A long evolution of knowledge of the psychostimulant caffeine led in the 1960s to another purine natural product, adenosine and its A2A receptor. Adenosine is a short‐lived autocrine/paracrine ...mediator that acts pharmacologically at four different adenosine receptors in a manner opposite to the pan‐antagonist caffeine and serves as an endogenous allostatic regulator. Although detrimental in the developing brain, caffeine appears to be cerebroprotective in aging. Moderate caffeine consumption in adults, except in pregnancy, may also provide benefit in pain, diabetes, and kidney and liver disorders. Inhibition of A2A receptors is one of caffeine's principal effects and we now understand this interaction at the atomic level. The A2A receptor has become a prototypical example of utilizing high‐resolution structures of GPCRs for the rational design of chemically diverse drug molecules. The previous focus on discovery of selective A2A receptor antagonists for neurodegenerative diseases has expanded to include immunotherapy for cancer, and clinical trials have ensued.
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This article is part of a themed issue on Structure Guided Pharmacology of Membrane Proteins (BJP 75th Anniversary). To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.14/issuetoc
Adenosine receptors (ARs) function in the body's response to conditions of pathology and stress associated with a functional imbalance, such as in the supply and demand of energy/oxygen/nutrients. ...Extracellular adenosine concentrations vary widely to raise or lower the basal activation of four subtypes of ARs. Endogenous adenosine can correct an energy imbalance during hypoxia and other stress, for example, by slowing the heart rate by A
AR activation or increasing the blood supply to heart muscle by the A
AR. Moreover, exogenous AR agonists, antagonists, or allosteric modulators can be applied for therapeutic benefit, and medicinal chemists working toward that goal have reported thousands of such agents. Thus, numerous clinical trials have ensued, using promising agents to modulate adenosinergic signaling, most of which have not succeeded. Currently, short-acting, parenteral agonists, adenosine and Regadenoson, are the only AR agonists approved for human use. However, new concepts and compounds are currently being developed and applied toward preclinical and clinical evaluation, and initial results are encouraging. This review focuses on key compounds as AR agonists and positive allosteric modulators (PAMs) for disease treatment or diagnosis. AR agonists for treating inflammation, pain, cancer, non-alcoholic steatohepatitis, angina, sickle cell disease, ischemic conditions and diabetes have been under development. Multiple clinical trials with two A
AR agonists are ongoing.
The A3 adenosine receptor (A3AR) subtype is a novel, promising therapeutic target for inflammatory diseases, such as rheumatoid arthritis (RA) and psoriasis, as well as liver cancer. A3AR is coupled ...to inhibition of adenylyl cyclase and regulation of mitogen‐activated protein kinase (MAPK) pathways, leading to modulation of transcription. Furthermore, A3AR affects functions of almost all immune cells and the proliferation of cancer cells. Numerous A3AR agonists, partial agonists, antagonists, and allosteric modulators have been reported, and their structure–activity relationships (SARs) have been studied culminating in the development of potent and selective molecules with drug‐like characteristics. The efficacy of nucleoside agonists may be suppressed to produce antagonists, by structural modification of the ribose moiety. Diverse classes of heterocycles have been discovered as selective A3AR blockers, although with large species differences. Thus, as a result of intense basic research efforts, the outlook for development of A3AR modulators for human therapeutics is encouraging. Two prototypical selective agonists, N6‐(3‐Iodobenzyl)adenosine‐5′‐N‐methyluronamide (IB‐MECA; CF101) and 2‐chloro‐N6‐(3‐iodobenzyl)‐adenosine‐5′‐N‐methyluronamide (Cl‐IB‐MECA; CF102), have progressed to advanced clinical trials. They were found safe and well tolerated in all preclinical and human clinical studies and showed promising results, particularly in psoriasis and RA, where the A3AR is both a promising therapeutic target and a biologically predictive marker, suggesting a personalized medicine approach. Targeting the A3AR may pave the way for safe and efficacious treatments for patient populations affected by inflammatory diseases, cancer, and other conditions.
A2B Adenosine Receptor and Cancer Gao, Zhan-Guo; Jacobson, Kenneth A.
International journal of molecular sciences,
10/2019, Letnik:
20, Številka:
20
Journal Article
Recenzirano
Odprti dostop
There are four subtypes of adenosine receptors (ARs), named A1, A2A, A2B and A3, all of which are G protein-coupled receptors (GPCRs). Locally produced adenosine is a suppressant in anti-tumor immune ...surveillance. The A2BAR, coupled to both Gαs and Gαi G proteins, is one of the several GPCRs that are expressed in a significantly higher level in certain cancer tissues, in comparison to adjacent normal tissues. There is growing evidence that the A2BAR plays an important role in tumor cell proliferation, angiogenesis, metastasis, and immune suppression. Thus, A2BAR antagonists are novel, potentially attractive anticancer agents. Several antagonists targeting A2BAR are currently in clinical trials for various types of cancers. In this review, we first describe the signaling, agonists, and antagonists of the A2BAR. We further discuss the role of the A2BAR in the progression of various cancers, and the rationale of using A2BAR antagonists in cancer therapy.
