Search Results (260)

X-ray free-electron lasers (XFELs) have revolutionized structural biology by enabling “diffraction-before-destruction” and capturing the ultrafast dynamics of life. However, the intrinsic sparsity and noise of XFEL diffraction snapshots, often complicated by multi-lattice overlaps, create a formidable computational bottleneck that limits data utilization and structural fidelity. Here, we present MCDPS-SFX, a robust indexing framework based on a reference-based, whole-pattern matching principle integrated with parallelized iterative refinement. By exhaustively sampling orientation space and progressively rejecting outliers, MCDPS-SFX significantly outperforms legacy algorithms—more than doubling crystal yields in heterogeneous datasets (e.g., 21,807 vs. 8792 for MOSFLM)—and achieves highly competitive yields comparable to state-of-the-art indexers, such as extracting over 90,000 lattices in the lysozyme benchmark. We demonstrate its efficacy on standard benchmarks and technically demanding G-protein-coupled receptor (GPCR) systems, including the rhodopsin–arrestin complex and the glucagon receptor. MCDPS-SFX consistently produces high-quality data statistics, enabling the high-resolution visualization of functionally critical, flexible regions such as phosphorylated receptor tails. Our results provide a powerful tool for enhancing the scientific output of XFEL experiments, offering a robust alternative for maximizing information recovery from weakly diffracting or overlapping crystalline samples. Full article

Chronic non-healing wounds, prevalent in diabetic and vascular diseases, arise from dysregulated chemokine signaling that disrupts angiogenesis, immune coordination, and tissue remodeling. This review synthesizes current knowledge on chemokine biology in wound repair, with a focus on their spatiotemporal regulation across the hemostasis, inflammation, proliferation, and remodeling phases. We detail chemokine classification (CC, CXC, CX3C, and C families), receptor interactions, and downstream pathways, including G protein-dependent and β-arrestin-biased mechanisms. Furthermore, we evaluate emerging therapeutic strategies, including neutralizing antibodies, receptor antagonists, engineered chemokines, and biomaterial-based delivery systems designed to restore chemokine gradient integrity and promote healing. Recent advances in structural biology and protein engineering are highlighted as enabling the design of biased ligands and multi-target inhibitors to overcome chemokine redundancy. The review concludes that precision modulation of chemokine networks offers a promising translational framework to redirect chronic inflammation toward regenerative healing, thereby addressing a significant unmet clinical need in chronic wound management. Full article

Background: Opioid receptors are a commonly used target for treatment of pain conditions. Most opioids used in therapy are linked to adverse effects such as tolerance, dependence, and respiratory depression. Indole alkaloids acting on opioid receptors may provide a novel molecular mechanism to confer analgesic effects. Results: Indole alkaloids such as ibogaine and mitragynine act on μ-opioid receptors as biased full or partial agonists that do not, or much less strongly, recruit β-arrestin compared to non-biased agonists. The recruitment of β-arrestin has been linked to adverse effects, most notably substantial respiratory depression. The molecular mechanism of biased activation has been proposed to be associated with accommodation of the indole structure that leads to a different spatial orientation of amino acid residues in transmembrane regions 2 and 3 of the μ-opioid receptor as well as extracellular helix 8. Conclusions: Naturally occurring indole alkaloids show biased G-protein coupled activation of opioid receptors with limited recruitment of β-arrestin, thus limiting commonly observed adverse effects. Indole alkaloids may present a feasible structure to develop new biased opioid modulators with an improved risk-to-benefit ratio. Full article

