Biology subjects

Bui, D.

Publications and source records attributed to Bui, D..

5 recordsLinked to original sources

bioRxiv2022

Viability of HepG2 and MCF-7 Cells is not Correlated with Mitochondrial Bioenergetics

Alterations in metabolism is a hallmark of cancer. It is unclear, however, if oxidative phosphorylation (OXPHOS) is required for tumor cell survival. We investigated the effect of severe hypoxia, site-specific inhibition of respiratory chain (RC) components, and uncouplers on the survival of HepG2 and MCF-7 2D cultured cells. Comparable respiratory complex activities were observed in both cell lines, but HepG2 cells exhibited much higher oxygen consumption rates (OCR) and respiratory capacity than the MCF-7 cells. Significant non-mitochondrial OCR was found in MCF-7 cells that was insensitive to acute combined inhibition of complexes I and III. However, pre-treatment of either cell line with RC inhibitors for 24-72 hours abolished respective complex activities and OCRs completely, and this was associated with a time-dependent decrease in citrate synthase activity, suggesting mitophagy. HepG2 cells viability was mostly unaffected by any pharmacological treatment or severe hypoxia as temporally recorded from high-content automated microscopy. Conversely, MCF-7 cells viability exhibited strong sensitivity to CIV or CV inhibition, severe hypoxia, and uncoupling, but were only moderately affected by CI, CII and CIII inhibition. CII, CIII and CIV-inhibitor mediated MCF-7 cell death were partially abrogated by aspartate. The data show that OXPHOS activity and viability are uncorrelated in these cell lines indicating that a linkage of OXPHOS to cancer cell survival must be cell- and condition-defined.

cancer biology↗

bioRxiv2022

Residual Complex I activity supports glutamate catabolism and mtSLP via canonical Krebs cycle activity during acute anoxia without OXPHOS

Anoxia halts oxidative phosphorylation (OXPHOS) causing an accumulation of reduced compounds in mitochondrial matrix which impedes dehydrogenases. By simultaneously measuring oxygen concentration, NADH autofluorescence, mitochondrial membrane potential and ubiquinone reduction extent in organello in real-time, we show that Complex I utilized endogenous quinones to oxidize NADH under acute anoxia. Untargeted or [U-13C]glutamate-targeted metabolomic analysis of matrix and effluxed metabolites extracted during anoxia in the presence or absence of site-specific inhibitors of the electron transfer system inferred that NAD+ regenerated by Complex I is reduced by the 2-oxoglutarate dehydrogenase complex yielding succinyl-CoA supporting mitochondrial substrate-level phosphorylation (mtSLP), releasing succinate. Yet, targeted metabolomic analysis using [U-13C]malate also revealed concomitant succinate dehydrogenase reversal during anoxia yielding succinate by reducing fumarate, albeit to a small extent. Our results highlight the importance of quinone availability to Complex I oxidizing NADH, thus maintaining glutamate catabolism and mtSLP in the absence of OXPHOS.

biochemistry↗

bioRxiv2022

Multisensory inputs control the regulation of time investment for mating by sexual experience in male Drosophila melanogaster

Males have finite resources to spend on reproduction. Thus, males rely on a time investment strategy to maximize their reproductive success. For example, male Drosophila melanogaster extends their mating duration when surrounded by conditions enriched with rivals. Here we report a novel form of behavioral plasticity whereby male fruit flies exhibit a shortened duration of mating when they are sexually experienced; we refer to this plasticity as shorter-mating-duration (SMD). SMD is a plastic behavior and requires sexually dimorphic taste neurons. We identified several neurons in the male foreleg and midleg that express specific sugar, pheromone and mechanosensory receptors. Using a cost-benefit model and behavioral experiments, we further show that SMD behavior exhibits adaptive behavioral plasticity in male flies. Thus, our study delineates the molecular and cellular basis of the sensory inputs required for SMD; this represents a plastic interval timing behavior that could serve as a model system to study how multisensory inputs converge to modify interval timing behavior for improved adaptation. ONE SENTENCE SUMMARYMale flies use information derived from their previous sexual experiences from multiple sensory inputs to optimize their investment in mating.

neuroscience↗

bioRxiv2022

In vivo selection reveals long non-coding RNAs implicated in colon to liver metastasis

Colorectal cancer (CRC) is the third most common malignancy in both American men and women. Most of the deaths attributed to CRC are a result of metastatic spread to the liver. In this study, colon cancer cells that highly metastasized to liver in vivo were compared to less metastatic parental cells to investigate the role for long non-coding RNAs (lncRNAs) in CRC metastasis. The highly metastatic daughter cells (LS-3B) were found to be 63-fold more metastatic than the parental cell line (LS-PAR) in vivo. A lncRNA microarray comparing LS-PAR and LS-3B cells revealed that 104 lncRNAs had fold changes > 2.0 and an FDR < 0.05. Real time PCR mediated validation revealed many lncRNAs exhibited high fold changes such as a 60-fold increase in LOC101448202, a 20-fold increase in MRPL23-AS1 and 50-fold decreases in GNAS-AS1 and LOC101928131. In vivo metastasis differences could be recapitulated in vitro as LS-3B cells closed wounds faster than their parental LS-PAR cells. However, intestinal epithelial cancer cells with robust downregulation of MRPL23-AS1, C1QTNF1-AS1, GNAS-AS1, LINCR-0002 and LOC101448202 failed to display differences in comparison to controls in in vitro migration assays. Three of the five lncRNAs with microarray probes for currently available GEO-datasets were significantly altered in liver CRC-associated tumor biopsies as compared to the primary tumor of non-metastatic CRC. Further studies on the lncRNAs identified will better define their roles in metastasis and how they might be useful if targeted therapeutically.

cancer biology↗

bioRxiv2022

Antibiotic-induced accumulation of lipid II sensitizes bacteria to antimicrobial fatty acids

Antibiotic tolerance and antibiotic resistance are the two major obstacles to the efficient and reliable treatment of bacterial infections. Identifying antibiotic adjuvants that sensitize resistant and tolerant bacteria to antibiotic killing may lead to the development of superior treatments with improved outcomes. Vancomycin, a lipid II inhibitor, is of major clinical importance for the treatment of Gram-positive bacterial infections. Here we show that unsaturated fatty acids (UFAs) and vancomycin act synergistically to rapidly kill S. aureus, including vancomycin tolerant and resistant populations. Our results suggest that antibiotic-mediated accumulation of lipid II at the septum facilitates membrane invasion by antimicrobial UFAs. UFA-vancomycin dual treatment generates large fluid patches of flexible lipids in the membrane leading to protein delocalization, aberrant septal formation, and loss of membrane integrity. This mechanism of synergy may be exploited for the development of new antibiotic therapies that target lipid II to combat both antibiotic tolerance and resistance.

microbiology↗