Formation of Toxic Fibrils of Alzheimer’s Amyloid β-Protein-(1–40) by Monosialoganglioside GM1, a Neuronal Membrane Component

A pathological hallmark of Alzheimer's disease (AD) is the deposition of amyloid β-protein (Aβ) in fibrillar form on neuronal cells. However, the role of Aβ fibrils in neuronal dysfunction is highly controversial. This study demonstrates that monosialoganglioside GM1 (GM1) released from damaged neurons catalyzes the formation of Aβ fibrils, the toxicity and the cell affinity of which are much stronger than those of Aβ fibrils formed in phosphate-buffered saline. Aβ-(1–40) was incubated with equimolar GM1 at 37 °C. After a lag period of 6–12 h, amyloid fibrils were formed, as confirmed by circular dichroism, thioflavin-T fluorescence, size-exclusion chromatography, and transmission electron microscopy. The fibrils showed significant cytotoxicity against PC12 cells differentiated with nerve growth factor. Trisialoganglioside GT1b also facilitated the fibrillization, although the effect was weaker than that of GM1. Our study suggests an exacerbation mechanism of AD and an importance of polymorphisms in Aβ fibrils during the pathogenesis of the disease.