Search Results (47)

G-protein-coupled receptors (GPCRs) are a group of various membrane proteins that mediate essential physiological processes by translating extracellular signals into intracellular responses. The β2-Adrenergic Receptor (β2-AR), a key GPCR, plays a critical role in smooth muscle relaxation, bronchodilation, and cardiovascular function, making it an important therapeutic target for diseases such as asthma and hypertension. Diketopiperazines (DPKs), as cyclic peptides, have shown promise as scaffolds for inhibiting protein interactions and modulating receptor activity, offering a potential alternative to traditional small-molecule inhibitors with reduced side effects. In this study, five DPK derivatives were selected from the PubChem database and evaluated for their binding affinity to the 3D structure of β2-AR (PDB ID = 2RH1) through molecular docking studies using AutoDock 4.6 and MGLTools. The binding energy and hydrogen bond formation of each compound were evaluated to determine their interaction efficiency. Among the compounds, tryptophan-proline diketopiperazine (compound 3) exhibited the highest binding affinity with a binding energy of −5.89 kcal/mol. This enhanced interaction is attributed to the aromatic nature of tryptophan, which promotes strong π-π stacking interactions, and the rigidity of proline, which optimally fits within the receptor’s binding pocket. Hydrophobic interactions further stabilized the complex. These findings highlight compound 3 as a promising β2-AR modulator, providing valuable insights for the design of peptide-based inhibitors targeting β2-AR-related pathologies. Full article

Recent bioassay studies have unexpectedly supported the high (computationally predicted) binding affinities of angiotensin receptor blockers (ARBs) at α-adrenergic receptors (αARs) in isolated smooth muscle. Computational predictions from ligand docking studies are consistent with very low concentrations of ARBs (e.g., sartans or bisartans) that partially reduce (20–50%) the contractile response to phenylephrine, suggesting that some ARBs may function as partial inverse agonists at αARs. Virtual ligand screening (docking) and molecular dynamics (MD) simulations were carried out to explore the binding affinities and stabilities of selected non-peptide ligands (e.g., ARBs and small-molecule opioids) for several G-protein coupled receptor (GPCR) types, including angiotensin II (AngII) type 1 receptor (AT₁R), α1AR, α2AR, and μ-(µOR) and ժ-opioid receptors (ժOR). Results: All ligands docked preferentially to the binding pocket on the cell surface domain of the GPCR types investigated. Drug binding was characterized by weak interactions (hydrophobic, hydrogen bonding, pi-pi) and stronger ionic and salt-bridge interactions (cation-pi and cation-anion interactions). Ligands specific to each GPCR category showed considerable cross-binding with alternative GPCRs, with small-molecule medications appearing less selective than their peptide or ARB functional equivalents. ARBs that exhibit higher affinities for AT₁R also demonstrate higher affinities for µORs and ժORs than opiate ligands, such as fentanyl and naltrexone. Moreover, ARBs had a higher affinity for αARs than either alpha agonists (epinephrine and phenylephrine) or inhibitors (prazosin and doxazosin). MD simulations of membrane-embedded ARB-GPCR complexes proved stable over nanosecond time scales and suggested that some ARBs may behave as agonists or antagonists depending on the GPCR type. Based on the results presented in this and related investigations, we propose that agonists bind to the resting A-site of GPCRs, while inverse agonists occupy the desensitizing D-site, which partial agonists like morphine and fentanyl share, contributing to addiction. ARBs block both AngII and alpha receptors, suggesting that they are more potent antihypertensive drugs than ACE inhibitors. ARBs have the potential to inhibit morphine tolerance and appear to disrupt receptor desensitization processes, potentially by competing at the D-site. Our results suggest the possible therapeutic potential of ARBs in treating methamphetamine and opiate addictions. Full article

