Project description:Venkatraman2011 - PLS-UPA behaviour in the presence of substrate competition The posibility of ultrasensitivity and bistable activation of PLS (Plasmin) and UPA (Urokinase-type plasminogen activator) in the presence of substrate competition is explained here using a mathematical model. This model is described in the article: Steady states and dynamics of urokinase-mediated plasmin activation in silico and in vitro. Venkatraman L, Li H, Dewey CF Jr, White JK, Bhowmick SS, Yu H, Tucker-Kellogg L. Biophys. J. 2011 Oct; 101(8): 1825-1834 Abstract: Plasmin (PLS) and urokinase-type plasminogen activator (UPA) are ubiquitous proteases that regulate the extracellular environment. Although they are secreted in inactive forms, they can activate each other through proteolytic cleavage. This mutual interplay creates the potential for complex dynamics, which we investigated using mathematical modeling and in vitro experiments. We constructed ordinary differential equations to model the conversion of precursor plasminogen into active PLS, and precursor urokinase (scUPA) into active urokinase (tcUPA). Although neither PLS nor UPA exhibits allosteric cooperativity, modeling showed that cooperativity occurred at the system level because of substrate competition. Computational simulations and bifurcation analysis predicted that the system would be bistable over a range of parameters for cooperativity and positive feedback. Cell-free experiments with recombinant proteins tested key predictions of the model. PLS activation in response to scUPA stimulus was found to be cooperative in vitro. Finally, bistability was demonstrated in vitro by the presence of two significantly different steady-state levels of PLS activation for the same levels of stimulus. We conclude that ultrasensitive, bistable activation of UPA-PLS is possible in the presence of substrate competition. An ultrasensitive threshold for activation of PLS and UPA would have ramifications for normal and disease processes, including angiogenesis, metastasis, wound healing, and fibrosis. The cooperativity parameter "ci" was missing in the original model. The parameter "ci" has been added to the added. This model is hosted on BioModels Database and identified by: BIOMD0000000630. To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

Project description:Data from clinical studies, cell culture, and animal models implicate the urokinase (uPA)/Plasminogen (Plg) system in the development of atherosclerosis and aneurysms. However, the mechanisms through which uPA/Plg stimulate these diseases are not yet defined. We used genetically modified, atherosclerosis-prone mice, including mice with macrophage-specific uPA overexpression to clarify mechanisms of uPA/Plg-accelerated atherosclerosis and aneurysm formation. Microarray studies were performed to identify potential mediators of uPA-accelerated atherosclerosis. These studies identified S100A8 and S100A9 mRNA as the most highly upregulated transcripts in uPA-overexpressing macrophages; upregulation of S100A9 protein in uPA-overexpressing macrophages was confirmed by Western blotting. S100A8/A9, which are atherogenic in mice and are expressed in human atherosclerotic plaques, are also upregulated in aortae of mice with uPA-overexpressing macrophages, and macrophage S100A9 mRNA is upregulated by exposure of wild-type macrophages to medium from uPA-overexpressing macrophages. Bioinformatics analysis of the microarray data suggest significant effects of uPA overexpression on cell migration and cell-matrix interactions. Our results confirm—in a second animal model—that macrophage-expressed uPA stimulates atherosclerosis and aortic dilation. They also implicate specific pathways in uPA/Plg-accelerated atherosclerosis and aneurysmal disease. Six independent biological replicate RNA samples were prepared from thioglycollate-elicited peritoneal macrophages from mice of two different genotypes: SR-uPA+/0 transgenic (overexpress uPA in macrophages) and nontransgenic, respectively), for a total of 12 independent RNA samples. Both transgenic and nontransgenic mice were Apoe-/- and were fed Western diet from 5-15 weeks before peritoneal macrophages were elicited. In addition, from the six samples of each genotype, a pooled sample was prepared by combining the six genotype-specific samples. Each of the two pooled samples was assayed on the BeadChip in two technical replicates, for a total of 16 hybridizations performed using two Illumina Mouse Ref-8 v1.1 chips.

Dataset Information

Mus musculus

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets