Peter Walter (West Berlin, Germany, 1955), with German and American citizenship, began chemistry studies at the Free University of Berlin in 1973. He subsequently switched to Vanderbilt University (Nashville, United States), where he completed his MSc in Organic Chemistry in 1977, going on to earn a PhD in Cell Biology from the Rockefeller University in 1981. Two years later, he joined the faculty at the University of California, San Francisco, where he has served as Chair of Department of Biochemistry and Biophysics and today holds the title of Distinguished Professor Emeritus. A Howard Hughes Medical Institute Investigator from 1997 to 2022, he is currently a Distinguished Investigator at the Altos Labs Bay Area Institute of Science. Walter is co-author of Molecular Biology of the Cell and Essential Cell Biology, two of the most widely used standard works in the field of molecular cell biology, and is a former president of the American Society of Cell Biology.
When the cell’s capacity to fold proteins is exceeded by the quantity of proteins in the pool or when folding conditions are subject to stress (due, for example, to lack of oxygen or nutrients), proteins cannot fold themselves correctly and acquire toxicity through aggregation. The next step is to either repair or remove them, very much as you would deal with a rubbish bin that needs emptying. This mechanism which does so is known as the unfolded protein response (UPR). While this machinery is in motion, the cell puts its protein production processes on hold until such time as it can reboot and resume normal function. Kazutoshi Mori and Peter Walter discovered this process simultaneously but independently (they have never signed a joint paper), and published their findings in Cell in the same year, 1993. They identified an enzyme, IRE1, that acts as a sensor of unfolded proteins and sends alarm signals to the cell nucleus to correct the misfolding and eliminate misfolded proteins. Both used yeast cells to start their research, since they operate like test tubes in a living system. And the final proof came when they were able to show that the salient features they had discovered in yeast also held true in human cells.