Examples of Hysteresis Phenomena in Biology
Hysteresis may occur in different spatiotemporal scales of consideration. From switches in protein-DNA interactions (Chatterjee et al. 2008 ), microscopic cellular signaling pathways with bistable molecular cascades (Angeli et al. 2004 ; Qiao 2007 ), cell
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Examples of Hysteresis Phenomena in Biology
Hysteresis may occur in different spatiotemporal scales of consideration. From switches in protein-DNA interactions (Chatterjee et al. 2008), microscopic cellular signaling pathways with bistable molecular cascades (Angeli et al. 2004; Qiao 2007), cell division, differentiation, cancer onset and apoptosis (Sha et al. 2003; Eissing et al. 2004; kim et al. 2007; Wilhelm 2009), protein folding (Andrews et al. 2013) and purinergic neuron-astrocyte interactions in the brain (Noori 2011) up to macroscopic biomechanics of cornea (Congdon et al. 2006) and lung deformations (Escolar and Escolar 2004), hysteresis phenomena are ubiquitous in biology. In this chapter, we will briefly discuss a few examples of hysteresis phenomena in biology, which may qualitatively resemble many other biological processes.
4.1 Hysteresis in Cell Biology and Genetics 4.1.1 Cell Cycle and Apoptosis The dynamics of the eukaryotic cell cycle is shown to be governed by sequential activation and inactivation of cyclin-dependent protein kinases (CDKs (Pines 1995; Harper et al. 2002)). The CDK for entry into mitosis is Cdc2, whose activation requires binding to cyclin B (a regulatory protein) and the activation of phosphorylation process. However, both processes appears to provide only necessary conditions for the activation of Cdc2, as it can still be inactivated by inhibitory phosphorylations, which are carried out by protein kinases Wee1 and Myt1. Cdc25 protein phosphatases (as the immediate triggers for entry into mitosis) remove these Inhibitory phosphorylations and in their presence, the conditions become also sufficient for Cdc2 activation. CDKs regulating further cell cycle transitions can also be inhibited by direct binding of inhibitory proteins. Mitotic cyclins are subject to ubiquitin-mediated degradation at the end of mitosis by the action of the anaphasepromoting complex. In addition, the proper functioning of the cell cycle relies on H. R. Noori, Hysteresis Phenomena in Biology, SpringerBriefs in Mathematical Methods, DOI: 10.1007/978-3-642-38218-5_4, © The Author(s) 2014
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4 Examples of Hysteresis Phenomena in Biology
control mechanisms ensuring the correct sequence of key cell cycle events. For instance, specific DNA replication checkpoint ensures that Cdc2 is not activated until DNA replication is complete and the spindle assembly checkpoint acting as a switch prevents cyclin degradation until all chromosomes form the proper alignment on the metaphase plate (Solomon 2003). By crushing frog eggs in the presence of minimal amounts of buffer one can obtain the Xenopus egg extracts that have lead to major advancements in understanding entry into and exit from mitosis (Pines 1995). Xenopus egg extracts are able to undergo multiple rapid cell cycles, due to either the morphology of added nuclei or by assays of Cdc2 activity. These cell cycles can be driven by the endogenous synthesis and degradation of cyclin, and in case of inhibited protein synthesis, by the addition and subsequent d
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