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Steroids Dec 2023Aldosterone plays a key role in controlling blood pressure (BP) values by maintaining body salt, water, and fluid homeostasis. Excess aldosterone production is...
Aldosterone plays a key role in controlling blood pressure (BP) values by maintaining body salt, water, and fluid homeostasis. Excess aldosterone production is associated with arterial hypertension, cardiovascular and metabolic diseases, partly via generation of an inflammatory state followed by fibrotic changes in the organs that are target of hypertension. Aldosterone exerts genomic effects that are known to involve activation of the mineralocorticoid receptor (MR). Other aldosterone effects, including those usually defined as 'rapid' or 'non genomic', involve additional receptors as the G-protein coupled estrogen receptor (GPER). To date, the receptor(s) implicated in the inflammatory action of aldosterone in cells of the innate and adaptive immunity are unknown. Considering the potential role of T-lymphocytes in adaptive immunity in arterial hypertension and related hypertension-mediated organ damage (HMOD), we herein investigated and quantified the expression of the MR and GPER in human CD4 and CD8 T-cells. Results provided compelling evidence for the presence at the mRNA and protein level and suggest a functional role of these receptors in the two T-lymphocyte subtypes, thus indicating that they can represent a potential target for modulation of steroid hormone-induced inflammation and ensuing HMOD.
Topics: Humans; Receptors, Mineralocorticoid; Aldosterone; Receptors, Estrogen; CD8-Positive T-Lymphocytes; Receptors, G-Protein-Coupled; Hypertension; GTP-Binding Proteins
PubMed: 37827440
DOI: 10.1016/j.steroids.2023.109327 -
The Journal of Biological Chemistry Dec 2020Rhodopsin is a canonical class A photosensitive G protein-coupled receptor (GPCR), yet relatively few pharmaceutical agents targeting this visual receptor have been...
Rhodopsin is a canonical class A photosensitive G protein-coupled receptor (GPCR), yet relatively few pharmaceutical agents targeting this visual receptor have been identified, in part due to the unique characteristics of its light-sensitive, covalently bound retinal ligands. Rhodopsin becomes activated when light isomerizes 11-cis-retinal into an agonist, all-trans-retinal (ATR), which enables the receptor to activate its G protein. We have previously demonstrated that, despite being covalently bound, ATR can display properties of equilibrium binding, yet how this is accomplished is unknown. Here, we describe a new approach for both identifying compounds that can activate and attenuate rhodopsin and testing the hypothesis that opsin binds retinal in equilibrium. Our method uses opsin-based fluorescent sensors, which directly report the formation of active receptor conformations by detecting the binding of G protein or arrestin fragments that have been fused onto the receptor's C terminus. We show that these biosensors can be used to monitor equilibrium binding of the agonist, ATR, as well as the noncovalent binding of β-ionone, an antagonist for G protein activation. Finally, we use these novel biosensors to observe ATR release from an activated, unlabeled receptor and its subsequent transfer to the sensor in real time. Taken together, these data support the retinal equilibrium binding hypothesis. The approach we describe should prove directly translatable to other GPCRs, providing a new tool for ligand discovery and mutant characterization.
Topics: Amino Acid Sequence; Animals; Arrestin; Fluorescence; Fluorescent Dyes; GTP-Binding Proteins; Light; Protein Binding; Protein Conformation; Receptors, G-Protein-Coupled; Rhodopsin; Signal Transduction
PubMed: 33453993
DOI: 10.1074/jbc.RA120.014631 -
Molecules (Basel, Switzerland) Oct 2021Enterovirus 71 (EV-A71) is one of the predominant etiological agents of hand, foot and mouth disease (HMFD), which can cause severe central nervous system infections in...
