Glypican-1 Mediates Both Prion Protein Lipid Raft Association and Disease Isoform Formation

PLoS Pathogens

David R. Taylor¹  Nigel M. Hooper¹  Isobel J. Whitehouse¹ 

[1]Proteolysis Research Group, Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, and Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds, United Kingdom

关键词: Small interfering RNAs;    Heparin;    Lipids;    Endocytosis;    Animal prion diseases;    Sulfates;    Immunoprecipitation;    Membrane proteins;   

DOI  :  10.1371/journal.ppat.1000666

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

In prion diseases, the cellular form of the prion protein, PrPC, undergoes a conformational conversion to the infectious isoform, PrPSc. PrPC associates with lipid rafts through its glycosyl-phosphatidylinositol (GPI) anchor and a region in its N-terminal domain which also binds to heparan sulfate proteoglycans (HSPGs). We show that heparin displaces PrPC from rafts and promotes its endocytosis, suggesting that heparin competes with an endogenous raft-resident HSPG for binding to PrPC. We then utilised a transmembrane-anchored form of PrP (PrP-TM), which is targeted to rafts solely by its N-terminal domain, to show that both heparin and phosphatidylinositol-specific phospholipase C can inhibit its association with detergent-resistant rafts, implying that a GPI-anchored HSPG targets PrPC to rafts. Depletion of the major neuronal GPI-anchored HSPG, glypican-1, significantly reduced the raft association of PrP-TM and displaced PrPC from rafts, promoting its endocytosis. Glypican-1 and PrPC colocalised on the cell surface and both PrPC and PrPSc co-immunoprecipitated with glypican-1. Critically, treatment of scrapie-infected N2a cells with glypican-1 siRNA significantly reduced PrPSc formation. In contrast, depletion of glypican-1 did not alter the inhibitory effect of PrPC on the β-secretase cleavage of the Alzheimer's amyloid precursor protein. These data indicate that glypican-1 is a novel cellular cofactor for prion conversion and we propose that it acts as a scaffold facilitating the interaction of PrPC and PrPSc in lipid rafts.

【 授权许可】

CC BY