So growth factors that we've learned about previously
often help move through the cell cycle
by interaction with receptor tyrosine kinases
and we've explored those in the second messenger systems lecture.
So how does this come into play?
Let's give an example.
Let's say that you're out in the field running around
and you cut your arm on a barbed wire fence.
So now you have a big gash in your arm.
So we've got some damaged tissue.
And your inflammatory response system is going to come into play
and a blood clot will form. Part of that blood clot are platelets.
Now platelets produce a growth factor called
platelet-derived growth factor
and that growth factor is going to promote division of cells
so that we can repair the tissues.
So platelet-derived growth factors can override these cell cycle controls
in order to make things move faster and accelerate cell division.
So this is a good thing.
Again, signals using receptor tyrosine kinases
can override the systems that are in play
to put the breaks on or the gas pedal.
These cell cycle controls, I think of them as a break pedal,
"We're not ready to go", or a gas pedal, "Let's move on", right.
So again, a quick review of how these
signal transduction cascades work.
We have our receptor tyrosine kinases in the membrane over here.
And when there are growth factor binds, those two dimerized
and we then will see that the switch,
the Ras switch would be turned on.
And that would allow the map kinase cascade, in this case,
a little bit different of a cascade, but the same kind of idea.
And then we end up with mitosis-activating protein kinases,
in this specific case, it's ERK.
It's not really important what that is,
but now we're allowed to move into the nucleus
and have transcription and translation of the necessary machinery
for whatever phase of the cell cycle it is.
So again this is just an example of
one of the means of cell communication that comes into play,
putting that into perspective with something real, otherwise
why on earth would you need to know all of these different cascades.
So there is some importance to that.