Electrochemical detection of anti-tau antibodies binding to tau protein and inhibition of GSK-3β-catalyzed phosphorylation

Anal Biochem. 2016 Mar 1;496:55-62. doi: 10.1016/j.ab.2015.12.002. Epub 2015 Dec 17.

Abstract

Tau protein hyperphosphorylation triggers tau aggregation and its toxicity, leading to neuronal death and cell-to-cell toxicity. Hence, inhibition of protein kinases is a viable tool toward reduction of tau toxicity. By targeting various epitopes of Tau441 protein immobilized on Au surface, the protein kinase inhibition by anti-tau antibodies was measured by surface electrochemistry. The electrochemical impedance spectroscopy was used to measure the charge transfer resistance (Rct) of nonphosphorylated tau-Au film (nTau-Au) and compared with the phosphorylated tau-Au film (pTau-Au). The pTau-Au films were characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS), which indicated high phosphorus content. The Rct factor was used as the measure of inhibition efficacies by anti-tau antibodies (D8, A10, P262, and Tau46) in addition to antibody formulation intravenous immunoglobulin (IVIG). The Rct factor for pTau-Au in the absence of antibodies was 0.25 ± 0.08, indicating a dramatic decrease in Rct on phosphorylation. The Rct factors for Tau46 and A10 were 0.57 ± 0.22 and 0.65 ± 0.26, respectively, indicating phosphorylation inhibition. All antibodies exhibited similar binding to nTau-Au. The proposed electrochemical assay may be used for detection of other posttranslational modifications.

Keywords: Antibodies; Impedance; Kinases; Phosphorylation; Tau.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies / immunology*
  • Biocatalysis
  • Glycogen Synthase Kinase 3 / antagonists & inhibitors*
  • Glycogen Synthase Kinase 3 / metabolism
  • Glycogen Synthase Kinase 3 beta
  • Phosphorylation
  • Photoelectron Spectroscopy
  • Spectrometry, Mass, Secondary Ion
  • Surface Properties
  • tau Proteins / immunology*

Substances

  • Antibodies
  • tau Proteins
  • Glycogen Synthase Kinase 3 beta
  • Glycogen Synthase Kinase 3