function, revealing a new molecular target for potential therapeutic intervention against myocardial ischemia.
CONCLUSIONS
These results uncover a new mechanism of ischemic injury in which ARRDC4 drives glucose deprivation-induced endoplasmic reticulum stress leading to cardiomyocyte death. Our findings establish ARRDC4 as a new scaffold protein for GLUT1 that regulates cardiac metabolism in response to ischemia and provide insight into the therapeutic strategy for ischemic heart disease.
Topics: Animals; Arrestin; Arrestins; Artificial Intelligence; Glucose; Glucose Transporter Type 1; Intracellular Signaling Peptides and Proteins; Mammals; Mice; Mice, Knockout; Myocardial Infarction; Myocardial Ischemia; Stress, Physiological
PubMed: 35950500
DOI: 10.1161/CIRCRESAHA.122.321351 -
Nature Communications Jan 2022G protein-coupled receptors (GPCRs) activate G proteins and undergo a complex regulation by interaction with GPCR kinases (GRKs) and the formation of receptor-arrestin...
G protein-coupled receptors (GPCRs) activate G proteins and undergo a complex regulation by interaction with GPCR kinases (GRKs) and the formation of receptor-arrestin complexes. However, the impact of individual GRKs on arrestin binding is not clear. We report the creation of eleven combinatorial HEK293 knockout cell clones lacking GRK2/3/5/6, including single, double, triple and the quadruple GRK knockout. Analysis of β-arrestin1/2 interactions for twelve GPCRs in our GRK knockout cells enables the differentiation of two main receptor subsets: GRK2/3-regulated and GRK2/3/5/6-regulated receptors. Furthermore, we identify GPCRs that interact with β-arrestins via the overexpression of specific GRKs even in the absence of agonists. Finally, using GRK knockout cells, PKC inhibitors and β-arrestin mutants, we present evidence for differential receptor-β-arrestin1/2 complex configurations mediated by selective engagement of kinases. We anticipate our GRK knockout platform to facilitate the elucidation of previously unappreciated details of GRK-specific GPCR regulation and β-arrestin complex formation.
Topics: Arrestin; G-Protein-Coupled Receptor Kinases; GTP-Binding Proteins; HEK293 Cells; Humans; Phosphorylation; Receptors, G-Protein-Coupled; Signal Transduction; beta-Arrestin 1; beta-Arrestin 2
PubMed: 35087057
DOI: 10.1038/s41467-022-28152-8 -
International Journal of Molecular... Nov 2022Vertebrate and fly rhodopsins are prototypical GPCRs that have served for a long time as model systems for understanding GPCR signaling. Although all rhodopsins seem to... (Review)
Review
Vertebrate and fly rhodopsins are prototypical GPCRs that have served for a long time as model systems for understanding GPCR signaling. Although all rhodopsins seem to become phosphorylated at their C-terminal region following activation by light, the role of this phosphorylation is not uniform. Two major functions of rhodopsin phosphorylation have been described: (1) inactivation of the activated rhodopsin either directly or by facilitating binding of arrestins in order to shut down the visual signaling cascade and thus eventually enabling a high-temporal resolution of the visual system. (2) Facilitating endocytosis of activated receptors via arrestin binding that in turn recruits clathrin to the membrane for clathrin-mediated endocytosis. In vertebrate rhodopsins the shutdown of the signaling cascade may be the main function of rhodopsin phosphorylation, as phosphorylation alone already quenches transducin activation and, in addition, strongly enhances arrestin binding. In the visual system rhodopsin phosphorylation is not needed for receptor inactivation. Its role here may rather lie in the recruitment of arrestin 1 and subsequent endocytosis of the activated receptor. In this review, we summarize investigations of fly rhodopsin phosphorylation spanning four decades and contextualize them with regard to the most recent insights from vertebrate phosphorylation barcode theory.
Topics: Animals; Rhodopsin; Drosophila; Arrestin; Arrestins; Phosphorylation; Clathrin
PubMed: 36499010
DOI: 10.3390/ijms232314674 -
The Journal of Neuroscience : the... Apr 2022Deactivation of G-protein-coupled receptors (GPCRs) involves multiple phosphorylations followed by arrestin binding, which uncouples the GPCR from G-protein activation....
