0:00
My name is Manu Hegde.
I'm a group leader
at the MRC Laboratory
of Molecular Biology
in Cambridge, England.
And today, I'm going to talk about
Protein Quality Control.
The goal of this lecture
is twofold.
First, I want to introduce you
to the concept
of protein quality control
and tell you a bit about
why it's important.
Second, I want to tell you
not just about what we know
but a little bit about
how quality control processes
are studied experimentally
and how we've come to learn
what we know today.
0:30
A good place to start
for any discussion
on protein quality control
is to consider
how incredibly complex
the inside of a cell is.
So what you're seeing
on this slide right now
is a textbook picture
of the inside of a liver cell,
and this is viewed
by electron microscopy.
And what you can see
is how incredibly compartmentalized
the cell is,
so there are lots
of different compartments
that you can see, for example,
I've labeled
the endoplasmic reticulum in green,
mitochondria in red,
peroxisomes in blue and so forth.
And all of these compartments
have unique complements of proteins
and these proteins of course
give these compartments
their unique functional properties.
1:10
A consequence of having
all of these
proteins compartmentalized
is that these proteins need
to be constantly replenished
and this is
particularly important in cells
that are rapidly growing
or dividing.
But in all cells, proteins
constantly are replenished.
So what that means
is that the ribosome
of which there are many millions
per cell
have to synthesize new proteins
and they do so at a rate
of approximately one protein
every one or two minutes.
And these new proteins
then have to be taken
to all the different compartments
that I just told you about
where they have
to be folded properly,
assembled,
associated with cofactors,
and finally achieve
a functional state.
1:51
Many proteins wind up going
to the endoplasmic reticulum,
so this is where about 25% to 30%
of all proteins wind up,
they either are imported
into the endoplasmic reticulum
or inserted
into the ER membrane.
Other proteins of course
have to stay in the cytosol
where they have to fold there
or assemble with other proteins
in order to make
functional complexes.
And yet other proteins wind up
going to other compartments
such as the mitochondria,
peroxisomes and so forth.