The neuropharmacology of psychedelics has traditionally focused on serotonergic mechanisms, particularly 5-HT2A receptor activation. However, this paradigm incompletely explains the diversity of neurobiological and therapeutic effects observed across psychedelic compounds. Non-classical psychedelics such as salvinorin A, the primary active constituent of Salvia divinorum, challenge this framework through direct kappa opioid receptor (KOR) agonism, representing a serotonin-independent pathway to altered consciousness. This review systematically examines the role of the endogenous opioid system in mediating psychedelic effects, with emphasis on salvinorin A’s unique KOR-dependent mechanisms. We synthesized preclinical and clinical evidence from in vitro studies, genetically modified animal models, optogenetic circuit dissection, and human neuroimaging trials. Salvinorin A’s selective KOR activation is characterized by pronounced β-arrestin-biased signaling, distinguishing it from endogenous dynorphins and classical KOR agonists. This produces rapid receptor desensitization, transient functional plasticity, and profound dissociative effects mediated through thalamocortical disruption, mesolimbic dopaminergic suppression, and fragmentation of large-scale brain networks. Classical serotonergic psychedelics indirectly engage opioid systems through downstream 5-HT2A signaling, contributing to analgesic and mood-regulatory effects via secondary MOR/DOR modulation. Despite being a potent opioid agonist, salvinorin A exhibits low abuse potential due to aversive phenomenology, dopaminergic suppression, and absence of positive reinforcement in animal models. Incorporating opioid receptor pharmacology into psychedelic neuroscience expands mechanistic understanding beyond serotonin-centric models, revealing multiple neurochemical pathways capable of inducing therapeutically relevant altered states. This framework enables rational development of biased KOR ligands and establishes salvinorin A as a paradigmatic model for non-serotonergic psychedelia with applications in treatment-resistant depression, addiction, and chronic pain. Full article

The G protein-coupled galanin receptors include three different subtypes: galanin receptor 1, 2 and 3 (GalR1, GalR2, GalR3). The neuropeptide galanin is the principal natural agonist of the galanin receptors, the so-called galaninergic system. Galanin-like peptide and spexin have also been identified as natural ligands of the galanin receptors. Galanin receptors are widely expressed in the brain; however, they can be found in other tissues, such as the skeletal muscle, the heart, and the gastrointestinal tract. The galaninergic system regulates diverse biological processes, including feeding behavior, neuroprotection, learning, memory, cardiovascular and renal function, and nociception. Its dysregulation is associated with various diseases, such as Alzheimer’s disease, diabetes mellitus, epilepsy, depression, and cancer. The stimulation of GalR1 and GalR3 leads to the Gαi/o-type G protein-mediated inhibition of cyclic AMP/protein kinase A, whereas GalR2 stimulation initiates phospholipase C activation via Gαq/11-type G proteins. A galanin-activated β-arrestin-dependent pathway has also been described for GalR2. In this review, we summarize the recent advances concerning galanin receptor signaling, including both the G protein-dependent and -independent pathways. A better understanding of the complex interplay of the signaling molecules, receptors, and various signaling pathways is crucial for the future development of specific agonists with therapeutic potential. Full article

Background/Objectives: Histamine H₁ receptors mediate multiple physiological and pathophysiological processes, including inflammation and allergy, by regulating downstream gene expression via transcription factors. cAMP response element-binding protein (CREB) is a major transcription factor whose phosphorylation is regulated by multiple signaling pathways. Although CREB is closely involved in multiple physiological and pathophysiological processes, the detailed intracellular signaling pathway of H₁ receptor-mediated CREB phosphorylation remains to be elucidated. We investigated the roles of G_q proteins and arrestins in H₁ receptor-mediated CREB phosphorylation. Methods: We constructed Chinese hamster ovary (CHO) expressing human wild-type (WT) H₁ receptors and two types of C-terminal mutants. One mutant was constructed by truncating the serine 487 residue only at the C-terminus (S487Trunc), and the other was constructed by substituting the serine 487 residue at the C-terminus with alanine (S487A). S487Trunc is a G_q protein-biased while S487A is an arrestin-biased receptor. The expressions of CREB and its phosphorylated form were assessed by immunoblotting. Results: Histamine promoted CREB phosphorylation in CHO cells expressing WT or S487Trunc receptors, but not in cells expressing S487A. Inhibitors of protein kinase C (PKC), extracellular signal-regulated kinase (ERK), or c-Jun N-terminal kinase (JNK), and Ca²⁺ chelator suppressed histamine-induced CREB phosphorylation in CHO cells expressing WT or S487Trunc receptors. Basal CREB phosphorylation levels increased following β-arrestin overexpression and decreased after their siRNA-mediated knockdown, thus modulating histamine-stimulated CREB phosphorylation in WT CHO cells. Conclusions: H₁ receptor-mediated CREB phosphorylation is induced through G_q protein/Ca²⁺/PKC-dependent ERK and JNK activation; arrestins can modulate this process by regulating basal CREB phosphorylation. Full article

