- [Voiceover] In previous videos on cell signaling,
we talk about the idea that if we have a cell
right over there and let's say it has some type of receptor.
It doesn't actually have to be on the cellular membrane,
but I'll put it there for now.
It can bind to some ligand, that when the ligand
binds to the receptor and it's usually particular,
the ligand is usually particular
to the receptor and vice versa,
it can set off a whole cascade of events.
In particular, once it binds, so let me actually draw
the ligand bound to the receptor,
you can have a signal that tells the cell to do something.
It might activate some genes, it might change
the metabolism of the cell in some way.
And this signal that goes from the receptor into the cell
to make the cell behave in some way,
we call that signal transduction.
We call it transduction, signal transduction.
In the previous video, I was kind of
hand wavy about it, and you might have been saying,
"Well how does a signal actually go into the cell?
"How does it actually move through the cell
"and how does it actually make things happen?"
And what I wanna do in this video is I'm not gonna
go into all of the details, but I'm gonna give you
an appreciation for how transduction can actually occur.
Hopefully it'll also give you appreciation
for how complex biological systems,
including you and me, and even each of our
individual cells actually are.
So this pathway that we're seeing up here,
and you can see that there's a bunch of pathways
that all kind of work together and overlap
in terms of the enzymes and the proteins that are involved.
This, as the diagram calls,
is the Classical Map kinase pathway.
If you're wondering, "What does Map kinase stand for?"
And oftentimes people will just say MAPK or M-A-P-K,
it stands for mitogen, M for mitogen,
mitogen-activated protein kinases.
And you might be saying, "What does mitogen mean?"
Well, mitogen refers to things that cause cells
to mitose, to actually
go into mitosis, to start replicating themselves.
Now, what is mitogen-activated?
So this pathway is going to be activated by a mitogen.
Mitogen-acivated protein kinase.
Well, a protein kinase,
a kinase, and we've seen kinases multiple times.
They're involved in many, many, many biological mechanisms.
These are general term for enzymes
that help take a higher energy phosphate,
or especially, I should say, a higher energy bond
or a phosphate, part of an ATP
or a GTP and transfers them to different molecules,
and as they transfer them to different molecules,
it's able to leverage that energy
to actually facilitate some type of a mechanism.
Now, as I said, I'm not gonna go into all the details here.
This is actually quite complex,
but I want to make a little bit sense of it.
And we're actually gonna talk about
a few proteins and a few enzymes that are actually
fairly important to modern biological research.
So what you have right over here,
I'll start with this molecule right over here.
This is the ligand.
This is the ligand, it's going to be released
by some other part of the biological system,
from some other cell.
And this EGF, this stands for epidermal growth factor.
The 1986 Nobel Prize in medicine was actually given
for the discovery of EGF, of epidermal growth factor.
Now this is going to be the ligand,
and this is essentially when this attaches
or when this binds to a receptor,
that's going to cause a signal to be transduced.
You're gonna have the transduction going into the cell.
And so you can imagine, it's going to bind
to this membrane receptor,
and so EGFR literally stands for
epidermal growth factor receptor, EGF receptor.
And it's part of this protein complex and once this binds,
it's able to help activate
RAS right over here.
RAS, once again, all of these names,
they have these interesting histories associated with them.
This stands for rat sarcoma,
and sarcomas are cancers
in certain tissues in the body.
It was first discovered associated with certain cancers,
that rats that had certain sarcomas,
that they were able to see that there were mutations
in the genes that produced the RAS protein.
Because of those mutations, the RAS protein
that the enzymes associated with it
were in their activated mode.
And because they were in the activated mode,
this mechanism was kind of overactive.
And any of the stop signals weren't actually happening.
And so you could imagine a mechanism right over here
that is about cell differentiation,
that if this mechanism proceeds, it's eventually
going to tell the DNA, some portions of the DNA,
especially the portions of the DNA
that are involved with DNA replication,
with cell division, with mitosis,
those are gonna go crazy,
and that's exactly what happens in cancer.
So this pathway is actually
a very important pathway in cancer.
You see right over here, you actually see the Map kinase,
it's often called, or was originally called ERK,
which is extracellular signal regulated kinase.
But this in an incredibly important pathway
to cancer researchers, and they actively are looking for
different types of drugs, different types of molecules
that can down regulate this type of pathway.
So the whole point of this video, once again,
I'm not going into all of the details
on the Map kinase pathway,
was to give you an appreciation
for how complex transduction is.
You have this cascade of this signal which is really
these phosphate groups originally transferred
from a GTP going to Ras, and it keeps cascading down
all the way until you actually have the DNA being told to,
or you start activating mechanisms
where the DNA is going to start replicating,
and then the cell itself
is going to proliferate and differentiate.
This needs to happen in practically every cells in our body,
but there's all sorts of kind of factors
that keep it from going crazy.
But if you have a mutation in something like
the Ras gene which codes for the Ras protein,
then you could end up with an actual cancer cell.
So hopefully this give you a little bit more appreciation
for how transduction actually occurs.