scholarly journals Tumor growth of neurofibromin-deficient cells is driven by decreased respiration and hampered by NAD+ and SIRT3

2021 ◽  
Author(s):  
Ionica Masgras ◽  
Giuseppe Cannino ◽  
Francesco Ciscato ◽  
Carlos Sanchez-Martin ◽  
Marco Pizzi ◽  
...  
Keyword(s):  
Succinate Dehydrogenase ◽  
Complex I ◽  
Nadh Dehydrogenase ◽  
Chain Complex ◽  
Respiratory Chain Complex ◽  
Succinate Dehydrogenase Activity ◽  
Nadh Ratio ◽  
Shed Light

Neurofibromin loss drives neoplastic growth and a rewiring of mitochondrial metabolism. Here, we report that neurofibromin ablation dampens expression and activity of NADH dehydrogenase, the respiratory chain complex I, in an ERK-dependent fashion. This provides cells with resistance to pro-oxidants targeting complex I and decreases both respiration and intracellular NAD+. Expression of the alternative NADH dehydrogenase NDI1 raises NAD+/NADH ratio, enhances the activity of the mitochondrial NAD+-dependent deacetylase SIRT3 and interferes with tumorigenicity in neurofibromin-deficient cells. This anti-neoplastic effect is mimicked both in vitro and in vivo by administration of NAD+ precursors or by rising expression of the NAD+ deacetylase SIRT3, and is synergistic with ablation of the mitochondrial chaperone TRAP1, which augments succinate dehydrogenase activity further contributing to block pro-neoplastic metabolic changes of these cells. These findings shed light on chemotherapeutic resistance and on bioenergetic adaptations of tumors lacking neurofibromin, linking complex I inhibition to mitochondrial NAD+/NADH unbalance and SIRT3 inhibition, as well as to down-regulation of succinate dehydrogenase. This metabolic rewiring could unveil attractive therapeutic targets for neoplasms related to neurofibromin loss.

scholarly journals The Dual-Functioning Fumarate Reductase Is the Sole Succinate:Quinone Reductase in Campylobacter jejuni and Is Required for Full Host Colonization

2009 ◽  
Vol 191 (16) ◽  
pp. 5293-5300 ◽  
Author(s):  
Rebecca A. Weingarten ◽  
Michael E. Taveirne ◽  
Jonathan W. Olson
Keyword(s):  
Organic Acids ◽  
Succinate Dehydrogenase ◽  
Campylobacter Jejuni ◽  
Growth Phase ◽  
Tca Cycle ◽  
Fumarate Reductase ◽  
Wild Type ◽  
Succinate Dehydrogenase Activity

ABSTRACT Campylobacter jejuni encodes all the enzymes necessary for a complete oxidative tricarboxylic acid (TCA) cycle. Because of its inability to utilize glucose, C. jejuni relies exclusively on amino acids as the source of reduced carbon, and they are incorporated into central carbon metabolism. The oxidation of succinate to fumarate is a key step in the oxidative TCA cycle. C. jejuni encodes enzymes annotated as a fumarate reductase (Cj0408 to Cj0410) and a succinate dehydrogenase (Cj0437 to Cj0439). Null alleles in the genes encoding each enzyme were constructed. Both enzymes contributed to the total fumarate reductase activity in vitro. The frdA::cat + strain was completely deficient in succinate dehydrogenase activity in vitro and was unable to perform whole-cell succinate-dependent respiration. The sdhA::cat + strain exhibited wild-type levels of succinate dehydrogenase activity both in vivo and in vitro. These data indicate that Frd is the only succinate dehydrogenase in C. jejuni and that the protein annotated as a succinate dehydrogenase has been misannotated. The frdA::cat + strain was also unable to grow with the characteristic wild-type biphasic growth pattern and exhibited only the first growth phase, which is marked by the consumption of aspartate, serine, and associated organic acids. Substrates consumed in the second growth phase (glutamate, proline, and associated organic acids) were not catabolized by the the frdA::cat + strain, indicating that the oxidation of succinate is a crucial step in metabolism of these substrates. Chicken colonization trials confirmed the in vivo importance of succinate oxidation, as the frdA::cat + strain colonized chickens at significantly lower levels than the wild type, while the sdhA::cat + strain colonized chickens at wild-type levels.

scholarly journals A yeast-based drug discovery platform to identify Plasmodium falciparum type II NADH dehydrogenase inhibitors

2021 ◽  
Author(s):  
Yu Cao ◽  
Chen Sun ◽  
Han Wen ◽  
Mengfei Wang ◽  
Pan Zhu ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Complex I ◽  
Nadh Dehydrogenase ◽  
Specific Inhibitor ◽  
Type I ◽  
Type Ii ◽  
Protein Activity ◽  
Asexual Blood Stage

