bims-glecem 2023-06-18 papers

Issue of 2023–06–18
six papers selected by
Dipsikha Biswas, Københavns Universitet

Proc Natl Acad Sci U S A. 2023 Jun 20. 120(25): e2300566120

Glycogen-fuelled metabolism supports rapid mucosal-associated invariant T cell responses.

Féaron C Cassidy, Nidhi Kedia-Mehta, Ronan Bergin, Andrea Woodcock, Ardena Berisha, Ben Bradley, Eva Booth, Benjamin J Jenkins, Odhrán K Ryan, Nicholas Jones, Linda V Sinclair, Donal O'Shea, Andrew E Hogan.

Mucosal-associated invariant T (MAIT) cells are a subset of unconventional T cells which recognize a limited repertoire of ligands presented by the MHC class-I like molecule MR1. In addition to their key role in host protection against bacterial and viral pathogens, MAIT cells are emerging as potent anti-cancer effectors. With their abundance in human, unrestricted properties, and rapid effector functions MAIT cells are emerging as attractive candidates for immunotherapy. In the current study, we demonstrate that MAIT cells are potent cytotoxic cells, rapidly degranulating and inducing target cell death. Previous work from our group and others has highlighted glucose metabolism as a critical process for MAIT cell cytokine responses at 18 h. However, the metabolic processes supporting rapid MAIT cell cytotoxic responses are currently unknown. Here, we show that glucose metabolism is dispensable for both MAIT cell cytotoxicity and early (<3 h) cytokine production, as is oxidative phosphorylation. We show that MAIT cells have the machinery required to make (GYS-1) and metabolize (PYGB) glycogen and further demonstrate that that MAIT cell cytotoxicity and rapid cytokine responses are dependent on glycogen metabolism. In summary, we show that glycogen-fueled metabolism supports rapid MAIT cell effector functions (cytotoxicity and cytokine production) which may have implications for their use as an immunotherapeutic agent.

Keywords: MAIT cells; cytotoxicity; immunometabolism

DOI: https://doi.org/10.1073/pnas.2300566120

Cell Commun Signal. 2023 Jun 14. 21(1): 131

Elraglusib (formerly 9-ING-41) possesses potent anti-lymphoma properties which cannot be attributed to GSK3 inhibition.

Josh T Coats, Sudhir Tauro, Calum Sutherland.

Elraglusib (formerly 9-ING-41) is an ATP-competitive inhibitor of glycogen synthase kinase-3β (GSK3β) undergoing clinical trials for the treatment of various cancers including non-Hodgkin lymphoma (NHL). The drug reduces proliferation of several NHL cell lines and has efficacy in xenograft models of the disease. To confirm the importance of its action on GSK3β, we treated 3 lymphoma cell lines with selective, structurally distinct GSK3 inhibitors: CT99021, SB216763, LY2090314, tideglusib, and elraglusib. Stabilization of β-catenin and reduced phosphorylation of CRMP2, two validated targets of GSK3, were used as functional read-outs for GSK3 inhibition. CT99021, SB216763, and LY2090314 failed to reduce proliferation or viability in any cell line at concentrations that stabilized β-catenin and reduced CRMP2 phosphorylation. There was partial reduction of CRMP2 phosphorylation but no significant effect on β-catenin at cytotoxic doses of elraglusib. There was no indication of GSK3 inhibition at doses of tideglusib that affected cell viability and apoptosis. Cell-free kinase screening confirmed several other targets of elraglusib, distinct from the GSK3 inhibitors with no anti-lymphoma actions, including PIM kinases and MST2. These data question GSK3 as the target of elraglusib in lymphoma, and hence the utility of GSK3 expression as a 'stand-alone', therapeutic biomarker in NHL. Video Abstract.

Keywords: 9-ING-41; Elraglusib; GSK3; Lymphoma

DOI: https://doi.org/10.1186/s12964-023-01147-8

Cell Rep. 2023 Jun 13. pii: S2211-1247(23)00644-7. [Epub ahead of print]42(6): 112633

Phosphatidylinositol 4-kinase IIα is a glycogen synthase kinase 3-regulated interaction hub for activity-dependent bulk endocytosis.

