STZ-treatment induces hyperphosphorylation of tau in pR5 and non-transgenic mice, but only in pR5 mice it induced tau insolubility.

<p>(<b><i>A</i></b>) Amygdalae of STZ- or sham-injected wild-type (WT) and pR5 mice were extracted with buffers of increasing stringency and separated by SDS-PAGE for Western blotting. RAB fractions contain soluble species of both transgenic human (triangle) and endogenous murine (asterisk) tau, as shown with HT7 and TAU5, respectively. Phosphorylation site-specific tau antibodies AT8, AT270, AT100, 12E8, PHF-1 and PS422 (for details on antibodies see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0007917#pone-0007917-t001" target="_blank">Table 1</a>) reveal increased phosphorylation of transgenic and endogenous tau at multiple sites upon STZ-treatment. In sham-treated controls, tau is slightly more phosphorylated in pR5 than WT mice. GAPDH confirmed equal loading. (<b><i>B</i></b>) RIPA fractions of STZ-treated mice contain higher amounts of both transgenic and endogenous tau than in sham-treated controls. Actin confirmed equal loading. (<b><i>C</i></b>) Insoluble proteins were extracted with formic acid (FA). In STZ-treated mice, HT7 and TAU5 show insoluble transgenic and endogenous tau, whereas no tau is detectable in STZ-treated non-transgenic (WT) or sham-injected non-transgenic and pR5 mice. (<b><i>D</i></b>) Extraction of sarkosyl-insoluble tau from amygdala reveals significant amounts of sarkosyl-insoluble transgenic human tau (HT7) were isolated from STZ-treated, but not sham-injected pR5 mice.