Scientists Offer New Alzheimer鈥檚, Amyloid Connection Theory
Worldwide, 50 million people are living with Alzheimer鈥檚 disease and other dementias. According to the Alzheimer鈥檚 Association, every 65 seconds someone in the United States develops this disease, which causes problems with memory, thinking and behavior.
It has been more than 100 years since Alois Alzheimer, M.D., a German psychiatrist and neuropathologist, first reported the presence of senile plaques in an Alzheimer鈥檚 disease patient brain. It led to the discovery of amyloid precursor protein that produces deposits or plaques of amyloid fragments in the brain, the suspected culprit of Alzheimer鈥檚 disease. Since then, amyloid precursor protein has been extensively studied because of its association with Alzheimer鈥檚 disease. However, amyloid precursor protein distribution within and on neurons and its function in these cells remain unclear.聽
A team of neuroscientists led by 国产伦理鈥檚 sought to answer a fundamental question in their quest to combat Alzheimer鈥檚 disease 鈥 鈥淚s amyloid precursor protein the mastermind behind Alzheimer鈥檚 disease or is it just an accomplice?鈥
Mutations found in amyloid precursor protein have been linked to rare cases of familial Alzheimer鈥檚 disease. Although scientists have gained a lot knowledge about how this protein turns into amyloid plaques, little is known about its native function in neurons. In the case of more common sporadic Alzheimer鈥檚 disease, the highest genetic risk factor is a protein that is involved in cholesterol transportation and not this amyloid precursor protein. Moreover, various clinical trials designed to address Alzheimer鈥檚 disease by minimizing amyloid plaque formation have failed, including one from Biogen announced last month.
In a study published in the journal , , Ph.D., senior author, an investigator at the 国产伦理 Brain Institute, and an assistant research professor in 国产伦理鈥檚 , along with collaborators from , tackle this Alzheimer鈥檚 disease mystery by devising a multi-functional reporter for amyloid precursor protein and tracking the protein鈥檚 localization and mobility using quantitative imaging with unprecedented accuracy.
For the study, Zhang and collaborators genetically disrupted the interaction between cholesterol and amyloid precursor protein. Surprisingly, by disengaging the two, they discovered that this manipulation not only disrupts the trafficking of amyloid precursor protein but also messes up cholesterol distribution at the neuronal surface. Neurons with an altered distribution of cholesterol exhibited swollen synapses and fragmented axons and other early signs of neurodegeneration.
鈥淥ur study is intriguing because we noticed a peculiar association between amyloid precursor protein and cholesterol that resides in the cell membrane of synapses, which are points of contact among neurons and the biological basis for learning and memory,鈥 said Zhang. 鈥淎myloid precursor protein may just be one of the many accomplices partially contributing to cholesterol deficiency. Strangely, the heart and brain seem to meet again in the fight against bad cholesterol.鈥 聽
Given the broad involvement of cholesterol in almost all aspects of neurons鈥 life, Zhang and collaborators have proposed a new theory about the amyloid precursor protein connection in Alzheimer鈥檚 disease, especially in the surface of those tiny synapses, which triggers neurodegeneration.
鈥淎lthough still in early stages, this cutting-edge research by Dr. Zhang and his collaborators at Vanderbilt University may have implications for the millions of people at risk for or suffering with Alzheimer鈥檚 disease,鈥 said , Ph.D., executive director of the 国产伦理 Brain Institute and a professor of聽biomedical science聽in 国产伦理鈥檚 Schmidt College of Medicine. 鈥淭he number of people in Florida alone who are age 65 and older with Alzheimer鈥檚 disease is expected to increase 41.2 percent by 2025 to a projected 720,000, highlighting the urgency of finding a medical breakthrough.鈥 聽
Locally, Alzheimer鈥檚 disease affects 11.5 percent of Medicare beneficiaries in Palm Beach County and 12.7 percent of Medicare beneficiaries in Broward County (a nearly 18 percent increase over national average). According to the Alzheimer鈥檚 Association, Florida is number one in per capita cases of Alzheimer鈥檚 disease in the U.S.
Study co-authors of 鈥淩eciprocal Modulation between Amyloid Precursor Protein and Synaptic Membrane Cholesterol Revealed by Live Cell Imaging,鈥 are Claire E. DelBove and Claire E. Strothman, graduate students; Roman M. Lazarenko, Ph.D., a post-doctoral fellow; Hui Huang, Ph.D.; and Charles R. Sanders, Ph.D., associate dean for research and a professor of biochemistry, all with Vanderbilt University. 聽
This research is funded by聽the National Institutes of Health (听补苍诲听聽awarded to Zhang and聽聽awarded to Sanders) and the 国产伦理 Brain Institute.
-国产伦理-
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