Role In Glycogen Metabolism Research Articles

Role of glycogen metabolism in Clostridioides difficile virulence.

Glycogen plays a vital role as an energy reserve in various bacterial and fungal species. Clostridioides difficile possesses a glycogen metabolism operon that contains genes for both glycogen synthesis and utilization. In our investigation, we focused on understanding the significance of glycogen metabolism in the physiology and pathogenesis of C. difficile. To explore this, we engineered a C. difficile JIR8094 strain lacking glycogen synthesis capability by introducing a group II intron into the glgC gene, the operon's first component. Quantification of intracellular glycogen levels validated the impact of this modification. Interestingly, the mutant strain exhibited a 1.5-fold increase in toxin production compared with the parental strain, without significant changes in the sporulation rate. Our analysis also revealed that wild-type C. difficile spores contained glycogen, whereas spores from the mutant strain lacking stored glycogen showed increased sensitivity to physical and chemical treatments and had a shorter storage life. By suppressing glgP expression, the gene coding for glycogen-phosphorylase, via CRISPRi, we demonstrated that glycogen accumulation but not the utilization is needed for spore resilience in C. difficile. Transmission electron microscopy analysis revealed a significantly lower core/cortex ratio in glgC mutant strain spores. In hamster challenge experiments, both the parental and glgC mutant strains colonized hosts similarly; however, the mutant strain failed to induce infection relapse after antibiotic treatment cessation. These findings highlight the importance of glycogen metabolism in C. difficile spore resilience and suggest its role in disease relapse.IMPORTANCEThis study on the role of glycogen metabolism in Clostridioides difficile highlights its critical involvement in the pathogen's energy management, its pathogenicity, and its resilience. Our results also revealed that glycogen presence in spores is pivotal for their structural integrity and resistance to adverse conditions, which is essential for their longevity and infectivity. Importantly, the inability of the mutant strain to cause infection relapse in hamsters post-antibiotic treatment pinpoints a potential target for therapeutic interventions, highlighting the importance of glycogen in disease dynamics. This research thus significantly advances our understanding of C. difficile physiology and pathogenesis, offering new avenues for combating its persistence and recurrence.

Genome-wide identification of the PP1 and PPP1R3 gene family in oyster Crassostrea gigas: Unraveling their roles in glycogen metabolism

High glycogen in oysters contributes to their flavor, quality, and hardiness, making it a crucial target trait for breeding purposes. Until now, the upstream regulatory mechanism for glycogen synthesis has remained unclear. Protein phosphatase-1 regulatory subunit 3 (PPP1R3) is a member of a family that directs the protein phosphatase-1 (PP1) to glycogen, resulting in the activation of glycogen synthase (GS) and the inactivation of glycogen phosphorylase (GP). However, their functions in molluscan species have remained unclear until now. In our study, we verified the function of the PP1α/PPP1R3D pathways in the glycogen metabolism process in Crassostrea gigas. Initially, we conducted a phylogenetic analysis and identified two PP1 and PPP1R3 members in molluscan species, emphasizing copy number variations in eukaryotic animals. Additionally, we identified distinct substitutions of conserved motifs specific to bivalves, Cephalopoda, or Gastropods, revealing functional diversity in PP1 and PPP1R3. Our primary focus was on PP1α/PPP1R3D in the oyster C.gigas, detected in the muscle glycogen fraction of bivalve species, with mRNA expression showing a positive correlation with glycogen content. By manipulating CgPPP1R3D expression in oysters through adenovirus-mediated overexpression or siRNA-mediated downregulation, we established a direct positive correlation between CgPPP1R3D expression levels and glycogen content. Colocation analysis confirmed protein interactions between CgPP1α and CgPPP1R3D. Furthermore, to elucidate the correlation between gene expression and glycogen accumulation, we conducted an association analysis and identified a cluster of significant SNP loci upstream of CgPPP1R3D significantly related to glycogen content. The high polymorphism observed may be linked to differential expressions of CgPPP1R3D in oyster individuals with high and low glycogen levels. These findings serve as a crucial reference for enhancing glycogen traits in molluscan species.

