Ammonia Derived from Glutaminolysis Is a Diffusible Regulator of Autophagy

Center for Integrative Biology and Biotherapeutics, Pfizer, Pearl River, NY 10965, USA.
Science Signaling (Impact Factor: 6.28). 04/2010; 3(119):ra31. DOI: 10.1126/scisignal.2000911
Source: PubMed


Autophagy is a tightly regulated catabolic process that plays key roles in normal cellular homeostasis and survival during periods of extracellular nutrient limitation and stress. The environmental signals that regulate autophagic activity are only partially understood. Here, we report a direct link between glutamine (Gln) metabolism and autophagic activity in both transformed and nontransformed human cells. Cells cultured for more than 2 days in Gln-containing medium showed increases in autophagy that were not attributable to nutrient depletion or to inhibition of mammalian target of rapamycin. Conditioned medium from these cells contained a volatile factor that triggered autophagy in secondary cell cultures. We identified this factor as ammonia derived from the deamination of Gln by glutaminolysis. Gln-dependent ammonia production supported basal autophagy and protected cells from tumor necrosis factor-alpha (TNF-alpha)-induced cell death. Thus, Gln metabolism not only fuels cell growth but also generates an autocrine- and paracrine-acting regulator of autophagic flux in proliferating cells.

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    • "H9c2 cells (CRL-1446) cells were purchased from American Type Culture Collection (Manassas, VA). U2OS cells stably expressing GFP-LC3 (U2OS-GFP-LC3 cells) [16] were a generous gift of Dr. Christina Eng (Pfizer Inc, Pearl River). These cells were maintained in high glucose Dulbecco’s Modification of Eagle’s Medium (DMEM, Life Technologies, Carlsbad, CA) supplemented with 10% (v/v) heat inactivated fetal bovine serum, 100 units/ml penicillin/streptomycin, and 2 mM L-glutamine (Life Technologies, Carlsbad, CA) at 37°C in a humidified air atmosphere at 5% CO2. "
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    PLoS ONE 11/2013; 8(11):e82481. DOI:10.1371/journal.pone.0082481 · 3.23 Impact Factor
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    • "NH3 plays an additional role in virulence of H. pylori by enhancing host cell apoptosis through its modulation of endocytic vesicle trafficking [63]. Furthermore, NH3 is increasingly recognized as an important signaling molecule in cellular responses to stress [64], [65]. In the context of inflammation, elevated NH3 levels inhibit neutrophil chemotaxis [66], phagocytosis, and degranulation while also stimulating spontaneous oxidative bursts [67]. "
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    PLoS ONE 10/2012; 7(10):e48475. DOI:10.1371/journal.pone.0048475 · 3.23 Impact Factor
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    • "One possibility is that Ras activates autophagy by direct (Kalas et al. 2011) or indirect Hif-1a-mediated activation of BNIP3, an inducer of autophagy. Additionally, it is also possible that increased glutaminolysis and ammonia production triggers autophagy induction under these conditions (Eng et al. 2010). The autophagy-mediated stress response mechanism may be particularly important in cancer cells to limit cell death and tissue inflammation, to recycle toxic damaged proteins and organelles, and to provide energy and metabolic substrates. "
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