| A predominant modern theory links Alzheimer's disease (AD)-related neurotoxicity to early-stage amyloid beta (Aβ) oligomers rather than mature Aβ fibers and plaques. It is believed that the process of Aβ fibrillization dictates Aβ toxicity, and that in vivo cofactors which mediate the kinetics of Aβ aggregation play a critical role in AD pathogenesis. As a potential modulator of Aβ aggregation, the effects of platelet surface receptor glycoprotein Ib alpha (GPIbα) on Aβ fibrillization were investigated. Time course thioflavin-T (ThT) fluorometry demonstrated that GPIb2V—a fully-sulfated GPIbα variant with platelet-type von Willebrand disease (Pt-vWD) mutations—dramatically enhanced Aβ fibrillization. Subsequent ThT studies indicated that the Pt-vWD mutations instigated Aβ aggregation, implying an interaction similar to that between GPIb2V and von Willebrand Factor (vWF). Bis-ANS fluorometry and far-UV circular dichroism showed that GPIb2V reduced the duration of Aβ oligomerization. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and size exclusion chromatography (SEC) demonstrated that Aβ aggregates and low molecular mass Aβ respectively appear and disappear more rapidly in the presence of GPIb2V, and that the latter co-aggregates with Aβ. Multiangle laser light scattering (MALLS) confirmed that Aβ aggregates observed on SEC were fibrillar in nature. A preliminary cell-based cytotoxicity assay suggested that GPIb2V alleviated Aβ neurotoxicity. These results revealed a potential link between this intrinsic "cardiovascular" protein and AD pathology. |