Physicochemical and Spectroscopic Characterization of Glycogen and Glycogen Phosphorylase b Complexes

Glycogen is a natural polysaccharide used as an energy storage macromolecule. The role of glycogen metabolism in type 2 diabetes mellitus has been under investigation for several years, along with its implication in cancer and cardiovascular and neurodegenerative diseases. Previous studies using pig liver glycogen with rabbit muscle glycogen phosphorylase (RMGPb), which catalyzes the first step of glycogen degradation to glucose-1-phosphate, showed that the surface of an average glycogen molecule is covered by a total of 20 RMGPb dimeric molecules. In this work, we selected oyster glycogen (Glyc) to investigate its interaction with RMGPb by employing biophysical techniques. Dynamic, static, and electrophoretic light scattering were used to investigate the solution behaviors and structures of both the Glyc molecule itself and the formed complexes between Glyc and GPb at different mixing ratios. It was established that the interaction between oyster Glyc and RMGPb is similar to that previously reported for pig liver glycogen. Moreover, the structure of the complexed GPb was monitored by fluorescence and FTIR spectroscopy.

PCK1-mediated glycogenolysis facilitates ROS clearance and chemotherapy resistance in cervical cancer stem cells

Cervical cancer, one of the most common gynecological cancers, is primarily caused by human papillomavirus (HPV) infection. The development of resistance to chemotherapy is a significant hurdle in treatment. In this study, we investigated the mechanisms underlying chemoresistance in cervical cancer by focusing on the roles of glycogen metabolism and the pentose phosphate pathway (PPP). We employed the cervical cancer cell lines HCC94 and CaSki by manipulating the expression of key enzymes PCK1, PYGL, and GYS1, which are involved in glycogen metabolism, through siRNA transfection. Our analysis included measuring glycogen levels, intermediates of PPP, NADPH/NADP+ ratio, and the ability of cells to clear reactive oxygen species (ROS) using biochemical assays and liquid chromatography–mass spectrometry (LC–MS). Furthermore, we assessed chemoresistance by evaluating cell viability and tumor growth in NSG mice. Our findings revealed that in drug-resistant tumor stem cells, the enzyme PCK1 enhances the phosphorylation of PYGL, leading to increased glycogen breakdown. This process shifts glucose metabolism towards PPP, generating NADPH. This, in turn, facilitates ROS clearance, promotes cell survival, and contributes to the development of chemoresistance. These insights suggest that targeting aberrant glycogen metabolism or PPP could be a promising strategy for overcoming chemoresistance in cervical cancer. Understanding these molecular mechanisms opens new avenues for the development of more effective treatments for this challenging malignancy.

Identification of New GSK3β Inhibitors through a Consensus Machine Learning-Based Virtual Screening.

Glycogen synthase kinase-3 beta (GSK3β) is a serine/threonine kinase that plays key roles in glycogen metabolism, Wnt/β-catenin signaling cascade, synaptic modulation, and multiple autophagy-related signaling pathways. GSK3β is an attractive target for drug discovery since its aberrant activity is involved in the development of neurodegenerative diseases such as Alzheimer's and Parkinson's disease. In the present study, multiple machine learning models aimed at identifying novel GSK3β inhibitors were developed and evaluated for their predictive reliability. The most powerful models were combined in a consensus approach, which was used to screen about 2 million commercial compounds. Our consensus machine learning-based virtual screening led to the identification of compounds G1 and G4, which showed inhibitory activity against GSK3β in the low-micromolar and sub-micromolar range, respectively. These results demonstrated the reliability of our virtual screening approach. Moreover, docking and molecular dynamics simulation studies were employed for predicting reliable binding modes for G1 and G4, which represent two valuable starting points for future hit-to-lead and lead optimization studies.

Isolated hepatomegaly became Her’s – a case report

Glycogen storage diseases (GSDs) are a group of inherited metabolic disorders caused by mutations in one of the several enzymes involved in glycogen synthesis or breakdown. GSD VI is caused by mutations of PYGL gene encoding hepatic glycogen phosphorylase on chromosome 14q22.1, which has a major role in glycogen metabolism. We report a case of 2year old girl child presented with complaints of slowly progressive abdominal distention of one year duration. Abdominal examination revealed hepatomegaly (liver span 9cm). Lab investigations revealed mild anemia, hypertriglyceridemia and normal liver function. Liver biopsy showed marked elevation of glycogen content in liver with structurally normal glycogen which was consistent with GSD. Sanger sequencing done to identify the subtype of GSD showed PYGL gene mutation, pathogenic variant of type-VIGSD. In the case of isolated hepatomegaly, a glycogen storage disease must be considered in the differential diagnosis and Sanger sequencing must be done for confirmation and prognostication

STAT3 transcriptionally regulates the expression of genes related to glycogen metabolism in developing motor neurons.

