Role of polysaccharide and lipid in lipopolysaccharide induced prion protein conversion

Abstract

Conversion of native cellular prion protein (PrPc) from an α-helical structure to a toxic and infectious β-sheet structure (PrPSc) is a critical step in the development of prion disease. There are some indications that the formation of PrPSc is preceded by a β-sheet rich PrP (PrPβ) form which is non-infectious, but is an intermediate in the formation of infectious PrPSc. Furthermore the presence of lipid cofactors is thought to be critical in the formation of both intermediate-PrPβ and lethal, infectious PrPSc. We previously discovered that the endotoxin, lipopolysaccharide (LPS), interacts with recombinant PrPc and induces rapid conformational change to a β-sheet rich structure. This LPS induced PrPβ structure exhibits PrPSc-like features including proteinase K (PK) resistance and the capacity to form large oligomers and rod-like fibrils. LPS is a large, complex molecule with lipid, polysaccharide, 2-keto-3-deoxyoctonate (Kdo) and glucosamine components. To learn more about which LPS chemical constituents are critical for binding PrPc and inducing β-sheet conversion we systematically investigated which chemical components of LPS either bind or induce PrP conversion to PrPβ. We analyzed this PrP conversion using resolution enhanced native acidic gel electrophoresis (RENAGE), tryptophan fluorescence, circular dichroism, electron microscopy and PK resistance. Our results indicate that a minimal version of LPS (called detoxified and partially de-acylated LPS or dLPS) containing a portion of the polysaccharide and a portion of the lipid component is sufficient for PrP conversion. Lipid components, alone, and saccharide components, alone, are insufficient for conversion.

Effect of Tea Tree Oil on the Expression of Genes Involved in the Innate Immune System in Goat Rumen Epithelial Cells

“…Goats with SARA experience certain stressful states and increased free LPS in the rumen [ 6 , 7 ]. Higher levels of LPS in rumen fluid may lead to localized inflammation of rumen epithelium [ 8 ], while LPS induces innate immune response via Toll-like receptors (TLR) [ 9 ]. TLR-2 and TLR-4 are the major recognition receptors for LPS identified so far out of 10 Toll-like receptors [ 10 , 11 ].…”

A simple in vitro assay for assessing the efficacy, mechanisms and kinetics of anti-prion fibril compounds

“…Using RENAGE it is possible to rapidly separate and quantify PrP monomers, oligomers and fibrils [26]. Previously we showed that RENAGE can be used to analyze cell-free recombinant PrP conversion using urea, acidic pH, lipopolysaccharide (LPS) or detoxified LPS as the catalysts for prion conversion [25,26,28,29]. We also showed that RENAGE can be used detect or quantify the formation of β-sheet rich PrP oligomers and/or fibrils.…”

Bacterial Lipopolysaccharides and Neuron Toxicity in Neurodegenerative Diseases

“…Sirt 1's role in neuron death is now connected to cellular proteins ( Figure 1) such as heat shock protein (HSP), cellular prion protein (PrPc), alpha-synuclein and tau that are connected to Aβ aggregation [15][16][17][18][19][20][21][22][23] and accelerated neuron death. LPS represses Sirt 1 [13] with HSP involved in the regulation of PrPc and Aβ aggregation relevant to mitochondrial apoptosis and neuron death [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. The nuclear receptor Sirt 1's role on neuron survival/apoptosis via LPS is primary with effects of LPS secondary on CD14 regulation of TLR-4 mediated neuron apoptosis [7,[10][11][12].…”