The mad cow disease, or bovine spongiform encephalopathy (BSE), outbreak that burst into the news in the United Kingdom in the late 1980s is caused by a harmful version of the prion protein. In affected cows, the misfolded prion protein results in the degeneration of the nervous system and eventual death. Alarmingly, the incidence of the human version of BSE, known as Creutzfeld-Jakob Disease (CJD), increased following the bovine epidemic, indicating that the disease could transfer from one species to another. How the misfolded version of the prion protein causes these neurodegenerative diseases is currently not understood.
Proteins have to be transported through the complex internal environment of a cell to reach their site of function. Nowhere is this more evident than in brain cells, or neurons, which communicate with each other over long distances at specialized sites of contact, called synapses. Through a poorly understood process, the neuron must sort through thousands of protein to identify a small set of proteins that must travel to the synapse.
If you forgot to add the zip code to a letter, would it still reach the correct destination? Eventually it should, thanks to the US Postal Service and the other address information. Cells also need to ensure their messages reach the correct destinations, and a recent paper in Molecular Biology of the Cell reveals that, just like the post office, cells use multiple layers of information to target messenger RNA transcripts (mRNAs) to an important cellular address.
Every cell in the body starts off with essentially the same genome, but sometimes the DNA sequence in a cell gets changed. Some of these changes are due to normal physiology (e.g. DNA is rearranged in immune cells to generate diversity in the adaptive immune system), but others are actual errors that occur when the DNA is copied during cell base. Some mistakes involve the introduction of long sequences in which short DNA "words" are repeated many times. Like a skipping CD (or an old school vinyl record), small areas of the genome are repeated over and over again and once it's copied in the DNA, all subsequent cellular offspring, have the repeated mistake.
Protein aggregates—abnormal clumps of misfolded proteins—are common feature in diseases such as Parkinson's, Huntington's, and Creutzfeldt-Jakob (CJD, the infamous "mad cow" disease). However, it's still a mystery as to whether these aggregates cause the disease or are simply an effect. If aggregates are the cause, how do they work?