Question

Stable β-sheet aggregates can form from many proteins, forming intertwined cross-beta strands that have the potential to kill cells or damage tissues. Which of the following is NOT true regarding these aggregates?

1) They form almost exclusively in the cells of the nervous system.
2) Different types of such aggregates can form from the same protein.
3) Their formation is associated with conditions such as Parkinson's disease and Kuru.
4) They can form spontaneously, but also can be triggered to form by an infection with the same aggregate.
5) Some healthy cells form these aggregates to store their secretory proteins.

Answer 1

The incorrect statement is that β-sheet aggregates form almost exclusively in the cells of the nervous system. They can form in various cells and tissues and are linked to a range of diseases. Aggregates may also serve functional roles in some healthy cells. The correct option is 1).

Step-by-step explanation:

The statement that is NOT true regarding β-sheet aggregates is: "They form almost exclusively in the cells of the nervous system." While it is true that amyloid plaques and protein aggregates are often associated with neurodegenerative conditions such as Parkinson's disease and Alzheimer's, these aggregates can form in various cell types and tissues and are not restricted to the nervous system. Some non-neurological diseases, like systemic conditions such as cystic fibrosis and type 2 diabetes, also manifest through the accumulation of misfolded proteins, though they may not form the same type of plaques.

Additionally, it's true that different types of aggregates can form from the same protein, demonstrating that proteins can misfold into multiple stable configurations, leading to a variety of diseases, a concept central to the study of proteopathy. Furthermore, not all aggregates are associated with disease, as some cells use these structures in a regulated manner for storing secretory proteins.

Lastly, the formation of protein aggregates can indeed be triggered both spontaneously and by an infectious process as seen in prion diseases, where an infectious protein aggregate can induce misfolding and aggregation of the same protein in a healthy individual.