Biology subjects

van den Bogaart, G.

Publications and source records attributed to van den Bogaart, G..

At least 19 recordsLinked to original sources

bioRxiv2026

Reverse engineering Lewy bodies suggests alpha-synuclein pathology as condensatopathy

Understanding how soluble monomeric alpha-synuclein transitions into pathological alpha-synuclein (Lewy bodies) has remained a central challenge in neurodegeneration. Existing models, largely based on treating cells and animals with pre-formed alpha-synuclein fibrils cannot account for the emergence of the first inclusion without pre-existing seeds. Here, we combine in vitro reconstitutions, computational modeling and a minimal cellular system to show that phase separation of alpha-synuclein with an interacting scaffold can recapitulate Lewy body-like structures. An unbiased proteomics screen, live-cell imaging, correlative light-electron microscopy, and soft X-ray tomography show that Lewy body-like structures are associated with redistribution of actin and membrane-bound organelles, with mitochondria accumulating at their periphery in an actin-dependent manner. Structural analyses further indicate that alpha-synuclein condensates provide local environments in which the insoluble beta-sheets can form. Together, these findings support a seed-independent trajectory from soluble alpha-synuclein through condensation and progressive immobilization to Lewy body-like assemblies and, subsequently, insoluble beta-sheet fibrils. This framework offers a new mechanistic route for understanding the disease progression and promises to guide the design of innovative therapeutic interventions.

neuroscience↗

bioRxiv2026

STED microscopy reveals mitotic stage-dependent CENP-A organization

Chromosome segregation is vital. Its disruption can cause aneuploidy, a hallmark of cancer. Centromere protein A (CENP-A) is an important protein during the segregation as it marks the location of the centromere, where the kinetochore assembles for microtubule attachment. Each mammalian centromere contains hundreds of CENP-A nucleosomes, whose spatial arrangement is expected to be critical for kinetochore function and error-free chromosome segregation. However, previous studies--mostly in fixed cells and focused on metaphase--have yielded conflicting results on CENP-A organization. Given the centromere's sub-diffraction size, we used stimulated emission depletion (STED) super-resolution microscopy to visualize the CENP-A organization in both living (about 45 nm resolution) and fixed (about 30 nm resolution) immortalized human retinal pigment epithelial cells (hTERT RPE-1). We found that CENP-A organization does not adopt a single architecture but spans a spectrum from dense clusters to fragmented subclusters, with mitotic stage-dependent abundance and morphology. CENP-A chromatin is most dispersed in prophase, and progressively compacts during prometaphase and metaphase as microtubules attach. In meta- and anaphase predominantly dense organizations are formed, often with a plate-like morphology. Yet, non-dense and non-plate-like organizations persist through metaphase and anaphase, suggesting CENP-A spatial reorganization is heterogeneous during cell division.

biophysics↗

bioRxiv2026

T cells compete via reverse MHC class I signaling at the synapse with dendritic cells to secure Golgi recruitment for activation

Interleukin-12 (IL-12) is a key immunostimulatory cytokine produced by dendritic cells (DCs) upon infection that plays a central role in the activation and differentiation of cytotoxic T cells. Notably, IL-12 is secreted in a highly polarized manner from late endosomes or lysosomes at the contact interface between a DC and a T cell, known as the immunological synapse. However, the signaling mechanisms initiating this spatially restricted cytokine release remain poorly defined. Here, using artificial T cell mimics, beads coated with T cell surface ligands, we show that antigen recognition induces recruitment of the DCs microtubule organizing center (MTOC) and Golgi apparatus to the immunological synapse via reverse MHC class I signaling. Our results further indicate that the signaling pathways governing MTOC polarization are highly conserved in DCs, consistent with mechanisms described in other immune cell types. As newly synthesized IL-12 traffics through the Golgi, this intracellular reorientation facilitates localized release of IL-12 directly at the site of T cell engagement, likely enabling DCs to focus their stimulatory capacity on responsive T cells within the crowded environment of secondary lymphoid organs. Furthermore, by applying spatially patterned antibody arrays targeting MHC class I, we reveal that MTOC polarization is biased toward sites exhibiting the strongest reverse MHC class I signaling. This suggests that IL-12 is preferentially released at synapses formed with T cells displaying higher T cell receptor affinity, providing a mechanism for selection of the most potent T cell.

