Increase in acetylated and tyrosinated α- and β-tubulin subunits but selective reduction in Glu-tubulin in astrocytes accumulating tau. Quantitative Western blots of total cell lysates (A-C), supernatants (S), and cytoskeletal fractions (P) (D) probed with antibodies against several different post-translationally modified forms of tubulin subunits, followed by [¹²⁵I]-labeled secondary antibodies. Synthesis of β-tubulin as monitored by [³⁵S]methionine metabolic labeling of the T40-AV-infected astrocytes, followed by immunoprecipitation with anti-β-tubulin antibody (C) were performed. Quantitative analysis of Western blots showed increases of Ac-tubulin and Tyr-tubulin with time up to 180% of the initial levels 24 hr after infection, concomitant with the increases of α- and β-tubulins, whereas Glu-tubulin decreased with time down to 30% of the initial level at 24 hr (B). These alterations occurred primarily on assembled MTs rather than free tubulin subunits because the changes in the intensity of the protein bands in the cytoskeletal fractions (P) resembled the changes in the total cell lysates (A, D). The increase radiolabeled β-tubulin (C) with time correlated with the increased accumulation of total tubulin shown in A: Ac-tub, acetylated tubulin; Tyr-tub, tyrosinated tubulin; Glu-tub, detyrosinated tubulin. Statistical differences of the means, ^*p < 0.05; ^**p < 0.01.