Enterovirus 71 (EV-A71) is one of the predominant etiological agents of hand, foot and mouth disease (HMFD), which can cause severe central nervous system infections in young children. There is no clinically approved vaccine or antiviral agent against HFMD. The SP40 peptide, derived from the VP1 capsid of EV-A71, was reported to be a promising antiviral peptide that targeted the host receptor(s) involved in viral attachment or entry. So far, the mechanism of action of SP40 peptide is unknown. In this study, interactions between ten reported cell receptors of EV-A71 and the antiviral SP40 peptide were evaluated through molecular docking simulations, followed by in vitro receptor blocking with specific antibodies. The preferable binding region of each receptor to SP40 was predicted by global docking using HPEPDOCK and the cell receptor-SP40 peptide complexes were refined using FlexPepDock. Local molecular docking using GOLD (Genetic Optimization for Ligand Docking) showed that the SP40 peptide had the highest binding score to nucleolin followed by annexin A2, SCARB2 and human tryptophanyl-tRNA synthetase. The average GoldScore for 5 top-scoring models of human cyclophilin, fibronectin, human galectin, DC-SIGN and vimentin were almost similar. Analysis of the nucleolin-SP40 peptide complex showed that SP40 peptide binds to the RNA binding domains (RBDs) of nucleolin. Furthermore, receptor blocking by specific monoclonal antibody was performed for seven cell receptors of EV-A71 and the results showed that the blocking of nucleolin by anti-nucleolin alone conferred a 93% reduction in viral infectivity. Maximum viral inhibition (99.5%) occurred when SCARB2 was concurrently blocked with anti-SCARB2 and the SP40 peptide. This is the first report to reveal the mechanism of action of SP40 peptide in silico through molecular docking analysis. This study provides information on the possible binding site of SP40 peptide to EV-A71 cellular receptors. Such information could be useful to further validate the interaction of the SP40 peptide with nucleolin by site-directed mutagenesis of the nucleolin binding site.
Topics: Antiviral Agents; Enterovirus A, Human; Humans; Molecular Docking Simulation; Peptides; Receptors, Cell Surface; Software
PubMed: 34770987
DOI: 10.3390/molecules26216576 -
The angiotensin II AT1 receptor structure-activity correlations in the light of rhodopsin structure.Physiological Reviews Apr 2007The most prevalent physiological effects of ANG II, the main product of the renin-angiotensin system, are mediated by the AT1 receptor, a rhodopsin-like AGPCR. Numerous... (Review)
Review
The most prevalent physiological effects of ANG II, the main product of the renin-angiotensin system, are mediated by the AT1 receptor, a rhodopsin-like AGPCR. Numerous studies of the cardiovascular effects of synthetic peptide analogs allowed a detailed mapping of ANG II's structural requirements for receptor binding and activation, which were complemented by site-directed mutagenesis studies on the AT1 receptor to investigate the role of its structure in ligand binding, signal transduction, phosphorylation, binding to arrestins, internalization, desensitization, tachyphylaxis, and other properties. The knowledge of the high-resolution structure of rhodopsin allowed homology modeling of the AT1 receptor. The models thus built and mutagenesis data indicate that physiological (agonist binding) or constitutive (mutated receptor) activation may involve different degrees of expansion of the receptor's central cavity. Residues in ANG II structure seem to control these conformational changes and to dictate the type of cytosolic event elicited during the activation. 1) Agonist aromatic residues (Phe8 and Tyr4) favor the coupling to G protein, and 2) absence of these residues can favor a mechanism leading directly to receptor internalization via phosphorylation by specific kinases of the receptor's COOH-terminal Ser and Thr residues, arrestin binding, and clathrin-dependent coated-pit vesicles. On the other hand, the NH2-terminal residues of the agonists ANG II and [Sar1]-ANG II were found to bind by two distinct modes to the AT1 receptor extracellular site flanked by the COOH-terminal segments of the EC-3 loop and the NH2-terminal domain. Since the [Sar1]-ligand is the most potent molecule to trigger tachyphylaxis in AT1 receptors, it was suggested that its corresponding binding mode might be associated with this special condition of receptors.
Topics: Animals; Humans; Receptor, Angiotensin, Type 1; Renin-Angiotensin System; Rhodopsin; Structure-Activity Relationship
PubMed: 17429042
DOI: 10.1152/physrev.00040.2005 -
Proceedings of the National Academy of... Feb 2023The human estrogen receptor (hER) is involved in the regulation of growth, development, and tissue homeostasis. Agonists that bind to the receptor's ligand-binding...
The human estrogen receptor (hER) is involved in the regulation of growth, development, and tissue homeostasis. Agonists that bind to the receptor's ligand-binding domain (LBD) lead to recruitment of coactivators and the enhancement of gene expression. In contrast, antagonists bind to the LBD and block the binding of coactivators thus decreasing gene expressions. In this work, we carry out simulations using the AWSEM (Associative memory, Water mediated, Structure and Energy Model)-Suite force field along with the 3SPN.2C force field for DNA to predict the structure of hER and study its dynamics when binding to DNA and coactivators. Using simulations of antagonist-bound hER and agonist-bound hER by themselves and also along with bound DNA and coactivators, principal component analyses and free energy landscape analyses capture the pathway of domain-domain communication for agonist-bound hER. This communication is mediated through the hinge domains that are ordinarily intrinsically disordered. These disordered segments manipulate the hinge domains much like the strings of a marionette as they twist in different ways when antagonists or agonists are bound to the ligand-binding domain.