immunology↗

bioRxiv2025

4-Hydroxynonenal suppresses IL-10 production during infection

Sepsis is a syndrome of life-threatening multiple organ failure induced by infection and hallmarked by the increased production of inflammatory cytokines and reactive oxygen species (ROS). The oxidation of lipids by ROS produces 4-hydroxynonenal (4-HNE), a highly reactive aldehyde that forms adducts with proteins and thereby impacts immune signaling. In this study, using blood samples from patients with sepsis at the emergency department, collected by the Acutelines data- and biobank, we show that 4-HNE selectively suppresses the production of the anti-inflammatory cytokine interleukin (IL)-10, while pro-inflammatory IL-6 and tumor necrosis factor (TNF)- are unaffected. Mechanistically, 4-HNE causes a pronounced transcriptional reorganization, leading to metabolic reprogramming and activation of HIF-1 signaling. In turn, this suppresses IL-10 production through inhibition of nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-{kappa}B) signaling, whereas IL-6 and TNF- are unaffected due to increased activation of p38 mitogen-activated protein kinase (MAPK) signaling. This suppression likely occurs in sepsis, because, whereas overall 4-HNE protein adduct levels are increased in blood samples of sepsis patients, they are decreased in monocytes and T cells and negatively correlate with IL-10 levels. Thus, our data show that 4-HNE selectively suppresses IL-10 production in sepsis. This is likely relevant to the clinical outcome of sepsis patients because IL-10 levels correlate with mortality. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=56 SRC="FIGDIR/small/690094v1_ufig1.gif" ALT="Figure 1"> View larger version (11K): org.highwire.dtl.DTLVardef@107d50dorg.highwire.dtl.DTLVardef@1344e23org.highwire.dtl.DTLVardef@f5f40borg.highwire.dtl.DTLVardef@16907e6_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2025

4-HNE reduces phagocytosis through the expression of Synaptotagmin 1 in human monocyte-derived macrophages

Reactive oxygen species (ROS) react with polyunsaturated fatty acids (PUFA) and generate the reactive aldehyde 4-hydroxynonenal (4-HNE). 4-HNE is a potent modulator of cell signaling, proliferation, and death. Our transcriptomics analysis revealed that upon treatment of human monocyte-derived macrophages with 4-HNE synaptotagmin-1 (SYT1), the main calcium sensor for neurotransmitter release, became the most strongly upregulated protein. This is surprising, as SYT1 expression is normally restricted to neurons and neuroendocrine cells. Using overexpression of SYT1 fused to a fluorescent reporter protein, we found SYT1 predominantly locates at the plasma membrane in macrophages. Based on this finding, and on the reported roles of other SYT forms in macrophages and other immune phagocytes, we tested the role of SYT1 in phagocytosis. Functional assays showed that SYT1 inhibited phagocytosis of pathogenic bacteria. Thus, our findings reveal an unexpected role of SYT1 in immune cells.

molecular biology↗

bioRxiv2025

Inhibition of SHP-1 /2 blocks antigen cross-presentation by human macrophages and dendritic cells

PD-1 immune checkpoint therapy aims to stimulate T-cell responses against cancer, but faces challenges due to resistance, rendering it ineffective for a significant subset of patients. Inhibitors of SHP-1 and SHP-2, widely expressed protein tyrosine phosphatases known for their pro-cancer and immunosuppressive properties, have attracted attention for their potential to enhance therapy efficacy and overcome resistance when combined with immune checkpoint PD-1 blockade. However, how SHP-1/2 inhibition affects antigen presenting cells is incompletely understood. In this study, we evaluated the effect of SHP-1/2 inhibition on antigen cross-presentation by human monocyte-derived macrophages and dendritic cells, using T cell reporter cell lines specific for epitopes derived from cancer antigens NY-ESO-1 and gp100. Our findings indicate that SHP-1/2 inhibitor NSC-87877 significantly reduces the cross-presentation efficiency of both antigens. Mechanistically, we show that SHP-1/2 inhibition blocks endo/lysosomal acidification and the activation of cathepsin proteases. The reduction of antigen cross-presentation upon SHP-1/2 inhibition potentially limits the effectiveness of the combination therapy with immune checkpoint inhibition.

immunology↗

bioRxiv2025

Butyrate blocks specific histone acetylation by preventing recruitment of p300 to acetylated histones

