UK scientists found a new step in how cells make protein which could explain how they respond to stress, such as starvation and being attacked by viruses.
Drs Graham Pavitt and Martin Jennings from the Faculty of Life Sciences at the University of Manchester, described their findings in a paper published online on 20 May in the journal Nature.
Making proteins is a major activity of cells and takes place in complex structures called ribosomes.
For cells to make proteins, they have to get the recipe and other instructions from the DNA in their genomes for each particular protein. Messenger (mRNA) translate the code in the DNA template and carry it to the ribosomes.
All this happens under the direction of protein synthesis factors, a special group of proteins involved in the initiation, elongation and termination of protein synthesis.
When cells are under stress something happens to protein synthesis and lab experiments have shown that this can lead to obesity, diabetes and even change memory function in the brain. We also know that pathogens like viruses exploit this feature, for instance, they intercept protein synthesis pathways and use them to replicate themselves.
Cells defend themselves against these stresses by shutting down protein synthesis. This study shed some light on how they do that by identifying the protein synthesis factor involved and the step it takes.
For the study, Pavitt and Jennings starved yeast cells of amino acids (a way of putting the cells under stress) and observed what happened to the protein synthesis factor eIF5 (eukaryotic translation initiation factor 5), which is necessary for protein synthesis in all cells.
Their investigation found that eIF5 not only initiates protein synthesis (by activating a second factor called eIF2, which plays a key role in the control of protein synthesis under conditions of nutrient deprivation, viral infection and memory formation), but it also controls it in a way that is separate and independent from this.
This second function of eIF5 locks eIF2 into a “switched off state”, thus making it an essential step of the process used by the cell to shut down protein production at times of stress.
Pavitt said that although they used yeast cells, the cellular processes they investigated are common to all cells including mammal cells.
He said:
“Further work is now required to determine if these new findings will have consequences for our deeper understanding of human health and disease.”
“eIF5 has GDI activity necessary for translational control by eIF2 phosphorylation.”
Martin D. Jennings, Graham D. Pavitt
DOI:10.1038/nature09003
Source: University of Manchester.
Written by: Catharine Paddock, PhD