Motor neurons in the spinal cord are essential for movement. During the embryonic period, developing motor neurons store glycogen to protect against hypoglycemic and hypoxic stress. However, the mechanisms by which glycogen metabolism is regulated in motor neurons remain unclear. We herein investigated the transcriptional regulation of genes related to glycogen metabolism in the developing spinal cord. We focused on the regulatory mechanism of glycogen synthase (Gys1) and glycogen phosphorylase brain isoform (PygB), which play central roles in glycogen metabolism, and found that the transcription factor STAT3 regulated the expression of Gys1 and PygB via cis-regulatory promoter sequences in the developing spinal cord. These results suggest that STAT3 is important for the regulation of glycogen metabolism during motor neuron development.

Genome-wide association study identifying genetic variants associated with carcass backfat thickness, lean percentage and fat percentage in a four-way crossbred pig population using SLAF-seq technology

BackgroundCarcass backfat thickness (BFT), carcass lean percentage (CLP) and carcass fat percentage (CFP) are important to the commercial pig industry. Nevertheless, the genetic architecture of BFT, CLP and CFP is still elusive. Here, we performed a genome-wide association study (GWAS) based on specific-locus amplified fragment sequencing (SLAF-seq) to analyze seven fatness-related traits, including five BFTs, CLP, and CFP on 223 four-way crossbred pigs.ResultsA total of 227, 921 highly consistent single nucleotide polymorphisms (SNPs) evenly distributed throughout the genome were used to perform GWAS. Using the mixed linear model (MLM), a total of 20 SNP loci significantly related to these traits were identified on ten Sus scrofa chromosomes (SSC), of which 10 SNPs were located in previously reported quantitative trait loci (QTL) regions. On SSC7, two SNPs (SSC7:29,503,670 and rs1112937671) for average backfat thickness (ABFT) exceeded 1% and 10% Bonferroni genome-wide significance levels, respectively. These two SNP loci were located within an intron region of the COL21A1 gene, which was a protein-coding gene that played an important role in the porcine backfat deposition by affecting extracellular matrix (ECM) remodeling. In addition, based on the other three significant SNPs on SSC7, five candidate genes, ZNF184, ZNF391, HMGA1, GRM4 and NUDT3 were proposed to influence BFT. On SSC9, two SNPs for backfat thickness at 6–7 ribs (67RBFT) and one SNP for CLP were in the same locus region (19 kb interval). These three SNPs were located in the PGM2L1 gene, which encoded a protein that played an indispensable role in glycogen metabolism, glycolysis and gluconeogenesis as a key enzyme. Finally, one significant SNP on SSC14 for CLP was located within the PLBD2 gene, which participated in the lipid catabolic process.ConclusionsA total of two regions on SSC7 and SSC9 and eight potential candidate genes were found for fatness-related traits in pigs. The results of this GWAS based on SLAF-seq will greatly advance our understanding of the genetic architecture of BFT, CLP, and CFP traits. These identified SNP loci and candidate genes might serve as a biological basis for improving the important fatness-related traits of pigs.

Liver glycogen phosphorylase is upregulated in glioblastoma and provides a metabolic vulnerability to high dose radiation

