Quality control of proteins mislocalized to the cytosol

Published on March 29, 2017   60 min

Other Talks in the Series: Protein Folding, Aggregation and Design

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.
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Quality control of proteins mislocalized to the cytosol

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