Recap – Second Messenger Systems

00:00 So, as we look at these two systems of receptor tyrosine kinases and G-protein coupled receptor mechanisms, we might see, you may have put it together that these two systems can often work together in synchrony in order to mediate cell processes. So here I'll provide an example how receptor tyrosine kinase, second messenger system and the G-protein coupled receptor system come into play together to elicit a cell response. First of all, we have our receptor tyrosine kinase.

00:41 We know that it activates a number of different proteins. And then it will activate the MAP kinase cascade that will result in a number of cellular responses. But it's not until we have activation of this other second messenger system involving G-proteins that we can turn on at that cascade.

01:03 In this case, RAS if you recall from earlier in the lecture is the switch that allows the connection between the protein kinases that are produced from the receptor tyrosine kinase and the MAP kinase cascade.

01:20 So the second messenger here is cyclic AMP. Once cyclic AMP is able to activate the RAS protein then the RAS protein can turn on the receptor, sorry the MAP kinase pathway resulting in a cellular effect with gene transcription and translation. So, in this example we've linked together both systems of the receptor tyrosine kinase, the G-protein coupled receptors and the molecular switches here exhibited by RAS protein. So, it's fairly complicated stuff but hopefully at this point in time, you're able to identify a variety of second messenger systems. And explain how they result in signal amplification.

02:14 And also have a good understanding of phosphorylation and how important it is to activate proteins further down in the cascade. Hopefully, after a little time perhaps but you'll be able to diagram a tyrosine kinase pathway as well as a G-protein mediated second messenger pathway.

02:39 And in the end maybe you could even pull together both and diagram how the receptor tyrosine kinase pathway comes together with the G-protein pathway and put the molecular switch in there.

02:51 Thank you so much for your attention. I look forward to seing you in future lectures.