The brain of a victim killed by prion diseases is clogged with clumps of prion protein (PrP) in a rare, misfolded state called PrPSc. Controversy has long raged about how these diseases get started and if the clumps of PrPSc actually kill brain cells--in some forms of the disease clumps aren't even there. The culprit responsible for the death of neurons is still a mystery.
Now research from Whitehead Institute Director Susan Lindquist and Jiyan Ma, now at Ohio State University, suggests a unifying theory that can help explain how these devastating diseases get started and how they kill. The results, published in two papers in the October 17, 2002 online issue of the journal Science, show that small amounts of PrP accumulating in the cellular space called the cytosol kill neurons in cultured cells and transgenic mice. Mice suffered from neurodegeneration and loss of muscle control, similar to patients with CJD and other prion diseases.
PrP normally sits on the cell surface. But if it misfolds before it gets to the surface, the cell's quality control mechanism sends it to the cytosol for destruction. The new research shows that if the quality control system becomes overwhelmed, even a small amount of PrP in the cytosol will kill the neuron.
In an accompanying paper, the lab reports also that when misfolded PrP accumulates in the cytosol, it can sometimes convert to the clumpy PrPSc-like form. A key feature of prion hypothesis is the "infectious" nature of its shape change--once PrPSc forms, it can coax other prion proteins into this alternative folding pattern and cause them to clump together. Lindquist and Ma have found a mechanism by which this infectious shape change can get started and demonstrated its self-propaga
Contact: Nadia Halim
Whitehead Institute for Biomedical Research