Information Processing under Physiological Pulsatile Stimulation in a G-protein Coupled Signaling Pathway

GPCR signaling;Pulsatile stimulation;Deterministic modeling;Temporal modulation;Biological noise;Microfluidics;Biomedical Engineering;Chemical Engineering;Physics;Engineering;Science;Biophysics

Sumit, MadhureshWood, Kevin ;

University of Michigan

关键词: GPCR signaling;    Pulsatile stimulation;    Deterministic modeling;    Temporal modulation;    Biological noise;    Microfluidics;    Biomedical Engineering;    Chemical Engineering;    Physics;    Engineering;    Science;    Biophysics;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/135745/msumit_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The cellular microenvironment is often dynamic, and several physiological ligands are released in pulsatile bursts. The main hypothesis driving this study is that cells are able to discern these time-varying dynamic inputs and must have evolved to exploit the temporal information available in their microenvironment to their advantage. Taking Muscarinic M3 (a G-protein coupled receptor)-mediated signaling as an example, this thesis explores how information is processed under pulsatile stimulation. Several experimental and computational approaches techniques including microfluidics, real-time multi-color fluorescence imaging of single cells, reaction kinetics modeling and information and noise analysis are implemented to gain mechanistic insights into the signaling circuit architecture. A major finding of this thesis is that receptor-mediated signaling forms a low pass filter while downstream calcium-induced NFAT (Nuclear Factor of Activated T-Lymphocytes, a transcription factor) nuclear translocation forms a high pass filter. The combination acts as a band-pass filter optimized for intermediate frequencies of stimulation. Sensitivity analysis shows that receptor and downstream kinetics determine critical features of the band-pass and that the band-pass may be shifted for different receptors or NFAT dynamics. Another important finding in this thesis is that for weak physiological inputs, cells exhibit apparent stochastic responses that can be explained within a deterministic framework. Computational analysis suggests that cells may utilize apparent stochasticity to enhance selectivity in downstream responses. This thesis also demonstrates that pulsatile inputs enhance information transfer downstream in noisy biochemical pathways. Finally, a microfluidic experimental method is developed to measure two microfluidic observables in the same cell, similar to a ;;two-reporter’ system, to estimate biochemical noise. Analysis with this method suggests that effect of drug action increases with increasing biochemical noise. Although this thesis focuses on one particular receptor and ligand, the conclusions from this work may be applied to several signaling systems. Investigation of band-pass processing may lead to gaining mechanistic insights into hidden or unknown regulatory motifs in several signaling pathways that are poorly understood. Using pulsatility to modulate selectivity and sensitivity of signaling response amidst biochemical noise provides tools to synthetic biologists and pharmacologists for developing enhanced lab-on-chip devices and pharmaceutical interventions.