Channelling of glucose via glycogen, known as the glycogen shunt, may play an important role in the metabolism of brain tumours, especially in hypoxic conditions. We aimed to dissect the role of glycogen degradation in glioblastoma (GBM) response to ionising radiation (IR). Knockdown of the glycogen phosphorylase liver isoform (PYGL), but not the brain isoform (PYGB), decreased clonogenic growth and survival of GBM cell lines and sensitised them to IR doses of 10–12 Gy. Two to five days after IR exposure of PYGL knockdown GBM cells, mitotic catastrophy and a giant multinucleated cell morphology with senescence-like phenotype developed. The basal levels of the lysosomal enzyme alpha-acid glucosidase (GAA), essential for autolysosomal glycogen degradation, and the lipidated forms of gamma-aminobutyric acid receptor-associated protein-like (GABARAPL1 and GABARAPL2) increased in shPYGL U87MG cells, suggesting a compensatory mechanism of glycogen degradation. In response to IR, dysregulation of autophagy was shown by accumulation of the p62 and the lipidated form of GABARAPL1 and GABARAPL2 in shPYGL U87MG cells. IR increased the mitochondrial mass and the colocalisation of mitochondria with lysosomes in shPYGL cells, thereby indicating reduced mitophagy. These changes coincided with increased phosphorylation of AMP-activated protein kinase and acetyl-CoA carboxylase 2, slower ATP generation in response to glucose loading and progressive loss of oxidative phosphorylation. The resulting metabolic deficiencies affected the availability of ATP required for mitosis, resulting in the mitotic catastrophy observed in shPYGL cells following IR. PYGL mRNA and protein levels were higher in human GBM than in normal human brain tissues and high PYGL mRNA expression in GBM correlated with poor patient survival. In conclusion, we show a major new role for glycogen metabolism in GBM cancer. Inhibition of glycogen degradation sensitises GBM cells to high-dose IR indicating that PYGL is a potential novel target for the treatment of GBMs.

Characterization of a cold-adapted debranching enzyme and its role in glycogen metabolism and virulence of Vibrio vulnificus MO6-24/O.

Vibrio vulnificus MO6-24/O has three genes annotated as debranching enzymes or pullulanase genes. Among them, the gene encoded by VVMO6_03032 (vvde1) shares a higher similarity at the amino acid sequence level to the glycogen debranching enzymes, AmyX of Bacillus subtilis (40.5%) and GlgX of Escherichia coli (55.5%), than those encoded by the other two genes. The vvde1 gene encoded a protein with a molecular mass of 75.56 kDa and purified Vvde1 efficiently hydrolyzed glycogen and pullulan to shorter chains of maltodextrin and maltotriose (G3), respectively. However, it hydrolyzed amylopectin and soluble starch far less efficiently, and β-cyclodextrin (β-CD) only rarely. The optimal pH and temperature of Vvde1 was 6.5 and 25°C, respectively. Vvde1 was a cold-adapted debranching enzyme with more than 60% residual activity at 5°C. It could maintain stability for 2 days at 25°C and 1 day at 35°C, but it destabilized drastically at 40°C. The Vvde1 activity was inhibited considerably by Cu2+, Hg2+, and Zn2+, while it was slightly enhanced by Co2+, Ca2+, Ni2+, and Fe2+. The vvde1 knock-out mutant accumulated more glycogen than the wild-type in media supplemented with 1.0% maltodextrin; however, the side chain length distribution of glycogen was similar to that of the wild-type except G3, which was much more abundant in the mutant. Therefore, Vvde1 seemed to debranch glycogen with the degree of polymerization 3 (DP3) as the specific target branch length. Virulence of the pathogen against Caenorhabditis elegans was attenuated significantly by the vvde1 mutation. These results suggest that Vvde1 might be a unique glycogen debranching enzyme that is involved in both glycogen utilization and shaping of glycogen molecules, and contributes toward virulence of the pathogen.

LUBAC: a new player in polyglucosan body disease.

Altered protein ubiquitination is associated with the pathobiology of numerous diseases; however, its involvement in glycogen metabolism and associated polyglucosan body (PB) disease has not been investigated in depth. In PB disease, excessively long and less branched glycogen chains (polyglucosan bodies, PBs) are formed, which precipitate in different tissues causing myopathy, cardiomyopathy and/or neurodegeneration. Linear ubiquitin chain assembly complex (LUBAC) is a multi-protein complex composed of two E3 ubiquitin ligases HOIL-1L and HOIP and an adaptor protein SHARPIN. Together they are responsible for M1-linked ubiquitination of substrates primarily related to immune signaling and cell death pathways. Consequently, severe immunodeficiency is a hallmark of many LUBAC deficient patients. Remarkably, all HOIL-1L deficient patients exhibit accumulation of PBs in different organs especially skeletal and cardiac muscle resulting in myopathy and cardiomyopathy with heart failure. This emphasizes LUBAC's important role in glycogen metabolism. To date, neither a glycogen metabolism-related LUBAC substrate nor the molecular mechanism are known. Hence, current reviews on LUBAC's involvement in glycogen metabolism are lacking. Here, we aim to fill this gap by describing LUBAC's involvement in PB disease. We present a comprehensive review of LUBAC structure, its role in M1-linked and other types of atypical ubiquitination, PB pathology in human patients and findings in new mouse models to study the disease. We conclude the review with recent drug developments and near-future gene-based therapeutic approaches to treat LUBAC related PB disease.

