Journal: PLoS Pathogens
Article Title: Glypican-1 Mediates Both Prion Protein Lipid Raft Association and Disease Isoform Formation
Figure Lengend Snippet: Heparin stimulates the endocytosis of PrP C in a dose-dependent manner and displaces it from detergent-resistant lipid rafts. ( A ) SH-SY5Y cells expressing PrP C were surface biotinylated and then incubated for 1 h at 37°C in the absence or presence of various concentrations of heparin diluted in OptiMEM. Prior to lysis cells were, where indicated, incubated with trypsin to digest cell surface PrP C . Cells were then lysed and PrP C immunoprecipitated from the sample using antibody 3F4. Samples were subjected to SDS PAGE and western blot analysis and the biotin-labelled PrP C detected with peroxidase-conjugated streptavidin. ( B ) Densitometric analysis of multiple blots from four separate experiments as described in (A) is shown. ( C ) SH-SY5Y cells expressing PrP C were surface biotinylated and then incubated in the absence or presence of 50 µM heparin prepared in OptiMEM for 1 h at 37°C. Cells were homogenised in the presence of 1% (v/v) Triton X-100 and subjected to buoyant sucrose density gradient centrifugation. PrP C was immunoprecipitated from equal volumes of each gradient fraction using 3F4 and subjected to SDS-PAGE and western blotting. The gradient fractions from both the untreated and heparin treated cells were analysed on the same SDS gel and immunoblotted under identical conditions. The biotin-labelled PrP C was detected with peroxidase-conjugated streptavidin. Flotillin-1 and transferrin receptor (TfR) were detected by immunoblotting as markers for DRM and detergent-soluble fractions, respectively. ( D ) Densitometric analysis of the proportion of total PrP C in the detergent soluble fractions of the plasma membrane. ( E ) Untransfected SH-SY5Y cells and SH-SY5Y cells expressing either PrP C or PrP-TM were grown to confluence and then incubated for 1 h in the presence or absence of 50 µM heparin prepared in OptiMEM. Media samples were collected and concentrated and cells harvested and lysed. Cell lysate samples were immunoblotted for PrP C using antibody 3F4, with β-actin used as a loading control. ( F ) Quantification of PrP C and PrP-TM levels after treatment of cells with heparin as in (E). Experiments were performed in triplicate and repeated on three occasions. * P
Article Snippet: Unless indicated otherwise, pelleted cells were lysed in ice cold lysis buffer (150 mM NaCl, 0.5% (v/v) Triton X-100, 0.5% (w/v) sodium deoxycholate, 50 mM Tris-HCl, pH 7.5) supplemented with a complete protease inhibitor cocktail (Roche Applied Science, Burgess Hill, U.K).
Techniques: Expressing, Incubation, Lysis, Immunoprecipitation, SDS Page, Western Blot, Gradient Centrifugation, SDS-Gel