Tau proteins (or τ proteins, after the Greek letter by that name) are proteins that stabilize microtubules. They are abundant in neurons of the central nervous system and are less common elsewhere, but are also expressed at very low levels in CNS astrocytes and oligodendrocytes.[1] Pathologies and dementias of the nervous system such as Alzheimer’s disease and Parkinson’s disease [2] are associated with tau proteins that have become defective and no longer stabilize microtubules properly. Tau proteins interact with tubulin to stabilize microtubules and promote tubulin assembly into microtubules. Tau has two ways of controlling microtubule stability: isoforms and phosphorylation.

Hyperphosphorylation of the tau protein (tau inclusions, pTau) can result in the self-assembly of tangles of paired helical filaments and straight filaments, which are involved in the pathogenesis of Alzheimer’s disease, frontotemporal dementia, and other tauopathies. All of the six tau isoforms are present in an often hyperphosphorylated state in paired helical filaments from Alzheimer’s disease brain.