G protein-coupled receptors (GPCRs) constitute the largest and most frequently used family of molecular drug targets. The simplicity of GPCR drug design results from their common seven-transmembrane-helix topology and well-understood signaling pathways. GPCRs are extremely sensitive to slight changes in the chemical structure of compounds, which allows for the reliable design of highly selective and specific drugs. Only recently has the number of GPCR structures, both in their active and inactive conformations, together with their active ligands, become sufficient to comprehensively apply machine learning in decision support systems to predict compound activity in drug design. Here, we describe GPCRVS, an efficient machine learning system for the online assessment of the compound activity against several GPCR targets, including peptide- and protein-binding GPCRs, which are the most difficult for virtual screening tasks. As a decision support system, GPCRVS evaluates compounds in terms of their activity range, the pharmacological effect they exert on the receptor, and the binding mode they could demonstrate for different types and subtypes of GPCRs. GPCRVS allows for the evaluation of compounds ranging from small molecules to short peptides provided in common chemical file formats. The results of the activity class assignment and the binding affinity prediction are provided in comparison with predictions for known active ligands of each included GPCR. Multiclass classification in GPCRVS, handling incomplete and fuzzy biological data, was validated on ChEMBL and Google Patents-retrieved data sets for class B GPCRs and chemokine CC and CXC receptors. Full article

G protein-coupled receptors (GPCRs) play essential roles in numerous physiological processes and are key targets for drug development. Among them, adhesion GPCRs (aGPCRs) stand out for their unique domain structures and diverse functions. ADGRG2 is a member of the aGPCR family and is involved in the regulation of various systems in the human body, including reproductive, nervous, cardiovascular, and endocrine systems. Investigating ADGRG2 antagonists enhances our understanding of its regulatory roles in diverse physiological processes, yet their precise mechanisms of action remain unclear. To address this, we investigated the antagonistic mechanism of ADGRG2 by examining its interactions with various antagonists, including short peptides (F601D, F601E) and small molecules (deoxycorticosterone, DOC). Using advanced metadynamics simulation, ligand binding assay and cAMP assay, we elucidated the binding modes of these antagonists. We identified five distinct F601D-ADGRG2 complex states, four F601E-ADGRG2 complex states, and three DOC-ADGRG2 complex states, which were each characterized by specific hydrogen bonds or polar interactions with their respective ligands. Although the ADGRG2 binding pocket consists of both polar and hydrophobic residues, our biochemical experiments revealed that mutations in polar amino acids significantly reduce the efficacy of the antagonists. Our results show that F601D, F601E, and DOC induce the formation of Y758^ECL2-N775^5.32-N860^7.46 polar networks within ADGRG2, effectively stabilizing its inactive state. Additionally, we compared the active and inactive states of ADGRG2, highlighting the structural changes induced by antagonist-stabilized polar networks and their impact on receptor conformation. These findings provide important insights into the biology of aGPCRs and provide theoretical support for the rational design of therapeutic drugs targeting ADGRG2. Full article

Neuropeptide CCHamide-1 (abbreviated as CCHa1) is a recently discovered peptide that is present in many arthropods and is the ligand of the CCHa1R, a member of the G protein-coupled receptors (GPCRs) superfamily, which plays a regulatory role in diverse physiological processes such as feeding, circadian rhythm, insulin production, lipid metabolism, growth, and reproduction. However, the function of this gene in aphids is still unknown. Here, we characterized and determined the potential role of CCHa1/CCHa1R signaling in the pea aphid, Acyrthosiphon pisum, which is a notorious pest in agriculture. The docking analysis revealed that the CCHa1 peptide binds to its receptor CCHa1R through specific amino acid residues, which are critical for maintaining the structural and functional integrity of the peptide–receptor complex. Quantitative real-time reverse transcription-PCR (qRT-PCR) revealed the expression levels of CCHa1/CCHa1R transcripts in different development stages and different tissues, indicating that the CCHa1 expression was high in the first nymphal instar compared to the upcoming nymphal instars and adults, and was predominantly high in the brain. The CCHa1/CCHa1R transcript levels were significantly upregulated in starved aphids compared to fed aphids. Moreover, RNAi knockdown by the injection of dsRNA-CCHa1 and dsRNA-CCHa1R significantly reduced the corresponding expression of the target gene and reduced their food intake in adult aphids, as revealed by the electrical penetration graph results. CCHa1/CCHa1R-silencing also reduced the reproduction, but not the survival, in A. pisum. Our data demonstrated that CCHa1/CCHa1R play a role in the regulation of feeding in A. pisum, suggesting a role of the CCHa1 signaling pathway in the aphids relating to their nutritional status. Full article

