RESUMEN
Atypical Chemokine Receptor 3 (ACKR3) belongs to the G protein-coupled receptor family but it does not signal through G proteins. The structural properties that govern the functional selectivity and the conformational dynamics of ACKR3 activation are poorly understood. Here, we combined hydrogen/deuterium exchange mass spectrometry, site-directed mutagenesis, and molecular dynamics simulations to examine the binding mode and mechanism of action of ACKR3 ligands of different efficacies. Our results show that activation or inhibition of ACKR3 is governed by intracellular conformational changes of helix 6, intracellular loop 2, and helix 7, while the DRY motif becomes protected during both processes. Moreover, we identified the binding sites and the allosteric modulation of ACKR3 upon ß-arrestin 1 binding. In summary, this study highlights the structure-function relationship of small ligands, the binding mode of ß-arrestin 1, the activation dynamics, and the atypical dynamic features in ACKR3 that may contribute to its inability to activate G proteins.
Asunto(s)
Simulación de Dinámica Molecular , Unión Proteica , Receptores CXCR , Humanos , Receptores CXCR/metabolismo , Receptores CXCR/genética , Sitios de Unión , Conformación Proteica , beta-Arrestina 1/metabolismo , beta-Arrestina 1/genética , Ligandos , Células HEK293 , Mutagénesis Sitio-Dirigida , Regulación Alostérica , Relación Estructura-ActividadRESUMEN
Recruitment of fibroblasts to tumors and their activation into cancer-associated fibroblasts (CAFs) is a strategy used by tumor cells to direct extracellular matrix (ECM) remodeling, invasion, and metastasis, highlighting the need to investigate the molecular mechanisms driving CAF function. Endothelin-1 (ET-1) regulates the communication between cancer and stroma and facilitates the progression of serous ovarian cancer (SOC). By binding to Endothelin A (ETA) and B (ETB) receptors, ET-1 enables the recruitment of ß-arrestin1 (ß-arr1) and the formation of signaling complexes that coordinate tumor progression. However, how ET-1 receptors might "educate" human ovarian fibroblasts (HOFs) to produce altered ECM and promote metastasis remains to be elucidated. This study identifies ET-1 as a pivotal factor in the activation of CAFs capable of proteolytic ECM remodeling and the generation of heterotypic spheroids containing cancer cells with a propensity to metastasize. An autocrine/paracrine ET-1/ETA/BR/ß-arr1 loop enhances HOF proliferation, upregulates CAF marker expression, secretes pro-inflammatory cytokines, and increases collagen contractility, and cell motility. Furthermore, ET-1 facilitates ECM remodeling by promoting the lytic activity of invadosome and activation of integrin ß1. In addition, ET-1 signaling supports the formation of heterotypic HOF/SOC spheroids with enhanced ability to migrate through the mesothelial monolayer, and invade, representing metastatic units. The blockade of ETA/BR or ß-arr1 silencing prevents CAF activation, invadosome function, mesothelial clearance, and the invasive ability of heterotypic spheroids. In vivo, therapeutic inhibition of ETA/BR using bosentan (BOS) significantly reduces the metastatic potential of combined HOFs/SOC cells, associated with enhanced apoptotic effects on tumor cells and stromal components. These findings support a model in which ET-1/ß-arr1 reinforces tumor/stroma interaction through CAF activation and fosters the survival and metastatic properties of SOC cells, which could be counteracted by ETA/BR antagonists.
Asunto(s)
Fibroblastos Asociados al Cáncer , Neoplasias Ováricas , Podosomas , beta-Arrestina 1 , Humanos , Femenino , Neoplasias Ováricas/metabolismo , Neoplasias Ováricas/patología , Neoplasias Ováricas/genética , beta-Arrestina 1/metabolismo , beta-Arrestina 1/genética , Fibroblastos Asociados al Cáncer/metabolismo , Fibroblastos Asociados al Cáncer/patología , Línea Celular Tumoral , Podosomas/metabolismo , Endotelina-1/metabolismo , Metástasis de la Neoplasia , Receptor de Endotelina A/metabolismo , Transducción de Señal , Matriz Extracelular/metabolismo , Movimiento Celular , Proliferación Celular , Animales , Fibroblastos/metabolismo , Invasividad NeoplásicaRESUMEN
The µ-opioid receptor (µOR) is an important target for pain management1 and molecular understanding of drug action on µOR will facilitate the development of better therapeutics. Here we show, using double electron-electron resonance and single-molecule fluorescence resonance energy transfer, how ligand-specific conformational changes of µOR translate into a broad range of intrinsic efficacies at the transducer level. We identify several conformations of the cytoplasmic face of the receptor that interconvert on different timescales, including a pre-activated conformation that is capable of G-protein binding, and a fully activated conformation that markedly reduces GDP affinity within the ternary complex. Interaction of ß-arrestin-1 with the µOR core binding site appears less specific and occurs with much lower affinity than binding of Gi.
