Researchers say that a potential cure for Alzheimer's disease may require a combination therapy, which will target the malformations of the proteins that characterize this condition.
Alzheimer's disease is characterized by two distinctive protein malformations: amyloid plaques, which are sticky deposits made up of a short protein called amyloid beta, and tau tangles, which are made of short filaments of the tau protein.
Referring to a previous study, the researchers at the University of Illinois at Chicago College of Medicine highlight the fact that tau tangles work together with amyloid beta to create a perfect storm that destroys neural function and memory.
They, however, insist that no study to date has been able to show as to how amyloid beta and the tau tangles wreak their damage on the nervous system.
Scott Brady, professor and head of anatomy and cell biology at the UIC College of Medicine, points out that when short assemblies of amyloid, rather than the long-chain plaques, get inside neurons, they interfere with the cells' transport system.
This, according to him, limits their ability to send vital proteins and vesicles to where they are needed within the cell, and interferes with the synaptic connections to other nerve cells.
Brady says that the new study has shown that the short assemblies of amyloid activate a transport-regulatory enzyme called CK2, which causes the motor protein to drop its cargo.
His team have also found that inhibition of CK2 is sufficient to prevent the effects of amyloid on transport.
An earlier study by the same researchers showed that tau tangles halt transport to the neuron periphery through other regulatory enzymes, by causing the motor protein to release the microtubule track.
The new study shows that the CK2 activated by amyloid also works as a primer for one of the enzymes activated by tau tangles, GSK3.
"Now we have the perfect storm. Both amyloid and tau tangles cause problems. But when you put them together, you exacerbate the problems, creating the cascade of events that cause Alzheimer's loss of neural connections," said Brady.
"It makes sense of why both have to be present to have Alzheimer's.
"It is also telling us that treating one is not going to be sufficient. We're going to have to think in terms of combination therapies that will allow us to address many targets at once. This may explain why attempts to manipulate one or the other haven't been successful in patients," he added.
A research article on the current study appears in the online edition of Proceedings of the National Academy of Sciences.