14-3-3 zeta is an effector of tau protein phosphorylation

Neurofibrillary tangles associated with Alzheimer's disease are composed ma inly of paired helical filaments that are formed by the aggregation of abno rmally phosphorylated microtubule-associated protein tau. 14-3-3, a highly conserved protein family that exists as seven isoforms and regulates divers e cellular processes is present in neurofibrillary tangles (Layfield, R., F ergusson, J., Aitken, k, Lowe, J., Landon, NI., Mayer, R. J. (1996) Neurosc i. Lett. 209, 57-60). The role of 14-3-3 in Alzheimer's disease pathogenesi s is not known. In this study, we found that the 14-3-3 zeta isoform is ass ociated with tau in brain extract and profoundly stimulates cAMP-dependent protein kinase catalyzed in vitro phosphorylation on Ser(262)/Ser(356) loca ted within the microtubule-binding region of tan. 14-3-3 zeta binds to both phosphorylated and nonphosphorylated tau, and the binding site is located within the microtubule-binding region of tan. From brain extract, 14-3-3 ze ta co-purifies with microtubules, and tubulin blocks 14-3-3 zeta-tau bindin g. Among four 14-3-3 isoforms tested, beta and zeta but not gamma and epsil on associate with tau. Our data suggest that 14-3-3(zeta) is a tau protein effector and may be involved in the abnormal tau phosphorylation occurring during Alzheimer's disease ontogeny.