Asunto(s)
Ligandos , Conformación Proteica , Receptores Opioides mu , Humanos , beta-Arrestina 1/química , beta-Arrestina 1/metabolismo , Sitios de Unión , Transferencia Resonante de Energía de Fluorescencia , Subunidades alfa de la Proteína de Unión al GTP Gi-Go/metabolismo , Subunidades alfa de la Proteína de Unión al GTP Gi-Go/química , Guanosina Difosfato/metabolismo , Guanosina Difosfato/química , Modelos Moleculares , Unión Proteica , Receptores Opioides mu/metabolismo , Receptores Opioides mu/química , Imagen Individual de MoléculaRESUMEN
The glucagon-like peptide 1 receptor (GLP-1R) is a validated clinical target for the treatment of type 2 diabetes and obesity. Unlike most G protein-coupled receptors (GPCRs), the GLP-1R undergoes an atypical mode of internalisation that does not require ß-arrestins. While differences in GLP-1R trafficking and ß-arrestin recruitment have been observed between clinically used GLP-1R agonists, the role of G protein-coupled receptor kinases (GRKs) in affecting these pathways has not been comprehensively assessed. In this study, we quantified the contribution of GRKs to agonist-mediated GLP-1R internalisation and ß-arrestin recruitment profiles using cells where endogenous ß-arrestins, or non-visual GRKs were knocked out using CRISPR/Cas9 genome editing. Our results confirm the previously established atypical ß-arrestin-independent mode of GLP-1R internalisation and revealed that GLP-1R internalisation is dependent on the expression of GRKs. Interestingly, agonist-mediated GLP-1R ß-arrestin 1 and ß-arrestin 2 recruitment were differentially affected by endogenous GRK knockout with ß-arrestin 1 recruitment more sensitive to GRK knockout than ß-arrestin 2 recruitment. Moreover, individual overexpression of GRK2, GRK3, GRK5 or GRK6 in a newly generated GRK2/3/4/5/6 HEK293 cells, rescued agonist-mediated ß-arrestin 1 recruitment and internalisation profiles to similar levels, suggesting that there is no specific GRK isoform that drives these pathways. This study advances mechanistic understanding of agonist-mediated GLP-1R internalisation and provides novel insights into how GRKs may fine-tune GLP-1R signalling.
Asunto(s)
Diabetes Mellitus Tipo 2 , Quinasas de Receptores Acoplados a Proteína-G , Humanos , Arrestinas/genética , Arrestinas/metabolismo , beta-Arrestina 1/metabolismo , Arrestina beta 2/genética , Arrestina beta 2/metabolismo , beta-Arrestinas/metabolismo , Quinasas de Receptores Acoplados a Proteína-G/genética , Quinasas de Receptores Acoplados a Proteína-G/metabolismo , Receptor del Péptido 1 Similar al Glucagón/metabolismo , Células HEK293 , Fosforilación , Receptores Acoplados a Proteínas G/metabolismoRESUMEN
The cannabinoid CB1 receptor (CB1) is a G protein-coupled receptor (GPCR) with widespread expression in the central nervous system. This canonically Gâºi/o-coupled receptor mediates the effects of Δ9-tetrahydrocannabinol (THC) and synthetic cannabinoid receptor agonists (SCRAs). Recreational use of SCRAs is associated with serious adverse health effects, making pharmacological research into these compounds a priority. Several studies have hypothesised that signalling bias may explain the different toxicological profiles between SCRAs and THC. Previous studies have focused on bias between G protein activation measured by cyclic adenosine monophosphate (cAMP) inhibition and ß-arrestin translocation. In contrast, the current study characterises bias between G⺠subtypes of the Gâºi/o family and ß-arrestins; this method facilitates a more accurate assessment of ligand bias by assessing signals that have not undergone major amplification. We have characterised G protein dissociation and translocation of ß-arrestin 1 and 2 using real-time BRET reporters. The responses produced by each SCRA across the G protein subtypes tested were consistent with the responses produced by the reference ligand AMB-FUBINACA. Ligand bias was probed by applying the operational analysis to determine biases within the Gâºi/o family, and between G protein subtypes and ß-arrestins. Overall, these results confirm SCRAs to be balanced, high-efficacy ligands compared to the low efficacy ligand THC, with only one SCRA, 4CN-MPP-BUT7IACA, demonstrating statistically significant bias in one pathway comparison (towards ß-arrestin 1 when compared with GâºoA/oB). This suggests that the adverse effects caused by SCRAs are due to high potency and efficacy at CB1, rather than biased agonism.