Eva-Maria Blumrich, Jessica C Nicholson-Fish, Marie Pronot, Elizabeth C Davenport, Dominic Kurian, Adam Cole, Karen J Smillie, Michael A Cousin.

Phosphatidylinositol 4-kinase IIα (PI4KIIα) generates essential phospholipids and is a cargo for endosomal adaptor proteins. Activity-dependent bulk endocytosis (ADBE) is the dominant synaptic vesicle endocytosis mode during high neuronal activity and is sustained by glycogen synthase kinase 3β (GSK3β) activity. We reveal the GSK3β substrate PI4KIIα is essential for ADBE via its depletion in primary neuronal cultures. Kinase-dead PI4KIIα rescues ADBE in these neurons but not a phosphomimetic form mutated at the GSK3β site, Ser-47. Ser-47 phosphomimetic peptides inhibit ADBE in a dominant-negative manner, confirming that Ser-47 phosphorylation is essential for ADBE. Phosphomimetic PI4KIIα interacts with a specific cohort of presynaptic molecules, two of which, AGAP2 and CAMKV, are also essential for ADBE when depleted in neurons. Thus, PI4KIIα is a GSK3β-dependent interaction hub that silos essential ADBE molecules for liberation during neuronal activity.

Keywords: CP: Cell biology; endocytosis; endosome; kinase; neuron; neurotransmitter; synapse; vesicle

DOI: https://doi.org/10.1016/j.celrep.2023.112633

Obesity (Silver Spring). 2023 Jun 13.

Gαi -coupled GPR41 activation increases Ca2+ influx in C2C12 cells and shows a therapeutic effect in diabetic animals.

Do-Hyung Lee, Kyung-Sun Heo, Chang-Seon Myung.

OBJECTIVE: This study aimed to investigate the possible mechanisms by which orphan G protein-coupled receptor GPR41 activation enhances glucose uptake into C2C12 myotubes using a GPR41-selective agonist, AR420626, and to examine the ability of this agent to improve insulin sensitivity and glucose homeostasis in vivo.
METHODS: Basal and insulin-stimulated glucose uptake and glucose transporter 4 translocations were measured in C2C12 myotubes. Ca2+ influx into cells was measured and GPR41-mediated signaling by AR420626 was examined. An oral glucose tolerance test was performed, and plasma insulin levels were measured in streptozotocin-treated or high-fat diet-fed diabetic mice. The glycogen content was measured in skeletal muscle tissue.
RESULTS: AR420626 increased basal and insulin-stimulated glucose uptake, which was reduced by pertussis toxin, an inhibitor of Gαi -mediated signaling, and treatment with small interfering RNA for GPR41 (siGPR41). AR420626 increased intracellular Ca2+ influx and phosphorylated Ca2+ /calmodulin-dependent protein kinase type II, cyclic AMP-responsive element-binding protein, and mitogen-activated protein kinase (p38) in C2C12 myotubes, which were inhibited by treating with pertussis toxin, amlodipine (Ca2+ channel blocker), and siGPR41. AR420626 increased plasma insulin levels and skeletal muscle glycogen content and improved glucose tolerance in streptozotocin- and high-fat diet-induced diabetic mouse models.
CONCLUSIONS: GPR41 activation with AR420626 increased glucose uptake mediated by Ca2+ signaling via GPR41, improving diabetes mellitus.

DOI: https://doi.org/10.1002/oby.23786

Acta Physiol (Oxf). 2023 Jun 12. e14012

Slow or fast: implications of myofibre type and associated differences for manifestation of neuromuscular disorders.

Erin M Lloyd, Gavin J Pinniger, Robyn M Murphy, Miranda D Grounds.