Background: This study is part of the HEAL ITALIA partnership, funded by the National Recovery and Resilience Plan (PNRR) and the European Union. Heart failure (HF) is a serious health problem, with a reduced density of the β1-adrenergic receptor (β1-AR) in the myocardium as a hallmark. It is unclear whether this downregulation causes dysfunction or represents an epiphenomenon. Recent evidence implicates oxidative stress and mitochondrial signaling, particularly through the 18 kDa translocator protein (TSPO), in the regulation of the β1-AR, with possible modulation by estrogen. Objectives: To determine (1) the role of β1-AR desensitization in the onset and development of HF; (2) whether monocytes can represent a suitable ex vivo model for sex-oriented mechanistic studies in the cardiac field; (3) whether monocytes isolated from peripheral blood of patients can represent a diagnostic and/or therapy response biomarker by monitoring β1-AR density; (4) whether and how the mitochondrial receptor TSPO is involved in the β1-AR dysregulation observed in HF; and (5) whether the mechanisms linked to the onset of HF are regulated in a sex-specific manner through the effect of estrogen and/or the X chromosome on the expression of specific microRNAs. Methods: Using an integrated in vitro-ex vivo-in vivo methodological approach, we will evaluate the density of β1/β2-AR receptors, the downstream signaling (GRK2/β-arrestin), mitochondrial and redox parameters, and miRNA profiles in human monocytes and cardiomyocytes, and in mouse hearts after HF following pressure overload. Conclusions: The goal is to better understand the mechanisms underlying β1-AR desensitization, verify monocytes as peripheral markers of disease progression and response to therapy, and provide potentially useful information for the development of gender-specific therapies for heart failure. Full article

In all arrestins, the gate loop is the central part of the lariat loop, which has an unusual shape and participates in maintaining the basal conformation. The gate loop supplies two out of five charges that constitute a stabilizing intramolecular interaction, aspartates in the polar core between the two domains. To elucidate the functional role of individual gate loop residues, we performed comprehensive site-directed mutagenesis and tested the effects of mutations on arrestin-1 binding to its preferred target, phosphorylated light-activated rhodopsin, and unphosphorylated activated form. Out of 34 mutations tested, 24 and 25 affected the binding to phosphorylated and unphosphorylated rhodopsin, respectively. Manipulation of residues following polar core aspartates reduced preference for phosphorylated over unphosphorylated light-activated rhodopsin as dramatically as replacing these negatively charged aspartates with positively charged arginine. The data show that numerous lariat loop residues play distinct roles in arrestin-1 binding and its exquisite preference for phosphorylated light-activated rhodopsin. Full article

This study compared the gonadotropin gene sequences (LH and FSH subunits) of Cynomolgus and Rhesus monkeys and produced recombinant single-chain LHβ/α and FSHβ/α proteins. The α- and FSHβ-subunit sequences were identical between species, while LHβ showed only minor synonymous differences. The recombinant hormones were successfully expressed and shown to be mainly N-glycosylated. Recombinant monkey FSHβ/α activated cAMP signaling in human FSH receptor-expressing cells, confirming its biological activity. β-arrestin 1 was found to have dual roles: its absence increased cAMP signaling (negative regulation), but it was required for ERK1/2 activation. ERK activation depended mainly on the cAMP/PKA pathway. Human and rat FSH receptors displayed different ERK activation timing, indicating species-specific signaling behavior. Overall, the study establishes a reliable system for producing functional recombinant monkey gonadotropins and clarifies how β-arrestin 1 differentially regulates FSH receptor signaling. Full article

G protein-coupled receptors (GPCRs) are the largest family of diverse receptors in eukaryotic organisms, playing a critical role in modulating human physiology. It therefore comes as no surprise that about 36% of all currently available drugs target this superfamily. When an agonist binds to a GPCR, it induces conformational changes in the receptor that allow it to interact with intracellular proteins. This interaction triggers downstream signaling cascades that alter the cell’s activity. GPCR signaling is complex, as GPCRs transmit signals through coupling with G proteins, arrestins, and numerous other intracellular effectors. Different ligands, receptor subtypes, and cellular environments can result in the activation of distinct signaling pathways. Biased signaling through GPCRs has emerged as a frontier area in pharmacological research efforts towards designing targeted therapeutic interventions and enhancing drug efficacy and safety. This review presents the types of bias associated with GPCRs and the mechanisms underlying biased signaling. Examples of biased ligands and their therapeutic implications will be discussed. In addition, the inherent challenges in measuring signaling bias, and especially the translational gap between in vitro and in vivo assays and clinical outcomes, will be outlined. Full article

