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Dynamics of Uptake and Metabolism of Small Molecules in Cellular Response Systems
KTH, School of Computer Science and Communication (CSC), Computational Biology, CB.
2009 (English)In: PLOS ONE, ISSN 1932-6203, Vol. 4, no 3Article in journal (Refereed) Published
Abstract [en]

Background: Proper cellular function requires uptake of small molecules from the environment. In response to changes in extracellular conditions cells alter the import and utilization of small molecules. For a wide variety of small molecules the cellular response is regulated by a network motif that combines two feedback loops, one which regulates the transport and the other which regulates the subsequent metabolism.

Results: We analyze the dynamic behavior of two widespread but logically distinct two-loop motifs. These motifs differ in the logic of the feedback loop regulating the uptake of the small molecule. Our aim is to examine the qualitative features of the dynamics of these two classes of feedback motifs. We find that the negative feedback to transport is accompanied by overshoot in the intracellular amount of small molecules, whereas a positive feedback to transport removes overshoot by boosting the final steady state level. On the other hand, the negative feedback allows for a rapid initial response, whereas the positive feedback is slower. We also illustrate how the dynamical deficiencies of one feedback motif can be mitigated by an additional loop, while maintaining the original steady-state properties.

Conclusions: Our analysis emphasizes the core of the regulation found in many motifs at the interface between the metabolic network and the environment of the cell. By simplifying the regulation into uptake and the first metabolic step, we provide a basis for elaborate studies of more realistic network structures. Particularly, this theoretical analysis predicts that FeS cluster formation plays an important role in the dynamics of iron homeostasis.

Place, publisher, year, edition, pages
2009. Vol. 4, no 3
Keyword [en]
Biology; Multidisciplinary Sciences
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:kth:diva-12091DOI: 10.1371/journal.pone.0004923ISI: 000265496500017Scopus ID: 2-s2.0-62849127949OAI: oai:DiVA.org:kth-12091DiVA: diva2:301251
Note
QC20100720Available from: 2010-03-03 Created: 2010-03-03 Last updated: 2010-07-20Bibliographically approved
In thesis
1. Studies of Cellular Regulatory Mechanisms: from Genetic Switches to Cell Migration
Open this publication in new window or tab >>Studies of Cellular Regulatory Mechanisms: from Genetic Switches to Cell Migration
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cellular behaviour depends ultimately on the transcription of genes. If we know how transcription is controlled we have a better chance of understanding cellular processes. This thesis presents six studies, all concerning cellular regulatory mechanisms. One study is purely experimental and five are computational studies.

A large part of the research concerns the Epstein-Barr virus (EBV). We investigate the latency programme switching of EBV, with an equilibrium statistical mechanics model that describes the transcription activities of two central viral promoters. We demonstrate that this system is bistable and predict promoter activities that correlate well with experimental data. Further we study the switching efficiency of one of the promoters, highlighting how competitive binding of transcription factors generates a more efficient geneticswitch.

The EBV protein EBNA1 is known to affect cellular gene expression. With a dinucleotide position weight matrix we search the complete human genome for regions with multiple EBNA1 binding sites. 40 potential binding regions are identified, with several of particular interest in relation to EBV infections. The final study on EBV is purely experimental, in which we demonstrate an interaction between the Syk kinase and integrin β4. Moreover, we show how reduced levels of these proteins affect migration of epithelial LMP2a positive cells, and hypothesise that these effects are due to the Syk-β4 interaction.

The two remaining studies presented in this thesis concern other cellular systems. Dynamic properties of two different regulatory feedback mechanisms for transport and metabolism of small molecules are investigated. The synergetic effect of adding a regulatory loop is exemplified with the iron metabolism in bacteria. The final project concerns the λ phage. With the equilibrium statistical mechanics method for describing promoter activities we characterise the equilibrium properties of λ mutants and compare with experimental findings. We argue that the observed differences between model and experiment are due to a larger perturbation of the genetic circuit than presumed.

The research presented in this thesis shed light on the properties of several regulatory mechanisms. As computational studies they add perspective to the experimental research in this field and provide new hypothesis for further research.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. xiv, 80 p.
Series
Trita-CSC-A, ISSN 1653-5723 ; 2010:02
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-12096 (URN)
Public defence
2010-03-18, Sal FB53, Roslagstullsbacken 21, AlbaNova, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC20100720Available from: 2010-03-03 Created: 2010-03-03 Last updated: 2010-07-20Bibliographically approved

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