The microtubule-associated protein tau favors microtubule nucleation and stabilization and plays a role in the elongation of axons. We have investigated the ability of glycogen synthase kinase-3β (GSK-3β) to control tau-induced processes outgrowth. Tau-transfected Chinese hamster ovary (CHO) cells developed processes containing microtubule bundles after cytochalasin treatment, but a significant reduction in the number of cells harboring processes was observed in tau/GSK-3β-co-transfected cells. Lithium, an inhibitor of GSK-3β, counteracted in a dose-dependent manner this inhibitory effect of GSK-3β. These findings suggest that GSK-3β modulates in a graded manner the ability of tau to control the microtubule-dependent induction of cell processes.
