Blowing ChunksCell Biology Team

Julia Bowsher, North Dakota State UniversityDavid Goldstein, Wright State UniversitySadie Hebert, University of Minnesota

Mill Miller, Wright State UniversityLisa Montplaisir, North Dakota State UniversityErika Offerdahl, North Dakota State University

Katie Reindl, North Dakota State University

Teachable Unit: Cell Signaling

• Teachable Tidbit: Perturbation of G-protein coupled receptor (GPCR) signaling by cholera toxin

Context of the Teachable Unit

• 200-level (sophomore) cell biology course for biology majors

• Prerequisite Coursework: introductory general chemistry, introductory biology

• Cell signaling generally taught in the second half of the course, in 2 lecture periods.

Prior Knowledge Assumed

• Basics of enzyme activity• Cell signaling terms – Ligand– Receptor– 2nd messenger

• Cell membranes are selectively permeable• Extracellular signals elicit cell responses• Basics of regulation– Feedback– Conformational changes– Enzyme regulation

Learning Goals

Students should understand 1. how a signal is transduced, relayed, and amplified to lead to a biological response.2. the regulation and termination of a biological signal and response.

Learning Goals

Students should understand 1. how a signal is transduced, relayed, amplified to lead to a biological response.2. the regulation & termination of a biological signal and response.

Day 1 of two lecture periods would focus on Learning Goal #1.

Learning Outcomes

• Compare receptor mediated vs. diffusible signals• Draw a model of the GPCR pathway on a diagram• Order the steps in a particular transduction (receptor

mediated) pathway• Compare/contrast transduction systems• Discriminate between genomic & non-genomic responses • Describe how a message is communicated by a signal• Predict how perturbing components of the pathway

impacts response• Analyze data to determine how cholera toxin affects cell

signaling

Pre-Assessments

• Online quiz– Completed before class– Multiple attempts allowed

• Begin class with clickers and Think-Pair-Share– Based on pre-class assessment data

• Review student-generated models

Review the Signaling Pathway

Results in fluid loss of nearly 25 liters per day in humans.

Teachable Tidbit: Introducing Cholera

“Few afflictions have attracted as much attention and impacted on as many

societal and biomedical areas as cholera.” -S. Schultz, 2007

Adv. Physiol. Educ. 31:288-293

Cholera VideoCholera

Cholera Toxin• Secreted by the bacterium Vibrio cholerae

• Multi-subunit protein1 alpha and 5 beta subunits

•87 kDa protein

http://www.bmsc.washington.edu/WimHol/figures/pt1figs/WimPrt1Figs1.html

Effects of Cholera Toxin on Intestinal Tissue

Guerrant et al. (1972) J. Infect. Diseases 125(4), 377

Generate Hypotheses

Knowing what we know from the previous figure, identify 3 potential targets where cholera toxin perturbs the signaling pathway.1. 2. 3.

Analyze data to determine how cholera toxin affects cell signaling.

Revisit the Model

What is the likely route of exposure of intestinal cells to the toxin? Indicate on your model.

Analyze data to determine how cholera toxin affects cell signaling.

Effect of cholera toxin on gut ion

transport

Lencer et al. JCB 117:1197 (1992)

Revisit the Model

Based on the previous data, can any potential targets now be eliminated as the target for cholera toxin?

Analyze data to determine how cholera toxin affects cell signaling.

Effect of cholera toxin

on GTPase activity

Cassel and Selinger. 1977 PNAS 74(8) 3307

Revisit the Model

Based on the previous data, what is the likely target of cholera toxin in the GPCR pathway?

Analyze data to determine how cholera toxin affects cell signaling.

Summative Assessment

• In-class group reflection – revisit each hypothesis generated. How do the data rule out each of your previous hypotheses OR how do the data support your previous hypotheses?

• Individual homework problem – give them a another signaling pathway or another agonist and ask the student to predict outcomes based on the prescribed perturbation.

Feedback from NANSI participantsNumbered points refer to reviewer responses. The indented material is our responses.

1. Connection between cholera and signaling• Cartoon of colon flux to connect with water flux at cell and organ level • Intentionally black box cAMP stimulating Na+ and water flux -or- add it to model after discussion

of Figure 1• After each graph, have a ‘processing’ or ‘debriefing’ event to ensure everyone is on the same

page.• Instructor must be aware of importance of students explicating and restating their hypotheses

after each data slide

2. Model of signaling pathway was complex• Supplement handout with animation• Use clicker questions to check understanding of model

3. Receptor in handout is too generic• VIP receptor

4. Is there a video for GPCR signaling• http://www.youtube.com/watch?v=V_0EcUr_txk

Implementation Notes

1. This is a very structured activity. Make sure you are familiar with the knowledge (aka prior knowledge) students must bring to class.

2. Transition between Cholera and cell signaling pathway needs to be carefully managed

3. Figure 1 may require significant discussiona) Directionality of H20 movement

b) Example or reframing using dehydration may be effective

4. Be prepared for student questions regarding the movement of the cholera toxin into the cell.

5. Embrace the messiness of the data.