Asunto(s)
Agonistas de Receptores de Cannabinoides , Cannabinoides , Agonistas de Receptores de Cannabinoides/farmacología , Agonistas de Receptores de Cannabinoides/metabolismo , beta-Arrestinas/metabolismo , Receptores de Cannabinoides/metabolismo , beta-Arrestina 1/metabolismo , Ligandos , Proteínas de Unión al GTP/metabolismo , Cannabinoides/farmacología , Receptor Cannabinoide CB1/metabolismo , Receptor Cannabinoide CB2/metabolismoRESUMEN
ß-arrestin-1 has been demonstrated to participate in the regulation of inflammatory reactions in several diseases. Thus, this study aimed to investigate the role of macrophage ß-arrestin-1 in the pathogenesis and progression of ulcerative colitis (UC). A myeloid ß-arrestin-1 conditional knockout mouse model was generated to explore the role of macrophage ß-arrestin-1. DSS was employed for the establishment of an ulcerative colitis mouse model, using TNF-α as an inflammatory stressor in vitro. The expression level of ß-arrestin-1 was detected via western blot and immunofluorescence assays, whilst disease severity was evaluated by clinical score and H&E staining in the DSS-induced colitis model. In the in vitro experiments, the levels of inflammatory cytokines were examined using real-time PCR. NF-κB activation was detected through the double luciferase reporter system, western blot, and electrophoretic mobility shift assay (EMSA). BAY11-7082 was used to inhibit NF-κB activation. Our results exposed that the level of ß-arrestin-1 was increased in monocytes/macrophages derived from DSS-induced colitis mice or under the TNF-α challenge. Moreover, conditionally knocking out the expression of myeloid ß-arrestin-1 alleviated disease severity, while knocking out the expression of ß-arrestin-1 decreased the levels of inflammatory cytokines. Additionally, NF-κB was identified as a central regulatory element of ß-arrestin-1 promoter, and using BAY11-7082 to inhibit NF-κB activation lowered the level of ß-arrestin-1 under TNF-α challenge. ß-arrestin-1 led to the activation of the NF-κB signaling pathway by enhancing binding to IκBα and IKK under the TNF-α challenge. Taken together, our findings demonstrated macrophage ß-arrestin-1 contributes to the deterioration of DSS-induced colitis through the interaction with NF-κB signaling, thus highlighting a novel target for the treatment of UC.
Asunto(s)
Colitis Ulcerosa , Colitis , Nitrilos , Sulfonas , Animales , Ratones , FN-kappa B/metabolismo , Colitis Ulcerosa/tratamiento farmacológico , Factor de Necrosis Tumoral alfa/metabolismo , beta-Arrestina 1/genética , beta-Arrestina 1/metabolismo , beta-Arrestina 1/uso terapéutico , Transducción de Señal , Colitis/inducido químicamente , Colitis/tratamiento farmacológico , Citocinas/metabolismo , Macrófagos/metabolismo , Sulfato de Dextran , Ratones Endogámicos C57BL , Modelos Animales de EnfermedadRESUMEN
Glucagon-like peptide-1 receptor (GLP-1R) is a prime drug target for type 2 diabetes and obesity. The ligand initiated GLP-1R interaction with G protein has been well studied, but not with ß-arrestin 1/2. Therefore, bioluminescence resonance energy transfer (BRET), mutagenesis and an operational model were used to evaluate the roles of 85 extracellular surface residues on GLP-1R in ß-arrestin 1/2 recruitment triggered by three representative GLP-1R agonists (GLP-1, exendin-4 and oxyntomodulin). Residues selectively regulated ß-arrestin 1/2 recruitment for diverse ligands, and ß-arrestin isoforms were identified. Mutation of residues K130-S136, L142 and Y145 on the transmembrane helix 1 (TM1)-extracellular domain (ECD) linker decreased ß-arrestin 1 recruitment but increased ß-arrestin 2 recruitment. Other extracellular loop (ECL) mutations, including P137A, Q211A, D222A and M303A selectively affected ß-arrestin 1 recruitment while D215A, L217A, Q221A, S223A, Y289A, S301A, F381A and I382A involved more in ß-arrestin 2 recruitment for the ligands. Oxyntomodulin engaged more broadly with GLP-1R extracellular surface to drive ß-arrestin 1/2 recruitment than GLP-1 and exendin-4; I147, W214 and L218 involved in ß-arrestin 1 recruitment, while L141, D215, L218, D293 and F381 in ß-arrestin 2 recruitment for oxyntomodulin particularly. Additionally, the non-conserved residues on ß-arrestin 1/2 C-domains contributed to interaction with GLP-1R. Further proteomic profiling of GLP-1R stably expressed cell line upon ligand stimulation with or without ß-arrestin 1/2 overexpression demonstrated both commonly and biasedly regulated proteins and pathways associated with cognate ligands and ß-arrestins. Our study offers valuable information about ligand induced ß-arrestin recruitment mediated by GLP-1R and consequent intracellular signaling events.
