Biology subjects

Takaine, M.

Publications and source records attributed to Takaine, M..

4 recordsLinked to original sources

bioRxiv2025

Conserved metabolic adaptation mechanisms in cancer cells and yeast against mitochondrial dysfunction indicate an additional role of aerobic glycolysis for cell survival

Eukaryotic cells primarily generate ATP through oxidative phosphorylation and substrate-level phosphorylation. Despite the superior efficiency of oxidative phosphorylation, eukaryotic cells often utilize both pathways as aerobic glycolysis even in the presence of oxygen. However, its role in cell survival remains poorly understood. In this study, aerobic glycolysis of the Warburg effect in breast cancer cells (MCF7) and the Crabtree effect in a laboratory strain of Saccharomyces cerevisiae (S288C) were compared following treatment with electron transport chain inhibitors, including FCCP, antimycin A, and oligomycin. MCF7 and S288C exhibited strikingly similar metabolic rewiring toward substrate-level phosphorylation against the inhibitor treatment, suggesting that mitochondrial oxidative phosphorylation and cytosolic substrate-level phosphorylation communicate through a common mechanism. Measurements of mitochondrial membrane potential (MMP) and ATP concentration further indicated that cytosolic ATP was transported into the mitochondria under conditions of reduced electron transport chain activity. This ATP was likely utilized by the reverse mode of H+/ATPase to maintain the MMP which contributed to avoiding programmed cell death. These results suggest that the ATP supply to mitochondria plays a conserved role in aerobic glycolysis across yeast and mammalian cancer cells. This mechanism likely contributes to cell survival under conditions of fluctuating oxygen availability.

cell biology↗

bioRxiv2023

Yeast PRPP amidotransferase assembles into fine granules to promote de novo purine synthesis through intermolecular substrate channeling

De novo purine synthesis (DPS) is up-regulated under conditions of high purine demand to ensure the production of genetic materials and chemical energy, thereby supporting cell proliferation. However, the regulatory mechanisms governing DPS remain largely unclear. We herein show that PRPP amidotransferase (PPAT), the rate-limiting enzyme in DPS, forms dynamic and motile condensates in Saccharomyces cerevisiae cells under a purine-depleted environment. The formation of condensates requires phase separation, which is driven by target of rapamycin complex 1 (TORC1)-induced ribosome biosynthesis. The self-assembly of PPAT molecules facilitates condensate formation, with intracellular PRPP and purine nucleotides both regulating this self-assembly. Moreover, molecular dynamics simulations suggest that clustering-mediated PPAT activation occurs through intermolecular substrate channeling. Cells unable to form PPAT condensates exhibit growth defects, highlighting the physiological importance of condensation. These results suggest that PPAT condensation is an adaptive mechanism that regulates DPS in response to both TORC1 activity and cellular purine demands. HighlightsO_LIPRPP amidotransferase (PPAT) in budding yeast forms dynamic intracellular condensates in response to environmental purine deprivation. C_LIO_LIRibosome crowding in the cytoplasm, induced by TORC1, drives the assembly of PPAT condensates. C_LIO_LIThe purified PPAT protein alone condensates into submicron-sized particles in vitro under molecular crowding conditions. C_LIO_LIPurine nucleotides inhibit the self-assembly of PPAT, while PRPP promotes this process and counteracts the inhibition. C_LIO_LIThe condensation of PPAT facilitates the intermolecular channeling of intermediates, thereby enhancing de novo purine synthesis. C_LI

cell biology↗

bioRxiv2020

Actin binding domain of Rng2 strongly inhibits actin movement on myosin II HMM through structural changes of actin filaments

Substoichiometric binding of certain actin-binding proteins induces conformational changes in a disproportionally large number of actin protomers in actin filaments. Here, we report a case in which such conformational changes in actin filaments have profound functional consequences. Rng2 is an IQGAP protein implicated in the assembly and contraction of contractile rings in Schizosaccharomyces pombe. We found that the calponin-homology actin-binding domain of Rng2 (Rng2CHD) strongly inhibits the motility of actin filaments on myosin II in vitro. On skeletal muscle myosin II-coated surfaces, Rng2CHD halved the sliding speed of actin filaments at a binding ratio of 1.3% (=1/77), and virtually stopped movement at a binding ratio of 11% (=1/9). Rng2CHD also inhibited actin movements on Dictyostelium myosin II, but in this case by inducing the detachment of actin filaments from myosin II-coated surfaces. Rng2CHD induced cooperative structural changes of actin filaments accompanied by shortening of the filament helical pitch, and reduced the affinity between actin filaments and subfragment 1 (S1) of muscle myosin II in the presence of ADP. Intriguingly, actin-activated ATPase of S1 was hardly inhibited by Rng2CHD. We suggest that sparsely bound Rng2CHD induces global structural changes of actin filaments and interferes with the force generation by actin-myosin II.

biophysics↗

bioRxiv2019

AMP-activated protein kinase and adenylate kinase prevent ATP catastrophe and cytotoxic protein aggregation

ATP at millimolar levels has recently been implicated in the solubilization of cellular proteins. However, the significance of this high ATP level under physiological conditions and the mechanisms that maintain ATP remain unclear. We herein demonstrated that AMP-activated protein kinase (AMPK) and adenylate kinase (ADK) cooperated to maintain cellular ATP levels regardless of glucose levels. Single cell imaging of ATP-reduced yeast mutants revealed that ATP levels in these mutants repeatedly underwent stochastic and transient depletion, which induced the cytotoxic aggregation of endogenous proteins and pathogenic proteins, such as huntingtin and -synuclein. Moreover, pharmacological elevations in ATP levels in an ATP-reduced mutant prevented the accumulation of -synuclein aggregates and its cytotoxicity. The removal of cytotoxic aggregates depended on proteasomes, and proteasomal activity cooperated with AMPK or ADK to resist proteotoxic stresses. The present study is the first to demonstrate that cellular ATP homeostasis ensures proteostasis and revealed that suppressing the high volatility of cellular ATP levels prevented cytotoxic protein aggregation, implying that AMPK and ADK are important factors that prevent proteinopathies, such as neurodegenerative diseases.

cell biology↗