Cardiolipin Is Required For Optimal Acetyl-Coa Metabolism

The phospholipid cardiolipin (CL) is crucial for many cellular functions and signaling pathways, both inside and outside of mitochondria. My thesis focuses on the role of CL in energy metabolism. Many reactions of electron transport and oxidative phosphorylation, the transport of metabolites needed for these processes, and the stabilization of electron transport chain supercomplexes, require CL. Recent studies indicate that CL is required for the synthesis of iron-sulfur (Fe-S) co-factors, which are essential for numerous metabolic pathways. Activation of carnitine-acetylcarnitine translocase, which transports acetyl-CoA into the mitochondria, is CL dependent. The presence of substantial amounts of CL in the peroxisomal membrane suggests that CL may be important for peroxisomal functions. Understanding the role of CL in energy metabolism may identify physiological modifiers that exacerbate the loss of CL and underlie the variation in symptoms observed in Barth syndrome, a genetic disorder of CL metabolism. In order to identify biochemical pathways exacerbated by the loss of CL, I carried out a Synthetic Genetic Array (SGA) screen of the yeast CL mutant crd1Δ. The results indicated that crd1Δ is synthetically lethal with mutants in pyruvate dehydrogenase (PDH), which catalyzes the conversion of pyruvate to acetyl-CoA. Previous studies have shown that synthesis of acetyl-CoA depends primarily on pyruvate conversion in the mitochondria and the cytosol. The crd1Δ mutant exhibited decreased acetyl-CoA levels and decreased growth on acetate as a sole carbon source. Gene expression and protein levels of PDH were increased, but PDH specific activity remained unaltered. These findings suggest that defective ability to convert acetate to acetyl-CoA and possibly decreased enzymatic activity of PDH may account for perturbed acetyl-CoA synthesis in CL-deficient cells. Consistent with a requirement for CL in acetyl-CoA synthesis, perturbation of CL synthesis leads to decreased activity of carnitine-acetylcarnitine translocase, a transporter found in the mitochondrial membrane specific for import of acetylcarnitine into the mitochondria. Growth of crd1Δ at elevated temperature and on acetate medium is restored by supplementation of carnitine, acetylcarnitine, or oleate. Interestingly, synthetic lethality was observed between crd1Δ and mutants in the glyoxylate cycle, suggesting that this cycle is essential to replenish TCA cycle intermediates in CL-deficient cells. The studies described in this thesis are the first to demonstrate that CL is required for synthesis and transport of acetyl-CoA. To obtain an understanding of tafazzin function, an SGA screen was carried out to identify mutants that synthetically interact with taz1Δ. Interesting interactions were observed with phospholipase B, ornithine carbamoyltransferase, and genes required for mitochondrial iron homeostasis and vacuolar protein sorting. These findings suggest that tafazzin may be involved in cellular processes other than CL remodeling

Fabricating Cu2ZnSnS4, Cu2ZnSn(S,Se)4 and CuIn(S,Se)2 light-absorbing thin films for low-cost solar devices.

In this thesis, Cu2ZnSnS4 (CZTS), Cu2ZnSn(S,Se)4 (CZTSSe) and CuIn(S,Se)2 (CISSe) thin-films have been optimized to use as the key light-absorbing and conversion layer for solar cells. CZTS nanocrystals (NCs) were solvothermally synthesized, etched with acetic acid and structurally analyzed using synchrotron spectroscopy. Electrodeposited CZTSSe films showed a non-ideal increase in sulfur with lower selenization temperature and post-process etching. Compositional studies of electrodeposited CISSe films confirmed the decrease in selenium after the acetic acid etching. Through PECMs and other conventional characterization techniques, it was determined that non-etched CZTSSe and CISSe solar devices performed better than their etched counterparts, achieving efficiencies of 5.3% and 2.1%, respectively. In contrast, the results of the CZTS NCs achieved a higher efficiency for the etched device at 6.5%. In the end, electrodeposition proved to be a cheaper, more replicable technique, while CZTSSe demonstrated to be the most cost-effective light-absorber-layer for efficient solar cells

Investigation on the Photoinduced Interaction Between Water Soluble CdTe Quantum Dots and Certain Antioxidants

Photoinduced interaction of thioglycolic acid (TGA) capped CdTe quantum dots (QDs) with certain antioxidants such as estrogens and flavonoids has been investigated by using steady state and time resolved fluorescence spectroscopy. Reduction of electron-hole recombination has been observed (i.e., fluorescence quenching) while adding antioxidants to CdTe QDs. The Stern-Volmer constant (K-SV), quenching rate constant (k(q)) and binding constants (K) were obtained from fluorescence quenching data. The antioxidant interacts with QDs through static quenching, which was confirmed by unaltered fluorescence lifetime

Stat3 promotes ovarian cancer by modulating the energy metabolism and develops drug resistance in patients

