chondroitin-sulfates and 1-palmitoyl-2-oleoylphosphatidylcholine

Glycosaminoglycans and serum albumin are important cellular components that regulate the fibril formation of proteins. Whereas the effects of cellular components on the fibrillation of amyloid proteins in bulk solution are widely studied, less attention has been paid to the effects of cellular components on amyloidogenesis occurring at cellular membranes. In this study, we focus on the impacts of chondroitin sulfate A (CSA) and bovine serum albumin (BSA) on the amyloidogenic behaviors of human islet amyloid polypeptide (hIAPP) at phospholipid membranes consisting of neutral POPC and anionic POPG. Using the thioflavin T fluorescence assay, atomic force microscopy, circular dichroism and nuclear magnetic resonance measurements, we demonstrate that CSA has an intensive promotion effect on the fibrillation of hIAPP at the POPC membrane, which is larger than the total effect of CSA alone and POPC alone. The further enhanced promotion of the fibrillation of hIAPP by CSA at the neutral membrane is associated with a specific interaction of CSA with POPC. In contrast, the activity of BSA as an inhibitor of hIAPP fibrillation observed in bulk solution decreases dramatically in the presence of POPG vesicles. The dramatic loss of the inhibition efficiency of BSA arises essentially from a specific interaction with the POPG component, but not simply from suppression by an opposite effect of the anionic membrane. The findings in this study suggest that the interactions between membranes and cellular components may have a significant effect on the activity of the cellular components in regulating the fibrillation of hIAPP.

Topics: Amyloid; Animals; Cattle; Chondroitin Sulfates; Humans; Islet Amyloid Polypeptide; Phosphatidylcholines; Phosphatidylglycerols; Phospholipids; Serum Albumin, Bovine; Unilamellar Liposomes

We have successfully synthesized a lipid containing the pyranine dye as the hydrophilic headgroup. This lipid was incorporated into liposomes with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine as the major component. The resultant liposomes displayed differential modulations in fluorescence emission intensity in the presence of nanomolar concentrations of different glycosaminoglycans. Linear discriminant analysis of the fluorescence response data demonstrate that the liposomes are able to distinguish between different GAGs. In addition, we also demonstrate that the liposomes incorporating the pyranine lipid are able to distinguish between dilute serum from healthy individuals and serum containing elevated chondroitin sulfate (simulated serum from an Alzheimer's disease patient).

Topics: Arylsulfonates; Chondroitin Sulfates; Discriminant Analysis; Fluorescent Dyes; Glycosaminoglycans; Humans; Liposomes; Phosphatidylcholines; Spectrometry, Fluorescence