Proteins behind mad-cow disease also help brain to develop

Nature News ^ | 14 February 2013 | Mo Costandi

[neverdem]

When not misfolded, prions lend a hand in forming neuronal connections.

Prions are best known as the infectious agents that cause ‘mad cow’ disease and the human versions of it, such as variant Creutzfeldt–Jakob Disease. But the proteins also have at least one known useful function, in the cells that insulate nerves, and are suspected to have more. Now researchers have provided the first direct evidence that the proteins play an important role in neurons themselves.

The team reports in the Journal of Neuroscience1 that prions are involved in developmental plasticity, the process by which the structure and function of neurons in the growing brain is shaped by experience.

Prions come in two main forms: the normal version and the misfolded, infectious version. The normal version, known as cellular prion protein (or PrPC), is present in every cell of the body and helps to maintain the myelin sheath in the cells that protect the nerves2.

But the molecule is abundant in neurons themselves, especially during development. Because it is tethered to the membrane, it is widely assumed to be involved in signalling between nerve cells, but little direct evidence has been found for this.

Neurobiologist Enrico Cherubini of the International School for Advanced Studies in Trieste, Italy, and his colleagues therefore decided to look at the effects of electrical stimulation on slices of tissue from the hippocampus of healthy 3–7-day-old mice and of animals genetically engineered to lack the gene that encodes the prion protein.

They used electrodes to stimulate individual cells at the same time as the networks of young neurons showed bursts of spontaneous electrical activity, or to simultaneously stimulate pairs of cells that are connected to each other...

[neverdem]

Ping

[yefragetuwrabrumuy]

While prions can be thought of like a disease, that is not a good description. Prions are just misfolded proteins, that can make similar proteins misfold as well.

To understand what this means, proteins can be compared to hundreds of springs attached together in a large blanket of springs. Some of the springs are extension springs, and some are contraction springs. To execute its function, a protein will fold up this blanket of springs into a ball.

And it will fold up exactly the same way every time.

But a prion is a mistake in the folding up process. If it folds up incorrectly, the protein does not work. And to make matters worse, it can “tell” other proteins of its type to fold up incorrectly as well.

Importantly, priors happen constantly in our bodies, and just as constantly, they are destroyed by our bodies. But infectious prions are not *recognized* as prions by our bodies, so they are not destroyed, and can try to tell all the other proteins like them to misfold as well. And once you have this, it will kill you.

Instead of cells going bad, causing cancer, this is like cancer but at a much smaller level.

To make things much, much worse, prions are *extremely* hard to destroy.

“Prions cannot be destroyed by boiling, alcohol, acid, standard autoclaving methods, or radiation. In fact, infected brains that have been sitting in formaldehyde for decades can still transmit spongiform disease.

“Prions can be destroyed through incineration providing the incinerator can maintain a temperature of 900 F for four hours. In an autoclave, prions can be deactivated by using a temperature of 270 F at 21 psi for 90 minutes. If the infectious material is in a solution of sodium hydroxide (pH 14), deactivation will occur after one hour at 250 F and 21 psi.

“A commercial disinfectant called Environ LpH(*) also has been shown to be effective at deactivating prions. Prion disinfection occurs with a 1 percent solution of LpH for 10 hours or with a 10 percent LpH solution for one hour.”

(*) Environ LpH contains:

Isopropyl alcohol
Organochloride of phenol
2-Phenylphenol - two linked benzene rings and a phenolic hydroxyl group.
Phosphoric Acid
Sulfonic acid

[khelus]

Thanks for the information. Very interesting!