Many neuromuscular disorders can have a differential impact on a specific myofibre-type, forming the central premise of this review. The many different skeletal muscles in mammals contain a spectrum of slow- to fast-twitch myofibres with varying levels of protein isoforms that determine their distinctive contractile, metabolic, and other properties. The variations in functional properties across the range of classic 'slow' to 'fast' myofibres are outlined, combined with exemplars of the predominantly slow-twitch soleus and fast-twitch extensor digitorum longus muscles, species comparisons, and techniques used to study these properties. Other intrinsic and extrinsic differences are discussed in the context of slow and fast myofibres. These include inherent susceptibility to damage, myonecrosis, and regeneration, plus extrinsic nerves, extracellular matrix, and vasculature, examined in the context of growth, ageing, metabolic syndrome, and sexual dimorphism. These many differences emphasise the importance of carefully considering the influence of myofibre-type composition on manifestation of various neuromuscular disorders across the lifespan for both sexes. Equally, understanding the different responses of slow and fast myofibres due to intrinsic and extrinsic factors can provide deep insight into the precise molecular mechanisms that initiate and exacerbate various neuromuscular disorders. This focus on the influence of different myofibre types is of fundamental importance to enhance translation for clinical management and therapies for many skeletal muscle disorders.

Keywords: Duchenne muscular dystrophy; MyHC composition; Myofibre types; ageing; amyotrophic lateral sclerosis; atrophy; dysferlinopathy; glycogen storage diseases; metabolic syndrome; muscle damage; myonecrosis; myosinopathies; neuromuscular disorders; sarcopenia; skeletal muscle; α-actinin-3 deficiency

DOI: https://doi.org/10.1111/apha.14012

Metabolism. 2023 Jun 12. pii: S0026-0495(23)00234-2. [Epub ahead of print] 155630

Protective effects of the succinate/SUCNR1 axis on damaged hepatocytes in NAFLD.

OBJECTIVE: Succinate and succinate receptor 1 (SUCNR1) are linked to fibrotic remodeling in models of non-alcoholic fatty liver disease (NAFLD), but whether they have roles beyond the activation of hepatic stellate cells remains unexplored. We investigated the succinate/SUCNR1 axis in the context of NAFLD specifically in hepatocytes.
METHODS: We studied the phenotype of wild-type and Sucnr1-/- mice fed a choline-deficient high-fat diet to induce non-alcoholic steatohepatitis (NASH), and explored the function of SUCNR1 in murine primary hepatocytes and human HepG2 cells treated with palmitic acid. Lastly, plasma succinate and hepatic SUCNR1 expression were analyzed in four independent cohorts of patients in different NAFLD stages.
RESULTS: Sucnr1 was upregulated in murine liver and primary hepatocytes in response to diet-induced NASH. Sucnr1 deficiency provoked both beneficial (reduced fibrosis and endoplasmic reticulum stress) and detrimental (exacerbated steatosis and inflammation and reduced glycogen content) effects in the liver, and disrupted glucose homeostasis. Studies in vitro revealed that hepatocyte injury increased Sucnr1 expression, which when activated improved lipid and glycogen homeostasis in damaged hepatocytes. In humans, SUCNR1 expression was a good determinant of NAFLD progression to advanced stages. In a population at risk of NAFLD, circulating succinate was elevated in patients with a fatty liver index (FLI) ≥60. Indeed, succinate had good predictive value for steatosis diagnosed by FLI, and improved the prediction of moderate/severe steatosis through biopsy when added to an FLI algorithm.
CONCLUSIONS: We identify hepatocytes as target cells of extracellular succinate during NAFLD progression and uncover a hitherto unknown function for SUCNR1 as a regulator of hepatocyte glucose and lipid metabolism. Our clinical data highlight the potential of succinate and hepatic SUCNR1 expression as markers to diagnose fatty liver and NASH, respectively.

Keywords: Glycogen; Hepatocyte; NASH; SUCNR1; Steatosis; Succinate

DOI: https://doi.org/10.1016/j.metabol.2023.155630