Second Messenger Systems: Definition

by Georgina Cornwall, PhD

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    00:00 So receptor tyrosine kinase pathways and G-protein coupled receptor pathways are two different approaches to second messenger systems. Basically, all of our second messenger systems can be grouped in either receptor tyrosine kinase or G-protein coupled receptors. So we are going to take a look at how each of these work and then explore each in a little bit more depth. So receptor tyrosine kinase pathways are generally involved in regulating normal cell processes. So when things go wrong with receptor tyrosine kinase pathways, we see that cancers can evolve or we could see neurological disorders because cells have lost their natural functioning. In fact, receptor tyrosine kinases are very active area of research currently.

    00:51 There are over 90 receptor tyrosine kinase genes that have been identified as of this point in 2015, and there are many more coming almost every day. So, the general principle is that the signal molecules will bind to two receptor tyrosine kinase modules and they will come together and diamerize, and they will be activated by phosphorylation just like many other systems. And that will activate a protein that will then activate a whole cellular response. We're going to look at it in much more detail.

    01:29 The other system that we have are G-protein coupled receptors. We've already taken a brief look at those.

    01:35 G-protein coupled receptor pathways are generally involved in mediating structural and metabolic changes.

    01:45 So, receptor tyrosine kinase is generally for normal processing of cells. Their normal daily activities.

    01:53 But if we wanted to make a change move, change the production, something like that we would be using G-protein coupled receptors. So first of all, what we see is a first messenger will bind to the receptor.

    02:06 And the receptor will then create a G-protein reaction. So the G-protein then goes to activate some other effector. An enzyme that's in the membrane. We'll look at a couple of different specific examples shortly.

    02:21 Then we have our inactive second messenger. Gets phosphates or drops off phosphates at our enzyme and becomes active. And that second messenger, these are our fire guys. Running out to take care of the fire.

    02:36 They'll amplify the signal activating some more kinase proteins and then activating a full cellular response.

    02:45 So, very similar things happening as a result of both receptor tyrosine kinase pathways and G-protein coupled receptor pathways. Just a slightly different mechanism of how they happen.

    02:59 So both of these second messenger systems can facilitate signal amplification.

    03:05 What we mean by signal amplification is simply that the first messenger will tell the second messenger.

    03:12 And the second messenger tells many other messengers. And they pass the message on to many others.

    03:17 And so with each step in the signal transduction pathway, the signal is amplified.

    03:25 So in that way one molecule reacting with one receptor can have a very large cellular response.

    About the Lecture

    The lecture Second Messenger Systems: Definition by Georgina Cornwall, PhD is from the course Cellular Structure.

    Included Quiz Questions

    1. …in normal cellular processes.
    2. …in structural changes in the cell.
    3. …during drastic metabolic changes in the cell.
    4. …to regulate the extracellular environment.
    5. …to regulate the gene expression to control structural and metabolic changes.
    1. Structural and metabolic changes.
    2. Normal cellular processes.
    3. Synthesis of the first messenger for receptor tyrosine kinase pathway.
    4. Regulation of electrolyte concentrations in the immediate surroundings of the cell.
    5. Regulation of receptor tyrosine kinase pathway.

    Author of lecture Second Messenger Systems: Definition

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD

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