Signal Transducers and Activators of Transcription (STAT) are a group of transcription factors that are known to play a major role in cancer progression. In ovarian cancer, increased STAT3 leads to cancer proliferation in response to cytokines and confers resistance to chemotherapy-induced apoptosis in epithelial malignancies. STAT3 is constitutively activated in patient derived ovarian cancer cells, and increased STAT3 expression is a predictor of poor prognosis. Apart from its function as a transcription factor, recently STAT3 has been shown to modulate mitochondrial function to promote carcinogenesis. The aim of our study was to investigate if STAT3 activation can modulate cellular metabolism of ovarian cancer cells. Stable clones expressing STAT3 were generated in A2780 ovarian cancer cells, along with empty vector clones. Ectopic expression of STAT3 in A2780 ovarian cancer cell line resulted in increased proliferation (p\u3c0.01) and colony formation ability (p\u3c0.001) in vitro and led to large ovarian tumors (p\u3c0.01) compared to parental and vector controls in xenograft mouse model. Bioenergetics profiling showed higher mitochondrial respiration (OCR) and glycolysis (ECAR) in STAT3 clones compared to parental and vector clones. Ratio of ECAR/OCR in the STAT3 overexpressing cells placed them in the \u27metabolically active\u27 phenotype, while parental A2780 and vector clones were in \u27metabolically less active\u27 phenotype. A selective inhibitor of STAT3, STATTIC, inhibited the STAT3 mediated growth of A2780 cells both in vitro (p\u3c0.01) and in vivo (p\u3c0.01). In addition, STATTIC treatments reversed the \u27metabolically active\u27 state of STAT3 overexpressing clones to a \u27lower metabolic state\u27, placing them in the same category as the control cells. In addition, STATTIC inhibited the cell proliferation and modulated bioenergetic phenotype of other ovarian cancer cells lines (PEO4, C200 and OVCAR3) that display a \u27metabolically active\u27 phenotype. Overall, STAT3 can induce metabolic changes in ovarian cancer cells, maybe as survival mechanism and enhances the cellular fitness of the ovarian cancer cell resulting in increased oncogenic abilities

Green Synthesis and Characterization of Cobalt Oxide Nanoparticles Using <i>Psidium guajava</i> Leaves Extracts and Their Photocatalytic and Biological Activities

The advanced technology for synthesizing nanoparticles utilizes natural resources in an environmentally friendly manner. Additionally, green synthesis is preferred to chemical and physical synthesis because it takes less time and effort. The green synthesis of cobalt oxide nanoparticles has recently risen due to its physico-chemical properties. In this study, many functional groups present in Psidium guajava leaf extracts are used to stabilize the synthesis of cobalt oxide nanoparticles. The biosynthesized cobalt oxide nanoparticles were investigated using UV-visible spectroscopic analysis. Additionally, Fourier-transform infrared spectroscopy revealed the presence of carboxylic acids, hydroxyl groups, aromatic amines, alcohols and phenolic groups. The X-ray diffraction analysis showed various peaks ranging from 32.35 to 67.35°, and the highest intensity showed at 36.69°. The particle size ranged from 26 to 40 nm and confirmed the average particle size is 30.9 nm. The green synthesized P. guajava cobalt oxide nanoparticles contain cobalt as the major abundant element, with 42.26 wt% and 18.75 at% confirmed by the EDAX techniques. SEM images of green synthesized P. guajava cobalt oxide nanoparticles showed agglomerated and non-uniform spherical particles. The anti-bacterial activity of green synthesized P. guajava cobalt oxide nanoparticles was evaluated against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli with a 7 to 18 mm inhibitory zone. The photocatalytic activity was evaluated using green synthesized P. guajava cobalt oxide nanoparticles and observed 79% of dye degradation. The MTT assay of P. guajava cobalt oxide nanoparticles showed an excellent cytotoxic effect against MCF 7 and HCT 116 cells compared to normal cells. The percentage of cell viability of P. guajava cobalt oxide nanoparticles was observed as 90, 83, 77, 68, 61, 58 and 52% for MCF-7 cells and 82, 70, 63, 51, 43, 40, and 37% for HCT 116 cells at the concentration of 1.53, 3.06, 6.12, 12.24, 24.48, 50, and 100 μg/mL compared to control cells. These results confirmed that green synthesized P. guajava cobalt oxide nanoparticles have a potential photocatalytic and anti-bacterial activity and also reduced cell viability against MCF-7 breast cancer and HCT 116 colorectal cancer cells

Cardiolipin-deficient cells depend on anaplerotic pathways to ameliorate defective TCA cycle function

Previous studies have shown that the cardiolipin (CL)-deficient yeast mutant, crd1Δ has decreased levels of acetyl-CoA and decreased activities of the TCA cycle enzymes aconitase and succinate dehydrogenase. These biochemical phenotypes are expected to lead to defective TCA cycle function. In this study, we report that signaling and anaplerotic metabolic pathways that supplement defects in the TCA cycle are essential in crd1Δ mutant cells. The crd1Δ mutant is synthetically lethal with mutants in the TCA cycle, retrograde (RTG) pathway, glyoxylate cycle, and pyruvate carboxylase 1. Glutamate levels were decreased, and the mutant exhibited glutamate auxotrophy. Glyoxylate cycle genes were up-regulated, and the levels of glyoxylate metabolites succinate and citrate were increased in crd1Δ. Import of acetyl-CoA from the cytosol into mitochondria is essential in crd1Δ as deletion of the carnitine-acetylcarnitine translocase led to lethality in the CL mutant. β-oxidation was functional in the mutant, and oleate supplementation rescued growth defects. These findings suggest that TCA cycle deficiency caused by the absence of CL necessitates activation of anaplerotic pathways to replenish acetyl-CoA and TCA cycle intermediates. Implications for Barth syndrome, a genetic disorder of CL metabolism, are discussed

Corrigendum to "Cardiolipin-deficient cells depend on anaplerotic pathways to ameliorate defective TCA cycle function" [Biochim. Biophys. Acta, Mol. Cell Biol. Lipids 1864/5(2019) 654-661]

The authors regret to report an error in Table 1 of this publication. The mating type of yeast strain BY4741 should have been listed as MATa rather than MATα as printed. All additional information in this table is correct. The authors would like to apologise for any inconvenience caused