Asunto(s)
Diabetes Mellitus Tipo 2 , Humanos , beta-Arrestina 1/metabolismo , Exenatida/farmacología , Arrestina beta 2/genética , Arrestina beta 2/metabolismo , Receptor del Péptido 1 Similar al Glucagón/agonistas , Ligandos , Oxintomodulina/farmacología , Proteómica , Péptido 1 Similar al Glucagón/metabolismo , beta-Arrestinas/metabolismoRESUMEN
G protein-coupled receptors (GPCRs) are leading druggable targets for several medicines, but many GPCRs are still untapped for their therapeutic potential due to poor understanding of specific signaling properties. The complement C3a receptor 1 (C3aR1) has been extensively studied for its physiological role in C3a-mediated anaphylaxis/inflammation, and in TLQP-21-mediated lipolysis, but direct evidence for the functional relevance of the C3a and TLQP-21 ligands and signal transduction mechanisms are still limited. In addition, C3aR1 G protein coupling specificity is still unclear, and whether endogenous ligands, or drug-like compounds, show ligand-mediated biased agonism is unknown. Here, we demonstrate that C3aR1 couples preferentially to Gi/o/z proteins and can recruit ß-arrestins to cause internalization. Furthermore, we showed that in comparison to C3a63-77, TLQP-21 exhibits a preference toward Gi/o-mediated signaling compared to ß-arrestin recruitment and internalization. We also show that the purported antagonist SB290157 is a very potent C3aR1 agonist, where antagonism of ligand-stimulated C3aR1 calcium flux is caused by potent ß-arrestin-mediated internalization. Finally, ligand-mediated signaling bias impacted cell function as demonstrated by the regulation of calcium influx, lipolysis in adipocytes, phagocytosis in microglia, and degranulation in mast cells. Overall, we characterize C3aR1 as a Gi/o/z-coupled receptor and demonstrate the functional relevance of ligand-mediated signaling bias in key cellular models. Due to C3aR1 and its endogenous ligands being implicated in inflammatory and metabolic diseases, these results are of relevance toward future C3aR1 drug discovery.
Asunto(s)
Calcio , Complemento C3a , beta-Arrestina 1/metabolismo , beta-Arrestinas/metabolismo , Calcio/metabolismo , Complemento C3a/metabolismo , Ligandos , Receptores Acoplados a Proteínas G/metabolismo , Humanos , Animales , Ratones , Línea CelularRESUMEN
T-2 toxin causes renal dysfunction with proteinuria and glomerular podocyte damage. This work explores the role of metabolic disorder/reprogramming-mediated epigenetic modification in the progression of T-2 toxin-stimulated podocyte injury. A metabolomics experiment is performed to assess metabolic responses to T-2 toxin infection in human podocytes. Roles of protein O-linked-N-acetylglucosaminylation (O-GlcNAcylation) in regulating T-2 toxin-stimulated podocyte injury in mouse and podocyte models are assessed. O-GlcNAc target proteins are recognized by mass spectrometry and co-immunoprecipitation experiments. Moreover, histone acetylation and autophagy levels are measured. T-2 toxin infection upregulates glucose transporter type 1 (GLUT1) expression and enhances hexosamine biosynthetic pathway in glomerular podocytes, resulting in a significant increase in ß-arrestin-1 O-GlcNAcylation. Decreasing ß-arrestin-1 or O-GlcNAc transferase (OGT) effectively prevents T-2 toxin-induced renal dysfunction and podocyte injury. Mechanistically, O-GlcNAcylation of ß-arrestin-1 stabilizes ß-arrestin-1 to activate the mammalian target of rapamycin (mTOR) pathway as well as to inhibit autophagy during podocyte injury by promoting H4K16 acetylation. To sum up, OGT-mediated ß-arrestin-1 O-GlcNAcylation is a vital regulator in the development of T-2 toxin-stimulated podocyte injury via activating the mTOR pathway to suppress autophagy. Targeting ß-arrestin-1 or OGT can be a potential therapy for T-2 toxin infection-associated glomerular injury, especially podocyte injury.
