Tight Coupling of Metabolic Oscillations and Intracellular Water Dynamics in <i>Saccharomyces cerevisiae</i>

We detected very strong coupling between the oscillating concentration of ATP and the dynamics of intracellular water during glycolysis in Saccharomyces cerevisiae. Our results indicate that: i) dipolar relaxation of intracellular water is heterogeneous within the cell and different from dilute conditions, ii) water dipolar relaxation oscillates with glycolysis and in phase with ATP concentration, iii) this phenomenon is scale-invariant from the subcellular to the ensemble of synchronized cells and, iv) the periodicity of both glycolytic oscillations and dipolar relaxation are equally affected by D2O in a dose-dependent manner. These results offer a new insight into the coupling of an emergent intensive physicochemical property of the cell, i.e. cell-wide water dipolar relaxation, and a central metabolite (ATP) produced by a robustly oscillating metabolic process

Is a constant low-entropy process at the root of glycolytic oscillations?

We measured temporal oscillations in thermodynamic variables such as temperature, heat flux, and cellular volume in suspensions of non-dividing yeast cells which exhibit temporal glycolytic oscillations. Oscillations in these variables have the same frequency as oscillations in the activity of intracellular metabolites, suggesting strong coupling between them. These results can be interpreted in light of a recently proposed theoretical formalism in which isentropic thermodynamic systems can display coupled oscillations in all extensive and intensive variables, reminiscent of adiabatic waves. This interpretation suggests that oscillations may be a consequence of the requirement of living cells for a constant low-entropy state while simultaneously performing biochemical transformations, i.e., remaining metabolically active. This hypothesis, which is in line with the view of the cellular interior as a highly structured and near equilibrium system where energy inputs can be low and sustain regular oscillatory regimes, calls into question the notion that metabolic processes are essentially dissipative.Fil: Thoke, Henrik Seir. University of Southern Denmark; Dinamarca. International and Interdisciplinary Research Network; DinamarcaFil: Olsen, Lars F.. International and Interdisciplinary Research Network; Dinamarca. University of Southern Denmark; DinamarcaFil: Duelund, Lars. University of Southern Denmark; Dinamarca. International and Interdisciplinary Research Network; DinamarcaFil: Stock, R. P.. International and Interdisciplinary Research Network; DinamarcaFil: Heimburg, Thomas. Universidad de Copenhagen; DinamarcaFil: Bagatolli, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; Argentina. International and Interdisciplinary Research Network; Dinamarc

Fluorescence response of DAN probes in resting cells.

<p>Panel <b>A</b>) Emission spectra of cells labeled with ACDAN (red), PRODAN (blue) and LAURDAN (black) measured in the fluorometer. Panel <b>B</b>) Spectral image of cells labeled with ACDAN (top) with spectra (bottom) of selected regions of interest: single B region (blue, ROI 1), single G region (green, ROI 2), and the overall spectrum (black, large circle defines ROI 3). Spectral resolution in the microscope is lower than in the spectrofluorometer. Image size is 15 x 15 μm. The spectral images of PRODAN and LAURDAN are not shown.</p

Oscillations in the Generalized Polarization (GP) function of ACDAN in oscillating cells.

<p><b>Panel A</b>) Oscillations of the values correspond to the weighted difference of the intensity of emission at the maxima shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117308#pone.0117308.g001" target="_blank">Fig. 1</a>. Panel <b>B</b>) Power spectrum of the frequency of the GP oscillations. The GP was calculated as described in supplementary text (equation <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117308#pone.0117308.e001" target="_blank">1</a>). Note that the GP function indicates that the blue (440 nm) and green (490 nm) emission intensities oscillate in a correlated manner, as would be expected if both the B and G regions of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117308#pone.0117308.g001" target="_blank">Fig. 1</a> were oscillating synchronously. The same behavior was observed with PRODAN.</p

Oscillatory behavior of glycolysis and DAN probes in the fluorometer.

<p>Panel <b>A</b>) Oscillations of NADH. Panel <b>B</b>) Oscillations of ACDAN (red), PRODAN (blue) and LAURDAN (black). Panel <b>C</b>) Non-oscillatory behavior of ANS labeled cells. Panel <b>D</b>) Phase relationships: ACDAN and NADH are expressed as fluorescence intensity, ATP is plotted in concentration units (mM). The arrows in panels <b>A</b>), <b>B</b>), and <b>C</b>) indicate the time of addition of 30 mM glucose followed by 5 mM KCN.</p

The effect of D₂O on NADH, ACDAN and PRODAN oscillations.

<p>The top panels show NADH oscillations in the presence of no D₂O (A), 10% D₂O (B) and 50% D₂O (C). The bottom panels show the power spectra of the oscillations of NADH (D), ACDAN (E) and PRODAN (F) with increasing concentrations of D₂O (black 0%, blue 10% and red 50%).</p