Butyrate, a short-chain fatty acid (SCFA) produced by microbial fermentation of dietary fiber, exerts beneficial metabolic and immunomodulatory functions through hyperactivation of the histone acetylase (HAT) p300 and inhibition of histone deacetylases (HDAC). These effects are widely believed to result in the acetylation of distinct histones that regulate specific genes, including at transcription starting sites (TSS) and enhancers. However, we show that this is not the case, as butyrate dose-dependently increases the acetylation of histones throughout the entire genome. Molecular dynamics simulations suggest that the RING-loop prevents the recruitment of p300 to acetylated histones through its bromodomain, and thereby cannot maintain the acetylation of specific histones through positive feedback. This was confirmed by showing that only catalytically inactive p300 stably binds to acetylated histones. Thus, the epigenetic regulation of specific genes by butyrate is limited, but butyrate instead increases histone acetylation globally resulting in opening of the entire chromatin structure.

molecular biology↗

bioRxiv2024

Catestatin improves heart metabolic flexibility by promoting mitochondrial structure and function

Hypertension, a major cause of cardiomyopathy, is one of the most critical risk factors for heart failure and mortality worldwide. Loss of metabolic flexibility of cardiomyocytes is one of the major causes of heart failure. Although Catestatin (CST) treatment is known to be both hypotensive and cardioprotective, its effect on cardiac metabolism is unknown. In this study, we undertook a transcriptomic approach to identify differentially expressed genes that were filtered using Boolean implication relationships to develop a model of gene regulation in saline or CST-supplemented CST knockout (CST-KO) mice. The analysis revealed a set of gene signatures (fibroblast, cardiomyocyte, and macrophage) rescued after CST supplemented CST-KO mice compared to wild-type. Furthermore, we independently validated these gene signature models using publicly available patient datasets. Since the gene signature includes genes related to glucose, fatty acid metabolism, and mitochondrial function, we assessed the glucose and fatty acid uptake after CST treatment. We found that CST treatment can restore the cardiac metabolic inflexibility in CST-KO heart due to the metabolic shift of glucose utilization to fatty acid as energy source. Binding studies after immunoprecipitation and mass spectrometry revealed CST binding with ATP synthase, supported by molecular simulation and computational modeling that predicted CST binding to /{beta} subunit of ATP synthase. Colocalization of CST with mitochondria and increased mitochondrial membrane potential and ATP production upon CST treatment in neonatal cardiomyocytes further exhibit CST as a key regulator of cardiac metabolism and mitochondrial function.

physiology↗

bioRxiv2023

Trafficking Machinery is Rapidly Primed to Facilitate Polarised IL-6 Secretion in Dendritic Cells

The mounting of an adaptive immune response is critical for removing pathogens from the body and generating immunological memory. Central to this process are myeloid cells, which sense pathogens through a variety of cell surface receptors, engulf and destroy pathogens and become activated. Activation is essential for the release of cytokines as well as the cell-surface presentation of pathogen-derived-antigens. Activation-induced cytokine release by myeloid cells requires a complex series of molecular events to facilitate cytokine expression. However, although the transcriptional machinery regulating cytokine expression is well defined, it is becoming increasingly clear that trafficking machinery has to be re-programmed through post-translational modifications to dynamically regulate cytokine secretory events. We demonstrate through quantitative total internal-resonance fluorescence (TIRF) microscopy that short-term stimulation with the pathogenic stimulus lipopolysaccharide (LPS) is sufficient to up-regulate IL-6 secretion rates in human blood monocyte-derived dendritic cells and that this secretion is asymmetric and thus polarised. Using bioinformatics analysis of our phosphoproteomic data, we demonstrate that LPS stimulation of monocyte-derived dendritic cells rapidly reprograms SNARE-associated membrane trafficking machinery, through phosphorylation/dephosphorylation events. Finally, we link this enhanced rate of secretion to the phosphorylation of the SNARE protein VAMP3 at serine 44 (48 in mice), by showing that this phosphorylation drives the release of VAMP3 by its chaperone WDFY2 and the complexing of VAMP3 with STX4 at the plasma membrane.

