MAPT and Alzheimer disease: The low concentration of p-tau used in assays shown in Figure 4 (≤ 1 μM, ~ 0.005% wt/vol) did not appear to be sufficient to elicit UPR directly, for in the normal cortex, tau is estimated to be about 2 μM; and in the AD brain, this level increased to 8–10 μM [11].