Deactivation of G-protein-coupled receptors (GPCRs) involves multiple phosphorylations followed by arrestin binding, which uncouples the GPCR from G-protein activation. Some GPCRs, such as rhodopsin, are reused many times. Arrestin dissociation and GPCR dephosphorylation are key steps in the recycling process. evidence suggests that visual arrestin (ARR1) binding to light-activated, phosphorylated rhodopsin hinders dephosphorylation. Whether ARR1 binding also affects rhodopsin dephosphorylation is not known. We investigated this using both male and female mice lacking ARR1. Mice were exposed to bright light and placed in darkness for different periods of time, and differently phosphorylated species of rhodopsin were assayed by isoelectric focusing. For WT mice, rhodopsin dephosphorylation was nearly complete by 1 h in darkness. Surprisingly, we observed that, in the KO rods, rhodopsin remained phosphorylated even after 3 h. Delayed dephosphorylation in KO rods cannot be explained by cell stress induced by persistent signaling, since it is not prevented by the removal of transducin, the visual G-protein, nor can it be explained by downregulation of protein phosphatase 2A, the putative rhodopsin phosphatase. We further show that cone arrestin (ARR4), which binds light-activated, phosphorylated rhodopsin poorly, had little effect in enhancing rhodopsin dephosphorylation, whereas mice expressing binding-competent mutant ARR1-3A showed a similar time course of rhodopsin dephosphorylation as WT. Together, these results reveal a novel role of ARR1 in facilitating rhodopsin dephosphorylation G-protein-coupled receptors (GPCRs) are transmembrane proteins used by cells to receive and respond to a broad range of extracellular signals that include neurotransmitters, hormones, odorants, and light (photons). GPCR signaling is terminated by two sequential steps: phosphorylation and arrestin binding. Both steps must be reversed when GPCRs are recycled and reused. Dephosphorylation, which is required for recycling, is an understudied process. Using rhodopsin as a prototypical GPCR, we discovered that arrestin facilitated rhodopsin dephosphorylation in living mice.
Topics: Animals; Arrestin; Female; GTP-Binding Proteins; Male; Mice; Phosphorylation; Retinal Rod Photoreceptor Cells; Rhodopsin
PubMed: 35332081
DOI: 10.1523/JNEUROSCI.0141-22.2022 -
Experimental & Molecular Medicine Feb 2024Arrestins are multifunctional proteins that regulate G-protein-coupled receptor (GPCR) desensitization, signaling, and internalization. The arrestin family consists of... (Review)
Review
Arrestins are multifunctional proteins that regulate G-protein-coupled receptor (GPCR) desensitization, signaling, and internalization. The arrestin family consists of four subtypes: visual arrestin1, β-arrestin1, β-arrestin2, and visual arrestin-4. Recent studies have revealed the multifunctional roles of β-arrestins beyond GPCR signaling, including scaffolding and adapter functions, and physically interacting with non-GPCR receptors. Increasing evidence suggests that β-arrestins are involved in the pathogenesis of a variety of neurodegenerative diseases, including Alzheimer's disease (AD), frontotemporal dementia (FTD), and Parkinson's disease (PD). β-arrestins physically interact with γ-secretase, leading to increased production and accumulation of amyloid-beta in AD. Furthermore, β-arrestin oligomers inhibit the autophagy cargo receptor p62/SQSTM1, resulting in tau accumulation and aggregation in FTD. In PD, β-arrestins are upregulated in postmortem brain tissue and an MPTP model, and the β2AR regulates SNCA gene expression. In this review, we aim to provide an overview of β-arrestin1 and β-arrestin2, and describe their physiological functions and roles in neurodegenerative diseases. The multifaceted roles of β-arrestins and their involvement in neurodegenerative diseases suggest that they may serve as promising therapeutic targets.
Topics: Humans; beta-Arrestins; Arrestin; Frontotemporal Dementia; Neurodegenerative Diseases; Receptors, G-Protein-Coupled; Alzheimer Disease
PubMed: 38212557
DOI: 10.1038/s12276-023-01144-4 -
Handbook of Experimental Pharmacology 2014Nonvisual arrestins (β-arrestin-1 and β-arrestin-2) are adaptor proteins that function to regulate G protein-coupled receptor (GPCR) signaling and trafficking.... (Review)
Review
Nonvisual arrestins (β-arrestin-1 and β-arrestin-2) are adaptor proteins that function to regulate G protein-coupled receptor (GPCR) signaling and trafficking. β-arrestins are ubiquitously expressed and function to inhibit GPCR/G protein coupling, a process called desensitization, and promote GPCR trafficking and arrestin-mediated signaling. β-arrestin-mediated endocytosis of GPCRs requires the coordinated interaction of β-arrestins with clathrin, adaptor protein 2 (AP2), and phosphoinositides. These interactions are facilitated by a conformational change in β-arrestin that is thought to occur upon binding to a phosphorylated activated GPCR. In this review, we provide an overview of the key interactions involved in β-arrestin-mediated trafficking of GPCRs.