cell biology↗

bioRxiv2022

Focal exocytosis of Syntaxin 3 and TRPML1 at pseudopodia of nascent phagosomes

Macrophages clear invading pathogens by phagocytosis. Phagocytosis is a complex mechanism involving the local expansion of the membrane, cytoskeletal remodeling, and the delivery of phagosomal proteins to the nascent phagosomes. However, the organelle trafficking events underlying this are largely unclear. Here, we show in human blood monocyte-derived macrophages that TRPML1, a calcium channel involved in the phagocytic process, is delivered to phagosomes in Syntaxin 3-positive vesicles. Syntaxin 3 is a SNARE protein previously shown to mediate the secretion of IL-6 by macrophages. Total Internal Reflection Microscopy (TIRF) revealed that Syntaxin 3 positive compartments carry TRPML1 to pseudopodia for focal exocytosis at the nascent phagosomes during E. coli uptake. Using siRNA knockdown, we show that both Syntaxin 3 and TRPML1 are required for E. coli uptake. Moreover, using TRPML1 agonists we show that increased TRPML1 activity leads to increased E. coli uptake, whereas calcium chelation decreased intracellular E. coli load. Understanding the membrane trafficking pathways is critical for understanding how macrophages clear invading pathogens. Key findingsO_LISyntaxin 3 positive vesicles are delivered at the plasma membrane site of phagocytosis. C_LIO_LISyntaxin 3-positive vesicles carry TRPML1 to pseudopodia. C_LIO_LIBacterial phagocytosis correlates with Syntaxin 3 and TRPML1 expression levels. C_LIO_LIBacterial phagocytosis depends on calcium flux through TRPML1. C_LIO_LISyntaxin-3 vesicles carry the cytokine interleukin-6. C_LI

cell biology↗

bioRxiv2022

Iron regulates contrasting toxicity of uropathogenic Eschericia coli in macrophages and epithelial cells.

By far most urinary tract infections are caused by genetically diverse uropathogenic Escherichia coli (UPEC). Knowledge of the virulence mechanisms of UPEC is critical for drug development, but most studies focus on only a single strain of UPEC. In this study, we compared the virulence mechanisms of four antibiotic-resistant and highly pathogenic UPEC isolates in human blood monocyte-derived macrophages and a bladder epithelial cell (BEC) line: ST999, ST131, ST1981 and ST95. We found that while non-pathogenic E. coli strains are efficiently killed by macrophages in bactericidal single membrane vacuoles, the UPEC strains survive within double-membrane vacuoles. On side-by-side comparison, we found that whereas ST999 only carries Fe3+ importers, ST95 carries both Fe2+ and Fe3+ importers and the toxins haemolysin and colibactin. Moreover, we found that ST999 grows in the Fe3+ rich vacuoles of BECs and macrophages with concomitant increased expression of haem receptor chuA and the hydrogen peroxide sensor oxyR. In contrast, ST95 produces toxins in iron-depleted conditions similar to that of the urinary tract. Whereas ST95 also persist in the iron rich vacuoles of BECs, it produces colibactin in response to low Fe3+ contributing to macrophage death. Thus, iron regulates the contrasting toxicities of UPEC strains in macrophages and bladder epithelial cells due to low and high labile iron concentrations, respectively. Key findingsO_LIAntibiotics resistant uropathogenic E. coli strains ST999, ST131, ST1981, and ST95 survive within spacious double membrane vacuoles. Non-pathogenic E. coli strains XL1 blue and MG1655 are cleared in single membrane vacuoles in macrophages. C_LIO_LIST999 lacks Fe2+ importer and toxins, and grows in iron rich vacuoles of macrophages and bladder epithelial cells. C_LIO_LIST95 carries both Fe2+ and Fe3+ importers and grows in iron low conditions. C_LIO_LIST95 expresses toxins and induces cell death of infected macrophages, but not of bladder epithelial cells. C_LIO_LIBladder epithelial cells have a higher pool of labile iron than macrophages. Differential expression of virulence factors by ST999 and ST95 in bladder epithelial cells and macrophages is dependent on iron concentration. C_LI

immunology↗

bioRxiv2022

T cell cholesterol efflux suppresses apoptosis and senescence and increases atherosclerosis in middle aged mice

Atherosclerosis is a chronic inflammatory disease driven by hypercholesterolemia. During aging, T-cells accumulate cholesterol, which could lead to a pro-inflammatory phenotype. However, the role of cholesterol efflux pathways mediated by ATP-binding cassette A1 and G1 (ABCA1/ABCG1) in T-cell-dependent age-related inflammation and atherosclerosis remains poorly understood. In this study, we generated mice with T-cell-specific Abca1/Abcg1-deficiency on the low-density-lipoprotein-receptor deficient (Ldlr-/-) background. T-cell Abca1/Abcg1-deficiency decreased blood, lymph node, and splenic T-cells, and increased T-cell activation and apoptosis. T-cell Abca1/Abcg1-deficiency induced a premature T-cell aging phenotype in middle-aged (12-13 months) Ldlr-/- mice, reflected by upregulation of senescence markers. Despite T-cell senescence and enhanced T-cell activation, T-cell Abca1/Abcg1-deficiency decreased atherosclerosis and aortic inflammation in middle-aged Ldlr-/- mice, accompanied by decreased T-cells in atherosclerotic plaques. We attribute these effects to T-cell apoptosis downstream of T-cell activation. Collectively, T-cell cholesterol efflux pathways are critical for maintaining T-cell numbers, suppress senescence, and induce atherosclerosis in middle-aged Ldlr-/- mice.