Chemerin is a chemotactic adipokine that participates in a multitude of physiological processes, including adipogenesis, leukocyte chemotaxis, and neuroinflammation. Chemerin exerts biological functions through binding to one or more of its G protein-coupled receptors (GPCRs), namely chemokine-like receptor 1 (CMKLR1), G protein-coupled receptor 1 (GPR1), and CC-motif receptor-like 2 (CCRL2). Of these receptors, CMKLR1 and GPR1 have been confirmed as signaling receptors of chemerin, whereas CCRL2 serves as a chemerin-binding protein without transmembrane signaling. High-resolution structures of two chemerin receptors are now available thanks to recent advancements in structure biology. This review focuses on the structural perspectives of the chemerin receptors with an emphasis on the structure–activity correlation, including key components of the two receptors for ligand recognition and conformational changes induced by chemerin and its derivative peptides for G protein activation. There are also comparisons between the two chemerin receptors and selected GPCRs with peptide ligands for better appreciation of the shared and distinct features of the chemerin receptors in ligand recognition and transmembrane signaling, and in the evolution of this subclass of GPCRs. Full article

The first member of the arrestin family, visual arrestin-1, was discovered in the late 1970s. Later, the other three mammalian subtypes were identified and cloned. The first described function was regulation of G protein-coupled receptor (GPCR) signaling: arrestins bind active phosphorylated GPCRs, blocking their coupling to G proteins. It was later discovered that receptor-bound and free arrestins interact with numerous proteins, regulating GPCR trafficking and various signaling pathways, including those that determine cell fate. Arrestins have no enzymatic activity; they function by organizing multi-protein complexes and localizing their interaction partners to particular cellular compartments. Today we understand the molecular mechanism of arrestin interactions with GPCRs better than the mechanisms underlying other functions. However, even limited knowledge enabled the construction of signaling-biased arrestin mutants and extraction of biologically active monofunctional peptides from these multifunctional proteins. Manipulation of cellular signaling with arrestin-based tools has research and likely therapeutic potential: re-engineered proteins and their parts can produce effects that conventional small-molecule drugs cannot. Full article

Corticotropin-releasing factor or hormone (CRF or CRH) and the urocortins regulate a plethora of physiological functions and are involved in many pathophysiological processes. CRF and urocortins belong to the family of CRF peptides (CRF family), which includes sauvagine, urotensin, and many synthetic peptide and non-peptide CRF analogs. Several of the CRF analogs have shown considerable therapeutic potential in the treatment of various diseases. The CRF peptide family act by interacting with two types of plasma membrane proteins, type 1 (CRF₁R) and type 2 (CRF₂R), which belong to subfamily B1 of the family B G-protein-coupled receptors (GPCRs). This work describes the structure of CRF peptides and their receptors and the activation mechanism of the latter, which is compared with that of other GPCRs. It also discusses recent structural information that rationalizes the selective binding of various ligands to the two CRF receptor types and the activation of receptors by different agonists. Full article

Studying primordial events in cancer is pivotal for identifying predictive molecular indicators and for targeted intervention. While the involvement of G-protein-coupled receptors (GPCRs) in cancer is growing, GPCR-based therapies are yet rare. Here, we demonstrate the overexpression of protease-activated receptor 2 (PAR2), a GPCR member in the fallopian tubes (FTs) of high-risk BRCA carriers as compared to null in healthy tissues of FT. FTs, the origin of ovarian cancer, are known to express genes of serous tubal intraepithelial carcinoma (STICs), a precursor lesion of high-grade serous carcinoma (HGSC). PAR2 expression in FTs may serve as an early prediction sensor for ovarian cancer. We show now that knocking down Par2 inhibits ovarian cancer peritoneal dissemination in vivo, pointing to the central role of PAR2. Previously we identified pleckstrin homology (PH) binding domains within PAR1,2&4 as critical sites for cancer-growth. These motifs associate with PH-signal proteins via launching a discrete signaling network in cancer. Subsequently, we selected a compound from a library of backbone cyclic peptides generated toward the PAR PH binding motif, namely the lead compound, Pc(4-4). Pc(4-4) binds to the PAR PH binding domain and blocks the association of PH-signal proteins, such as Akt or Etk/Bmx with PAR2. It attenuates PAR2 oncogenic activity. The potent inhibitory function of Pc(4-4) is demonstrated via inhibition of ovarian cancer peritoneal spread in mice. While the detection of PAR2 may serve as a predictor for ovarian cancer, the novel Pc(4-4) compound may serve as a powerful medicament in STICs and ovarian cancer. This is the first demonstration of the involvement of PAR PH binding motif signaling in ovarian cancer and Pc(4-4) as a potential therapy treatment. Full article

