Need to know Ch. 12 Chapter 12. Signal Transduction There are six major features of signal transduction pathways. You should be able to think of examples that we discussed in class that illustrate the ideas of specificity, amplification, modularity, densensitization/adaptation, integration, and localized response. Of these, amplification, modularity, and desensitization are the most essential to understand. In class, we discussed four major classes of receptors: GPCRs, receptor enzymes, including receptor tyrosine kinases and receptor guanylyl cyclases, steroid hormone receptors, and ion channels. You should be able to name a major distinguishing feature of each of these four classes. What makes it unique from the other three? You should also be able to think of examples of each, and understand the kinds of timescales on which each transduces signals. We spent the most time in lecture talking about GPCRs. You should understand all of the steps and molecular players between epinephrine binding and cAMP production, and you should understand that these first steps are all localized at the plasma membrane. At what step does the signal transduction pathway move into the cytosol? You should understand the major conceptual difference between signal termination and desensitization, and be able to think of examples of both in the context of b-adrenergic receptor. You should understand that G-proteins are enzymes, and be able to explain why it is important that G-proteins have GTPase activity. Second messengers are very important. You should be able to recognize AMP (this is easy because you already know AMP and the numbering of the ribose ring, right?). You should also be familiar with IP3, diacylglycerol, Ca2+, and cGMP. You should be able to identify proteins that create second messengers in in the signal transduction cascade (for example, phospholipase C or adenylyl cyclase), as well as proteins that specifically bind to and sense the presence of second messengers (calmodulin, protein kinase A, protein kinase C, Ca2+ channels activated by IP3). You should also be familiar with the idea that phosphorylation is a major mechanism by which signals are transduced, and dephosphorylation is a major mechanism by which signals are turned off, and that these processes compete with each other to fine tune signal transduction. We covered ion channels in Ch. 11. Remind yourself of the big ideas: gating mechanisms, “electrodiffusion,” the idea that ions flow down their electrochemical gradient. How does acetylcholine esterase fit into the six major features of signal transduction? We covered steroid hormones in Ch. 10. You should understand the physical properties that allow these molecules to reach their receptors in the nucleus, and how they are transported through the