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15 Publications visible to you, out of a total of 15
Inhibitor titrations reveal low control of glyceraldehyde 3-phosphate dehydrogenase and high control of hexokinase on glycolytic flux in an aggressive triple-negative breast cancer cell line

Abstract

Not specified

Authors: Theresa Kouril, Craig October, Stephanie Hollocks, Christoff Odendaal, David D. van Niekerk, Jacky L. Snoep

Date Published: 1st Sep 2023

Publication Type: Journal

A combined experimental and modelling approach for the Weimberg pathway optimisation

Abstract (Expand)

The oxidative Weimberg pathway for the five-step pentose degradation to α-ketoglutarate is a key route for sustainable bioconversion of lignocellulosic biomass to added-value products and biofuels. The … oxidative pathway from Caulobacter crescentus has been employed in in-vivo metabolic engineering with intact cells and in in-vitro enzyme cascades. The performance of such engineering approaches is often hampered by systems complexity, caused by non-linear kinetics and allosteric regulatory mechanisms. Here we report an iterative approach to construct and validate a quantitative model for the Weimberg pathway. Two sensitive points in pathway performance have been identified as follows: (1) product inhibition of the dehydrogenases (particularly in the absence of an efficient NAD+ recycling mechanism) and (2) balancing the activities of the dehydratases. The resulting model is utilized to design enzyme cascades for optimized conversion and to analyse pathway performance in C. cresensus cell- free extracts.

Authors: Lu Shen, Martha Kohlhaas, Junichi Enoki, Roland Meier, Bernhard Schönenberger, Roland Wohlgemuth, Robert Kourist, Felix Niemeyer, David van Niekerk, Christopher Bräsen, Jochen Niemeyer, Jacky Snoep, Bettina Siebers

Date Published: 1st Dec 2020

Publication Type: Not specified

Phosphofructokinase controls the acetaldehyde-induced phase shift in isolated yeast glycolytic oscillators

Abstract (Expand)

Abstract The response of oscillatory systems to external perturbations is crucial for emergent properties such as synchronisation and phase locking and can be quantified in a phase response curve (PRC). …hase response curve (PRC). In individual, oscillating yeast cells, we characterised experimentally the phase response of glycolytic oscillations for external acetaldehyde pulses and followed the transduction of the perturbation through the system. Subsequently, we analysed the control of the relevant system components in a detailed mechanistic model. The observed responses are interpreted in terms of the functional coupling and regulation in the reaction network. We find that our model quantitatively predicts the phase-dependent phase shift observed in the experimental data. The phase shift is in agreement with an adaptation leading to synchronisation with an external signal. Our model analysis establishes that phosphofructokinase plays a key role in the phase shift dynamics as shown in the PRC and adaptation time to external perturbations. Specific mechanism-based interventions, made possible through such analyses of detailed models, can improve upon standard trial and error methods, e.g. melatonin supplementation to overcome jet-lag, which are error-prone, specifically, since the effects are phase dependent and dose dependent. The models by Gustavsson and Goldbeter discussed in the text can be obtained from the JWS Online simulation database: (https://jjj.bio.vu.nl/models/gustavsson5 and https://jjj.bio.vu.nl/models/goldbeter1)

Authors: David D. van Niekerk, Anna-Karin Gustavsson, Martin Mojica-Benavides, Caroline B. Adiels, Mattias Goksör, Jacky L. Snoep

Date Published: 31st Jan 2019

Publication Type: Journal

FAIRDOMHub: a repository and collaboration environment for sharing systems biology research.

Abstract (Expand)

The FAIRDOMHub is a repository for publishing FAIR (Findable, Accessible, Interoperable and Reusable) Data, Operating procedures and Models (https://fairdomhub.org/) for the Systems Biology community. … It is a web-accessible repository for storing and sharing systems biology research assets. It enables researchers to organize, share and publish data, models and protocols, interlink them in the context of the systems biology investigations that produced them, and to interrogate them via API interfaces. By using the FAIRDOMHub, researchers can achieve more effective exchange with geographically distributed collaborators during projects, ensure results are sustained and preserved and generate reproducible publications that adhere to the FAIR guiding principles of data stewardship.

Authors: K. Wolstencroft, O. Krebs, J. L. Snoep, N. J. Stanford, F. Bacall, M. Golebiewski, R. Kuzyakiv, Q. Nguyen, S. Owen, S. Soiland-Reyes, J. Straszewski, D. D. van Niekerk, A. R. Williams, L. Malmstrom, B. Rinn, W. Muller, C. Goble

Date Published: 4th Jan 2017

Publication Type: Journal

Targeting glycolysis in the malaria parasite Plasmodium falciparum

Abstract (Expand)

Glycolysis is the main pathway for ATP production in the malaria parasite Plasmodium falciparum and essential for its survival. Following a sensitivity analysis of a detailed kinetic model for glycolysis … in the parasite, the glucose transport reaction was identified as the step whose activity needed to be inhibited to the least extent to result in a 50% reduction in glycolytic flux. In a subsequent inhibitor titration with cytochalasin B, we confirmed the model analysis experimentally and measured a flux control coefficient of 0.3 for the glucose transporter. In addition to the glucose transporter, the glucokinase and phosphofructokinase had high flux control coefficients, while for the ATPase a small negative flux control coefficient was predicted. In a broader comparative analysis of glycolytic models, we identified a weakness in the P. falciparum pathway design with respect to stability towards perturbations in the ATP demand.

