Microtubule-associated protein tau, paired helical filaments, and phosphorylation.

This paper summarizes our recent studies on microtubule-associated protein tau and its pathological state resembling that of the paired helical filaments of Alzheimer's disease. The Alzheimer-like state of tau protein can be identified and analyzed in terms of certain phosphorylation sites and phosphorylation-dependent antibody epitopes. It can be induced by protein kinases which tend to phosphorylate serine or threonine residues followed by a proline; this includes mitogen-activated protein kinase (MAPK) and glycogen-synthase kinase 3 (GSK-3). Both of these are tightly associated with microtubules as well as with paired helical filaments. Structurally, tau appears as a rod-like molecule; it tends to self-associate into dimers whose monomers are antiparallel. Constructs of truncated tau made up of antiparallel dimers of the microtubule binding domain can be assembled into paired helical filaments in vitro.