Direct High Affinity Interaction between Aβ42 and GSK3α Stimulates Hyperphosphorylation of Tau. A New Molecular Link in Alzheimer’s Disease?

Abstract

Amyloid β peptide (Aβ42) assemblies are considered central to the development of Alzheimer’s disease, but the mechanism of this toxicity remains unresolved. We screened protein microarrays with on-pathway oligomeric Aβ42 to identify candidate proteins interacting with toxic Aβ42 species. Samples prepared from Alexa546-Aβ42 and Aβ42 monomers at 1:5 molar ratio were incubated with the array during a time window of the amyloid fibril formation reaction during which the maximum number of transient oligomers exist in the reaction flux. A specific interaction was detected between Aβ42 and glycogen synthase kinase 3α (GSK3α), a kinase previously implicated in the disease pathology. This interaction was validated with anti-GSK3α immunoprecipitation assays in neuronal cell lysates. Confocal microscopy studies further identified colocalization of Aβ42 and GSK3α in neurites of mature primary mouse neurons. A high binding affinity (KD = 1 nM) was measured between Alexa488-Aβ42 and GSK3α in solution using thermophoresis. An even lower apparent KD was estimated between GSK3α and dextran-immobilized Aβ42 in surface plasmon resonance experiments. Parallel experiments with GSK3β also identified colocalization and high affinity binding to this isoform. GSK3α-mediated hyperphosphorylation of the protein tau was found to be stimulated by Aβ42 in in vitro phosphorylation assays and identified a functional relationship between the proteins. We uncover a direct and functional molecular link between Aβ42 and GSK3α, which opens an important avenue toward understanding the mechanism of Aβ42-mediated neuronal toxicity in Alzheimer’s disease.

High affinity binding of amyloid β -peptide to calmodulin: Structural and functional implications

“…A binding affinity in the low nanomolar range has been calculated using surface plasmon resonance for Aβ1-42 interaction with the major intracellular target tau [27]. Noteworthy, the Aβ1-42 dissociation constant from Aβ-CaM complex is nearly identical to the reported dissociation constant of Aβ from PrP c [28], a cellular prion protein that has been proposed to mediate Aβ-induced synaptic dysfunction in the mouse brain [25], and also from glycogen synthase kinase 3α (GSK3α), a kinase that mediates hyperphosphorylation of tau and that it is stimulated in vitro by Aβ1-42 [29]. Alzheimer's disease modulated by calmodulin [8; 9; 11] and the major role of calmodulin-binding proteins in neuronal plasticity and activity [7; 8], it is likely that the interaction between Aβ and Ca 2+ /CaM will have major functional consequences for brain physiology.…”

Microtubule-associated protein tau is associated with the resistance to docetaxel in prostate cancer cell lines

“…Tau has been proved to play a significant role in Alzheimer’s disease 6. In addition, the abnormal expression of tau protein was previously reported in many cancers, and the role of tau in cancer treatment has also been reported by others, such as gastric carcinoma,13,14 breast cancer,12,15,16 and ovarian cancer 9,17…”

“…In the previous studies, tau can interact with Fyn and with Pin1 and both the interactions have been thought to be associated with Alzheimer’s disease 5. Moreover, direct interaction between Aβ42 and GSK3α facilitates hyperphosphorylation of tau and this mechanism may be a new molecular signaling link in Alzheimer’s disease 6. What’s more, in prostate cancer, overexpression of tau was markedly associated with lower Gleason score, indicating that tau may be a potential prognostic marker in prostate cancer 7.…”

Phage display and kinetic selection of antibodies that specifically inhibit amyloid self-replication

“…Previous studies have identified a series of microscopic steps in the process of aggregation that together contribute to the overall macroscopic kinetic profile of the reaction and have revealed the importance of the catalytic conversion of monomeric species into aggregates as a result of secondary nucleation on fibril surfaces. This process results in the production of neurotoxic oligomeric species (20,21) with distinct intracellular targets (29).…”