Scientists from the Florida campus of The Scripps Research Institute have identified a single prion protein that causes neuronal death similar to that seen in "mad cow" disease, but is at least 10 times more lethal than larger prion species. This toxic single molecule or "monomer" challenges the prevailing concept that neuronal damage is linked to the toxicity of prion protein aggregates called "oligomers." The study was published in an advance, online edition of the journal Proceedings of the National Academy of Sciences. "By identifying a single molecule as the most toxic species of prion proteins, we've opened a new chapter in understanding how prion-induced neurodegeneration occurs, " said Scripps Florida Professor Corinne LasmÃ zas, who led the new study. "We didn't think we would find neuronal death from this toxic monomer so close to what normally happens in the disease state.
Memories in our brains are maintained by connections between neurons called "synapses". But how do these synapses stay strong and keep memories alive for decades? Neuroscientists at the Stowers Institute for Medical Research have discovered a major clue from a study in fruit flies: Hardy, self-copying clusters or oligomers of a synapse protein are an essential ingredient for the formation of long-term memory. The finding supports a surprising new theory about memory, and may have a profound impact on explaining other oligomer-linked functions and diseases in the brain, including Alzheimer's disease and prion diseases. "Self-sustaining populations of oligomers located at synapses may be the key to the long-term synaptic changes that underlie memory; in fact, our finding hints that oligomers play a wider role in the brain than has been thought, " says Kausik Si, Ph.
Medical researchers in Canada and the United States recently published their joint findings that fatal prion diseases, which include BSE or "mad cow disease, " have a hidden signature. Findings published this month in the peer-reviewed journal, Public Library of Science (PLoS) Pathogens, demonstrate that up to seven months before an animal shows physical signs of having a prion infection, a particular prion protein in the brain was being eradicated. This member of the prion family is known as shadoo protein. "What we discovered is that as the early prion disease process unfolds in an infected brain, that the shadoo protein is simultaneously disappearing, " said lead author and co-principal investigator, David Westaway, a researcher in the Faculty of Medicine & Dentistry at the University of Alberta.
Hirano bodies are almost indescribably tiny objects found in nerve cells of people suffering from conditions such as Alzheimer's, mad cow and Lou Gehrig's diseases. Yet for decades, researchers weren't sure if these structures helped cause the conditions or appeared after onset of the disease and had some other role. Now, in research at the University of Georgia, a cellular biologist and his colleagues have found that Hirano bodies may play a protective role in the progression of neurodegenerative diseases such as Alzheimer's. And to find out why this may be happening, they have developed the world's first transgenic mouse model that has Hirano bodies, which will open new frontiers on how these poorly understood structures may be involved with some of humankind's most difficult-to-treat diseases.
It's a chicken and egg question. Where do the infectious protein particles called prions come from? Essentially clumps of misfolded proteins, prions cause neurodegenerative disorders, such as mad cow/Creutzfeld-Jakob disease, in humans and animals. Prions trigger the misfolding and aggregation of their properly folded protein counterparts, but they usually need some kind of "seed" to get started. Biochemists at Emory University School of Medicine have identified a yeast protein called Lsb2 that can promote spontaneous prion formation. This unstable, short-lived protein is strongly induced by cellular stresses such as heat. Lsb2's properties also illustrate how cells have developed ways to control and regulate prion formation. Research in yeast has shown that sometimes, prions can actually help cells adapt to different conditions.