34,691 research outputs found
Network Features and Pathway Analyses of a Signal Transduction Cascade
The scale-free and small-world network models reflect the functional units of networks. However, when we investigated the network properties of a signaling pathway using these models, no significant differences were found between the original undirected graphs and the graphs in which inactive proteins were eliminated from the gene expression data. We analyzed signaling networks by focusing on those pathways that best reflected cellular function. Therefore, our analysis of pathways started from the ligands and progressed to transcription factors and cytoskeletal proteins. We employed the Python module to assess the target network. This involved comparing the original and restricted signaling cascades as a directed graph using microarray gene expression profiles of late onset Alzheimer's disease. The most commonly used method of shortest-path analysis neglects to consider the influences of alternative pathways that can affect the activation of transcription factors or cytoskeletal proteins. We therefore introduced included k-shortest paths and k-cycles in our network analysis using the Python modules, which allowed us to attain a reasonable computational time and identify k-shortest paths. This technique reflected results found in vivo and identified pathways not found when shortest path or degree analysis was applied. Our module enabled us to comprehensively analyse the characteristics of biomolecular networks and also enabled analysis of the effects of diseases considering the feedback loop and feedforward loop control structures as an alternative path
Uniformly curated signaling pathways reveal tissue-specific cross-talks and support drug target discovery
Motivation: Signaling pathways control a large variety of cellular processes.
However, currently, even within the same database signaling pathways are often
curated at different levels of detail. This makes comparative and cross-talk
analyses difficult. Results: We present SignaLink, a database containing 8
major signaling pathways from Caenorhabditis elegans, Drosophila melanogaster,
and humans. Based on 170 review and approx. 800 research articles, we have
compiled pathways with semi-automatic searches and uniform, well-documented
curation rules. We found that in humans any two of the 8 pathways can
cross-talk. We quantified the possible tissue- and cancer-specific activity of
cross-talks and found pathway-specific expression profiles. In addition, we
identified 327 proteins relevant for drug target discovery. Conclusions: We
provide a novel resource for comparative and cross-talk analyses of signaling
pathways. The identified multi-pathway and tissue-specific cross-talks
contribute to the understanding of the signaling complexity in health and
disease and underscore its importance in network-based drug target selection.
Availability: http://SignaLink.orgComment: 9 pages, 4 figures, 2 tables and a supplementary info with 5 Figures
and 13 Table
Integration of a Phosphatase Cascade with the MAP Kinase Pathway provides for a Novel Signal Processing Function
We mathematically modeled the receptor-activated MAP kinase signaling by
incorporating the regulation through cellular phosphatases. Activation induced
the alignment of a phosphatase cascade in parallel with the MAP kinase pathway.
A novel regulatory motif was thus generated, providing for the combinatorial
control of each MAPK intermediate. This ensured a non-linear mode of signal
transmission with the output being shaped by the balance between the strength
of input signal, and the activity gradient along the phosphatase axis. Shifts
in this balance yielded modulations in topology of the motif, thereby expanding
the repertoire of output responses. Thus we identify an added dimension to
signal processing, wherein the output response to an external stimulus is
additionally filtered through indicators that define the phenotypic status of
the cell.Comment: Whole Manuscript 33 pages inclduing Main text, 7 Figures and
Supporting Informatio
Computational and Mathematical Modelling of the EGF Receptor System
This chapter gives an overview of computational and mathematical modelling of the EGF receptor system. It begins with a survey of motivations for producing such models, then describes the main approaches that are taken to carrying out such modelling, viz. differential equations and individual-based modelling. Finally, a number of projects that applying modelling and simulation techniques to various aspects of the EGF receptor system are described
A structured approach for the engineering of biochemical network models, illustrated for signalling pathways
http://dx.doi.org/10.1093/bib/bbn026Quantitative models of biochemical networks (signal transduction cascades, metabolic pathways, gene regulatory circuits) are a central component of modern systems biology. Building and managing these complex models is a major challenge that can benefit from the application of formal methods adopted from theoretical computing science. Here we provide a general introduction to the field of formal modelling, which emphasizes the intuitive biochemical basis of the modelling process, but is also accessible for an audience with a background in computing science and/or model engineering. We show how signal transduction cascades can be modelled in a modular fashion, using both a qualitative approach { Qualitative Petri nets, and quantitative approaches { Continuous Petri Nets and Ordinary Differential Equations. We review the major elementary building blocks of a cellular signalling model, discuss which critical design decisions have to be made during model building, and present ..