immunology↗

bioRxiv2021

Chromogranin A plays a crucial role in the age-related development of insulin resistance and hypertension

Aging is associated with the development of metabolic disorders, including insulin resistance and hypertension. Young mice that are negative for the neuroendocrine prohormone Chromogranin A (CgA knockout, CgA-KO) display two opposite aging phenotypes: hypertension but heightened insulin sensitivity. We determined these phenotypes in aging CgA mice. In comparison, aging wild-type (WT) mice gradually lost glucose tolerance and insulin sensitivity. Moreover, while aging WT mice had increased inflammation with higher plasma TNF-, IFN-{gamma} and CCL2 and increased mitochondrial fission, these phenotypes were the opposite in aging CgA-KO mice. CgA-KO mice also showed increased expression of mitochondrial and nuclear-encoded complex I genes, implying that they were healthier than WT mice. Most intriguingly, the hypertension in CgA-KO mice was spontaneously reversed with aging. Supplementation of CgA-KO mice with pancreastatin, a hyperglycemic peptide produced from CgA by proteolysis, increased both blood glucose levels and blood pressure, implicating hyperglycemia, and hypertension. We conclude that age-related insulin resistance and hypertension are caused by CgA.

physiology↗

bioRxiv2021

Transmembrane helices are an overlooked and evolutionarily conserved source of major histocompatibility complex class II epitopes

Cytolytic T cell responses are predicted to be biased towards membrane proteins. The peptide-binding grooves of most haplotypes of histocompatibility complex class I (MHC-I) are relatively hydrophobic, therefore peptide fragments derived from human transmembrane helices (TMHs) are predicted to be presented more often as would be expected based on their abundance in the proteome. However, the physiological reason of why membrane proteins might be over-presented is unclear. In this study, we show that the over-presentation of TMH-derived peptides is general, as it is predicted for bacteria and viruses and for both MHCI and MHC-II. Moreover, we show that TMHs are evolutionarily more conserved, because single nucleotide polymorphisms (SNPs) are present relatively less frequently in TMH-coding chromosomal regions compared to regions coding for extracellular and cytoplasmic protein regions. Thus, our findings suggest that both cytolytic and helper T cells respond more to membrane proteins, because these are evolutionary more conserved. We speculate that TMHs therefore are less prone to escape mutations that enable pathogens to evade T cell responses.

immunology↗

bioRxiv2021

Fluorescence lifetime imaging of pH along the secretory pathway

Many cellular processes are dependent on correct pH levels, and this is especially important for the secretory pathway. Defects in pH homeostasis in distinct organelles cause a wide range of diseases, including disorders of glycosylation and lysosomal storage diseases. Ratiometric imaging of the pH-sensitive mutant of green fluorescent protein (GFP), pHLuorin, has allowed for targeted pH measurements in various organelles, but the required sequential image acquisition is intrinsically slow and therefore the temporal resolution is unsuitable to follow the rapid transit of cargo between organelles. We therefore applied fluorescence lifetime imaging microscopy (FLIM) to measure intraorganellar pH with just a single excitation wavelength. We first validated this method by confirming the pH in multiple compartments along the secretory pathway and compared the pH values obtained by the FLIM-based measurements with those obtained by conventional ratiometric imaging. Then, we analyzed the dynamic pH changes within cells treated with Bafilomycin A1, to block the vesicular ATPase, and Brefeldin A, to block ER-Golgi trafficking. Finally, we followed the pH changes of newly-synthesized molecules of the inflammatory cytokine tumor necrosis factor (TNF)- while they were in transit from the endoplasmic reticulum via the Golgi to the plasma membrane. The toolbox we present here can be applied to measure intracellular pH with high spatial and temporal resolution, and can be used to assess organellar pH in disease models.

