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