Alzheimer's Disease and Tau Self-Assembly: In the Search of the Missing Link

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease characterized by progressive cognitive impairment, apathy, and neuropsychiatric disorders. Two main pathological hallmarks have been described: neurofibrillary tangles, consisting of tau oligomers (hyperphosphorylated tau) and Aβ plaques. The influence of protein kinases and phosphatases on the hyperphosphorylation of tau is already known. Hyperphosphorylated tau undergoes conformational changes that promote its self-assembly. However, the process involving these mechanisms is yet to be elucidated. In vitro recombinant tau can be aggregated by the action of polyanions, such as heparin, arachidonic acid, and more recently, the action of polyphosphates. However, how that process occurs in vivo is yet to be understood. In this review, searching the most accurate and updated literature on the matter, we focus on the precise molecular events linking tau modifications, its misfolding and the initiation of its pathological self-assembly. Among these, we can identify challenges regarding tau phosphorylation, the link between tau heteroarylations and the onset of its self-assembly, as well as the possible metabolic pathways involving natural polyphosphates, that may play a role in tau self-assembly.