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Nature Communications Jun 2024Glucagon, a hormone released from pancreatic α-cells, is critical for maintaining euglycemia and plays a key role in the pathophysiology of diabetes. To stimulate the...
Glucagon, a hormone released from pancreatic α-cells, is critical for maintaining euglycemia and plays a key role in the pathophysiology of diabetes. To stimulate the development of new classes of therapeutic agents targeting glucagon release, key α-cell signaling pathways that regulate glucagon secretion need to be identified. Here, we focused on the potential importance of α-cell G signaling on modulating α-cell function. Studies with α-cell-specific mouse models showed that activation of α-cell G signaling causes a marked increase in glucagon secretion. We also found that intra-islet adenosine plays an unexpected autocrine/paracrine role in promoting glucagon release via activation of α-cell G-coupled A adenosine receptors. Studies with α-cell-specific Gα knockout mice showed that α-cell G also plays an essential role in stimulating the activity of the Gcg gene, thus ensuring proper islet glucagon content. Our data suggest that α-cell enriched G-coupled receptors represent potential targets for modulating α-cell function for therapeutic purposes.
Topics: Glucagon; Animals; Glucagon-Secreting Cells; Signal Transduction; Mice, Knockout; Mice; GTP-Binding Protein alpha Subunits, Gs; Adenosine; Receptor, Adenosine A2A; Male; Mice, Inbred C57BL; Islets of Langerhans
PubMed: 38879678
DOI: 10.1038/s41467-024-49537-x -
Nature Communications Jun 2024Neurofibromatosis Type II (NFII) is a genetic condition caused by loss of the NF2 gene, resulting in activation of the YAP/TAZ pathway and recurrent Schwann cell tumors,...
Neurofibromatosis Type II (NFII) is a genetic condition caused by loss of the NF2 gene, resulting in activation of the YAP/TAZ pathway and recurrent Schwann cell tumors, as well as meningiomas and ependymomas. Unfortunately, few pharmacological options are available for NFII. Here, we undertake a genome-wide CRISPR/Cas9 screen to search for synthetic-lethal genes that, when inhibited, cause death of NF2 mutant Schwann cells but not NF2 wildtype cells. We identify ACSL3 and G6PD as two synthetic-lethal partners for NF2, both involved in lipid biogenesis and cellular redox. We find that NF2 mutant Schwann cells are more oxidized than control cells, in part due to reduced expression of genes involved in NADPH generation such as ME1. Since G6PD and ME1 redundantly generate cytosolic NADPH, lack of either one is compatible with cell viability, but not down-regulation of both. Since genetic deficiency for G6PD is tolerated in the human population, G6PD could be a good pharmacological target for NFII.
Topics: Schwann Cells; Humans; CRISPR-Cas Systems; Glucosephosphate Dehydrogenase; Neurofibromin 2; Coenzyme A Ligases; Synthetic Lethal Mutations; Animals; Neurofibromatosis 2; NADP; Mice; Oxidation-Reduction
PubMed: 38879607
DOI: 10.1038/s41467-024-49298-7 -
Nature Communications Jun 2024One open question in the biology of growth factor receptors is how a quantitative input (i.e., ligand concentration) is decoded by the cell to produce specific...
One open question in the biology of growth factor receptors is how a quantitative input (i.e., ligand concentration) is decoded by the cell to produce specific response(s). Here, we show that an EGFR endocytic mechanism, non-clathrin endocytosis (NCE), which is activated only at high ligand concentrations and targets receptor to degradation, requires a tripartite organelle platform involving the plasma membrane (PM), endoplasmic reticulum (ER) and mitochondria. At these contact sites, EGFR-dependent, ER-generated Ca oscillations are sensed by mitochondria, leading to increased metabolism and ATP production. Locally released ATP is required for cortical actin remodeling and EGFR-NCE vesicle fission. The same biochemical circuitry is also needed for an effector function of EGFR, i.e., collective motility. The multiorganelle signaling platform herein described mediates direct communication between EGFR signaling and mitochondrial metabolism, and is predicted to have a broad impact on cell physiology as it is activated by another growth factor receptor, HGFR/MET.
Topics: Mitochondria; ErbB Receptors; Endoplasmic Reticulum; Humans; Signal Transduction; Adenosine Triphosphate; Endocytosis; Animals; Cell Membrane; Calcium Signaling; Calcium
PubMed: 38879572
DOI: 10.1038/s41467-024-49543-z -
Arthritis Research & Therapy Jun 2024Janus kinase (JAK) inhibitors, such as baricitinib, are widely used to treat rheumatoid arthritis (RA). Clinical studies show that baricitinib is more effective at...