Beta-arrestin 1 (ARRB1) is a multifunctional adaptor protein that regulates diverse signaling pathways beyond its canonical role in G-protein-coupled receptor desensitization. While ARRB1 has been implicated in cancer progression, its role in modulating host immunity against multiple myeloma (MM) remains unexplored. Here, we demonstrate that host ARRB1 deficiency significantly enhances anti-myeloma immunity and prolongs survival in a syngeneic murine MM model. Using Vk*MYC myeloma cells transplanted into wild-type and ARRB1 knockout mice, we show that ARRB1 deficiency in the host microenvironment promotes robust T cell infiltration and activation while reducing immunosuppressive myeloid populations. Notably, ARRB1 knockout mice exhibited markedly decreased programmed cell death protein-1 (PD-1) expression on both T cells and myeloid-derived suppressor cells, indicating reduced immune exhaustion. Furthermore, ARRB1 deficiency conferred protection against myeloma-induced bone disease, suggesting a dual role in immune regulation and bone homeostasis. These findings establish ARRB1 as a critical negative regulator of host anti-myeloma immunity and identify it as a potential therapeutic target for enhancing immunotherapy efficacy in MM. Full article

Inhibition of agonist-induced M₂ muscarinic receptor (M₂R) activation by functional anti-M₂R autoantibodies has been associated with cardiac parasympathetic dysfunction in patients with chronic Chagas disease (CD). This study explored the allosteric nature of that inhibitory effect by assessing the ability of serum IgG from patients with CD and dysautonomia (DCD IgG) to modulate the interaction between M₂R and β-arrestins in HEK 293T cells using bioluminescence resonance energy transfer. DCD IgG alone did not stimulate arrestin-2 or arrestin-3 recruitment. When cells were preincubated with DCD IgG and then treated with carbachol, arrestin-2 translocation decreased in a concentration-dependent manner, while arrestin-3 recruitment remained unaffected. Inhibition curve analysis showed a submaximal inhibitory effect (68.1 ± 2.4%) and a Hill slope less than −1 (−4.03 ± 0.39). Carbachol concentration–response assays after preincubation with DCD IgG revealed a noncompetitive inhibition of arrestin-2 recruitment, with no change in arrestin-3 translocation. Unlikely, simultaneous exposure to DCD IgG and carbachol potentiated agonist-induced Arr-2 recruitment. We conclude that anti-M₂R autoantibodies selectively inhibit agonist-induced arrestin-2 recruitment, acting as negative allosteric modulators of agonist efficacy. The direction of autoantibody-induced allosteric modulation depends on the timing of IgG application relative to the agonist and the duration of receptor exposure to autoantibodies. Full article

This review addresses the growing concern of oral side effects, particularly dry mouth, associated with semaglutide, a glucagon-like peptide-1 receptor agonist (GLP-1RA) widely used for diabetes and obesity. A literature search of PubMed/MEDLINE, Scopus, Web of Science, and Google Scholar (March–September 2025) identified studies on GLP-1 receptor signaling, semaglutide pharmacology, salivary gland biology, biased agonism, β-arrestin, and cAMP pathways, and reported oral adverse effects. Of 183 records screened, 78 met inclusion criteria and were narratively synthesized across 5 mechanistic domains linking the molecular mechanisms that may underly semaglutide-induced alteration in salivary function by exploring GLP-1 receptor (GLP-1R) expression and signaling in salivary glands. The available literature data shows that different GLP-1 receptor agonists exhibit distinct patterns of GLP-1R activation, engaging the cAMP- and β-arrestin–dependent pathways to varying extents, which may thus differentially regulate exocytosis and cellular protection. Furthermore, semaglutide’s strong albumin binding leads to prolonged receptor activation, and may disturb the rhythmic calcium and cAMP cross-talk essential for normal salivary secretion. Persistent stimulation may cause receptor desensitization, β-arrestin–mediated internalization, and reduced gland responsiveness. Clinical pharmacovigilance data indicate disproportionality signals, suggesting that semaglutide may be reported more frequently with oral side effects compared with other GLP-1 receptor agonists, although spontaneous-report databases cannot confirm causality. These insights underscore the need for patient counseling, preventive oral care, and further studies on receptor signaling bias, contributing to personalized approach when using GLP-1RAs. Full article

