Bio 93: Cytoskeleton

Before we begin: 1. Find a seat in your TA’s section 2. Ponder volunteering for another demo today 3. Review your video notes 4. Look up “cannabinoids”

Lecture Overview Which of the following was most confusing?

A. Describe the structure and diameter of actin and microtubules

B. List the main functions and locations of actin and microtubules

C. Describe the plus and minus ends, assembly of cytoskeleton

D. Draw and label the basic structure of a motor protein

E. Describe the differences between kinesin, dynein and myosin

F. Compare the cytoskeletal fiber and motor protein organization in vesicle transport, a flagellum, and a skeletal muscle cell

Cannabinoids and cytoskeletons Case study: The effect of external cannabinoids on the development of neurons.

Made by the body (anandamide):

Made by plants (THC):

Chemical agonists (WIN 55,212-2):

Cannabinoids and cytoskeletons Brain cells grow and are pruned back during early development. Natural cannabinoids are believed to stop growth in the wrong directions. Act on microtubules or actin?

DOI: 10.1016/j.neuron.2007.10.016

Plasma membrane: jump rope People: microtubules PVC pipe: actin People: myosin

Cannabinoids and cytoskeletons

This is a single brain neuron in a dish. The actin fibers have been stained with a fluorescent green dye. At time zero, a chemical “WIN” is added. How would you describe the results?

Roland, A. B., Ricobaraza, A., Carrel, D., Jordan, B. M., Rico, F., Simon, A. C., ... & Lenkei, Z. (2014). Cannabinoid-induced actomyosin contractility shapes neuronal morphology and growth. eLife, 3.

Cannabinoids and cytoskeletons In the second experiment, they first gave a drug “nocodazole” that makes microtubules fall apart. They then gave “WIN.” Describe the results of a) nicodazole and b) WIN.

Roland, A. B., Ricobaraza, A., Carrel, D., Jordan, B. M., Rico, F., Simon, A. C., ... & Lenkei, Z. (2014). Cannabinoid-induced actomyosin contractility shapes neuronal morphology and growth. eLife, 3.

Cannabinoids and cytoskeletons In the third experiment, they first gave a drug “cytochalasin D” that makes actin microfilaments fall apart. They then gave “WIN.” Describe the results of a) cytochalasin D and b) WIN.

Roland, A. B., Ricobaraza, A., Carrel, D., Jordan, B. M., Rico, F., Simon, A. C., ... & Lenkei, Z. (2014). Cannabinoid-induced actomyosin contractility shapes neuronal morphology and growth. eLife, 3.

Cannabinoids and cytoskeletons

1. What type of graph is this?

a. Line plot

b. Regression / Correlation

c. Bar graph

d. Histogram

Cannabinoids and cytoskeletons

2. How would you describe the dependent variable “Distance” to a friend?

3. What do the lines under the words WIN, Nocodazole, and Cytochalasin D represent?

4. What hypothesis is being tested in these figures?

Cannabinoids and cytoskeletons

Hypothesis:

The retraction of neuron growth caused by cannabinoids is caused by actomyosin contraction,

not microtubule depolymerization.

Is the hypothesis supported?

A. Yes

B. No

Cannabinoids and cytoskeletons Which is the best conclusion based on these results?

A. Nocozadole prevents microtubule assembly

B. Microtubules are required for axon growth, but actin is what causes axon retraction

C. The primary effect of WIN is to block the extension of microtubules.

D. WIN has little effect on axon growth

A Different Sample Exam Question According to these data, which are true? (MRA)

A. Nocozadole prevents microtubule assembly

B. Microtubules are the structural element that directs axon growth

C. The motor protein associated with axon retraction is dynein

D. Marijuana may affect developing neurons more than mature neurons