Tag Archives: Prion

A laboratory study indicates that the main protein involved in Parkinson’s disease pathology does not behave as a prion when overexpressed.

In Parkinson’s disease, the protein alpha-synuclein aggregates within neurons of patients and appears to propagate across interconnected areas of the brain. How this happens remains largely unknown. It has been proposed that alpha-synuclein may behave like a prion: pathological forms of the protein may be capable of changing the conformation of normal alpha-synuclein and thus triggering its aggregation and neuron-to-neuron propagation (a phenomenon referred to as “seeding”). Recent findings by scientists reveal that aggregation, spreading and pathology caused by alpha-synuclein do not necessarily involve prion-like seeding. Instead, they could be triggered by enhanced alpha-synuclein expression and trans-neuronal passage of monomeric and oligomeric forms of the protein.

“We believe that these findings bear a number of important implications for disease pathogenesis. Not only can we conclude that long-distance diffusion of alpha-synuclein does not necessarily require the generation of prion-like species,” said researcher Donato Di Monte. “Our data also reveal that spreading and pathology can be triggered by simple overexpression of the protein and are mediated, at least initially, by monomeric and/or oligomeric alpha-synuclein.”

Researchers report on this in the journal Brain.

Source: DZNE

Research has uncovered further evidence of a system in the brain that persistently maintains memories for long periods of time. And paradoxically, it works in the same way as mechanisms that cause mad cow disease and other degenerative brain diseases.

In four papers published in Neuron and Cell Reports, researchers show how prion-like proteins – similar to the prions behind mad cow disease in cattle and Creutzfeld-Jakob disease in humans – are critical for maintaining long-term memories in mice, and probably in other mammals. The lead authors of the four papers are Luana Fioriti, Joseph Stephan, Luca Colnaghi and Bettina Drisaldi.

When long-term memories are created in the brain, new connections are made between neurons to store the memory. But those physical connections must be maintained for a memory to persist, or else they will disintegrate and the memory will disappear within days.Many researchers have searched for molecules that maintain long-term memory, but their identity has remained elusive.These memory molecules are a normal version of prion proteins, according to new research.

In one of many experiments described in the paper by Luana Fioriti, the researchers challenged mice to repeatedly navigate a maze, allowing the animals to create a long-term memory. But when the researchers knocked out the animal’s CPEB3 gene two weeks after the memory was made, the memory disappeared.

The researchers then discovered how CPEB3 works inside the neurons to maintain long-term memories. “Like disease-causing prions, functional prions come in two varieties, a soluble form and a form that creates aggregates,” said. Kandel. “When we learn something and form long-term memories, new synaptic connections are made, the soluble prions in those synapses are converted into aggregated prions. The aggregated prions turn on protein synthesis necessary to maintain the memory.”

As long as these aggregates are present, Kandel says, long-term memories persist. Prion aggregates renew themselves by continually recruiting newly made soluble prions into the aggregates. “This ongoing maintenance is crucial,” said Dr. Kandel. “It’s how you remember, for example, your first love for the rest of your life.”

A similar protein exists in humans, suggesting that the same mechanism is at work in the human brain, but more research is needed. “It’s possible that it has the same role in memory, but until this has been examined, we won’t know,” said Dr. Kandel. “There are probably other regulatory components involved,” he added. “Long-term memory is a complicated process, so I doubt this is the only important factor.

Source: Medical News Net

Some cases of Alzheimer’s disease progress quickly, mimicking prion-based Creutzfeldt-Jakob disease (CJD). Many people with this form of Alzheimer’s are misdiagnosed, because clinicians have no reliable way to distinguish between the two disorders.

In the January 5 JAMA Neurology, researchers led by Isabelle Quadrio at Hospices Civils de Lyon, Bron, France, propose using levels of total prion protein (t-PrP) in cerebrospinal fluid (CSF) to differentiate CJD from AD. The authors found that people with prion disease had lower CSF levels of this protein than AD patients did. In a study of 209 patients with either disorder, t-PrP classified patients much more accurately than the currently accepted biomarker, 14-3-3 protein, they report. When they combined t-PrP with CSF tau, they correctly identified 96 percent of patients with atypical, fast-progressing AD in this study, as compared with 57 percent using 14-3-3 alone.

Source: AlzForum