“Control of local protein synthesis and initial events in myelination by action potentials”

    2. (15 points) From Wake et al., “Control of local protein synthesis and initial events in myelination by action potentials”. H. Wake, P.R. Lee, R.D Fields, Science 333, 1647 (2011), available on Canvas with this exam. A. Please read the abstract and 1st paragraph of this paper. What was the authors’ big question and why is it interesting? 3 pts B. How did they make their measurements? 4 pts C. Explain in your own words what is shown in Figure 1B and 1C and what this signifies. BnTX is botulinum toxin A and TnTX is tetanus toxin; both block transmitter vesicle exocytosis. 4 pts D. Explain what is shown in Figure 2H and 2I. GCaMP2 is a genetically encoded Ca2+ reporter. Other, later figures show that activation of OPC glutamate receptors is required for synthesis of myelin protein. 4 pts 3. (20 points) You are studying the properties of a giant axon from an alien creature discovered by the Perseverance Rover on Mars. From your experiments you know that the membrane is only permeable to potassium ions when at rest and that the threshold for generating an action potential is -20 mV. A. During one experiment, you accidentally spill a solution of KCl into the dish holding the axon. After the spill, your recording electrode tells you that Vm is at -58 mV. From your notes, you know that you filled the axon with a solution containing 100 mM NaCl and 700 mM KCl. Assuming the intracellular solution did not change during your unfortunate accident, what is the concentration of K+ in the extracellular solution after the spill? Please show relevant equation(s) and intermediate steps for full credit. Label the units of your answer. 1