JUL 03, 2015 01:02 PM PDT

Fixing the Garbage Disposal

Are the very systems that are supposed to dispose of cellular waste making it worse? A study at Yale University in New Haven, Connecticut, thinks that might be the case in terms of lysosomes and the amyloid plaques that are believed to cause Alzheimer's disease. The study, published in the Proceedings of the National Academy of Sciences and reported in Medical News Today, refutes the idea that massive accumulations of lysosomes surrounding beta-amyloid deposits in the brains of people with Alzheimer's disease are helping to degrade and remove the faulty protein. Instead, say the Yale researchers, the lysosomes are making it worse (http://www.medicalnewstoday.com/articles/296207.php).
Lysosomes -- in magenta -- accumulate near amyloid plaques. A new study implicates the lysosomes in contributing to the disease.
According to the National Center for Biotechnology Information of the national Institutes of Health, lysosomes are "membrane-enclosed organelles that contain an array of enzymes capable of breaking down all types of biological polymers - proteins, nucleic acids, carbohydrates, and lipids." Functioning as the cell's digestive system, lysosomes degrade material taken up from outside the cell and digest obsolete components of the cell (http://www.ncbi.nlm.nih.gov/books/NBK9953/).

Alzheimer's disease, the most common form of dementia,affects the part of the brain that controls thought, memory and language. Affecting as many as 5 million Americans aged 65 years or older in 2013, it could rise to 13.8 million by 2050, according to the Centers for Disease Control. The Yale team's discovery could lead to new types of treatment that correct the faulty lysosomes, enabling them to do their job properly, clear away the beta-amyloid and keep it from clogging the brain.

The researchers explain that the lysosomes accumulate in swollen axons or nerve fibers that contact the amyloid deposits outside of the brain cells. The lysosomes have unusually high levels of beta-secretase, the enzyme that triggers the production of the toxic beta-amyloid protein. They are unable to break down the enzyme, because they are not fully mature. To achieve maturity, they have to move along the axons. When the beta-amyloid plaques block the lysosomes from traveling along the axons, there is a larger accumulation of beta-secretase, which in turn brings about additional beta-amyloid production. According to first author Swetha Gowrishankar, a postdoctoral scientist in the lab of senior author Shawn Ferguson, assistant professor of cell biology, "We think this represents a vicious circle."

To eliminate the enzyme that increases Alzheimer's plaques, the lysosomes have to be able to travel and mature. However, their ability to do so is hampered by Alzheimer's plaques. Faulty lysosomes have also been implicated in other neurodegenerative diseases including Parkinson's and frontotemporal dementia, the researchers say.The Howard Hughes Medical Institute, the Ellison Medical Foundation, the National Institutes of Health and the Consortium for Frontotemporal Dementia Research funded the study.
About the Author
  • Ilene Schneider is the owner of Schneider the Writer, a firm that provides communications for health care, high technology and service enterprises. Her specialties include public relations, media relations, advertising, journalistic writing, editing, grant writing and corporate creativity consulting services. Prior to starting her own business in 1985, Ilene was editor of the Cleveland edition of TV Guide, associate editor of School Product News (Penton Publishing) and senior public relations representative at Beckman Instruments, Inc. She was profiled in a book, How to Open and Operate a Home-Based Writing Business and listed in Who's Who of American Women, Who's Who in Advertising and Who's Who in Media and Communications. She was the recipient of the Women in Communications, Inc. Clarion Award in advertising. A graduate of the University of Pennsylvania, Ilene and her family have lived in Irvine, California, since 1978.
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