Search Results (794)

Janus kinase is critical for cytokine-mediated signaling, and its hyperactivation due to mutations drives various diseases. The activation of Janus kinase 1 (JAK1) involves a conformational transition from a closed to an open state, but the underlying mechanism remains unclear. This study investigates the roles of two tyrosine residues, Y1034 and Y1035, within the activation loop of the tyrosine kinase domain. Molecular dynamics simulations reveal that phosphorylation, particularly bisphosphorylation at Y1034 and Y1035, promotes the transition to the open conformation, with pY1035 exerting a greater influence than pY1034. Phosphorylation increases the negative charge on the TK domain surface, facilitating its dissociation from the FERM domain, while also weakening TK-FERM interactions. However, the loop between the TK and PK domains formed stable hydrogen bonds with other domains, hindering the full activation process. Using 1 µs molecular dynamics simulations is not sufficient for full activation. These findings elucidate the molecular mechanisms governing the JAK1 initial activation and provide insights for targeting its regulation in disease contexts. Full article

Glioblastoma (GBM) is a highly aggressive brain tumor with limited treatment options and poor prognosis. Proline-rich tyrosine kinase 2 (Pyk2) has been implicated in regulation of GBM invasion, proliferation, and recurrence. Its activation, driven by tumor-infiltrating microglia and macrophage-derived extracellular factors such as EGF, PDGFB, SDF-1α, IL-6, and IL-8, enhances tumor cell motility and survival. Experimental studies demonstrate that pharmacological inhibition or genetic knockdown of Pyk2 significantly reduces glioma cell migration and proliferation. Furthermore, recurrent GBM tumors exhibit elevated Pyk2 phosphorylation in mouse GBM models, correlating with increased tumor growth. Inhibition of Pyk2 and the structurally related focal adhesion kinase (FAK) signaling has shown promising results in preclinical studies, reducing tumor recurrence and improving survival outcomes. This review summarizes recent findings and underscores the pivotal role of Pyk2 in GBM pathophysiology, highlighting its potential as a therapeutic target. Full article

Resveratrol (RSV), a polyphenol found in a variety of berries and wines, is known for its anti-inflammatory, anticancer, and antioxidant properties. It has been suggested that RSV may play a role in the regulation of metabolic disorders, including diabetes and insulin resistance. However, in recent years, it has been reported to completely inhibit Akt kinase function in liver cells. Akt is a central protein involved in the metabolic function of insulin and is regulated by the phosphatidylinositol-3-kinase (PI3K) pathway. In this study, we examined the effect of RSV on insulin-induced insulin receptor (IR) phosphorylation and proteins involved in the PI3K/Akt pathway in a hepatic cell model, clone 9 (C9), and in hepatoma cells, Hepa 1-6 (H1-6). In both cell lines, RSV inhibited tyrosine phosphorylation of IR and insulin-induced activation of Akt. We also evaluated the effect of RSV on the activation of protein tyrosine phosphatase 1B (PTP1B), which is associated with IR dephosphorylation, and found that RSV increased PTP1B-Tyr¹⁵² phosphorylation in a time- and concentration-dependent manner. Furthermore, we found that the protein kinase C (PKC) inhibitors BIM and Gö6976 prevented the inhibition of Akt phosphorylation by RSV and increased the phosphorylation of Ser/Thr residues in IR, suggesting that PKC is involved in the inhibition of the insulin pathway by RSV. Thus, classical PKC isoforms impair the PI3K/Akt pathway at the IR and GSK3 and GS downstream levels; however, IRS-Tyr⁶³² phosphorylation remains unaffected. These results suggest that RSV can lead to insulin resistance by activating PTP1B and PKC, consequently affecting glucose homeostasis in hepatic cells. Full article

