β-adrenergic Receptor Signaling

by Kevin Ahern, PhD

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    Now if we look at what’s happening with this system, and by the way this system is known as the β-adrenergic receptor. What’s happening in this system? We can actually see the overall process. There’s the hormone that binds to the receptor, there is the activation of the G-protein with the α subunit getting a GTP. The interaction of the α subunit with the adenylate cyclase. The formation of cyclic AMP. The activation of protein kinase A, the activation of phosphorylase kinase. The inactivation of glycogen synthase. The activation of glycogen phosphorylase-a. And the breakdown of glycogen. This process happens very rapidly. Everything that we see here is an enzymatic reaction. And enzymes work really, really quickly. You notice that in this pathway, there’s no movement into the nucleus. This is important because movement into the nucleus and activation of gene expression is a very slow process. In our cells it takes about 24 hours for that to happen. Well it’s important if you’re in a dark alley for example because imagine that someone’s chasing you. You need to have energy and you need to have that energy right now. You can’t wait 24 hours for gene expression to occur so that you can make something that can make you some glucose. This pathway which regulates the activity of enzymes and doesn’t have anything to do with gene expression is an example of one that works very, very quickly. Now, when we think about turning on a system which I’ve described here, that’s pretty straightforward. But we think, cells can’t continually have the system turned on because if they left the system turned on all the time, they would be continually breaking down their glycogen. They wouldn’t have any glycogen. And glycogen’s a pretty important storage molecule for energy. So...

    About the Lecture

    The lecture β-adrenergic Receptor Signaling by Kevin Ahern, PhD is from the course Hormones and Signal Transduction. It contains the following chapters:

    • β-adrenergic Receptor Signaling
    • G-protein Inactivation
    • cAMP

    Included Quiz Questions

    1. ...cAMP is broken down by phosphodiesterase.
    2. None of the answers are true.
    3. ...caffeine inhibits glycogen phosphorylase.
    4. ...arrestin favors exocytosis.
    5. All of the answers are true.
    1. ...the a-subunit of the G-protein turns itself off.
    2. ...phosphoprotein phosphatase converts GTP to GDP.
    3. ...turning off the breakdown pathway also turns off the synthesis pathway.
    4. None of the answers are true.
    5. All of the answers are true.

    Author of lecture β-adrenergic Receptor Signaling

     Kevin Ahern, PhD

    Kevin Ahern, PhD

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