Background: This research sought to screen potential biomarkers in diagnosing breast diseases and elucidating their immune-related mechanisms. Methods: Three datasets were attained from the Gene Expression Omnibus (GEO) database. LIMMA package and weighted gene co-expression network analysis (WGCNA) were used to ascertain differentially expressed genes (DEGs) and key modules in benign breast disease (BBD) and breast cancer (BC). The intersecting genes underwent functional enrichment analysis. Three machine learning (ML) methods (encompassing LASSO regression, random forest, and support vector machine recursive feature elimination (SVM-RFE)) were implemented to select core genes. The diagnostic performance of the core genes was evaluated by comparing their expression levels, plotting receiver operating characteristic (ROC) curves, and constructing a Nomogram. The TCGA-BRCA dataset was used to estimate the prognostic capability of the core genes among individuals with BC. Finally, the IC infiltration was ascertained utilizing the CIBERSORT algorithm. Results: In total, 2579 DEGs were identified in BBD. WGCNA exhibited that the 1652 genes in green and pink modules were strongly correlated with BBD. In BC, 2742 DEGs were identified. The turquoise and red modules contained 7286 genes exhibiting strong correlations with BC. After intersecting, 41 common genes were obtained, which were predominantly enriched in immune and inflammation regulation pathways. Through integrated screening with three ML algorithms, Arrestin Domain Containing 1 (ARRDC1) and ATPase Sarcoplasmic/Endoplasmic Reticulum Ca²⁺ Transporting 2 (ATP2A2) were identified as core genes. The ROC curve exhibited that the AUC for the two genes was greater than 0.8. The calibration curve of the nomogram signified a strong alignment between the anticipated risk and detected results. Survival analysis in TCGA-BRCA showed that the high expression of the two genes exhibited a significantly positive association with unfavorable prognosis. Immune infiltration analysis further demonstrated the dysregulation of multiple immune cells in patient samples. Conclusions:ARRDC1 and ATP2A2 are strongly linked to BBD and BC. These findings might enhance our comprehension of the pathogenesis and progression of both BBD and BC, offering prospective biological biomarkers and therapeutic targets for clinical treatment. Full article

Background/Objectives: G protein-coupled receptors (GPCRs) can promote ligand-biased signaling, yet the mechanisms that promote bias are not well understood. We have shown that C-C Chemokine Ligand 19 (CCL19) and CCL21 promote ligand-biased internalization and signaling of C-C Chemokine Receptor 7 (CCR7) in T cells. The roles of GPCR kinases (GRKs) in regulating biased CCR7 internalization and biased signaling in T cells are unclear. GRK2 is a serine/threonine kinase that phosphorylates GPCRs in response to ligand binding and is recruited to the plasma membrane via its C-terminal pleckstrin homology domain to phosphatidylinositol 4,5-bisphosphate (PIP₂). Methods: Human embryonic kidney cells (HEK293) transfected to express wild-type and mutant GRK2 and human CCR7, human T cell lines harboring heterozygous deletions of GRK2, and naïve primary T cells from GRK2 heterozygous (GRK2^+/−) or GRK2^f/f CD4-Cre mice were used to examine the effects of GRK2 on ligand-induced CCR7 signaling in T cells. We used flow cytometry to assay the effect of GRK2 on CCR7 internalization, Fluorescence Resonance Energy Transfer (FRET) to define the effect of GRK2 on CCR7 activation of Gα_i isoforms and transwell migration assays to examine the effect of GRK2 on chemotaxis. Since chemotaxis via CCR7 is mediated by phospholipase Cγ1 (PLCγ1), Western blot assays were used to measure the effect of GRK2 during downstream signaling via phosphorylation of PLCγ1. Results: We found that following CCL19 binding, GRK2 promoted kinase-dependent CCR7 recruitment of arrestin-3, rapid CCR7 internalization and Gα_i3 recruitment to CCR7. In contrast, following binding of CCL21 to CCR7, GRK2 slowed CCR7 internalization, induced recruitment of Gα_i2 to the activated receptor_, and promoted chemotaxis. Since we have shown that CCL21 promotes chemotaxis via PLCγ1, we examined the effect of GRK2 on PLCγ1 activation and found that GRK2 had no effect on CCL21-mediated PLCγ1 phosphorylation. Conclusions: GRK2 promotes differential signaling downstream of CCR7 activation by CCL19 and CCL21 and provides a model for biased signaling downstream of a GPCR driven by GRK2. Full article