Although exercise is known to exert anti-inflammatory effects in neurodegenerative diseases, its specific impact and underlying mechanisms in Parkinson’s disease (PD) remain poorly understood. This study explores the effects of exercise on microglia-mediated neuroinflammation and apoptosis in a PD model, focusing on the role of irisin signaling in mediating these effects. Using a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model, we found that a 10-week treadmill exercise regimen significantly enhanced motor function, reduced dopaminergic neuron loss, attenuated neuronal apoptosis, and alleviated neuroinflammation. Exercise also shifted microglia from a pro-inflammatory to an anti-inflammatory phenotype. Notably, levels of irisin, phosphorylated AMP-activated protein kinase (p-AMPK), and sirtuin 1 (Sirt1), which were decreased in the PD brain, were significantly increased following exercise. These beneficial effects were abolished by blocking the irisin receptor with cyclic arginine–glycine–aspartic acid–tyrosine–lysine (cycloRGDyk). Our results indicate that exercise promotes neuroprotection in PD by modulating microglial activation and the AMPK/Sirt1 pathway through irisin signaling, offering new insights into exercise-based therapeutic approaches for PD. Full article

T-cells constitute an essential component of the adaptive immune response, mount a protective response against foreign pathogens and are important regulators of anti-tumor immunotherapy. In this context, the activation of T-cells and chimeric antigen receptor (CAR)-expressing T-cells is orchestrated by various signaling pathways, involving the initiation of a protein tyrosine phosphorylation cascade. For T-cells, this involves initiation of the phosphorylation cascade via src-related protein-tyrosine kinase p56^lck, which we show to associate with the co-receptors CD4 and CD8 for the induction of a phosphorylation cascade needed for the activation of T-cells. Likewise, p56^lck phosphorylation of the antigen receptor immunoreceptor tyrosine-based activation motifs (ITAMs) and key CD28 tyrosine motifs ensures the functionality and the survival of CARs, while their phospho-targets are also inhibited by PD-1, a key component of the immune checkpoint blockade. This review covers historic and current elements of our knowledge of CD4/CD8–p56^lck-induced activation events and their importance to the development of CAR T-cell immunotherapies. Full article

Acinetobacter baumannii is a multidrug-resistant bacterium that has gained significant attention in recent years due to its involvement in a growing number of hospital-acquired infections. The World Health Organization has classified it as a critical priority pathogen, underscoring the urgent need for new therapeutic strategies. Post-translational modifications (PTMs), such as phosphorylation, play essential roles in various bacterial processes, including antibiotic resistance, virulence or biofilm formation. Although proteomics has increasingly enabled their characterization, the identification of phosphorylated peptides remains challenging, primarily due to the enrichment procedures. In this study, we focused on characterizing serine, threonine, and tyrosine phosphorylation in the A. baumannii ATCC 17978 strain. We optimized three parameters for phosphopeptide enrichment using titanium dioxide (TiO₂) beads (number of enrichment fractions between the phosphopeptides and TiO₂ beads, the quantity peptides and type of loading buffer) to determine the most effective conditions for maximizing phosphopeptide identification. Using this optimized protocol, we identified 384 unique phosphorylation sites across 241 proteins, including 260 novel phosphosites previously unreported in A. baumannii. Several of these phosphorylated proteins are involved in critical bacterial processes such as antimicrobial resistance, biofilm formation or pathogenicity. We discuss these proteins, focusing on the potential functional implications of their phosphorylation. Notably, we identified 34 phosphoproteins with phosphosites localized at functional sites, such as active sites, multimer interfaces, or domains important for structural integrity. Our findings significantly expand the current phosphoproteomic landscape of A. baumannii and support the hypothesis that PTMs, particularly phosphorylation, play a central regulatory role in its physiology and pathogenic potential. Full article

The dynamic phosphorylation of the human RNA Pol II CTD establishes a code applicable to all eukaryotic transcription processes. However, the ability of these specific post-translational modifications to convey molecular signals through structural changes remains unclear. We previously explained that each gene can be modeled as a combination of n circuits connected in parallel. RNA Pol II accesses these circuits and, through a series of pulses, matches the resonance frequency of the DNA qubits, enabling it to extract genetic information and quantum teleport it. Negatively charged phosphates react under RNA Pol II catalysis, which increases the electron density on the deoxyribose acceptor carbon (2’C in the DNA sugar backbone). The phosphorylation effect on the stability of a carbon radical connects tyrosine to the nitrogenous base, while the subsequent pulses link the protein to molecular water through hydrogen bonds. The selective activation of inert C(sp³)–H bonds begins by reading the quantum information stored in the nitrogenous bases. The coupling of hydrogen proton transfer with electron transfer in water generates a supercurrent, which is explained by the correlation of pairs of the same type of fermions exchanging a boson. All these changes lead to the formation of a molecular protein–DNA–water transcriptional condensate. Full article

