Table 1.

Effect of phosphorylation by cdk5, GSK-3 or cdk5 plus GSK-3 on the binding of different free or MT-bound tau isoforms to microtubules

τ isoform used	Kinase used (1st, 2nd)	τ bound to MT (%)(phosphorylation of τ followed by binding to MT)	τ remained bound to MT (%)(phosphorylation of MT-bound τ)
τ3	–	100 ± 2	100 ± 2
	–, cdk5	98 ± 4	92 ± 3
	–, GSK-3	89 ± 2	86 ± 2
	cdk5, GSK-3	60 ± 4*	76 ± 1*
τ4	–	100 ± 2	100 ± 3
	–, cdk5	96 ± 2	92 ± 3
	–, GSK-3	87 ± 2	86 ± 2
	cdk5, GSK-3	56 ± 4*	75 ± 3*
τ3L	–	100 ± 2	100 ± 3
	–, cdk5	93 ± 3	88 ± 2
	–, GSK-3	89 ± 2	81 ± 2
	cdk5, GSK-3	21 ± 3**	51 ± 5**
τ4L	–	100 ± 3	100 ± 2
	–, cdk5	95 ± 2	88 ± 2
	–, GSK-3	89 ± 2	81 ± 3
	cdk5, GSK-3	19 ± 4**	54 ± 4**

^*p<0.05;

^**p<0.01