Asunto(s)
Enfermedades Renales , Podocitos , Toxina T-2 , Ratones , Humanos , Animales , Acetilación , Histonas/metabolismo , Podocitos/metabolismo , beta-Arrestina 1/metabolismo , Toxina T-2/metabolismo , Serina-Treonina Quinasas TOR/metabolismo , Enfermedades Renales/metabolismo , Mamíferos/metabolismoRESUMEN
ß-arrestins are a family of intracellular signaling proteins that play a key role in regulating the activity of G protein-coupled receptors. The angiotensin-II type 1 receptor is an important G protein-coupled receptor involved in the regulation of cardiovascular function and has been implicated in the progression of cardiovascular diseases. In addition to canonical G protein signaling, G protein-coupled receptors including the angiotensin-II type 1 receptor can signal via ß-arrestin. Dysregulation of ß-arrestin signaling has been linked to several cardiovascular diseases including hypertension, atherosclerosis, and heart failure. Understanding the role of ß-arrestins in these conditions is critical to provide new therapeutic targets for the treatment of cardiovascular disease. In this review, we will discuss the beneficial and maladaptive physiological outcomes of angiotensin-II type 1 receptor-dependent ß-arrestin activation in different cardiovascular diseases.
Asunto(s)
Enfermedades Cardiovasculares , Humanos , beta-Arrestinas , Arrestinas/metabolismo , Transducción de Señal , Receptor de Angiotensina Tipo 1/metabolismo , Angiotensinas/metabolismo , Arrestina beta 2/genética , Arrestina beta 2/metabolismo , beta-Arrestina 1/metabolismo , Angiotensina II/metabolismoRESUMEN
GPR101 is an orphan G protein-coupled receptor that promotes growth hormone secretion in the pituitary. The microduplication of the GPR101 gene has been linked with the X-linked acrogigantism, or X-LAG, syndrome. This disease is characterized by excessive growth hormone secretion and abnormal rapid growth beginning early in life. Mechanistically, GPR101 induces growth hormone secretion through constitutive activation of multiple heterotrimeric G proteins. However, the full scope of GPR101 signaling remains largely elusive. Herein, we investigated the association of GPR101 to multiple transducers and uncovered an important basal interaction with Arrestin 2 (ß-arrestin 1) and Arrestin 3 (ß-arrestin 2). By using a GPR101 mutant lacking the C-terminus and cell lines with an Arrestin 2/3 null background, we show that the arrestin association leads to constitutive clathrin- and dynamin-mediated GPR101 internalization. To further highlight GPR101 intracellular fate, we assessed the colocalization of GPR101 with Rab protein markers. Internalized GPR101 was mainly colocalized with the early endosome markers, Rab5 and EEA-1, and to a lesser degree with the late endosome marker Rab7. However, GPR101 was not colocalized with the recycling endosome marker Rab11. These findings show that the basal arrestin recruitment by GPR101 C-terminal tail drives the receptor constitutive clathrin-mediated internalization. Intracellularly, GPR101 concentrates in the endosomal compartment and is degraded through the lysosomal pathway. In conclusion, we uncovered a constitutive intracellular trafficking of GPR101 that potentially represents an important layer of regulation of its signaling and function.
Asunto(s)
Arrestinas , Receptores Acoplados a Proteínas G , beta-Arrestina 1/metabolismo , beta-Arrestinas/metabolismo , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismo , Arrestinas/genética , Arrestinas/metabolismo , Arrestina beta 2/metabolismo , Hormona del Crecimiento , Clatrina/metabolismo , EndocitosisRESUMEN
It has been documented that increased sympathetic activity contributes to the development of cardiovascular diseases, such as hypertension. We previously reported that ß-arrestin-1, a multifunctional cytoskeletal protein, was downregulated in the rostral ventrolateral medulla (RVLM) of the spontaneously hypertensive rat (SHR), and its overexpression elicited an inhibitory effect on sympathetic activity in hypertension. microRNA (miR)-22-3p has been reported to be associated with the pathological progress of hypertension. The purpose of this study was to determine the role of miR-22-3p in ß-arrestin-1-mediated central cardiovascular regulation in hypertension. It was observed that miR-22-3p was upregulated in the RVLM of SHRs compared with normotensive Wistar-Kyoto (WKY) rats, and it was subsequently confirmed to target the ß-arrestin-1 gene using a dual-luciferase reporter assay. miR-22-3p was downregulated in the RVLM using adeno-associated virus with 'tough decoys', which caused a significant increase of ß-arrestin-1 expression and decrease of noradrenaline and blood pressure (BP) in SHRs. However, upregulation of miR-22-3p using lentivirus in the RVLM of WKY rats significantly increased BP. In in vitro PC12 cells, enhanced oxidative stress activity induced by angiotensin II was counteracted by pretreatment with miR-22-3p inhibitor, and this effect could be abolished by ß-arrestin-1 gene knockdown. Furthermore, microglia exhaustion significantly diminished miR-22-3p expression, and enhanced ß-arrestin-1 expression in the RVLM of SHRs. Activation of BV2 cells in vitro evoked a significant increase of miR-22-3p expression, and this BV2 cell culture medium was also able to facilitate miR-22-3p expression in PC12 cells. Collectively, our findings support a critical role for microglia-derived miR-22-3p in inhibiting ß-arrestin-1 in the RVLM, which is involved in central cardiovascular regulation in hypertension. KEY POINTS: Impairment of ß-arrestin-1 function in the rostral ventrolateral medulla (RVLM) has been reported to be associated with the development of sympathetic overactivity in hypertension. However, little is known about the potential mechanisms of ß-arrestin-1 dysfunction in hypertension. miR-22-3p is implicated in multiple biological processes, but the role of miR-22-3p in central regulation of cardiovascular activity in hypertension remains unknown. We predicted that miR-22-3p could directly bind to the ß-arrestin-1 gene (Arrb1), and this hypothesis was confirmed by using a dual-luciferase reporter assay. Inhibition of ß-arrestin-1 by miR-22-3p was further verified in both in vivo and in vitro experiments. Furthermore, our results suggested miR-22-3p as a risk factor for oxidative stress in the RVLM, thus contributing to sympatho-excitation and hypertension. Our present study provides evidence that microglia-derived miR-22-3p may underlie the pathogenesis and progression of neuronal hypertension by inhibiting ß-arrestin-1 in the RVLM.