Activation of G protein-coupled receptors upon agonist binding is a critical step in the signaling cascade for this family of cell surface proteins. We report the crystal structure of the A(2A) ...adenosine receptor (A(2A)AR) bound to an agonist UK-432097 at 2.7 angstrom resolution. Relative to inactive, antagonist-bound A(2A)AR, the agonist-bound structure displays an outward tilt and rotation of the cytoplasmic half of helix VI, a movement of helix V, and an axial shift of helix III, resembling the changes associated with the active-state opsin structure. Additionally, a seesaw movement of helix VII and a shift of extracellular loop 3 are likely specific to A(2A)AR and its ligand. The results define the molecule UK-432097 as a "conformationally selective agonist" capable of receptor stabilization in a specific active-state configuration.
Sodium ions are endogenous allosteric modulators of many G-protein-coupled receptors (GPCRs). Mutation of key residues in the sodium binding motif causes a striking effect on G-protein signaling. We ...report the crystal structures of agonist complexes for two variants in the first sodium coordination shell of the human A2A adenosine receptor, D522.50N and S913.39A. Both structures present an overall active-like conformation; however, the variants show key changes in the activation motif NPxxY. Changes in the hydrogen bonding network in this microswitch suggest a possible mechanism for modified G-protein signaling and enhanced thermal stability. These structures, signaling data, and thermal stability analysis with a panel of pharmacological ligands provide a basis for understanding the role of the sodium-coordinating residues on stability and G-protein signaling. Utilizing the D2.50N variant is a promising method for stabilizing class A GPCRs to accelerate structural efforts and drug discovery.
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•X-ray structures of A2AAR variants D2.50N and S3.39A agonist complexes•A2AAR-D2.50N shows striking loss of G-protein signaling•Structural changes near activation motif correspond to loss of signaling•D2.50N improves GPCR stability for accelerating drug discovery
White and Eddy et al. report agonist-bound structures of human A2AAR variants that disrupt allosteric sodium effects. The structures reveal changes in hydrogen bonding near a conserved activation motif that correspond to striking differences in signaling, providing a rationale for increased variant receptor stability.
N-linked glycans on immunoglobulin G (IgG) have been associated with pathogenesis of diseases and the therapeutic functions of antibody-based drugs; however, low-abundance species are difficult to ...detect. Here we show a glycomic approach to detect these species on human IgGs using a specialized microfluidic chip. We discover 20 sulfated and 4 acetylated N-glycans on IgGs. Using multiple reaction monitoring method, we precisely quantify these previously undetected low-abundance, trace and even ultra-trace N-glycans. From 277 patients with rheumatoid arthritis (RA) and 141 healthy individuals, we also identify N-glycan biomarkers for the classification of both rheumatoid factor (RF)-positive and negative RA patients, as well as anti-citrullinated protein antibodies (ACPA)-positive and negative RA patients. This approach may identify N-glycosylation-associated biomarkers for other autoimmune and infectious diseases and lead to the exploration of promising glycoforms for antibody therapeutics.Post-translational modifications can affect antibody function in health and disease, but identification of all variants is difficult using existing technologies. Here the authors develop a microfluidic method to identify and quantify low-abundance IgG N-glycans and show some of these IgGs can be used as biomarkers for rheumatoid arthritis.
Adenosine receptors are major targets of caffeine, the most commonly consumed drug in the world. There is growing evidence that they could also be promising therapeutic targets in a wide range of ...conditions, including cerebral and cardiac ischaemic diseases, sleep disorders, immune and inflammatory disorders and cancer. After more than three decades of medicinal chemistry research, a considerable number of selective agonists and antagonists of adenosine receptors have been discovered, and some have been clinically evaluated, although none has yet received regulatory approval. However, recent advances in the understanding of the roles of the various adenosine receptor subtypes, and in the development of selective and potent ligands, as discussed in this review, have brought the goal of therapeutic application of adenosine receptor modulators considerably closer.
Signaling across cellular membranes, the 826 human G protein-coupled receptors (GPCRs) govern a wide range of vital physiological processes, making GPCRs prominent drug targets. X-ray crystallography ...provided GPCR molecular architectures, which also revealed the need for additional structural dynamics data to support drug development. Here, nuclear magnetic resonance (NMR) spectroscopy with the wild-type-like A2A adenosine receptor (A2AAR) in solution provides a comprehensive characterization of signaling-related structural dynamics. All six tryptophan indole and eight glycine backbone 15N–1H NMR signals in A2AAR were individually assigned. These NMR probes provided insight into the role of Asp522.50 as an allosteric link between the orthosteric drug binding site and the intracellular signaling surface, revealing strong interactions with the toggle switch Trp 2466.48, and delineated the structural response to variable efficacy of bound drugs across A2AAR. The present data support GPCR signaling based on dynamic interactions between two semi-independent subdomains connected by an allosteric switch at Asp522.50.
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•Comprehensive view of GPCR signaling pathways using NMR probes•Allosteric signaling monitored by NMR probes distributed throughout A2AAR•Function-related conformational polymorphisms at intracellular A2AAR surface•Strong coupling between allosteric switch and signaling-activation motif
Monitoring dynamics of GPCR signaling using stable isotope NMR reveals the path of communication enabling an allosteric response to ligand binding.
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