Baricitinib ameliorates inflammatory and neuropathic pain in collagen antibody-induced arthritis mice by modulating the IL-6/JAK/STAT3 pathway and CSF-1 expression in dorsal root ganglion neurons.
BACKGROUND
Janus kinase (JAK) inhibitors, such as baricitinib, are widely used to treat rheumatoid arthritis (RA). Clinical studies show that baricitinib is more effective at reducing pain than other similar drugs. Here, we aimed to elucidate the molecular mechanisms underlying the pain relief conferred by baricitinib, using a mouse model of arthritis.
METHODS
We treated collagen antibody-induced arthritis (CAIA) model mice with baricitinib, celecoxib, or vehicle, and evaluated the severity of arthritis, histological findings of the spinal cord, and pain-related behaviours. We also conducted RNA sequencing (RNA-seq) to identify alterations in gene expression in the dorsal root ganglion (DRG) following baricitinib treatment. Finally, we conducted in vitro experiments to investigate the direct effects of baricitinib on neuronal cells.
RESULTS
Both baricitinib and celecoxib significantly decreased CAIA and improved arthritis-dependent grip-strength deficit, while only baricitinib notably suppressed residual tactile allodynia as determined by the von Frey test. CAIA induction of inflammatory cytokines in ankle synovium, including interleukin (IL)-1β and IL-6, was suppressed by treatment with either baricitinib or celecoxib. In contrast, RNA-seq analysis of the DRG revealed that baricitinib, but not celecoxib, restored gene expression alterations induced by CAIA to the control condition. Among many pathways changed by CAIA and baricitinib treatment, the interferon-alpha/gamma, JAK-signal transducer and activator of transcription 3 (STAT3), and nuclear factor kappa B (NF-κB) pathways were considerably decreased in the baricitinib group compared with the celecoxib group. Notably, only baricitinib decreased the expression of colony-stimulating factor 1 (CSF-1), a potent cytokine that causes neuropathic pain through activation of the microglia-astrocyte axis in the spinal cord. Accordingly, baricitinib prevented increases in microglia and astrocytes caused by CAIA. Baricitinib also suppressed JAK/STAT3 pathway activity and Csf1 expression in cultured neuronal cells.
CONCLUSIONS
Our findings demonstrate the effects baricitinib has on the DRG in relation to ameliorating both inflammatory and neuropathic pain.
Topics: Animals; Azetidines; Sulfonamides; Pyrazoles; STAT3 Transcription Factor; Purines; Arthritis, Experimental; Ganglia, Spinal; Neuralgia; Janus Kinases; Signal Transduction; Mice; Interleukin-6; Male; Neurons; Mice, Inbred DBA; Inflammation; Janus Kinase Inhibitors
PubMed: 38879555
DOI: 10.1186/s13075-024-03354-1 -
Nature Communications Jun 2024Factor-dependent termination uses molecular motors to remodel transcription machineries, but the associated mechanisms, especially in eukaryotes, are poorly understood....
Factor-dependent termination uses molecular motors to remodel transcription machineries, but the associated mechanisms, especially in eukaryotes, are poorly understood. Here we use single-molecule fluorescence assays to characterize in real time the composition and the catalytic states of Saccharomyces cerevisiae transcription termination complexes remodeled by Sen1 helicase. We confirm that Sen1 takes the RNA transcript as its substrate and translocates along it by hydrolyzing multiple ATPs to form an intermediate with a stalled RNA polymerase II (Pol II) transcription elongation complex (TEC). We show that this intermediate dissociates upon hydrolysis of a single ATP leading to dissociation of Sen1 and RNA, after which Sen1 remains bound to the RNA. We find that Pol II ends up in a variety of states: dissociating from the DNA substrate, which is facilitated by transcription bubble rewinding, being retained to the DNA substrate, or diffusing along the DNA substrate. Our results provide a complete quantitative framework for understanding the mechanism of Sen1-dependent transcription termination in eukaryotes.
Topics: Saccharomyces cerevisiae Proteins; Saccharomyces cerevisiae; RNA Polymerase II; Transcription Termination, Genetic; Adenosine Triphosphate; DNA Helicases; Single Molecule Imaging; RNA Helicases; Transcription, Genetic; RNA, Fungal; DNA, Fungal; Hydrolysis
PubMed: 38879529
DOI: 10.1038/s41467-024-49527-z -
Cell Death & Disease Jun 2024Tamoxifen has been the mainstay therapy to treat early, locally advanced, and metastatic estrogen receptor-positive (ER + ) breast cancer, constituting around 75% of...
