1) Microtubule-associated proteins that are mainly expressed in neurons. Tau proteins constitute several isoforms and play an important role in the assembly of tubulin monomers into microtubules and in maintaining the cytoskeleton and axonal transport. Aggregation of specific sets of tau proteins in filamentous inclusions is the common feature of intraneuronal and glial fibrillar lesions (neurofibrillary tangles; neurophil threads) in numerous neurodegenerative disorders (Alzheimer disease; tauopathies).

2) Family of structural proteins of microtubules which serve to crosslink and therefore stabilize tubulin chains.

3) A protein that binds to and regulates the assembly and stability of neuronal microtubules and that is found in an abnormal form as the major component of neurofibrillary tangles.