Figure 6. 12E8 but not other tau epitopes aggregates and co-localizes with AC rods during actin depolymerization.

Primary chick neurons were treated with 1 µg/ml Latrunculin B (Lat B) for 15 min, fixed and immunostained. We first confirmed formation of both AC and 12E8-MAP/tau positive rods in Lat B treated cultures (data not shown), as has previously been observed [20] and then co-stained cultures for ADF with numerous tau epitopes. Whereas an abundance of AC rods were induced by Lat B (A, arrows), label for all tau epitopes, except 12E8, remained relatively smooth and evenly distributed throughout neurites, as shown here for AT100 (A) (other epitopes not shown). Western blots of lysates of Lat B-treated neurons were probed with the same battery of antibodies to tau phospho-epitopes. While most epitopes such as S396 (shown here) showed little change in phosphorylation during Lat B treatment, the 12E8 epitope was strongly phosphorylated within 2 min of treatment (B, C). Band intensities were quantified for each time-point for 12E8 and S396 immunoblots (C) with each lane normalized to individual β-actin loading controls and then calculated as a percentage of control band intensities. At 2 min, 12E8 phosphorylation was 2.9±0.1-fold higher than control means (mean ±min/max intensities). Scale bar = 10 µm.