Tamoxifen has been the mainstay therapy to treat early, locally advanced, and metastatic estrogen receptor-positive (ER + ) breast cancer, constituting around 75% of all cases. However, the emergence of resistance is common, necessitating the identification of novel therapeutic targets. Here, we demonstrated that long-noncoding RNA LINC00152 confers tamoxifen resistance by blocking tamoxifen-induced ferroptosis, an iron-mediated cell death. Mechanistically, inhibiting LINC00152 reduces the mRNA stability of phosphodiesterase 4D (PDE4D), leading to activation of the cAMP/PKA/CREB axis and increased expression of the TRPC1 Ca channel. This causes cytosolic Ca overload and generation of reactive oxygen species (ROS) that is, on the one hand, accompanied by downregulation of FTH1, a member of the iron sequestration unit, thus increasing intracellular Fe levels; and on the other hand, inhibition of the peroxidase activity upon reduced GPX4 and xCT levels, in part by cAMP/CREB. These ultimately restore tamoxifen-dependent lipid peroxidation and ferroptotic cell death which are reversed upon chelating Ca or overexpressing GPX4 or xCT. Overexpressing PDE4D reverses LINC00152 inhibition-mediated tamoxifen sensitization by de-activating the cAMP/Ca/ferroptosis axis. Importantly, high LINC00152 expression is significantly correlated with high PDE4D/low ferroptosis and worse survival in multiple cohorts of tamoxifen- or tamoxifen-containing endocrine therapy-treated ER+ breast cancer patients. Overall, we identified LINC00152 inhibition as a novel mechanism of tamoxifen sensitization via restoring tamoxifen-dependent ferroptosis upon destabilizing PDE4D, increasing cAMP and Ca levels, thus leading to ROS generation and lipid peroxidation. Our findings reveal LINC00152 and its effectors as actionable therapeutic targets to improve clinical outcome in refractory ER+ breast cancer.
Topics: Humans; Tamoxifen; Breast Neoplasms; Ferroptosis; Female; RNA, Long Noncoding; Cyclic AMP; Calcium; Drug Resistance, Neoplasm; Cell Line, Tumor; Animals; Receptors, Estrogen; Mice; Reactive Oxygen Species; MCF-7 Cells
PubMed: 38879508
DOI: 10.1038/s41419-024-06814-3 -
BMC Surgery Jun 2024Patients with gout are at risk for increased serum uric acid (SUA) levels and gout attacks in the short term after undergoing bariatric surgery, and the purpose of this...
BACKGROUND/PURPOSE
Patients with gout are at risk for increased serum uric acid (SUA) levels and gout attacks in the short term after undergoing bariatric surgery, and the purpose of this study was to evaluate the benefits of short-term treatment with uric acid-lowering medication after bariatric surgery for the control of gout attacks and SUA levels in patients with gout.
METHODS
71 patients who underwent SG from January 2020 to December 2022 were prospectively included. These patients were diagnosed with hyperuricemia before surgery and had a history of gout attacks. Patients were classified into a drug-treatment group (DTG, n = 32) and a non-drug-treatment group (NDTG, n = 39) according to whether they took uric acid-lowering medication after surgery. Changes in the number of gout attacks, body mass index (BMI), and SUA levels at 1 week, 1 month, 3 months, and 6 months after bariatric surgery were measured in both groups.
RESULTS
In the DTG, 22 patients (68.8%) experienced an increase in SUA within 1 week, 3 patients (9.4%) had an acute attack of gout within the first month, and no patients had a gout attack thereafter. In the NDTG, 35 patients (89.7%) experienced an increase in SUA within 1 week, 7 patients (17.9%) had an acute gout attack within the first month, and 4 patients (10.3%) experienced gout attacks between month 1 and month 3 postoperatively. Both groups were free of gout attacks between the 3rd and 6th postoperative month and showed a significant decrease in SUA and BMI by the sixth month.
CONCLUSION
In patients with gout, continued use of uric acid-lowering medication after bariatric surgery is beneficial in reducing the number of gout attacks and the risk of rising SUA.
