14-3-3 Connects Glycogen Synthase Kinase-3β to Tau within a Brain Microtubule-associated Tau Phosphorylation Complex

Alka Agarwal-Mawal,Hamid Y Qureshi,Patrick W Cafferty,Zongfei Yuan,Dong Han,Rongtian Lin,Hemant K Paudel

doi:10.1074/jbc.m211491200

Alka Agarwal-Mawal, Hamid Y Qureshi + Show 5 more

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https://doi.org/10.1074/jbc.m211491200

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Abstract

In a recent study, we reported that in bovine brain extract, glycogen synthase kinase-3beta and tau are parts of an approximately 400-500 kDa microtubule-associated tau phosphorylation complex (Sun, W., Qureshi, H. Y., Cafferty, P. W., Sobue, K., Agarwal-Mawal, A., Neufield, K. D., and Paudel, H. K. (2002) J. Biol. Chem. 277, 11933-11940). In this study, we find that when purified brain microtubules are subjected to Superose 12 gel filtration column chromatography, the dimeric scaffold protein 14-3-3 zeta co-elutes with the tau phosphorylation complex components tau and GSK3 beta. From gel filtration fractions containing the tau phosphorylation complex, 14-3-3 zeta, GSK3 beta, and tau co-immunoprecipitate with each other. From extracts of bovine brain, COS-7 cells, and HEK-293 cells transfected with GSK3 beta, 14-3-3 zeta co-precipitates with GSK3 beta, indicating that GSK3 beta binds to 14-3-3 zeta. From HEK-293 cells transfected with tau, GSK3 beta, and 14-3-3 zeta in different combinations, tau co-immunoprecipitates with GSK3 beta only in the presence of 14-3-3 zeta. In vitro, approximately 10-fold more tau binds to GSK3 beta in the presence of than in the absence of 14-3-3 zeta. In transfected HEK-293 cells, 14-3-3 zeta stimulates GSK3 beta-catalyzed tau phosphorylation in a dose-dependent manner. These data indicate that in brain, the 14-3-3 zeta dimer simultaneously binds and bridges tau and GSK3 beta and stimulates GSK3 beta-catalyzed tau phosphorylation.

Highlights

In a recent study, we reported that in bovine brain extract, glycogen synthase kinase-3␤ and tau are parts of an ϳ400 –500 kDa microtubule-associated tau phosphorylation complex
We find that when purified brain microtubules are subjected to Superose 12 gel filtration column chromatography, the dimeric scaffold protein 14-3-3␨ coelutes with the tau phosphorylation complex components tau and Glycogen synthase kinase-3 (GSK3)␤
We showed that within brain microtubules, GSK3␤ and tau are parts of a multiprotein complex that elutes from an FPLC gel filtration column used in this study to generate Fig. 2A with an ϳ400 –500-kDa size [20]

Summary

Introduction

We reported that in bovine brain extract, glycogen synthase kinase-3␤ and tau are parts of an ϳ400 –500 kDa microtubule-associated tau phosphorylation complex In transfected HEK-293 cells, 14-3-3␨ stimulates GSK3␤-catalyzed tau phosphorylation in a dose-dependent manner These data indicate that in brain, the 14-3-3␨ dimer simultaneously binds and bridges tau and GSK3␤ and stimulates GSK3␤-catalyzed tau phosphorylation. Studies suggest that tau regulates microtubule dynamics, axonal transport, and neuronal morphology by binding and stabilizing the microtubule structure [1,2,3]. In AD brain, GSK3␤ is activated in pretangle neurons and accumulates in paired helical filaments [16, 17] These observations suggest that GSK3␤ phosphorylates tau in both normal and AD brain. Previous studies have shown that a large amount of GSK3␤ in brain is associated with microtubules (18 –20), and microtubule-associated GSK3␤ is part of an ϳ400 –500-kDa multiprotein complex containing tau and GSK3␤ [20]. The identification of all the complex components and the determination of their functions within the complex are essential to understanding the mechanism by which GSK3␤ phosphorylates tau in the brain

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