Regulation of V-ATPase Reassembly by the Glycolysis Flow in PFK-1 Deficient Yeast Cells.
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Yeast 6-phosphofructo-1-kinase (PFK-1) has two subunits, Pfk1p and Pfk2p. Deletion of Pfk2p alters glucose-dependent V-ATPase reassembly and vacuolar acidification (Chan CY and Parra KJ, J. Biol. Chem. 2014 289(28): 19448-57). This study capitalized on the mechanisms suppressing V-ATPase in pfk2Δ to gain new knowledge of the mechanisms underlying glucose-dependent V-ATPase regulation. Since V-ATPase is fully assembled in pfk2Δ and glycolysis partially suppressed at steady state, we manipulated glycolysis and assessed its direct involvement on V-ATPase function. At steady state, the ratio of proton transport to ATP hydrolysis increased 24% after increasing the glucose concentration from 2% to 4% to enhance the glycolysis flow in pfk2Δ. Tighter coupling restored vacuolar pH when glucose was abundant and glycolysis operated below capacity. After re-addition of glucose to glucose-deprived cells, glucose-dependent V1Vo reassembly was proportional to the glycolysis flow. Re-addition of 2% glucose to pfk2Δ cells, which restored 62% of ethanol concentration led to equivalent 60% V1Vo reassembly levels. Steady state level of assembly (100% reassembly) was reached at 4% glucose when glycolysis reached a threshold in pfk2Δ (≥ 40% the wild-type flow). At 4% glucose, the level of Pfk1p co-immunoprecipitated with V-ATPase decreased 58% in pfk2Δ, suggesting that Pfk1p binding to V-ATPase may be inhibitory in the mutant. We concluded that V-ATPase activity, at steady state, and V-ATPase reassembly, after re-addition of glucose to glucose-deprived cells, are controlled by the glycolysis flow. We propose a new mechanism by which glucose regulates V-ATPase catalytic activity that occurs at steady state without changing V1Vo assembly.Copyright © 2016, The American Society for Biochemistry and Molecular Biology.
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