The tau protein is implicated in several types of neurodegenerative diseases, which collectively are called tauopathies. These conditions include Alzheimer’s disease (AD), as well as progressive supranuclear palsy (PSP), chronic traumatic encephalopathy (CTE), and corticobasal syndrome (CBS). Some forms of frontotemporal dementia (FTD) and primary progressive aphasia (PPA) are also related to tau protein abnormalities.
The precise function of tau is not known, but it may help stabilize the shape and structure of the part of the neuron called the axon, a long thin projection that stretches away from the cell body and carries information from one neuron to another. It probably has a variety of other important roles in neurons.
In neurodegenerative diseases, the protein becomes misfolded, and the misfolded tau clumps together in “tangles” both inside and outside the cell, which damage it. Abnormal tau proteins are believed to infect other tau proteins in neighboring neurons, spreading the tangles—and disease—throughout the brain. Many of the treatments being tested are antibodies that block the spread of misfolded tau from neuron to neuron, stopping the degeneration and death of cells.