Getting Out of the Loop of Alzheimer’s Disease

Scientists from UCLA recently pinpointed a possible physical origin of Alzheimer’s disease. The amyloid-beta protein has long been known to clump in the brain and be involved in the progression of the disease. The UCLA team identified a loop in the protein that is likely to enable amyloid-beta’s adhesion process. This discovery suggests new ways to treat the disorder’s cause, rather than just the symptoms.
 Professor David Teplow (Credit: David Geffen School of Medicine at UCLA)
Professor David Teplow
(Credit: David Geffen School
of Medicine at UCLA)

Alzheimer’s disease (AD) is the most common cause of late-life dementia. It is estimated to affect 24 million people worldwide, and half of the people over 85 may suffer from it. This fatal disorder is characterized by a decline in the individuals’ memory and in their ability to think and function independently. Current drugs treat the symptoms of Alzheimer’s but not the underlying cause of the disease. 

A protein called the amyloid-beta protein (A-beta) is thought to be a key cause of AD. A-beta proteins apparently stick together to form toxic deposits in the brain. Self-associations of A-beta can form various clump structures called “amyloid plaques”. Recent studies suggest that these plaques have potent neurotoxic activities that may kill brain cells. 

UCLA scientists, headed by David Teplow, Professor of Neurology at the David Geffen School of Medicine at UCLA, have recently identified a loop in the A-beta protein that is likely to be responsible for the adhesion process. The UCLA team employed an interdisciplinary research strategy. Among other methods, they have revealed morphologic, conformational, and aggregation features of synthetic A-beta in a tube (‘in vitro’), examined the effects of various A-beta assemblies on the physiology of cultured neuronal cell lines (‘in vivo’) and used computerized methods (‘in silico’) to produce models of A-beta structures and to study its conformational dynamics and assembly. The researchers thus discovered that gene mutations in A-beta increase the flexibility of the protein’s loop, enabling it to join easily with loops of other A-beta proteins to form clumps. The loop is also located in the region of the protein that regulates the formation of A-beta and its amount.  

 Amyloid β protein loop. The broken red lines indicate a loop in the amyloid-B protein that enables it to attach to other proteins and form clumps that kill brain cells. (Credit: UCLA)
Amyloid β protein loop. The broken red
lines indicate a loop in the amyloid-B
protein that enables it to attach to
other proteins and form clumps that kill
brain cells. (Credit: UCLA)

Understanding how the toxic A-beta clumps form in the brain could aid the design of new drugs that both block the production of A-beta and prevent it from clumping. Such drugs could be used to prevent or treat the disease. Furthermore, the A-beta assemblies are now known to share properties with other proteins linked to an increasing number of human diseases of aging. This revelation suggests the existence of a common pathogenetic pathway. Therefore, research conducted on AD is likely to advance efforts to understand and treat other disorders. 

TFOT previously covered a couple of other AD related researches. One of them led to the discovery of a protein complex named Ab*56 (amyloid beta star 56), which is thought to be a dominant factor in the early development of AD, while the other one developed a method to decrease neuron loss rates

More information on this AD research is available in Professor David Teplow’s webpage in the UCLA website.

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