Just like traffic jams clog a city’s roads, sometimes proteins in our body break down and clog up our cells.

As this ScienCentral News video reports, when this happens in our brain, it leads to devastating illnesses.

Protein Misfolding

Proteins, the basic components of all living cells, are made up of different combinations of amino acids. In order to carry out their biochemical function, each protein must first take on a particular shape, which happens when the amino acids fold into place. This delicate process of protein folding is critical, and when the amino acids do not fold correctly (i.e. "misfold"), the misshapen proteins form clumps, called aggregates, within the cell. These aggregates then start to attract other healthy proteins that are essential for cell function, which in turn bend and stop working. As this process continues, cells shut down and die, and this can lead to devastating neurodegenerative diseases like Alzheimer’s, new variant Creutzfeldt-Jakob Disease (the human form of Mad Cow Disease), and Huntington’s Disease, to name a few.

Richard Morimoto, professor of biochemistry at Northwestern University, says his laboratory “has focused on the question of whether our cells contain other good proteins that are present to prevent disease-causing proteins such as in Huntington’s.”

Good proteins to the rescue

Morimoto’s team at Northwestern studied molecular chaperones, another class of proteins that are present in all cells that seem to prevent misfolding of proteins. While studying aggregates in Huntington’s patients, Morimoto, lead author of the study published in the October issue of Nature Cell Biology, says they noticed that, “a chaperone recognizes an abnormal protein, binds to that protein and in doing so allows that bad protein to change and perhaps adopt its normal function.”

Morimoto says that, “molecular chaperons, by binding to these aggregates that appear in Huntington’s cells, are causing the release of good proteins that would otherwise be trapped irreversibly in the aggregate.”

The scientists were able to observe all of this in real time by using a technique called dynamic microscopy. With a high-powered microscope they could visualize and record the cells in action as the different proteins interacted with the Huntington’s aggregates.

Says Morimoto, “it’s like the comparison between a still photograph versus a movie. In a still photograph you get a sense of what event might have occurred but no sense of how anything got there or how anything else will change.” Likewise in Huntington’s, Morimoto believes, this technique allowed them to see that there are some proteins that are irreversibly brought into the aggregates while others were seen going into the aggregate and releasing from the aggregate very rapidly.

“This is exciting”, Morimoto says, “because it suggests that the aggregate itself in Huntington’s is not a permanent structure that’s irreversible. It means that proteins by coming and going, in particular the chaperones, provides a hint to us for how we might move to the next step. That is, design drugs or molecules that enhance the removal of proteins from the aggregates,” and allow the cells to function better. The study thus provides a tool for screening and identifying such new and effective drugs.

The research was supported by the National Institutes of Health, the Huntington’s Disease Society of America, Coalition for the Cure, the Hereditary Disease Foundation and the Netherlands Organization for Scientific Research.