Conventional methods utilizing in vitro protein activity assay or in vivo parasite survival to screen for malaria inhibitors suffer from high experimental background and/or inconvenience. Here we introduce a yeast-based system to facilitate chemical screen for specific protein or pathway inhibitors. The platform comprises several isogeneic Pichia strains that only differ in the target of interest, so that a compound which inhibits one strain but not the other is implicated in working specifically against the target. We used Plasmodium falciparum NDH2(PfNDH2), a type II NADH dehydrogenase, as a proof of principle to show how well this works. Three isogenic Pichia strains harboring respectively exogeneously introduced PfNDH2, its own complex I (a type I NADH dehydrogenase), and PfNDH2 with its own complex I were constructed. In a pilot screen of more than2000 compounds, we identified a highly specific inhibitor that acts on PfNDH2. This compound poorly inhibit the parasites at the asexual blood stage, however, is highly effective in repressing oocyst maturation in the mosquito stage. Our results demonstrate that the yeast cell based screen platform is feasible, efficient, economical and with very low background noise. Similar strategies could be extended to the functional screen for interacting molecules of other targets.

Mitochondrial complex I, aconitase, and succinate dehydrogenase during hypoxia-reoxygenation: modulation of enzyme activities by MnSOD

2003 ◽  
Vol 285 (1) ◽  
pp. L189-L198 ◽  
Author(s):  
Charles S. Powell ◽  
Robert M. Jackson
Keyword(s):  
Epithelial Cell ◽  
Succinate Dehydrogenase ◽  
Enzyme Activities ◽  
Complex I ◽  
Nadh Dehydrogenase ◽  
Alveolar Epithelial Cell ◽  
A549 Cells ◽  
Enzyme Inactivation ◽  
Hypoxia Reoxygenation

Both NADH dehydrogenase (complex I) and aconitase are inactivated partially in vitro by superoxide ([Formula: see text]) and other oxidants that cause loss of iron from enzyme cubane (4Fe-4S) centers. We tested whether hypoxia-reoxygenation (H-R) by itself would decrease lung epithelial cell NADH dehydrogenase, aconitase, and succinate dehydrogenase (SDH) activities and whether transfection with adenoviral vectors expressing MnSOD (Ad.MnSOD) would inhibit oxidative enzyme inactivation and thus confirm a mechanism involving [Formula: see text]. Human lung carcinoma cells with alveolar epithelial cell characteristics (A549 cells) were exposed to <1% O2-5% CO2(hypoxia) for 24 h followed by air-5% CO2for 24 h (reoxygenation). NADH dehydrogenase activity was assayed in submitochondrial particles; aconitase and SDH activities were measured in cell lysates. H-R significantly decreased NADH dehydrogenase, aconitase, and SDH activities. Ad.MnSOD increased mitochondrial MnSOD substantially and prevented the inhibitory effects of H-R on enzyme activities. Addition of α-ketoglutarate plus aspartate, but not succinate, to medium prevented cytotoxicity due to 2,3-dimethoxy-1,4-naphthoquinone. After hypoxia, cells displayed significantly increased dihydrorhodamine fluorescence, indicating increased mitochondrial oxidant production. Inhibition of NADH dehydrogenase, aconitase, and SDH activities during reoxygenation are due to excess [Formula: see text] produced in mitochondria, because enzyme inactivation can be prevented by overexpression of MnSOD.

scholarly journals Cofactor bypass variants reveal a conformational control mechanism governing cell wall polymerase activity

2016 ◽  
Vol 113 (17) ◽  
pp. 4788-4793 ◽  
Author(s):  
Monica Markovski ◽  
Jessica L. Bohrhunter ◽  
Tania J. Lupoli ◽  
Tsuyoshi Uehara ◽  
Suzanne Walker ◽  
...  
Keyword(s):  
Polymerase Activity ◽  
Activation Mechanism ◽  
Phenotypic Analysis ◽  
Outer Membranes ◽  
Division Site ◽  
Physiological Relevance ◽  
Membrane Lipoproteins ◽  
Shed Light

To fortify their cytoplasmic membrane and protect it from osmotic rupture, most bacteria surround themselves with a peptidoglycan (PG) exoskeleton synthesized by the penicillin-binding proteins (PBPs). As their name implies, these proteins are the targets of penicillin and related antibiotics. We and others have shown that the PG synthases PBP1b and PBP1a ofEscherichia colirequire the outer membrane lipoproteins LpoA and LpoB, respectively, for their in vivo function. Although it has been demonstrated that LpoB activates the PG polymerization activity of PBP1b in vitro, the mechanism of activation and its physiological relevance have remained unclear. We therefore selected for variants of PBP1b (PBP1b*) that bypass the LpoB requirement for in vivo function, reasoning that they would shed light on LpoB function and its activation mechanism. Several of these PBP1b variants were isolated and displayed elevated polymerization activity in vitro, indicating that the activation of glycan polymer growth is indeed one of the relevant functions of LpoB in vivo. Moreover, the location of amino acid substitutions causing the bypass phenotype on the PBP1b structure support a model in which polymerization activation proceeds via the induction of a conformational change in PBP1b initiated by LpoB binding to its UB2H domain, followed by its transmission to the glycosyl transferase active site. Finally, phenotypic analysis of strains carrying a PBP1b* variant revealed that the PBP1b–LpoB complex is most likely not providing an important physical link between the inner and outer membranes at the division site, as has been previously proposed.

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