How do you control the
magnitude of a response?
Because in cell-to-cell
you have one cell releasing a
packet or a quanta of information
then it travels to another
spot to signal it.
But the cell does have, the
target cell has a way to respond.
The way it responds is based upon the
number of receptors that it has.
How can that cell modulate the
number of receptors that it has?
There can be a down
regulation of receptors
and there can be up
regulation of receptors
a very easy way to modify
the target effect.
Sometimes if you have signals
that are too high for too long,
you might down regulate the
receptor response of this.
Other times there might be a clinical
condition in which that you have up regulated
the number of receptors and therefore you’re
hyper responsive to a certain signal.
Another way to modulate the receptor
cell signaling interactions
is by having a certain set of receptors
internalized within the cell.
This is a handy way to quickly adjust the
number of receptors that are expressed.
With up regulation and down regulation,
it involves making new receptors
or pulling them
off the membrane.
That takes time.
If you simply had a group
of internalized receptors,
in certain conditions, you could have
them express on the cell surface.
And once they’re expressed
on the cell surface,
you would be able to increase that
signal that’s being sent to the cell.
A final way to adjust the
sensitivity of a particular
response to a quanta or
amount of signaling molecule
is by something called
sensitization or desensitization
and this is exactly
how it sounds.
You have a similar
number of receptors
but you make them less responsive
to the ligand that’s coming.
This could be done
in a number of ways.
You could have that particular receptor
not transduce the signal in as well
or maybe you have less secondary
messenger signals that are sent
or less protein phosphorylation that occurs
in response to the binding of the ligand.
The opposite could happen in where
you bind to a particular receptor
and that response is up
regulated and is exaggerated
than you would have in
a normal condition.
That exaggerated response
then allows for that
signal to be amplified.
So sensitization and desensitization
are very important aspects
along with up regulation and
down regulation to respond to
signals that have been placed
for long periods of time.
The internalization and
externalization of receptors
are usually certain
kind of strategy to deal with the
types of signals they’re getting.
While the up regulation and down regulation,
desensitization and sensitization
are ones that which you can control
to a little greater extent.