Asunto(s)
Hipertensión , MicroARNs , Animales , Ratas , beta-Arrestina 1/genética , beta-Arrestina 1/metabolismo , Presión Sanguínea/fisiología , Luciferasas/metabolismo , Bulbo Raquídeo/fisiología , MicroARNs/genética , MicroARNs/metabolismo , Ratas Endogámicas SHR , Ratas Endogámicas WKYRESUMEN
Cannabis activates the cannabinoid receptor 1 (CB1), which elicits analgesic and emotion regulation benefits, along with adverse effects, via Gi and ß-arrestin signaling pathways. However, the lack of understanding of the mechanism of ß-arrestin-1 (ßarr1) coupling and signaling bias has hindered drug development targeting CB1. Here, we present the high-resolution cryo-electron microscopy structure of CB1-ßarr1 complex bound to the synthetic cannabinoid MDMB-Fubinaca (FUB), revealing notable differences in the transducer pocket and ligand-binding site compared with the Gi protein complex. ßarr1 occupies a wider transducer pocket promoting substantial outward movement of the TM6 and distinctive twin toggle switch rearrangements, whereas FUB adopts a different pose, inserting more deeply than the Gi-coupled state, suggesting the allosteric correlation between the orthosteric binding pocket and the partner protein site. Taken together, our findings unravel the molecular mechanism of signaling bias toward CB1, facilitating the development of CB1 agonists.
Asunto(s)
Arrestina , Receptor Cannabinoide CB1 , Transducción de Señal , Arrestina/metabolismo , beta-Arrestina 1/metabolismo , beta-Arrestinas/metabolismo , Microscopía por Crioelectrón , Receptor Cannabinoide CB1/metabolismo , Humanos , Animales , Línea CelularRESUMEN
Cannabinoid CB2 receptor (CB2R) is a class A G protein-coupled receptor (GPCR) involved in a broad spectrum of physiological processes and pathological conditions. For that reason, targeting CB2R might provide therapeutic opportunities in neurodegenerative disorders, neuropathic pain, inflammatory diseases, and cancer. The main components from Cannabis sativa, such as Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD), have been therapeutically exploited and synthetically-derived analogs have been generated. One example is cannabidiol-dimethylheptyl (CBD-DMH), which exhibits anti-inflammatory effects. Nevertheless, its pharmacological mechanism of action is not yet fully understood and is hypothesized for multiple targets, including CB2R. The aim of this study was to further investigate the molecular pharmacology of CBD-DMH on CB2R while CBD was taken along as control. These compounds were screened in equilibrium and kinetic radioligand binding studies and various functional assays, including G protein activation, inhibition of cAMP production and ß-arrestin-2 recruitment. In dissociation studies, CBD-DMH allosterically modulated the radioligand binding. Furthermore, CBD-DMH negatively modulated the G protein activation of reference agonists CP55,940, AEA and 2-AG, but not the agonist-induced ß-arrestin-2 recruitment. Nevertheless, CBD-DMH also displayed competitive binding to CB2R and partial agonism on G protein activation, inhibition of cAMP production and ß-arrestin-2 recruitment. CBD did not exhibit such allosteric behavior and only very weakly bound CB2R without activation. This study shows a dual binding mode of CBD-DMH, but not CBD, to CB2R with the suggestion of two different binding sites. Altogether, it encourages further research into this dual mechanism which might provide a new class of molecules targeting CB2R.
