In the normal central nervous system, tau protein is found mostly in axons, the long processes that conduct impulses to other neurons, where it modulates the length and stability of microtubules necessary for signaling between neurons. In a pathological situation, such as dementias like Alzheimer’s disease (AD), tau dissociates from microtubules leading to their disintegration. Tau oligomers redistribute to other parts of the neuron including the cell body and dendrites where they self-associate to form toxic oligomers, small soluble aggregates of tau, and into very large insoluble fibrils that form tangles.
The neurofibrillary tangles are a pathological hallmark of AD and related tauopathies, but are increasingly thought to be protective structures. Multiple studies have shown that tau oligomers, not fibrils or tangles, are closely correlated with neuronal loss and memory impairment. Significantly, Oligomerix has shown that tau oligomers cause disruption of neuronal signaling and inhibit the formation of memory in mice.