Gain-of-function gene alterations in rearranged during transfection (RET), a receptor tyrosine kinase, are observed in both sporadic and hereditary medullary thyroid cancers (MTCs) and pheochromocytomas and paragangliomas (PPGLs). Several tyrosine kinase inhibitors (TKIs) that target RET have been proven to be effective on MTCs and PCCs. Recently, TKIs, namely, sunitinib and selpercatinib, which were clinically used to target PPGLs, have been reported to decrease catecholamine levels without reducing tumor size. Our clinical case of metastatic medullary thyroid cancer, which is associated with RET mutations undergoing treatment with vandetanib, also suggests that vandetanib can decrease catecholamine levels. Therefore, we investigated the effect of vandetanib, a representative multi-targeted TKI for RET-related MTC, on cell proliferation and catecholamine synthesis in rat pheochromocytoma PC12 cells. Vandetanib reduced viable cells in a concentration-dependent manner. The dopamine and noradrenaline levels of the cell lysate were reduced in a concentration-dependent manner. They also decreased more prominently at lower concentrations of vandetanib compared to the inhibition of cell proliferation. The RNA knockdown study of Ret revealed that this inhibitory effect on catecholamine synthesis is mainly mediated by the suppression of RET signaling. Next, we focused on two signaling pathways downstream of RET, namely, ERK and AKT signaling. Treatment with vandetanib reduced both ERK and AKT phosphorylation in PC12 cells. Moreover, both an MEK inhibitor U0126 and a PI3K/AKT inhibitor LY294002 suppressed catecholamine synthesis without decreasing viable cells. This study in rat pheochromocytoma PC12 cells reveals the direct inhibitory effects of vandetanib on catecholamine synthesis via the suppression of RET-ERK and RET-AKT signaling. Full article

The internal tandem duplication mutation of FMS-like tyrosine kinase 3 (FLT3-ITD) is associated with high recurrence and mortality rates in acute myeloid leukemia (AML), making it a critical target for anti-AML therapies. Plinabulin is a diketopiperazines derivative that exhibits extensive anti-cancer potency by targeting β-tubulin. We designed and synthesized a novel FLT3 inhibitor, namely 5-3, based on the structure of plinabulin and evaluated its effect on FLT3-ITD mutant AML cells. The results indicated that 5-3 potently and selectively inhibits the growth of mutant FLT3-expressingleukemia cells, and had no effect on FLT3 wide-type cancer cells, suggesting the antiproliferative activity of 5-3 depends highly on FLT3-ITD expression. Mechanically, 5-3 significantly suppressed the phosphorylation of FLT3 signaling pathway, including STAT5, Erk and Akt. Moreover, the efficiency of compound 5-3 is not associated with Plinabulin’s typical target, β-tubulin. In conclusion, the study identified diketopiperazine derivative as a novel FLT3-ITD selective inhibitor. These results demonstrated that 5-3 might be a drug candidate for the treatment of FLT3-ITD-positive AML. Full article

Oximes have been reported to exhibit useful pharmaceutical properties, including compounds with anticancer, anti-arthritis, antibacterial, and neuroprotective activities. Many oximes are kinase inhibitors and have been shown to inhibit various kinases. Herein, a panel of oxime derivatives of tricyclic isatins was synthesized and evaluated for inhibition of cellular inflammatory responses and binding affinity to several kinases. Compounds 5a and 5d (a.k.a. NS-102), which have an unsubstituted oxime group, inhibited lipopolysaccharide (LPS)-induced nuclear factor-κB/activating protein 1 (NF-κB/AP-1) transcriptional activity in human THP-1Blue monocytic cells and interleukin-6 (IL-6) production in human MonoMac-6 monocytic cells, with IC₅₀ values in the micromolar range. These compounds also inhibited LPS-induced production of several other proinflammatory cytokines, including IL-1α, IL-1β, monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor (TNF) in MonoMac-6 cells. Compounds 5a and 5d exhibited nanomolar/submicromolar binding affinity toward several kinase targets. The most potent inhibitor, 5d (3-(hydroxyimino)-5-nitro-1,3,6,7,8,9-hexahydro-2H-benzo[g]indol-2-one), demonstrated high binding affinity for 12 kinases, including DYRK1A, DYRK1B, PIM1, Haspin, HIPK1-3, IRAK1, NEK10, and DAPK1-3. Molecular modeling suggested modes of binding interaction of selected compounds in the DYRK1A and PIM1 catalytic sites that agreed with the experimental binding data. Our results demonstrate that tricyclic isatin oximes could be potential candidates for developing anti-inflammatory drugs with neuroprotective effects for treating neurodegenerative diseases. Full article

