Regulatory role of non‐phosphorylated tau 441 and its antibodies on tubulin polymerization

Abstract

Tau protein is a microtubule (MT) associated protein which functions to promote polymerization and stability of microtubules (MT) in neuronal cells. When tau undergoes post‐translational modification, it misfolds and aggregates, forming cytotoxic species which lead to neurodegeneration. Immunotherapies against tauopathies have shown promise in animal models by inducing clearance of tau pathology. However, the exact mechanisms of antibody‐based inhibition of neurodegeneration remain unidentified. We have reported on anti‐tau antibodies to non‐phosphorylated tau441 and their inhibition of tau aggregation in vitro. We also showed that phosphorylation of tau441 at Ser199, by GSK‐3β, may be inhibited by anti‐tau phosphospecific antibodies. Here, we have evaluated polymerization of tubulin in the presence of non‐phosphorylated tau441 and anti‐tau antibodies to non‐phosphorylated tau [targeting epitopes in the N‐terminal, R4, and C‐terminal]. ELISA was used to determine antigen‐antibody binding affinities between tau, tubulin and anti‐tau antibodies. An anti‐tubulin antibody was used as a control in the polymerization and ELISA experiments. Using the tubulin fluorescence polymerization assay, we have discovered that the antibodies specific to non‐phosphorylated tau441 reduced tubulin polymerization. In the presence of non‐phosphorylated tau441, we observed successful tubulin polymerization even in the presence of anti‐tau antibodies. These studies indicate that tau plays a regulatory/competitive role in MT formationSupport or Funding InformationNIH/NIGMS/R15GM11905301