Authors: David D. van Niekerk, Gerald P. Penkler, Francois du Toit, Jacky L. Snoep

Date Published: 1st Feb 2016

Publication Type: Not specified

Quantitative analysis of drug effects at the whole-body level: a case study for glucose metabolism in malaria patients

Abstract (Expand)

We propose a hierarchical modelling approach to construct models for disease states at the whole-body level. Such models can simulate effects of drug-induced inhibition of reaction steps on the whole-body … physiology. We illustrate the approach for glucose metabolism in malaria patients, by merging two detailed kinetic models for glucose metabolism in the parasite Plasmodium falciparum and the human red blood cell with a coarse-grained model for whole-body glucose metabolism. In addition we use a genome-scale metabolic model for the parasite to predict amino acid production profiles by the malaria parasite that can be used as a complex biomarker.

Authors: J. L. Snoep, K. Green, J. Eicher, D. C. Palm, G. Penkler, F. du Toit, N. Walters, R. Burger, H. V. Westerhoff, D. D. van Niekerk

Date Published: 27th Nov 2015

Publication Type: Not specified

Entrainment of heterogeneous glycolytic oscillations in single cells

Abstract (Expand)

Cell signaling, gene expression, and metabolism are affected by cell-cell heterogeneity and random changes in the environment. The effects of such fluctuations on cell signaling and gene expression … have recently been studied intensively using single-cell experiments. In metabolism heterogeneity may be particularly important because it may affect synchronisation of metabolic oscillations, an important example of cell-cell communication. This synchronisation is notoriously difficult to describe theoretically as the example of glycolytic oscillations shows: neither is the mechanism of glycolytic synchronisation understood nor the role of cell-cell heterogeneity. To pin down the mechanism and to assess its robustness and universality we have experimentally investigated the entrainment of glycolytic oscillations in individual yeast cells by periodic external perturbations. We find that oscillatory cells synchronise through phase shifts and that the mechanism is insensitive to cell heterogeneity (robustness) and similar for different types of external perturbations (universality).

Authors: Anna-Karin Gustavsson, Caroline B. Adiels, Bernhard Mehlig, Mattias Goksör

Date Published: 1st Aug 2015

Publication Type: Not specified

Construction and validation of a detailed kinetic model of glycolysis in Plasmodium falciparum

Abstract (Expand)

The enzymes in the Embden–Meyerhof–Parnas pathway of Plasmodium falciparum trophozoites were kinetically characterized and their integrated activities analyzed in a mathematical model. For validation … of the model, we compared model predictions for steady-state fluxes and metabolite concentrations of the hexose phosphates with experimental values for intact parasites. The model, which is completely based on kinetic parameters that were measured for the individual enzymes, gives an accurate prediction of the steady-state fluxes and intermediate concentrations. This is the first detailed kinetic model for glucose metabolism in P. falciparum, one of the most prolific malaria-causing protozoa, and the high predictive power of the model makes it a strong tool for future drug target identification studies. The modelling workflow is transparent and reproducible, and completely documented in the SEEK platform, where all experimental data and model files are available for download.

Authors: Gerald Penkler, Francois du Toit, Waldo Adams, Marina Rautenbach, Daniel C. Palm, David D. van Niekerk, Jacky L. Snoep

Date Published: 1st Apr 2015

Publication Type: Not specified

Allosteric regulation of phosphofructokinase controls the emergence of glycolytic oscillations in isolated yeast cells

Abstract

Not specified

Authors: Anna-Karin Gustavsson, David D. van Niekerk, Caroline B. Adiels, Bob Kooi, Mattias Goksör, Jacky L. Snoep

Date Published: 1st Jun 2014

Publication Type: Not specified

Heterogeneity of glycolytic oscillatory behaviour in individual yeast cells

Abstract

Not specified

Authors: Anna-Karin Gustavsson, David D. van Niekerk, Caroline B. Adiels, Mattias Goksör, Jacky L. Snoep

Date Published: 3rd Jan 2014

Publication Type: Not specified

Sustained glycolytic oscillations in individual isolated yeast cells

Abstract

Not specified

Authors: Anna-Karin Gustavsson, David D. van Niekerk, Caroline B. Adiels, Franco B. du Preez, Mattias Goksör, Jacky L. Snoep

Date Published: 1st Aug 2012

Publication Type: Not specified

Division of labor by dual feedback regulators controls JAK2/STAT5 signaling over broad ligand range

Abstract (Expand)

Cellular signal transduction is governed by multiple feedback mechanisms to elicit robust cellular decisions. The specific contributions of individual feedback regulators, however, remain unclear. Based … on extensive time-resolved data sets in primary erythroid progenitor cells, we established a dynamic pathway model to dissect the roles of the two transcriptional negative feedback regulators of the suppressor of cytokine signaling (SOCS) family, CIS and SOCS3, in JAK2/STAT5 signaling. Facilitated by the model, we calculated the STAT5 response for experimentally unobservable Epo concentrations and provide a quantitative link between cell survival and the integrated response of STAT5 in the nucleus. Model predictions show that the two feedbacks CIS and SOCS3 are most effective at different ligand concentration ranges due to their distinct inhibitory mechanisms. This divided function of dual feedback regulation enables control of STAT5 responses for Epo concentrations that can vary 1000-fold in vivo. Our modeling approach reveals dose-dependent feedback control as key property to regulate STAT5-mediated survival decisions over a broad range of ligand concentrations.