One of the most common malignant tumors worldwide is lung cancer, and it is associated with the highest death rate among all cancers. Traditional treatment options for lung cancer include radiation, chemotherapy, targeted therapy, and surgical resection. However, the survival rate is low, and the outlook is still dreadfully dire. The pursuit of a paradigm change in treatment approaches is, therefore, imperative. Tyrosine kinases (TKs), a subclass of protein kinases, regulate vital cellular function by phosphorylating tyrosine residues in proteins. Mutations, overexpression, and autocrine paracrine stimulation can transform TKs into oncogenic drivers, causing cancer pathogenesis. Tyrosine kinase inhibitors (TKIs) have emerged as an attractive targeted therapy option, especially for non-small cell lung cancer (NSCLC). However, resistance to TKIs, and adverse cardiovascular effects such as heart failure, atrial fibrillation, hypertension, and sudden death, are among the most common adverse effects of TKIs. There is increasing interest in plant-derived natural products in the hunt for powerful chemosensitizer and pathway modulators for enhancing TKI activity and/or overcoming resistance mechanisms. This highlights the mechanism of TKs’ activation in cancer, the role of TKIs in NSCLC mechanisms, and the challenges posed by TKI-acquired resistance. Additionally, we explored various plant-derived natural products’ bioactive compounds with the chemosensitizer and pathway-modulating potential with TKs’ inhibitory and anticancer effects. Our review suggests that a combination of natural products with TKIs may provide a novel and promising strategy for overcoming resistance in lung cancer. In future, further preclinical and clinical studies are advised. Full article

Cancer remains a major global health burden driven by complex biological mechanisms, and while targeted therapies like tyrosine kinase inhibitors (TKIs) have revolutionized treatment, their efficacy and safety are significantly influenced by drug–drug interactions (DDIs). Tyrosine-kinase receptors (RTKs) regulate critical cellular processes, and their dysregulation through mutations or overexpression drives oncogenesis, with TKIs designed to inhibit these aberrant signaling pathways by targeting RTK phosphorylation. Pharmacokinetic DDIs can critically impact the efficacy and safety of TKIs such as erlotinib, gefitinib, and pazopanib by affecting their absorption, distribution, and metabolism. The modification of pH can influence drug absorption; furthermore, the inhibition or induction of metabolizing enzymes may affect biotransformation, while distribution can be altered through the modulation of transmembrane transporters. Additionally, ensuring quality of life during TKI treatment requires vigilant monitoring and management of adverse events, which range from mild (e.g., rash, diarrhea, fatigue) to severe (e.g., hepatotoxicity, cardiotoxicity). Drug-specific toxicities, such as hyperlipidemia with lorlatinib or visual disturbances with crizotinib, must be assessed using specific criteria, with dose adjustments and supportive care tailored to individual patient responses. Thus, optimal TKI therapy relies on managing drug interactions through multidisciplinary care, monitoring, and patient education to ensure safety and treatment efficacy. Full article