Effects of intracerebroventricularly administered opioid peptide antagonists on tissue glycogen levels in rats after exercise

Background/aim Physical exercise is a state of physiological stress that requires adaptation of the organism to physical activity. Glycogen is an important and essential energy source for muscle contraction. Skeletal muscle and liver are two important glycogen stores, and the energy required to maintain exercise in rodents are provided by destruction of this glycogen depot. In this study, the effects of endogenous opioid peptide antagonism at the central nervous system level on tissue glycogen content after exhaustive exercise were investigated. Materials and methods Rats had intracerebroventricularly (icv) received nonspecific opioid peptide receptor antagonist, naloxone (50 μg/10 μL in saline) and δ-opioid receptor-selective antagonist naltrindole (50 μg/10 μL in saline) and then exercised till exhaustion. After exhaustion, skeletal muscle, heart, and liver were excised immediately. Results Both opioid peptide antagonists decreased glycogen levels in skeletal muscle. Although, in soleus muscle, this decrease was not statistically significant (p > 0.05), in gastrocnemius muscle, it was significant in the icv naloxone administered group compared with control (p < 0.05). Heart glycogen levels increased significantly in both naloxone and naltrindole groups compared to control and sham-operated groups (p < 0.05). Heart glycogen levels were higher in the naloxone group than naltrindole (p < 0.05). Liver glycogen levels were elevated significantly with icv naloxone administration compared with the control group (p < 0.05). Glycogen levels in the naloxone group was also significantly higher than the naltrindole group (p < 0.05). Conclusion Our findings indicate that icv administered opioid peptide antagonists may play a role in glycogen metabolism in peripheral tissues such as skeletal muscle, heart, and liver.

Male inheritance of X-linked liver glycogenosis from an undiagnosed maternal grandfather in a Chinese pedigree: a report of two cases

Abstract Hepatic phosphorylase kinase (PhK) plays an important role in glycogen metabolism by activating phosphorylase. Patients with PhK deficiency may get glycogen storage disease (GSD) type-IXa, an X-linked liver glycogenosis disease. To inform genetic counseling in a family with two affected GSD brothers, we performed a genetic analysis. The GSD in the older brother was confirmed by histological examination of a liver biopsy, which showed glycogen accumulation in liver cells. A liver biopsy was not available from the younger brother. The two patients and their parents were analyzed by whole exome sequencing. A pathogenic mutation in a gene encoding a regulatory subunit of PhK, PHKA2 located on chromosome Xp22, was identified as c.G3373A (p.E1125K) and confirmed by Sanger sequencing. The proband's maternal grandparents and the brothers and sisters of the proband's maternal grandfather were physically examined and genetically tested by Sanger sequencing. Pedigree analysis showed that the mother was a carrier and that the two patients inherited the mutation from their undiagnosed maternal grandfather. Moreover, among the maternal grandfather and four granduncles, three of them possessed the same mutation and four suffered from fatty liver. This is the first report of this mutation causing X-linked liver glycogenosis in a Chinese family and shows that GSD IXa is a mild form of glycogenosis in terms of clinical symptoms, indicating that GSD may be undiagnosed or underestimated. Nevertheless, to provide appropriate intervention and genetic counseling, early identification of the genetic cause is imperative. This study was approved by the Ethics Committee of First Affiliated Hospital, Hunan University of Chinese Medicine (approval No. HN-LL-ZFKY-2018-001-01) on January 12, 2018.

Beyond energy storage: roles of glycogen metabolism in health and disease.

