title: Electrochemical detection of anti-tau antibodies binding to tau protein and inhibition of GSK-3β-catalyzed phosphorylation.
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.
authors.affiliation: Department of Chemistry, Oakland University, Rochester, MI 48309, USA.
authors.forename: Jose O
authors.initials: JO
authors.lastname: Esteves-Villanueva
authors.affiliation: Department of Chemistry, Oakland University, Rochester, MI 48309, USA. Electronic address: martic@oakland.edu.
authors.forename: Sanela
authors.initials: S
authors.lastname: Martic-Milne
mesh_terms: D000906:Antibodies / Q000276:immunology*; D055162:Biocatalysis; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D010766:Phosphorylation; D056951:Photoelectron Spectroscopy; D018629:Spectrometry, Mass, Secondary Ion; D013499:Surface Properties; D016875:tau Proteins / Q000276:immunology*
chemical_list: D000906:Antibodies; D016875:tau Proteins; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3
keywords: Antibodies; Impedance; Kinases; Phosphorylation; Tau