Topics: Humans; Receptors, Estrogen; Estrogen Receptor alpha; Ligands; Binding Sites; DNA; Communication; Protein Binding
PubMed: 36730193
DOI: 10.1073/pnas.2216906120 -
The Journal of General Physiology Apr 2019Receptors alternate between resting↔active conformations that bind agonists with low↔high affinity. Here, we define a new agonist attribute, energy efficiency (η),...
Receptors alternate between resting↔active conformations that bind agonists with low↔high affinity. Here, we define a new agonist attribute, energy efficiency (η), as the fraction of ligand-binding energy converted into the mechanical work of the activation conformational change. η depends only on the resting/active agonist-binding energy ratio. In a plot of activation energy versus binding energy (an "efficiency" plot), the slope gives η and the y intercept gives the receptor's intrinsic activation energy (without agonists; ΔG). We used single-channel electrophysiology to estimate η for eight different agonists and ΔG in human endplate acetylcholine receptors (AChRs). From published equilibrium constants, we also estimated η for agonists of K1.1 (BK channels) and muscarinic, γ-aminobutyric acid, glutamate, glycine, and aryl-hydrocarbon receptors, and ΔG for all of these except K1.1. Regarding AChRs, η is 48-56% for agonists related structurally to acetylcholine but is only ∼39% for agonists related to epibatidine; ΔG is 8.4 kcal/mol in adult and 9.6 kcal/mol in fetal receptors. Efficiency plots for all of the above receptors are approximately linear, with η values between 12% and 57% and ΔG values between 2 and 12 kcal/mol. Efficiency appears to be a general attribute of agonist action at receptor binding sites that is useful for understanding binding mechanisms, categorizing agonists, and estimating concentration-response relationships.
Topics: Binding Sites; HEK293 Cells; Humans; Ion Channel Gating; Models, Chemical; Mutation; Protein Conformation; Protein Engineering; Protein Subunits; Receptors, Cholinergic; Thermodynamics
PubMed: 30635369
DOI: 10.1085/jgp.201812215 -
American Journal of Physiology.... Dec 2014Connecting Peptide, or C-peptide, is a product of the insulin prohormone, and is released with and in amounts equimolar to those of insulin. While it was once thought... (Review)
Review
Connecting Peptide, or C-peptide, is a product of the insulin prohormone, and is released with and in amounts equimolar to those of insulin. While it was once thought that C-peptide was biologically inert and had little biological significance beyond its role in the proper folding of insulin, it is now known that C-peptide binds specifically to the cell membranes of a variety of tissues and initiates specific intracellular signaling cascades that are pertussis toxin sensitive. Although it is now clear that C-peptide is a biologically active molecule, controversy still remains as to the physiological significance of the peptide. Interestingly, C-peptide appears to reverse the deleterious effects of high glucose in some tissues, including the kidney, the peripheral nerves, and the vasculature. C-peptide is thus a potential therapeutic agent for the treatment of diabetes-associated long-term complications. This review addresses the possible physiologically relevant roles of C-peptide in both normal and disease states and discusses the effects of the peptide on sensory nerve, renal, and vascular function. Furthermore, we highlight the intracellular effects of the peptide and present novel strategies for the determination of the C-peptide receptor(s). Finally, a hypothesis is offered concerning the relationship between C-peptide and the development of microvascular complications of diabetes.
Topics: Animals; C-Peptide; Diabetes Complications; Diabetes Mellitus; Humans; Hypoglycemic Agents; Receptor, Insulin
PubMed: 25249503
DOI: 10.1152/ajpendo.00130.2014 -
Frontiers in Microbiology 2022Merkel cell polyomavirus (MCV) contains double-stranded DNA as its genome and is the fifth polyomavirus that infects humans. The virus causes Merkel cell carcinoma...