Yes-associated protein (YAP) in pancreatic cancer: at the epicenter of a targetable signaling network associated with patient survival.
Pancreatic ductal adenocarcinoma (PDAC) is generally a fatal disease with no efficacious treatment modalities. Elucidation of signaling mechanisms that will lead to the identification of novel targets for therapy and chemoprevention is urgently needed. Here, we review the role of Yes-associated protein (YAP) and WW-domain-containing Transcriptional co-Activator with a PDZ-binding motif (TAZ) in the development of PDAC. These oncogenic proteins are at the center of a signaling network that involves multiple upstream signals and downstream YAP-regulated genes. We also discuss the clinical significance of the YAP signaling network in PDAC using a recently published interactive open-access database (www.proteinatlas.org/pathology) that allows genome-wide exploration of the impact of individual proteins on survival outcomes. Multiple YAP/TEAD-regulated genes, including AJUBA, ANLN, AREG, ARHGAP29, AURKA, BUB1, CCND1, CDK6, CXCL5, EDN2, DKK1, FOSL1,FOXM1, HBEGF, IGFBP2, JAG1, NOTCH2, RHAMM, RRM2, SERP1, and ZWILCH, are associated with unfavorable survival of PDAC patients. Similarly, components of AP-1 that synergize with YAP (FOSL1), growth factors (TGFα, EPEG, and HBEGF), a specific integrin (ITGA2), heptahelical receptors (P2Y2R, GPR87) and an inhibitor of the Hippo pathway (MUC1), all of which stimulate YAP activity, are associated with unfavorable survival of PDAC patients. By contrast, YAP inhibitory pathways (STRAD/LKB-1/AMPK, PKA/LATS, and TSC/mTORC1) indicate a favorable prognosis. These associations emphasize that the YAP signaling network correlates with poor survival of pancreatic cancer patients. We conclude that the YAP pathway is a major determinant of clinical aggressiveness in PDAC patients and a target for therapeutic and preventive strategies in this disease
Quantifying the implicit process flow abstraction in SBGN-PD diagrams with Bio-PEPA
For a long time biologists have used visual representations of biochemical
networks to gain a quick overview of important structural properties. Recently
SBGN, the Systems Biology Graphical Notation, has been developed to standardise
the way in which such graphical maps are drawn in order to facilitate the
exchange of information. Its qualitative Process Diagrams (SBGN-PD) are based
on an implicit Process Flow Abstraction (PFA) that can also be used to
construct quantitative representations, which can be used for automated
analyses of the system. Here we explicitly describe the PFA that underpins
SBGN-PD and define attributes for SBGN-PD glyphs that make it possible to
capture the quantitative details of a biochemical reaction network. We
implemented SBGNtext2BioPEPA, a tool that demonstrates how such quantitative
details can be used to automatically generate working Bio-PEPA code from a
textual representation of SBGN-PD that we developed. Bio-PEPA is a process
algebra that was designed for implementing quantitative models of concurrent
biochemical reaction systems. We use this approach to compute the expected
delay between input and output using deterministic and stochastic simulations
of the MAPK signal transduction cascade. The scheme developed here is general
and can be easily adapted to other output formalisms
Regulation of tomato fruit ripening
Fruit ripening is a sophisticatedly orchestrated developmental process, unique to plants, that
results in major physiological and metabolic changes, ultimately leading to fruit decay and seed
dispersal. Because of their strong impact on fruit nutritional and sensory qualities, the ripeningassociated
changes have been a matter of sustained investigation aiming at unravelling the
molecular and genetic basis of fruit ripening. Tomato rapidly emerged as the model of choice for
fleshy fruit research and a wealth of genetic resources and genomics tools have been developed,
providing new entries into the regulatory mechanisms involved in the triggering and coordination
of the ripening process. Some of the key components participating in the control of tomato fruit
ripening have been uncovered, but our knowledge of the network of signalling pathways engaged in
this complex developmental process remains fragmentary. This review highlights the main
advances and emphasizes issues still to be addressed using the rapidly developing ‘omics’
approaches
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