by National Institute for Physiological Sciences

The process of alternating elongation and pausing of amyloid β (Aβ) fibrils was captured by combining high-speed atomic force microscopy (HS-AFM) and Monte Carlo simulations. The study revealed the mechanism by which the 4396C antibody selectively binds to the “paused state” of fibril growth, effectively inhibiting further elongation of Aβ fibrils. Credit: The Authors

A collaborative research group has uncovered a new mechanism in the growth of amyloid β (Aβ) fibrils, which are closely associated with Alzheimer’s disease. Using advanced high-speed atomic force microscopy (HS-AFM), the team was able to observe Aβ fibril growth at the molecular level in real time. The work is published in the Journal of the American Chemical Society.

This breakthrough sheds new light on how these fibrils grow and how their progression can be effectively halted.

Alzheimer’s disease is a serious neurodegenerative disorder that leads to cognitive decline and memory loss. One of the main contributors to the disease is the accumulation of Aβ proteins in the brain, which clump together to form fibrils.

These fibrils interfere with brain function, and understanding how they grow and can be stopped is essential for developing new treatments. However, the exact growth mechanisms of Aβ fibrils and ways to halt them have remained unclear—until now.

The researchers, including teams from the Exploratory Research Center on Life and Living Systems and the Institute for Molecular Science of the National Institutes of Natural Sciences, as well as Nagoya City University, Nagoya University, and University of Tsukuba, found that each Aβ fibril is composed of two thin strands, called protofilaments. These protofilaments grow in an alternating pattern, with individual Aβ molecules adding to the ends of each strand one at a time.

HS-AFM observation of Aβ fibril with 4396C antibody. Credit: Koichi Kato and Takayuki Uchihashi

A critical finding of the study was that when the ends of these two protofilaments align, the fibril enters a “paused state,” where growth temporarily stops. This pause in growth is a crucial step in the Aβ fibril formation process and could be key to understanding how Alzheimer’s disease progresses.

One of the most notable discoveries was the role of an antibody, 4396C, which selectively binds to the ends of the Aβ fibrils during this paused state. Once the antibody binds, the fibril is locked in this state, and further growth is prevented. This finding reveals a promising new approach to stopping Aβ fibril growth and, potentially, slowing the progression of Alzheimer’s disease.

The detailed high-resolution observations made with HS-AFM allowed the research team to uncover this alternating growth and pause mechanism, which had not been previously identified. By targeting the paused state of Aβ fibrils, this study opens up new possibilities for developing treatments that can delay or halt Alzheimer’s disease at the molecular level.

In the future, the team plans to further investigate the action of the 4396C antibody, with the hope of applying these findings to create new therapeutic approaches for Alzheimer’s disease. Additionally, the discovery may have broader implications for other amyloid-related diseases, as the insights gained from this study could inform treatments for a range of conditions involving protein aggregation.