Mechanism Of Lipid Regulating Amyloid Fibrosis

The misfolding of amyloid is related to the pathogenesis of many neurodegenerative diseases.For example,Aβ protein may undergo misfolding,aggregation and fibrosis in the body,leading to the formation of amyloid plaques,which will cause toxicity to neurons and cause neurons in the cerebral cortex to degenerate,thereby causing Alzheimer’s disease(AD).There is evidence that the deposition of amyloid in the body is highly related to the structure of various biofilms,and small-sized synaptic vesicles and extracellular vesicles can not be ignored.However,how the characteristic lipid components and physicochemical properties of this type of biofilm structure mediate this process remains to be fully studied.In response to the above problems,we take Aβ(1-42)amyloid,the key protein that causes Alzheimer’s disease,as our research object.By establishing contains ganglioside(this),the sphingomyelin(SM),cholesterol(Chol),and other key neuronal membrane lipid vesicles model,system research the vesicle lipid constituents and lipid membrane curvature of Aβ(1-42)protein conformation changes and fibrosis of dynamics,the influence of the proposed lipid vesicles regulating mechanism of amyloid fibrosis.The specific research content is as follows:(1)Multicomponent lipid vesicles with uniform particle size and good dispersion were prepared by ultrasonic and extrusion methods.It is confirmed by particle size characterization that the addition of cholesterol and ganglioside can promote the fusion of vesicles and widen the distribution of vesicles and increase the particle size.By changing the particle size of the extruded filter membrane,lipid vesicles with different sizes,that is,different curvatures can be prepared.Atomic force microscope was used to characterize the morphology of the constructed lipid interface.A large number of GM1 clusters were found on the GM1/Chol/SM lipid interface,while few similar ones were observed on the Chol/SM,SM,and Chol interfaces.structure.The results show that due to the interaction between the GM1 head groups,GM1 molecules fuse with each other,resulting in phase separation on the lipid membrane(SLB).(2)The effects of GM1/Chol/SM ternary lipid vesicles on the conformational changes and fibrosis dynamics of Aβ(1-42)protein were systematically analyzed.We found that the GM1 component in vesicles can regulate the fibrosis process of Aβprotein by promoting Aβ(1-42)conformational transition to β-sheet structure.In addition,vesicles containing GM1 can induce the formation of Aβ(1-42)fibrils at low concentrations and cause toxicity to nerve cells.Using single-molecule fluorescence tracer technology to explain the role of GM1 in this lipid membrane structure at the molecular level,it was further confirmed that the GM1 cluster can be used as a protein attachment site to promote the aggregation behavior of Aβ(1-42).(3)The effects of lipid vesicles with different curvatures on the fibrosis of Aβ(1-42)were investigated.The results show that for both ternary GM1/Chol/SM lipid vesicles and binary Chol/SM lipid vesicles,the membrane curvature has a significant effect on the fibrosis process of Aβ(1-42).Among them,when the curvature of the vesicle membrane is large,it can significantly shorten the lag time and accelerate the growth of fibrils.As the curvature of the film decreases,the promoting effect on the fibrosis process gradually weakens,and even the suppressing effect is produced.It is shown that the uneven accumulation of lipid bilayers in vesicles with high membrane curvature can induce the formation of polymorphic amyloid;while vesicles with low membrane curvature have reduced defects and reduced affinity,preventing amyloid nucleation,thereby inhibiting the fibrosis process.