Background/Objectives: Allergens can trigger severe immune responses in hypersensitive individuals, with mast cells releasing inflammatory mediators via IgE-FcɛRI signaling. Spleen tyrosine kinase (Syk) is a key regulator in this pathway, making it a promising therapeutic target. Natural modulators of Syk-mediated mast cell activation remain underexplored. This study investigated the anti-allergic effects of a 70% ethanol extract of Salvia miltiorrhiza (SME) using in vitro and in vivo models. Methods: SME was evaluated using IgE-sensitized RBL-2H3 cells, a passive cutaneous anaphylaxis model, and a DNCB-induced atopic dermatitis-like mouse model. Allergic responses were assessed via degranulation assays, histopathology, serum IgE levels, and the spleen index. Results: SME significantly inhibited mast cell degranulation by 44.4 ± 1.6% in RBL-2H3 cells at 100 µg/mL following 30 min of treatment compared to the untreated control. Western blot analysis demonstrated dose-dependent suppression of protein kinase B (PKB, also known as AKT), c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and spleen tyrosine kinase (Syk) phosphorylation, indicating inhibition of key allergic signaling pathways. In an IgE/Ag-induced passive cutaneous anaphylaxis model in ICR mice, SME (100 mg/kg, orally) significantly attenuated vascular permeability, as evidenced by a 20.6 ± 9.7% reduction in Evans blue extravasation relative to the Ag-treated group. In a 1-chloro-2,4-dinitrobenzene (DNCB)-induced atopic dermatitis (AD)-like model, six treatments of SME significantly improved the skin condition, reduced spleen enlargement associated with allergic inflammation, and decreased serum IgE levels by 43.3 ± 11.2% compared to the DNCB group. Conclusions: These findings suggest that SME may help to alleviate allergic responses and AD by modulating key immune signaling pathways. Full article

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the virus responsible for Coronavirus Disease 2019 (COVID-19), utilizes its spike protein to infect host cells. In addition to angiotensin-converting enzyme 2 (ACE2) and neuropilin-1 (NRP1), AXL acts as a spike protein receptor and mediates infection, especially in respiratory cells with low ACE2 expression. Angiotensin II (1–8) can be cleaved into shorter peptides within the biological system. Antibody-based binding assays showed that angiotensin II causes a two-fold increase in the binding between the spike protein and AXL, but not ACE2 or NRP1. While a longer peptide, angiotensin I (1–10), did not affect the spike–AXL binding, shorter lengths of angiotensin peptides exhibited enhancing effects. The C-terminal deletions of angiotensin II to angiotensin (1–7) or angiotensin (1–6) resulted in peptides with enhanced activity toward spike–AXL binding with a similar capacity as angiotensin II. In contrast, the N-terminal deletions of angiotensin II to angiotensin III (2–8) or angiotensin IV (3–8) as well as the N-terminal deletions of angiotensin (1–7) to angiotensin (2–7) or angiotensin (5–7) produced peptides with a more potent ability to enhance spike–AXL binding (2.7-fold increase with angiotensin IV). When valine was substituted for tyrosine at position 4 in angiotensin II or when tyrosine at position 4 was phosphorylated, spike–AXL binding was increased, suggesting that modifications to tyrosine trigger enhancement. Angiotensin IV also enhances spike protein binding to ACE2 and NRP1. Thus, angiotensin peptides may contribute to COVID-19 pathogenesis by enhancing spike protein binding and thus serve as therapeutic targets. Full article

Cytochrome c (Cytc) is a multifunctional protein, essential for respiration and intrinsic apoptosis. Post-translational modifications of Cytc have been linked to physiological and pathophysiologic conditions, including cancer. Cytc tyrosine 67 (Y67) is a conserved residue that is important to the structure and function of Cytc. We here report the phosphorylation of Y67 of Cytc purified from bovine heart mapped by mass spectrometry. We characterized the functional effects of Y67 Cytc modification using in vitro and cell culture models. Y67 was mutated to the phosphomimetic glutamate (Y67E) and to phenylalanyl (Y67F) as a control. The phosphomimetic Y67E Cytc inhibited cytochrome c oxidase (COX) activity, redirecting energy metabolism toward glycolysis, and decreased the pro-apoptotic capabilities of Cytc. The phosphomimetic Y67E Cytc showed a significantly impaired rate of superoxide scavenging and a reduced rate of oxidation by hydrogen peroxide, suggesting a lower ability to transfer electrons and scavenge reactive oxygen species (ROS). Phosphomimetic Y67E replacement led to an almost complete loss of cardiolipin peroxidase activity, pointing to a central role of Y67 for this catalytic function of Cytc. In intact cells, phosphomimetic replacement leads to a reduction in cell respiration, mitochondrial membrane potential, and ROS levels. We propose that Y67 phosphorylation is cardioprotective and promotes cell survival. Full article