Asunto(s)
Cannabidiol , Cannabidiol/farmacología , Receptores de Cannabinoides/metabolismo , beta-Arrestina 1/metabolismo , Proteínas de Unión al GTP/metabolismo , Receptor Cannabinoide CB2/metabolismo , Dronabinol , Receptor Cannabinoide CB1/metabolismo , Agonistas de Receptores de CannabinoidesRESUMEN
G protein-coupled receptor (GPCR) signaling and trafficking are regulated by multiple mechanisms, including posttranslational modifications such as ubiquitination by E3 ubiquitin ligases. E3 ligases have been linked to agonist-stimulated ubiquitination of GPCRs via simultaneous binding to ßarrestins. In addition, ßarrestins have been suggested to assist E3 ligases for ubiquitination of key effector molecules, yet mechanistic insight is lacking. Here, we developed an in vitro reconstituted system and show that ßarrestin1 (ßarr1) serves as an adaptor between the effector protein signal-transducing adaptor molecule 1 (STAM1) and the E3 ligase atrophin-interacting protein 4. Via mass spectrometry, we identified seven lysine residues within STAM1 that are ubiquitinated and several types of ubiquitin linkages. We provide evidence that ßarr1 facilitates the formation of linear polyubiquitin chains at lysine residue 136 on STAM1. This lysine residue is important for stabilizing the ßarr1:STAM1 interaction in cells following GPCR activation. Our study identifies atrophin-interacting protein 4 as only the second E3 ligase known to conjugate linear polyubiquitin chains and a possible role for linear ubiquitin chains in GPCR signaling and trafficking.
Asunto(s)
Poliubiquitina , Ubiquitina-Proteína Ligasas , beta-Arrestina 1 , Lisina/metabolismo , Poliubiquitina/metabolismo , Ubiquitina/metabolismo , Ubiquitina-Proteína Ligasas/metabolismo , Ubiquitinación , beta-Arrestina 1/metabolismoRESUMEN
ß-Arrestins (ßarrs) are functionally versatile proteins that play critical roles in the G-protein-coupled receptor (GPCR) signaling pathways. While it is well established that the phosphorylated receptor tail plays a central role in ßarr activation, emerging evidence highlights the contribution from membrane lipids. However, detailed molecular mechanisms of ßarr activation by different binding partners remain elusive. In this work, we present a comprehensive study of the structural changes in critical regions of ßarr1 during activation using 19F NMR spectroscopy. We show that phosphopeptides derived from different classes of GPCRs display different ßarr1 activation abilities, whereas binding of the membrane phosphoinositide PIP2 stabilizes a distinct partially activated conformational state. Our results further unveil a sparsely-populated activation intermediate as well as complex cross-talks between different binding partners, implying a highly multifaceted conformational energy landscape of ßarr1 that can be intricately modulated during signaling.
Asunto(s)
Receptores Acoplados a Proteínas G , Transducción de Señal , beta-Arrestina 1/genética , beta-Arrestina 1/metabolismo , beta-Arrestinas/metabolismo , Transducción de Señal/fisiología , Receptores Acoplados a Proteínas G/metabolismo , Arrestina beta 2/metabolismo , FosforilaciónRESUMEN
Glucagon-like peptide 1 (GLP-1R) and glucose-dependent insulinotropic polypeptide (GIPR) receptors are G-protein-coupled receptors involved in glucose homeostasis. Diabetogenic conditions decrease ß-arrestin 2 (ARRB2) levels in human islets. In mouse ß cells, ARRB2 dampens insulin secretion by partially uncoupling cyclic AMP (cAMP)/protein kinase A (PKA) signaling at physiological doses of GLP-1, whereas at pharmacological doses, the activation of extracellular signal-related kinase (ERK)/cAMP-responsive element-binding protein (CREB) requires ARRB2. In contrast, GIP-potentiated insulin secretion needs ARRB2 in mouse and human islets. The GIPR-ARRB2 axis is not involved in cAMP/PKA or ERK signaling but does mediate GIP-induced F-actin depolymerization. Finally, the dual GLP-1/GIP agonist tirzepatide does not require ARRB2 for the potentiation of insulin secretion. Thus, ARRB2 plays distinct roles in regulating GLP-1R and GIPR signaling, and we highlight (1) its role in the physiological context and the possible functional consequences of its decreased expression in pathological situations such as diabetes and (2) the importance of assessing the signaling pathways engaged by the agonists (biased/dual) for therapeutic purposes.