Beyond storing and supplying energy in the liver and muscles, glycogen also plays critical roles in cell differentiation, signaling, redox regulation, and stemness under various physiological and pathophysiological conditions. Such versatile functions have been revealed by various forms of glycogen storage diseases. Here, we outline the source of carbon flux in glycogen metabolism and discuss how glycogen metabolism guides CD8+ T-cell memory formation and maintenance. Likewise, we review how this affects macrophage polarization and inflammatory responses. Furthermore, we dissect how glycogen metabolism supports tumor development by promoting tumor-repopulating cell growth in hypoxic tumor microenvironments. This review highlights the essential role of the gluconeogenesis-glycogenesis-glycogenolysis-PPP metabolic chain in redox homeostasis, thus providing insights into potential therapeutic strategies against major chronic diseases including cancer.

Glycogen Metabolism Supports Early Glycolytic Reprogramming and Activation in Dendritic Cells in Response to Both TLR and Syk-Dependent CLR Agonists.

Dendritic cells (DCs) increase their metabolic dependence on glucose and glycolysis to support their maturation, activation-associated cytokine production, and T-cell stimulatory capacity. We have previously shown that this increase in glucose metabolism can be initiated by both Toll-like receptor (TLR) and C-type lectin receptor (CLR) agonists. In addition, we have shown that the TLR-dependent demand for glucose is partially satisfied by intracellular glycogen stores. However, the role of glycogen metabolism in supporting CLR-dependent DC glycolytic demand has not been formally demonstrated. In this work, we have shown that DCs activated with fungal-associated β-glucan ligands exhibit acute glycolysis induction that is dependent on glycogen metabolism. Furthermore, glycogen metabolism supports DC maturation, inflammatory cytokine production, and priming of the nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome in response to both TLR- and CLR-mediated activation. These data support a model in which different classes of innate immune receptors functionally converge in their requirement for glycogen-dependent glycolysis to metabolically support early DC activation. These studies provide new insight into how DC immune effector function is metabolically regulated in response to diverse inflammatory stimuli.

Complete genome sequencing of Shigella sp. PAMC 28760: Identification of CAZyme genes and analysis of their potential role in glycogen metabolism for cold survival adaptation

Shigella sp. PAMC 28760 (isolated from Himantormia sp. lichen in Antarctica) is a gram-negative, non-sporulating bacterium that has cellulolytic and amylolytic characteristics as well as glycogen metabolic pathways. In this study, we isolated S. sp. PAMC 28760 from Antarctic lichen, and present the complete genome sequence with annotations describing its unique features. The genome sequence has 58.85% GC content, 4,278 coding DNA sequences, 85 tRNAs, and 22 rRNA operons. 16S rRNA gene sequence analyses revealed strain PAMC 28760 as a potentially new species of genus Shigella, showing various differences from pathogenic bacteria reported previously. dbCAN2 analyses revealed 91 genes related to carbohydrate-metabolizing enzymes. S. sp. PAMC 28760 likely degrades polysaccharide starch to obtain glucose for energy conservation. This study provides a foundation for understanding Shigella survival adaptation mechanisms under extremely cold Antarctic conditions.

Glycogen phosphorylase inhibition activates intrinsic apoptosis pathway and potentiates multi‐kinase inhibitors in liver cancer cells

Hepatocellular carcinoma (HCC) is one of the leading cancers in terms of incidence and mortality. There are fewer chemotherapies with HCC with a low survival rate. One of the prominent features of cancer is metabolic reprogramming and thus metabolic proteins are viable targets for cancer treatment. Glycogen is a polymer of glucose, which acts as a reservoir of energy in mammalian cells. The levels of glycogen have been found to correlate with biological processes in cancer cells, however, the role of glycogen metabolism in carcinogenesis, cancer cell growth, metastasis, and chemoresistance is not completely understood. Thus, we studied the cellular processes involved in the inhibition of glycogen metabolism in HCC. Pharmacological inhibition of glycogen phosphorylase (GP) by CP‐91149, a rate‐limiting enzyme in glycogen catabolism, led to a decrease in HepG2 viability. GP inhibition induced the intrinsic apoptosis pathway causing HepG2 cell death. This process was accompanied by mitochondrial dysfunction and autophagic adaptations, whereas endoplasmic reticulum stress, necrosis, and necroptosis were not involved. In addition, GP inhibition potentiated the effects of the multi‐kinase inhibitors sorafenib and regorafenib, which are key drugs in advanced‐stage HCC therapy. Our study provides mechanistic insights into cell death by perturbations of glycogen metabolism and identifies GP inhibition as a potential cancer pharmacotherapy target.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The Role of Glycogen Metabolism in Glycolytic Reprogramming Required for Dendritic Cell Immune Responses