Tetrazole heterocycle is a promising scaffold in drug design, and it is incorporated into active pharmaceutical ingredients of medications of various actions: hypotensives, diuretics, antihistamines, antibiotics, analgesics, and others. This heterocyclic system is metabolically stable and easily participates in various intermolecular interactions with different biological targets through hydrogen bonding, conjugation, or van der Waals forces. In the present review, a systematic analysis of the activity of tetrazole derivatives against type 2 diabetes mellitus (T2DM) has been performed. As it was shown, the tetrazolyl moiety is a key fragment of many antidiabetic agents with different activities, including the following: peroxisome proliferator-activated receptors (PPARs) agonists, protein tyrosine phosphatase 1B (PTP1B) inhibitors, aldose reductase (AR) inhibitors, dipeptidyl peptidase-4 (DPP-4) inhibitors and glucagon-like peptide 1 (GLP-1) agonists, G protein-coupled receptor (GPCRs) agonists, glycogen phosphorylases (GP) Inhibitors, α-glycosidase (AG) Inhibitors, sodium glucose co-transporter (SGLT) inhibitors, fructose-1,6-bisphosphatase (FBPase) inhibitors, IkB kinase ε (IKKε) and TANK binding kinase 1 (TBK1) inhibitors, and 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). In many cases, the tetrazole-containing leader compounds markedly exceed the activity of medications already known and used in T2DM therapy, and some of them are undergoing clinical trials. In addition, tetrazole derivatives are very often used to act on diabetes-related targets or to treat post-diabetic disorders. Full article

G protein-coupled receptor 83 (GPR83) is a class A G protein-coupled receptor with predominant expression in the cerebellum and proposed function in the regulation of food intake and in anxiety-like behavior. The neuropeptide PEN has been suggested as a specific GPR83 ligand. However, conflicting reports exist about whether PEN is indeed able to bind and activate GPR83. This study was initiated to evaluate PEN as a potential ligand of GPR83. Employing several second messenger and other GPCR activation assays as well as a radioligand binding assay, and using multiple GPR83 plasmids and PEN peptides from different sources, no experimental evidence was found to support a role of PEN as a GPR83 ligand. Full article

The ErbB RTKs (EGFR, HER2, HER3, and HER4) have been well-studied in cancer. EGFR, HER2, and HER3 stimulate cancer proliferation, principally by activating the phosphatidylinositol-3-kinase and extracellular signal-regulated kinase (ERK) pathways, resulting in increased cancer cell survival and proliferation. Cancer cells have high densities of the EGFR, HER2, and HER3 causing phosphorylation of tyrosine amino acids on protein substrates and tyrosine amino acids near the C-terminal of the RTKs. After transforming growth factor (TGF) α binds to the EGFR, homodimers or EGFR heterodimers form. HER2 forms heterodimers with the EGFR, HER3, and HER4. The EGFR, HER2, and HER3 are overexpressed in lung cancer patient tumors, and monoclonal antibodies (mAbs), such as Herceptin against HER2, are used to treat breast cancer patients. Patients with EGFR mutations are treated with tyrosine kinase inhibitors, such as gefitinib or osimertinib. Peptide GPCRs, such as NTSR1, are present in many cancers, and neurotensin (NTS) stimulates the growth of cancer cells. Lung cancer proliferation is impaired by SR48692, an NTSR1 antagonist. SR48692 is synergistic with gefitinib at inhibiting lung cancer growth. Adding NTS to lung cancer cells increases the shedding of TGFα, which activates the EGFR, or neuregulin-1, which activates HER3. The transactivation process is impaired by SRC, matrix metalloprotease, and reactive oxygen species inhibitors. While the transactivation process is complicated, it is fast and occurs within minutes after adding NTS to cancer cells. This review emphasizes the use of tyrosine kinase inhibitors and SR48692 to impair transactivation and cancer growth. Full article