Asunto(s)
Células Secretoras de Insulina , Ratones , Humanos , Animales , Células Secretoras de Insulina/metabolismo , Péptido 1 Similar al Glucagón/metabolismo , Insulina/metabolismo , Arrestina beta 2/metabolismo , beta-Arrestina 1/metabolismo , Glucosa/metabolismoRESUMEN
G protein-coupled receptors (GPCRs) utilize complex cellular systems to respond to diverse ligand concentrations. By taking BLT1, a GPCR for leukotriene B4 (LTB4 ), as a model, our previous work elucidated that this system functions through the modulation of phosphorylation status on two specific residues: Thr308 and Ser310 . Ser310 phosphorylation occurs at a lower LTB4 concentration than Thr308 , leading to a shift in ligand affinity from a high-to-low state. However, the implications of BLT1 phosphorylation in signal transduction processes or the underlying mechanisms have remained unclear. Here, we identify the sequential BLT1-engaged conformations of ß-arrestin and subsequent alterations in signal transduction. Stimulation of the high-affinity BLT1 with LTB4 induces phosphorylation at Ser310 via the ERK1/2-GRK pathway, resulting in a ß-arrestin-bound low-affinity state. This configuration, referred to as the "low-LTB4 -induced complex," necessitates the finger loop region and the phosphoinositide-binding motif of ß-arrestins to interact with BLT1 and deactivates the ERK1/2 signaling. Under high LTB4 concentrations, the low-affinity BLT1 again binds to the ligand and triggers the generation of the low-LTB4 -induced complex into a different form termed "high-LTB4 -induced complex." This change is propelled by The308 -phosphorylation-dependent basal phosphorylation by PKCs. Within the high-LTB4 -induced complex, ß-arrestin adapts a unique configuration that involves additional N domain interaction to the low-affinity BLT1 and stimulates the PI3K/AKT pathway. We propose that the stepwise phosphorylation of BLT1 defines the formation of complex assemblies, wherein ß-arrestins perform distinct functions.
Asunto(s)
Fosfatidilinositol 3-Quinasas , Transducción de Señal , Fosforilación , beta-Arrestinas/metabolismo , Fosfatidilinositol 3-Quinasas/metabolismo , Ligandos , beta-Arrestina 1/metabolismo , Receptores de Leucotrieno B4/metabolismo , Leucotrieno B4/metabolismoRESUMEN
The vasopressin type 2 receptor (V2R) is an essential G protein-coupled receptor (GPCR) in renal regulation of water homeostasis. Upon stimulation, the V2R activates Gαs and Gαq/11, which is followed by robust recruitment of ß-arrestins and receptor internalization into endosomes. Unlike canonical GPCR signaling, the ß-arrestin association with the V2R does not terminate Gαs activation, and thus, Gαs-mediated signaling is sustained while the receptor is internalized. Here, we demonstrate that this V2R ability to co-interact with G protein/ß-arrestin and promote endosomal G protein signaling is not restricted to Gαs, but also involves Gαq/11. Furthermore, our data imply that ß-arrestins potentiate Gαs/Gαq/11 activation at endosomes rather than terminating their signaling. Surprisingly, we found that the V2R internalizes and promote endosomal G protein activation independent of ß-arrestins to a minor degree. These new observations challenge the current model of endosomal GPCR signaling and suggest that this event can occur in both ß-arrestin-dependent and -independent manners.
Asunto(s)
Arrestinas , Receptores de Vasopresinas , beta-Arrestinas/metabolismo , Arrestinas/metabolismo , beta-Arrestina 1/metabolismo , Endosomas/metabolismo , Proteínas de Unión al GTP/metabolismo , Vasopresinas/metabolismoRESUMEN
Autophagy in atherosclerotic plaque macrophage contributes to the alleviation of atherosclerosis through the promotion of lipid metabolism. ß-arrestins are multifunctional proteins participating various kinds of cellular signaling pathways. Here we aimed to determine the role of ß-arrestin-1, an important member of ß-arrestin family, in atherosclerosis, and whether autophagy was involved in this process. ApoE-/-ß-arrestin-1fl/flLysM-Cre mice were created through bone marrow transplantation for the atherosclerosis model with conditional myeloid knocking out ß-arrestin-1. Bone marrow-derived macrophages (BMDMs) were used for the in vitro studies. Oil red O staining was used to detect the lesional area. F4/80, Masson trichrome and picro-Sirius red staining were applied for the determination of plaque stability. Real-time PCR was used for the detection of levels of lipid metabolism-related receptors. Electron microscopy and tandem fluorescent mRFP-GFP-LC3 plasmid was applied to test autophagy level. We found that ß-arrestin-1 was highly increased in expression in plaque macrophage on the occurrence of atherosclerosis. Conditional myeloid knocking out ß-arrestin-1 largely promotes plaque formation and vulnerability. In murine macrophage with lipid loading, knocking down ß-arrestin-1 enhanced foam cell formation and levels of plasma and cellular cholesterol, while overexpressing ß-arrestin-1 led to the opposite effects. The alleviative effects induced by macrophage ß-arrestin-1 in atherosclerosis were involved in autophagy, based on the reduction of autophagy level with the knocking down of macrophage ß-arrestin-1 and administration of autophagy inhibitors which largely attenuated the decreasing effect on foam cell formation. Our results demonstrated for the first time that macrophage ß-arrestin-1 protected against atherosclerosis through the induction of autophagy.