Authors: J. Bachmann, A. Raue, M. Schilling, M. E. Bohm, C. Kreutz, D. Kaschek, H. Busch, N. Gretz, W. D. Lehmann, J. Timmer, U. Klingmuller

Date Published: 2011

Publication Type: Not specified

Design principles of nuclear receptor signaling: how complex networking improves signal transduction

Abstract (Expand)

The topology of nuclear receptor (NR) signaling is captured in a systems biological graphical notation. This enables us to identify a number of ‘design’ aspects of the topology of these networks that … might appear unnecessarily complex or even functionally paradoxical. In realistic kinetic models of increasing complexity, calculations show how these features correspond to potentially important design principles, e.g.: (i) cytosolic ‘nuclear’ receptor may shuttle signal molecules to the nucleus, (ii) the active export of NRs may ensure that there is sufficient receptor protein to capture ligand at the cytoplasmic membrane, (iii) a three conveyor belts design dissipating GTP-free energy, greatly aids response, (iv) the active export of importins may prevent sequestration of NRs by importins in the nucleus and (v) the unspecific nature of the nuclear pore may ensure signal-flux robustness. In addition, the models developed are suitable for implementation in specific cases of NR-mediated signaling, to predict individual receptor functions and differential sensitivity toward physiological and pharmacological ligands.

Authors: Alexey N Kolodkin, Frank J Bruggeman, Nick Plant, Martijn J Moné, Barbara M Bakker, Moray J Campbell, Johannes P T M van Leeuwen, Carsten Carlberg, Jacky L Snoep, Hans V Westerhoff

Date Published: 21st Dec 2010

Publication Type: Not specified

From steady-state to synchronized yeast glycolytic oscillations II: model validation.

Abstract (Expand)

UNLABELLED: In an accompanying paper [du Preez et al., (2012) FEBS J279, 2810-2822], we adapt an existing kinetic model for steady-state yeast glycolysis to simulate limit-cycle oscillations. Here we … validate the model by testing its capacity to simulate a wide range of experiments on dynamics of yeast glycolysis. In addition to its description of the oscillations of glycolytic intermediates in intact cells and the rapid synchronization observed when mixing out-of-phase oscillatory cell populations (see accompanying paper), the model was able to predict the Hopf bifurcation diagram with glucose as the bifurcation parameter (and one of the bifurcation points with cyanide as the bifurcation parameter), the glucose- and acetaldehyde-driven forced oscillations, glucose and acetaldehyde quenching, and cell-free extract oscillations (including complex oscillations and mixed-mode oscillations). Thus, the model was compliant, at least qualitatively, with the majority of available experimental data for glycolytic oscillations in yeast. To our knowledge, this is the first time that a model for yeast glycolysis has been tested against such a wide variety of independent data sets. DATABASE: The mathematical models described here have been submitted to the JWS Online Cellular Systems Modelling Database and can be accessed at http://jjj.biochem.sun.ac.za/database/dupreez/index.html.

Authors: F. B. du Preez, D. D. van Niekerk, J. L. Snoep

Date Published: No date defined

Publication Type: Not specified

From steady-state to synchronized yeast glycolytic oscillations I: model construction.

Abstract (Expand)

UNLABELLED: An existing detailed kinetic model for the steady-state behavior of yeast glycolysis was tested for its ability to simulate dynamic behavior. Using a small subset of experimental data, the … original model was adapted by adjusting its parameter values in three optimization steps. Only small adaptations to the original model were required for realistic simulation of experimental data for limit-cycle oscillations. The greatest changes were required for parameter values for the phosphofructokinase reaction. The importance of ATP for the oscillatory mechanism and NAD(H) for inter-and intra-cellular communications and synchronization was evident in the optimization steps and simulation experiments. In an accompanying paper [du Preez F et al. (2012) FEBS J279, 2823-2836], we validate the model for a wide variety of experiments on oscillatory yeast cells. The results are important for re-use of detailed kinetic models in modular modeling approaches and for approaches such as that used in the Silicon Cell initiative. DATABASE: The mathematical models described here have been submitted to the JWS Online Cellular Systems Modelling Database and can be accessed at http://jjj.biochem.sun.ac.za/database/dupreez/index.html.

Authors: F. B. du Preez, D. D. van Niekerk, B. Kooi, J. M. Rohwer, J. L. Snoep

Date Published: No date defined

Publication Type: Not specified

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