CC chemokine receptor 6 (CCR6) is one of the members of the G-protein-coupled receptor (GPCR) family that is upregulated in many immune-related cells, such as B lymphocytes, effector and memory T cells, regulatory T cells, and immature dendritic cells. The coordination between CCR6 and its ligand CC motif chemokine ligand 20 (CCL20) is deeply involved in the pathogenesis of various diseases, such as cancer, psoriasis, and autoimmune diseases. Thus, CCR6 is an attractive target for therapy and is being investigated as a diagnostic marker for various diseases. In a previous study, we developed an anti-mouse CCR6 (mCCR6) monoclonal antibody (mAb), C₆Mab-13 (rat IgG₁, kappa), that was applicable for flow cytometry by immunizing a rat with the N-terminal peptide of mCCR6. In this study, we investigated the binding epitope of C₆Mab-13 using an enzyme-linked immunosorbent assay (ELISA) and the surface plasmon resonance (SPR) method, which were conducted with respect to the synthesized point-mutated-peptides within the 1–20 amino acid region of mCCR6. In the ELISA results, C₆Mab-13 lost its ability to react to the alanine-substituted peptide of mCCR6 at Asp11, thereby identifying Asp11 as the epitope of C₆Mab-13. In our SPR analysis, the dissociation constants (K_D) could not be calculated for the G9A and D11A mutants due to the lack of binding. The SPR analysis demonstrated that the C₆Mab-13 epitope comprises Gly9 and Asp11. Taken together, the key binding epitope of C₆Mab-13 was determined to be located around Asp11 on mCCR6. Based on the epitope information, C₆Mab-13 could be useful for further functional analysis of mCCR6 in future studies. Full article

Parathyroid Hormone (PTH) plays a crucial role in the maintenance of calcium homeostasis directly acting on bone and kidneys and indirectly on the intestine. However, a large family of PTH-related peptides exists that exerts other physiological effects on different tissues and organs, such as the Central Nervous System (CNS). In humans, PTH-related peptides are Parathyroid Hormone (PTH), PTH-like hormones (PTHrP and PTHLH), and tuberoinfundibular peptide of 39 (TIP39 or PTH2). With different affinities, these ligands can bind parathyroid receptor type 1 (PTH1R) and type 2 (PTH2R), which are part of the type II G-protein-coupled-receptors (GPCRs) family. The PTH/PTHrP/PTH1R system has been found to be expressed in many areas of the brain (hippocampus, amygdala, hypothalamus, caudate nucleus, corpus callosum, subthalamic nucleus, thalamus, substantia nigra, cerebellum), and literature data suggest the system exercises a protective action against neuroinflammation and neurodegeneration, with positive effects on memory and hyperalgesia. TIP39 is a small peptide belonging to the PTH-related family with a high affinity for PTH2R in the CNS. The TIP39/PTH2R system has been proposed to mediate many regulatory and functional roles in the brain and to modulate auditory, nociceptive, and sexual maturation functions. This review aims to summarize the knowledge of PTH-related peptides distribution and functions in the CNS and to highlight the gaps that still need to be filled. Full article

Heterotrimeric guanine nucleotide-binding proteins (G proteins) are among the most important cellular signaling components, especially G protein-coupled receptors (GPCRs). G proteins comprise three subunits, Gα, Gβ, and Gγ. Gα is the key subunit, and its structural state regulates the active status of G proteins. Interaction of guanosine diphosphate (GDP) or guanosine triphosphate (GTP) with Gα switches G protein into basal or active states, respectively. Genetic alteration in Gα could be responsible for the development of various diseases due to its critical role in cell signaling. Specifically, loss-of-function mutations of Gαs are associated with parathyroid hormone-resistant syndrome such as inactivating parathyroid hormone/parathyroid hormone-related peptide (PTH/PTHrP) signaling disorders (iPPSDs), whereas gain-of-function mutations of Gαs are associated with McCune–Albright syndrome and tumor development. In the present study, we analyzed the structural and functional implications of natural variants of the Gαs subtype observed in iPPSDs. Although a few tested natural variants did not alter the structure and function of Gαs, others induced drastic conformational changes in Gαs, resulting in improper folding and aggregation of the proteins. Other natural variants induced only mild conformational changes but altered the GDP/GTP exchange kinetics. Therefore, the results shed light on the relationship between natural variants of Gα and iPPSDs. Full article