title: Endogenous Brain Lipids Inhibit Prion Amyloid FormationIn Vitro.
abstract: The normal cellular prion protein (PrPC) resides in detergent-resistant outer membrane lipid rafts in which conversion to the pathogenic misfolded form is believed to occur. Once misfolding occurs, the pathogenic isoform polymerizes into highly stable amyloid fibrils.In vitroassays have demonstrated an intimate association between prion conversion and lipids, specifically phosphatidylethanolamine, which is a critical cofactor in the formation of synthetic infectious prions. In the current work, we demonstrate an alternative inhibitory function of lipids in the prion conversion process as assessedin vitroby real-time quaking-induced conversion (RT-QuIC). Using an alcohol-based extraction technique, we removed the lipid content from chronic wasting disease (CWD)-infected white-tailed deer brain homogenates and found that lipid extraction enabled RT-QuIC detection of CWD prions in a 2-log10-greater concentration of brain sample. Conversely, addition of brain-derived lipid extracts to CWD prion brain or lymph node samples inhibited amyloid formation in a dose-dependent manner. Subsequent lipid analysis demonstrated that this inhibitory function was restricted to the polar lipid fraction in brain. We further investigated three phospholipids commonly found in lipid membranes, phosphatidylethanolamine, phosphatidylcholine, and phosphatidylinositol, and found all three similarly inhibited RT-QuIC. These results demonstrating polar-lipid, and specifically phospholipid, inhibition of prion-seeded amyloid formation highlight the diverse roles lipid constituents may play in the prion conversion process.IMPORTANCEPrion conversion is likely influenced by lipid interactions, given the location of normal prion protein (PrPC) in lipid rafts and lipid cofactors generating infectious prions inin vitromodels. Here, we use real-time quaking-induced conversion (RT-QuIC) to demonstrate that endogenous brain polar lipids can inhibit prion-seeded amyloid formation, suggesting that prion conversion is guided by an environment of proconversion and anticonversion lipids. These experiments also highlight the applicability of RT-QuIC to identify potential therapeutic inhibitors of prion conversion.
authors.affiliation: Prion Research Center, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Clare E
authors.initials: CE
authors.lastname: Hoover
authors.affiliation: Prion Research Center, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Kristen A
authors.initials: KA
authors.lastname: Davenport
authors.affiliation: Prion Research Center, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Davin M
authors.initials: DM
authors.lastname: Henderson
authors.affiliation: Prion Research Center, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Zabel
authors.affiliation: Prion Research Center, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA edward.hoover@colostate.edu.
authors.forename: Edward A
authors.initials: EA
authors.lastname: Hoover
mesh_terms: D000682:Amyloid / Q000378:metabolism*; D000686:Amyloidosis / Q000473:pathology*; D000818:Animals; D001921:Brain / Q000473:pathology*; D002462:Cell Membrane / Q000378:metabolism; D003670:Deer; D010713:Phosphatidylcholines / Q000378:metabolism*; D010714:Phosphatidylethanolamines / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*; D018621:PrPC Proteins / Q000378:metabolism*; D017510:Protein Folding; D034081:Wasting Disease, Chronic / Q000473:pathology*
chemical_list: D000682:Amyloid; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010716:Phosphatidylinositols; D018621:PrPC Proteins; C483858:phosphatidylethanolamine
keywords: prions; real-time quaking-induced conversion