cell biology↗

bioRxiv2021

Catestatin regulates the colonic mucus layer in inflammatory bowel disease

BackgroundThe pro-hormone chromogranin A (CgA) and its bioactive cleavage product catestatin (CST) are both associated with inflammatory bowel disease (IBD) and dysregulated barrier functions, but their exact role has remained elusive. Here, we demonstrate that CST regulates the colonic mucus layer. MethodsCST levels were measured in feces of IBD patients. The mucus layer, goblet cells, and immune cell infiltration were analyzed by histology and electron microscopy in colon tissue from IBD patients and mice with selective deletion of the CST-coding region of the CgA gene. ResultsCST levels were elevated in feces of IBD patients compared to healthy controls. The thickness of the mucus layer was increased in non-affected, but not in inflamed, regions of the colon in IBD patients. The thickness of the mucus layer and concomitant mucus production were also increased in the CST-KO mouse. This mucus phenotype in CST-KO mice could be reversed by bone marrow transplantation from wildtype mice. ConclusionsCST produced by bone-marrow derived immune cells reduces production of the mucus layer in the intestine. This might contribute to the reduced mucus layer in inflamed colon regions of IBD patients. Additionally, CST feces levels might be a biomarker for IBD.

immunology↗

bioRxiv2020

The anti-inflammatory peptide Catestatin blocks chemotaxis

Increased levels of the anti-inflammatory peptide catestatin (CST), a cleavage product of the pro-hormone chromogranin A, correlates with less severe outcomes in hypertension, colitis and diabetes. However, it is unknown how CST reduces the infiltration of monocytes and macrophages in inflamed tissues. Here, we report that CST blocks leukocyte migration towards inflammatory chemokines. By in vitro and in vivo migration assays, we show that although CST itself is weakly chemotactic, it blocks migration of monocytes and granulocytes to inflammatory attracting factor CC-chemokine ligand 2 (CCL2) and macrophage inflammatory protein 2 (MIP-2). Moreover, it directs CX3CR1+ macrophages away from pancreatic islets. These findings support the emerging notion that CST is a key anti-inflammatory modulator.

cell biology↗

bioRxiv2020

Catestatin reduces hyperglycemia in insulin-resistant mice by redirecting glucose-6-phosphate from the gluconeogenic to the glycogenic pathway

AimDefects in hepatic glycogen synthesis contribute to postprandial hyperglycemia in type 2 diabetic (T2D) patients. Chromogranin A (CgA) peptide Catestatin (CST: hCgA352-372) has been shown to improve glucose tolerance in insulin-resistant mice. Here, we seek to determine whether CST also reduces hyperglycemia by increasing hepatic glycogen synthesis. MethodsWe determined liver glycogen, glucose-6-phosphate (G6P), uridine diphosphate glucose (UDPG), and glycogen synthase (GYS2) activities; plasma insulin, glucagon, norepinephrine (NE), and epinephrine (EPI) levels in fed and fasted liver of lean and obese mice as well as in CST knockout (CST-KO) mice after treatments with saline, CST, or insulin. We also determined glycogen synthesis and glycogenolysis in primary hepatocytes. In addition, we analyzed phosphorylation signals of Insulin receptor (IR), insulin receptor substrate-1 (IRS-1), phosphatidylinositol dependent kinase-1 (PDK-1), GYS2, glycogen synthase kinase-3{beta} (GSK-3{beta}), AKT (an enzyme in AKR mouse that produces Thymoma)/PKB (protein kinase B) and mTOR (mammalian/mechanistic target of rapamycin) by immunoblotting. ResultsCST stimulated glycogen accumulation in fed and fasted liver and in primary hepatocytes. CST reduced plasma NE and EPI levels, suggesting that CST promotes glycogenesis by inhibiting catecholamine-induced glycogenolysis. CST also directly stimulated glycogenesis and inhibited NE and EPI-induced glycogenolysis in hepatocytes. CST elevated the levels of UDPG and increased GYS2 activity, thus redirecting G6P to the glycogenic pathway. CST-KO mice had decreased liver glycogen that was restored by treatment with CST, reinforcing the crucial role of CST in hepatic glycogenesis. CST can improve insulin signals downstream of insulin receptor IR and IRS-1 by enhancing phospho-AKT signals through stimulation of PDK-1 and mTORC2 (mTOR complex 2) activities. ConclusionsWe conclude that CST directly promotes the glycogenic pathway and reduces plasma glucose levels in insulin-resistant mice by (i) reducing glucose production, (ii) increasing glycogen synthesis from UDPG, and (iii) reducing glycogenolysis. This is achieved by enhancing downstream insulin signaling.

physiology↗