Tubastatin treatment promotes reduction of total tau levels but not phosphorylated tau. (A) Levels of total human tau were examined by immunoblotting with H150 antibody (1:1,000 in 1 μg protein) in saline-treated (lanes 1 and 2) or tubastatin-treated (lanes 3 to 5) nontransgenic (ntg) mice, and in saline-treated (lanes 6 to 10) or tubastatin-treated (lanes 11 to 15) rTg4510 mice littermates. Levels of phosphorylated tau present in the brain homogenate were examined using Ser396, Ser199/202 and PHF1 antibodies (1:1,000 dilution). No positive immunoreaction was measured in saline-treated or tubastatin-treated ntg mice. (B) Quantification of immunoreactivity normalized to glyceraldehyde 3-phosphate dehydrogenase (GAPDH) revealed a significant decrease in levels of total tau in rTg4510 mice treated with tubastatin compared with saline-treated rTg4510 mice (*P < 0.05). All data are presented as average SEM.