Topics: Humans; Gout; Bariatric Surgery; Male; Female; Middle Aged; Uric Acid; Gout Suppressants; Adult; Prospective Studies; Hyperuricemia; Body Mass Index; Postoperative Complications; Treatment Outcome
PubMed: 38877436
DOI: 10.1186/s12893-024-02472-6 -
Nature Communications Jun 2024Cytosine base editors (CBEs) and adenine base editors (ABEs) enable precise C-to-T and A-to-G edits. Recently, ABE8e, derived from TadA-8e, enhances A-to-G edits in...
Cytosine base editors (CBEs) and adenine base editors (ABEs) enable precise C-to-T and A-to-G edits. Recently, ABE8e, derived from TadA-8e, enhances A-to-G edits in mammalian cells and plants. Interestingly, TadA-8e can also be evolved to confer C-to-T editing. This study compares engineered CBEs derived from TadA-8e in rice and tomato cells, identifying TadCBEa, TadCBEd, and TadCBEd_V106W as efficient CBEs with high purity and a narrow editing window. A dual base editor, TadDE, promotes simultaneous C-to-T and A-to-G editing. Multiplexed base editing with TadCBEa and TadDE is demonstrated in transgenic rice, with no off-target effects detected by whole genome and transcriptome sequencing, indicating high specificity. Finally, two crop engineering applications using TadDE are shown: introducing herbicide resistance alleles in OsALS and creating synonymous mutations in OsSPL14 to resist OsMIR156-mediated degradation. Together, this study presents TadA-8e derived CBEs and a dual base editor as valuable additions to the plant editing toolbox.
Topics: Gene Editing; Cytosine; Oryza; Plants, Genetically Modified; CRISPR-Cas Systems; Solanum lycopersicum; Adenine; Herbicide Resistance; Genome, Plant
PubMed: 38877035
DOI: 10.1038/s41467-024-49473-w -
Cell Metabolism Jun 2024Mitochondria house many metabolic pathways required for homeostasis and growth. To explore how human cells respond to mitochondrial dysfunction, we performed...
Mitochondria house many metabolic pathways required for homeostasis and growth. To explore how human cells respond to mitochondrial dysfunction, we performed metabolomics in fibroblasts from patients with various mitochondrial disorders and cancer cells with electron transport chain (ETC) blockade. These analyses revealed extensive perturbations in purine metabolism, and stable isotope tracing demonstrated that ETC defects suppress de novo purine synthesis while enhancing purine salvage. In human lung cancer, tumors with markers of low oxidative mitochondrial metabolism exhibit enhanced expression of the salvage enzyme hypoxanthine phosphoribosyl transferase 1 (HPRT1) and high levels of the HPRT1 product inosine monophosphate. Mechanistically, ETC blockade activates the pentose phosphate pathway, providing phosphoribosyl diphosphate to drive purine salvage supplied by uptake of extracellular bases. Blocking HPRT1 sensitizes cancer cells to ETC inhibition. These findings demonstrate how cells remodel purine metabolism upon ETC blockade and uncover a new metabolic vulnerability in tumors with low respiration.
PubMed: 38876105
DOI: 10.1016/j.cmet.2024.05.014 -
PloS One 2024The analysis of nucleic acids is one of the fundamental parts of modern molecular biology and molecular diagnostics. The information collected predominantly depends on...
The analysis of nucleic acids is one of the fundamental parts of modern molecular biology and molecular diagnostics. The information collected predominantly depends on the condition of the genetic material. All potential damage induced by oxidative stress may affect the final results of the analysis of genetic material obtained using commonly used techniques such as polymerase chain reaction or sequencing. The aim of this work was to evaluate the effects of high temperature and pH on DNA structure in the context of the occurrence of oxidative damage, using square-wave voltammetry and two independent research protocols. We resulted in visible oxidation damage registered in acidic conditions after the thermal denaturation process (pH 4.7) with changes in the intensity of guanine and adenine signals. However, using phosphate buffer (pH 7.0) for DNA denaturation negatively affected the DNA structure, but without any oxidized derivatives present. This leads to the conclusion that oxidation occurring in the DNA melting process results in the formation of various derivatives of nucleobases, both electrochemically active and inactive. These derivatives may distort the results of molecular tests due to the possibility of forming complementary bonds with various nucleobases. For example, 8-oxoguanine can form pairs with both cytosine and adenine.
Topics: DNA; Oxidative Stress; Nucleic Acid Denaturation; Temperature; Oxidation-Reduction; DNA Damage; Hydrogen-Ion Concentration; Guanine; Electrochemical Techniques; Adenine
PubMed: 38875261
DOI: 10.1371/journal.pone.0305590