The Frequency Dependence of Osmo-Adaptation in Saccharomyces cerevisiae Alexander van Oudenaarden Lab 20.309 Final Presentation Mashaal Sohail Emily Suter

Motivation Cells respond to stimuli using complicated systems of biochemical reactions Systems may comprise of hundreds of reactions Interest in determining dominant processes that dictate system dynamics Cells are constantly sensing and responding to their environments, and they do so through complex systems of biochemical reactions. Signaling cascades can consist of up to hundreds of different reactions. And each can occur over different time scales. Ligand-receptor interactions happen quickly, for example, whereas downstream gene expression is a much slower response. The motivation behind this group’s experiment was to determine which time scale, and therefore which reactions, dominates a particular response…

Hog1 MAPK Pathway High-Osmolarity Glycerol (HOG) Mitogen-Activated Protein Kinase (MAPK) pathway in budding yeast Saccharomyces cerevisiae Core pathway of the hyperosmotic shock response To do this, they utilized the Hog1 MAPK pathway in budding yeast This is the principle pathway of the hyperosmotic shock response in the cell. Hyperosmotic shock respose occurs when a cell experiences a rise in extracellular osmolarity, and then is forced to compensate lest it become dehydrated and shrivel.

Hog1 MAPK Pathway Hog1 cell nucleus High-Osmolarity Glycerol (HOG) Mitogen-Activated Protein Kinase (MAPK) pathway in budding yeast Saccharomyces cerevisiae Core pathway of the hyperosmotic shock response Hog1 cell nucleus

high osmolarity solution Hog1 MAPK Pathway High-Osmolarity Glycerol (HOG) Mitogen-Activated Protein Kinase (MAPK) pathway in budding yeast Saccharomyces cerevisiae Core pathway of the hyperosmotic shock response high osmolarity solution Membrane proteins trigger a signal transduction cascade which culminates in the activation of Hog 1

Hog1 MAPK Pathway High-Osmolarity Glycerol (HOG) Mitogen-Activated Protein Kinase (MAPK) pathway in budding yeast Saccharomyces cerevisiae Core pathway of the hyperosmotic shock response Then travels to the nucleus

Hog1 MAPK Pathway High-Osmolarity Glycerol (HOG) Mitogen-Activated Protein Kinase (MAPK) pathway in budding yeast Saccharomyces cerevisiae Core pathway of the hyperosmotic shock response where it activates a broad transcription response to the osmotic stress.

Hog1 MAPK Pathway High-Osmolarity Glycerol (HOG) Mitogen-Activated Protein Kinase (MAPK) pathway in budding yeast Saccharomyces cerevisiae Core pathway of the hyperosmotic shock response These proteins then help to increase the internal osmolarity and accommodate for the osmotic stress.

Experimental Setup

Experimental Setup

Experimental Setup

Experimental Setup

Fourier analysis approximates output signal as sin curve Took this data and performed a fourier analysis and approximated the output as a sin curve. AsThe graph shows the red dots as in the previous slide

Linear time invariant model predicts system response to input signal Hog1 Response to Single NaCl Step by analyzing the frequency dependence of amplitude and phase shift, the authors were then able to develop a rpedictive model for the respose to osmotic signals. They created this predictive model by fitting linear time invariant model and used the parameters to predict the response to a one step input of 0.2 M NaCl. The red line is the model and those blue circles are the actually experimental data. It accurately predicted the response in tearms of both amplitude and time scale of response.

Pulsed-input analysis corresponds to biological network

Hog1-dependent feedback loop plays major role in rapid response Hog1 Response to Single NaCl Step

Gene expression facilitates response to osmotic shocks on longer time scales Wild Type Inhibited Hog1 Expression Response R(t) time [min]

Significance/Conclusions Showed that Hog1 MAPK pathway is governed by two different response time scales Demonstrated use of frequency-response analysis on cellular networks Utilized engineering principles to predict the response of dynamic stimuli

Significance/Conclusions Showed that Hog1 MAPK pathway is governed by two different response time scales Demonstrated use of frequency-response analysis on cellular networks Utilized engineering principles to predict the response of dynamic stimuli Thank you