Abstract Dendritic cells (DCs) are potent professional antigen presenting cells of the immune system and serve as a bridge between innate and adaptive immune responses. Activated DCs undergo a process of maturation defined by cytokine &amp; chemokine secretion, co-stimulatory molecule expression, antigen processing and presentation, and the ability to activate T cells. DC maturation is coupled with an increase in energy demand, which is fulfilled by a TLR-driven burst in glycolytic metabolism. Up-regulation of glycolysis in activated DCs provides these cells with molecular building blocks and cellular energy required for DC effector function. Inhibition of glycolysis impairs both the survival and effector function of activated DCs. According to the prevailing model, TLR-driven glycolysis in DCs is sustained primarily by increases in extracellular glucose uptake. While non-immune cells, specifically hepatocytes and muscle cells, can store glucose in the form of glycogen as an intracellular energy reserve, the role of glycogen metabolism in supporting DC immune responses has not previously been described. Our data show that DCs possess intracellular glycogen stores and express enzymes essential for glycogen metabolism. Furthermore, inhibition of glycogen metabolism significantly impairs key activation parameters and effector functions of these cells. We further report that DCs exhibit functional compartmentalization of glucose- and glycogen-derived carbons, where these substrates preferentially contribute to distinct metabolic pathways. This work provides novel insights into nutrient homeostasis in DCs, demonstrating that differential utilization of glycogen and glucose metabolism regulates their optimal immune function.

Update on new muscle glycogenosis

The field of muscle glycogenoses has progressed in recent years by the identification of new disorders, and by reaching a better understanding of pathophysiology of the disorders and the physiology of glycogen metabolism. In this review, we describe the clinical and pathological features of the three most recently described muscle glycogenoses caused by recessive mutations in GYG1, RBCK1 and PGM1. The three involved enzymes play different roles in glycogen metabolism. Glycogenin-1 (GYG1) is involved in the initial steps of glycogen synthesis, whereas phosphoglucomutase catalyzes two metabolic pathways; the connection between galactose and glycogen on one side, and glucose metabolism on the other side. The metabolic consequences of mutations in the ubiquitin ligase gene RBCK1 are still poorly understood. GYG1 deficiency has been associated with cardiomyopathies with abnormal storage material in the heart, but most cases present with a polyglucosan body myopathy without cardiac involvement. The recent identification of new glycogenosis not only allows to improve the knowledge of glycogen metabolism, but also builds bridges with protein glycosylation and immune system.

Abstract 1545: Loss of glycogen debranching enzyme (AGL) promotes rapid growth of non-small cell lung cancer cells

Abstract Glycogen Debranching Enzyme (AGL) is involved in glycogen breakdown. Compromise in glycogen breakdown due to loss of function mutations in the AGL gene lead to metabolic disease - Glycogen Storage Disease Type III. We have previously shown that loss of AGL results in rapid growth of bladder cancer cells using extensive in vitro and in vivo experiments. Here we test whether AGL regulate growth of non-small cell lung cancer (NSCLC) cells. We show that loss of AGL promotes rapid growth of NSCLC cells using anchorage independent growth assay. Loss of AGL also resulted in rapid xenograft growth of NSCLC cells when injected subcutaneously in immunocompromised mice. Whereas overexpression of AGL reduce the growth of these NSCLC cells. Further loss of glycogen phosphorylase the other enzyme involved in glycogen breakdown does not promote aggressive growth of these cancer cells. This observation is similar to our findings in bladder cancer which confirms that AGL regulates tumor growth independent of its role in glycogen metabolism. Thus using in vitro and in vivo experiments we show that AGL can regulate the growth of multiple tumor types such as bladder cancer and NSCLC. The exact mechanism on how AGL regulates NSCLC growth needs further investigation. Citation Format: David R. Meier, Benjamin Weinhaus, Darby Oldenburg, Sunny Guin. Loss of glycogen debranching enzyme (AGL) promotes rapid growth of non-small cell lung cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1545. doi:10.1158/1538-7445.AM2017-1545