Topics: Adaptor Protein Complex 2; Arrestins; Clathrin; Endocytosis; Humans; Phosphatidylinositols; Phosphorylation; Protein Binding; Protein Conformation; Protein Transport; Receptors, G-Protein-Coupled; Signal Transduction; beta-Arrestin 1; beta-Arrestin 2; beta-Arrestins
PubMed: 24292830
DOI: 10.1007/978-3-642-41199-1_9 -
Nature Communications Sep 2022β-arrestins mediate regulatory processes for over 800 different G protein-coupled receptors (GPCRs) by adopting specific conformations that result from the geometry of...
β-arrestins mediate regulatory processes for over 800 different G protein-coupled receptors (GPCRs) by adopting specific conformations that result from the geometry of the GPCR-β-arrestin complex. However, whether β-arrestin1 and 2 respond differently for binding to the same GPCR is still unknown. Employing GRK knockout cells and β-arrestins lacking the finger-loop-region, we show that the two isoforms prefer to associate with the active parathyroid hormone 1 receptor (PTH1R) in different complex configurations ("hanging" and "core"). Furthermore, the utilisation of advanced NanoLuc/FlAsH-based biosensors reveals distinct conformational signatures of β-arrestin1 and 2 when bound to active PTH1R (P-R*). Moreover, we assess β-arrestin conformational changes that are induced specifically by proximal and distal C-terminal phosphorylation and in the absence of GPCR kinases (GRKs) (R*). Here, we show differences between conformational changes that are induced by P-R* or R* receptor states and further disclose the impact of site-specific GPCR phosphorylation on arrestin-coupling and function.
Topics: Arrestins; G-Protein-Coupled Receptor Kinases; Luciferases; Parathyroid Hormone; Phosphorylation; Protein Isoforms; Receptors, G-Protein-Coupled; Signal Transduction; beta-Arrestin 1; beta-Arrestin 2; beta-Arrestins
PubMed: 36163356
DOI: 10.1038/s41467-022-33307-8 -
Trends in Biochemical Sciences Jun 2018Arrestins are a small family of proteins with four isoforms in humans. Remarkably, two arrestins regulate signaling from >800 G protein-coupled receptors (GPCRs) or... (Review)
Review
Arrestins are a small family of proteins with four isoforms in humans. Remarkably, two arrestins regulate signaling from >800 G protein-coupled receptors (GPCRs) or nonreceptor activators by simultaneously binding an activator and one out of hundreds of other signaling proteins. When arrestins are bound to GPCRs or other activators, the affinity for these signaling partners changes. Thus, it is proposed that an activator alters arrestin's ability to transduce a signal. The comparison of all available arrestin structures identifies several common conformational rearrangements associated with activation. In particular, it identifies elements that are directly involved in binding to GPCRs or other activators, elements that likely engage distinct downstream effectors, and elements that likely link the activator-binding sites with the effector-binding sites.
Topics: Animals; Arrestin; Humans; Models, Molecular; Signal Transduction
PubMed: 29636212
DOI: 10.1016/j.tibs.2018.03.005 -
British Journal of Pharmacology May 2024GPR84 is an understudied rhodopsin-like class A G protein-coupled receptor, which is arousing particular interest from a therapeutic perspective. Not least this reflects... (Review)
Review
GPR84 is an understudied rhodopsin-like class A G protein-coupled receptor, which is arousing particular interest from a therapeutic perspective. Not least this reflects that gpr84 expression is significantly up-regulated following acute inflammatory stimuli and in inflammatory diseases, and that receptor activation plays a role in regulating pro-inflammatory responses and migration of cells of the innate immune system such as neutrophils, monocytes, macrophages and microglia. Although most physiological responses of GPR84 reflect receptor coupling to G-proteins, several studies indicate that agonist-activated GPR84 can recruit arrestin adaptor proteins and this regulates receptor internalisation and desensitisation. To date, little is known on the patterns of either basal or ligand regulated GPR84 phosphorylation and how these might control these processes. Here, we consider what is known about the regulation of GPR84 signalling with a focus on how G protein receptor kinase-mediated phosphorylation regulates arrestin protein recruitment and receptor function. LINKED ARTICLES: This article is part of a themed issue GPR84 Pharmacology. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.10/issuetoc.
Topics: Arrestin; Macrophages; Phosphorylation; Receptors, G-Protein-Coupled; Signal Transduction; Humans
PubMed: 37085331
DOI: 10.1111/bph.16098