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 Scientists Identify Machinery that Helps Make Memories

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Date posted: 03/11/2008

Duke University Medical Center researchers have identified a missing-link molecule that helps to explain the process of plasticity (rearranging neural connections in learning and forming memories) and could lead to new therapies.

The discovery of a molecule that moves new receptors to the synapse so that the neuron (nerve cell) can respond more strongly helps to explain several observations about plasticity, said Michael Ehlers, MD, PhD, a Duke professor of neurobiology and senior author of the study published in the Oct. 31 issue of Cell. "This may be a general delivery system in the brain and in other types of cells, and could have significance for all cell signaling."

Ehlers said this could be a general way for all cells to locally modify their membranes with receptors, a process critical for many activities -- cell signaling, tumor formation and tissue development.

"Part of plasticity involves getting receptors to the synaptic connections of nerve cells," Ehlers said. "The movement of neurotransmitter (chemical) receptors occurs through little packages that deliver molecules to the synapse when new memories form. What we have discovered is the molecular motor that moves these packages when synapses are active."

"One of earliest changes in Alzheimer's disease is synapse dysfunction, so this molecule might be a new target for that disease," he said. "Abnormal movement of receptors may be implicated in brain development, in autism." He said the molecule potentially is involved "in the abnormal electrical activity of epilepsy and the overactive brain pathways of addiction."

In a series of biochemistry and microscopic imaging experiments, Ehlers and colleagues found that the myosin Vb (five-b) molecule in hippocampal neurons responded to a flow of calcium ions from the synaptic space by popping up and into action. One end of the myosin is attached to meshlike actin filaments so it can "walk" to the end of the nerve cells where receptors are. On its other end, it tows an endosome, a packet that contains new receptors.

"These endosomes are like little memories waiting to happen," Ehlers said. "They are reservoirs of neurotransmitter receptors that brain cells deploy to add more receptors to a particular synapse. More receptors equals stronger synapses."

See the full Story via external site: www.dukehealth.org



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