Hanover, NH For some proteins made deep within a cell, those that work elsewhere in the body have a complex journey aboard carrier vessels with many possible stops before they exit the cell and continue through the blood to reach their destination. Now Dartmouth Medical School biochemists have discovered a key receptor for sorting which proteins stay and which leave, documenting for the first time what many scientists theorized but had not confirmed about how proteins travel through cells for export.
Their results, published in the November 16 Science, help resolve a major piece of the cell traffic puzzle, paving the way for further understanding of how hormones such as insulin as well as other important factors are conveyed through cells for secretion into the blood stream. The authors are Charles Barlowe, PhD, associate professor of biochemistry and William J. Belden, a graduate student.
Transporting proteins that need to get out of the cell to function is essential. After they are manufactured on membranes in the cell interior, the proteins are captured in little vesicles that take them to the cell boundary to be discharged. Packaging the proteins to board the vesicles takes a series of steps not yet well delineated.
"Internal membranes have thousands of proteins in them and some of those proteins depend on vesicles to travel to another location. But the first step is getting it into a vesicle. Thats called sorting," says Barlowe.
He makes the analogy of a bus. "If there is a bus to carry passengers and the passengers need seats, then if we look at the bus carefully we should be able to find some seats." Barlowe, using bakers yeast as a model system, has found a seat on the cellular bus.
A popular cell transport model holds that a receptor will bind to a protein that needs to travel and capture it into the vesicle. However, no receptors that actually operate on this theory of selected transport had been found. Now
Contact: Hali Wickner
Dartmouth Medical School