Merkel cell polyomavirus (MCV) contains double-stranded DNA as its genome and is the fifth polyomavirus that infects humans. The virus causes Merkel cell carcinoma (aggressive skin cancer). Till present, no proper drug or vaccines are available to treat/prevent the virus infection and stop the emergence of Merkel cell carcinoma. In this study, computational vaccine design strategies were applied to design a chimeric-epitopes vaccine against the virus. The complete proteome comprised of four proteins was filtered through various vaccine candidacy parameters and as such two proteins, namely, capsid protein VP1 and capsid protein VP2, were considered as good vaccine targets. Furthermore, they harbor safe and potential B and T cell epitopes, which can be used in a chimeric multiepitopes-based vaccine design. The epitopes of the vaccine have maximum world population coverage of 95.04%. The designed vaccine structure was modeled in 3D that reported maximum residues in favored regions (95.7%) of the Ramachandran plot. The interactions analysis with different human immune receptors like TLR3, MHC-I, and MHC-II illustrated vaccine's good binding affinity and stable dynamics. The structural deviations of the vaccine receptor(s) complexes are within 5 Å, where majority of the receptors residues remain in good equilibrium in the simulation time. Also, the vaccine was found to form between 60 and 100 hydrogen bonds to receptors. The vaccine stimulated strong immune responses in addition to interferon and cytokines. The strength of vaccine-receptor(s) binding was further affirmed by binding energies estimation that concluded <-150.32 kcal/mol of net binding energy. All these findings suggest the vaccine as a promising candidate that needs further experimental testing to disclose its real immune protective efficacy. Furthermore, the designed vaccine might accelerate vaccine development against the MCV and could save time and expenses.
PubMed: 35836414
DOI: 10.3389/fmicb.2022.929669 -
Biomolecules Mar 2019Protein phosphorylation often switches cellular activity from one state to another, and this post-translational modification plays an important role in gene regulation... (Review)
Review
Protein phosphorylation often switches cellular activity from one state to another, and this post-translational modification plays an important role in gene regulation by the nuclear hormone receptor superfamily, including the glucocorticoid receptor (GR). Cell signaling pathways that regulate phosphorylation of the GR are important determinants of GR actions, including lymphoid cell apoptosis, DNA binding, and interaction with coregulatory proteins. All major functionally important phosphorylation sites in the human GR are located in its N-terminal domain (NTD), which possesses a powerful transactivation domain, AF1. The GR NTD exists as an intrinsically disordered protein (IDP) and undergoes disorder-order transition for AF1's efficient interaction with several coregulatory proteins and subsequent AF1-mediated GR activity. It has been reported that GR's NTD/AF1 undergoes such disorder-order transition following site-specific phosphorylation. This review provides currently available information regarding the role of GR phosphorylation in its action and highlights the possible underlying mechanisms of action.
Topics: Animals; Humans; Intrinsically Disordered Proteins; Phosphorylation; Receptors, Glucocorticoid
PubMed: 30862072
DOI: 10.3390/biom9030095 -
Neuroscience Letters Apr 2014Agonist-activated μ-opioid receptor (OPRM1) undergoes robust receptor phosphorylation by G protein-coupled receptor kinases and subsequent β-arrestin recruitment,...
Agonist-activated μ-opioid receptor (OPRM1) undergoes robust receptor phosphorylation by G protein-coupled receptor kinases and subsequent β-arrestin recruitment, triggering receptor internalization and desensitization. Morphine, a widely prescribed opioid, induces receptor phosphorylation inefficiently. Previously we reported that FK506 binding protein 12 (FKBP12) specifically interacts with OPRM1 and such interaction attenuates receptor phosphorylation and facilitates morphine-induced recruitment and activation of protein kinase C. In the current study, we demonstrated that the association of FKBP12 with OPRM1 also affects morphine-induced receptor internalization and G protein-dependent adenylyl cyclase desensitization. Morphine induced faster receptor internalization and adenylyl cyclase desensitization in cells expressing OPRM1 with Pro(353) mutated to Ala (OPRM1P353A), which does not interact with FKBP12, or in the presence of FK506 which dissociates the receptor-FKBP12 interaction. Furthermore, knockdown of cellular FKBP12 level by siRNA accelerated morphine-induced receptor internalization and adenylyl cyclase desensitization. Our study further demonstrated that peptidyl prolyl cis-trans isomerase activity of FKBP12 probably plays a role in inhibition of receptor phosphorylation. In the view that internalized receptor recycles and thus counteracts the development of analgesic tolerance, receptor's association with FKBP12 could also contribute to the development of morphine tolerance through modulation of receptor trafficking.
Topics: Adenylyl Cyclases; HEK293 Cells; Humans; Morphine; Mutation; Phosphorylation; RNA, Small Interfering; Receptors, Opioid, mu; Tacrolimus; Tacrolimus Binding Protein 1A
PubMed: 24607931
DOI: 10.1016/j.neulet.2014.02.059