Fig. 7. The succinylation of K311 on tau promotes AD like features in tau pathology.

a Succinylation promotes self-aggregation of tau. Tau peptides (10 μM) were in presence of 2.5 μM heparin: PHF6 (blue squares), S-PHF6 (magenta circles), PHF6:S-PHF6 = 9:1 (purple triangle), PHF6* (yellow square), A-PHF6* (lake green triangle). Error bars represent SEM deviation from the mean. All statistical analysis was implemented at time = 5000 s (n = 3, one-way ANOVA followed by Tukey’s multiple comparisons test). Experiments repeated three times with similar results. b–d Negative stain electron microscopy of in vitro polymerized PHFs after 24 h incubation. b 50 μM PHF6; c 50 μM S-PHF6; d 50 μM mixture (PHF6:S-PHF6 = 9:1). White arrows denote paired helical filaments. N = 3 independent biological replicates. Scale bar is 100 nm. e, f The width and height of the fiber helix found in polymerized PHFs after 24 h incubation in vitro. Error bars represent SEM deviation from the mean (n = 3 different fields per group, one-way ANOVA followed by Tukey’s multiple comparisons test). g Inhibition of assembly reaction of K19 and microtubules by succinylation of K19. Incubations (30 min) were with 30 μM succinylated K19 (magenta circles) or non-succinylated K19 (blue Squares). Error bars represent SEM deviation from the mean. All statistical analysis was implemented at time = 80 min (n = 3, two-way ANOVA followed by Bonferroni’s multiple comparisons test). Experiments repeated three times with similar results. h, i Succinylation of K19 weakens its interactions with T2R.¹H,¹⁵N HSQC spectra were recorded for unmodified and succinylated K19 in the absence (black) and in the presence (red for unmodified K19, orange for succinylated K19) of T2R. Unmodified or succinylated ¹⁵N K19 spectra (assignments for well-resolved residues as indicated) exhibit intensity loss for multiple residues including Ile³⁰⁸, Val³⁰⁹, Tyr³¹⁰, Lys³¹¹ in the presence of T2R. j, k Succinylation of K311 weakens the interactions of tau peptide (296–321) with tubulin. Comparison of 1D ¹H spectra (black) and saturation transfer difference NMR spectra (blue) of unmodified tau peptide (296–321) or K311-succinylated tau peptide (296–321) in the presence of 20 μM tubulin. Source data are provided as a Source Data file.