title: Mutant prion protein expression is associated with an alteration of the Rab GDP dissociation inhibitor alpha (GDI)/Rab11 pathway.
abstract: The prion protein (PrP) is a glycosylphosphatidylinositol-anchored membrane glycoprotein that plays a vital role in prion diseases, a class of fatal neurodegenerative disorders of humans and animals. Approximately 20% of human prion diseases display autosomal dominant inheritance and are linked to mutations in the PrP gene on chromosome 20. PrP mutations are thought to favor the conformational conversion of PrP into a misfolded isoform that causes disease by an unknown mechanism. The PrP mutation D178N/Met-129 is linked to fatal familial insomnia, which causes severe sleep abnormalities and autonomic dysfunction. We showed by immunoelectron microscopy that this mutant PrP accumulates abnormally in the endoplasmic reticulum and Golgi of transfected neuroblastoma N2a cells. To investigate the impact of intracellular PrP accumulation on cellular homeostasis, we did a two-dimensional gel-based differential proteomics analysis. We used wide range immobilized pH gradient strips, pH 4-7 and 6-11, to analyze a large number of proteins. We found changes in proteins involved in energy metabolism, redox regulation, and vesicular transport. Rab GDP dissociation inhibitor alpha (GDI) was one of the proteins that changed most. GDI regulates vesicular protein trafficking by acting on the activity of several Rab proteins. We found a specific reduction in the level of functional Rab11 in mutant PrP-expressing cells associated with impaired post-Golgi trafficking. Our data are consistent with a model by which mutant PrP induces overexpression of GDI, activating a cytotoxic feedback loop that leads to protein accumulation in the secretory pathway.
authors.affiliation: Dulbecco Telethon Institute (DTI) c/o Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
authors.forename: Tania
authors.initials: T
authors.lastname: Massignan
authors.forename: Emiliano
authors.initials: E
authors.lastname: Biasini
authors.forename: Eliana
authors.initials: E
authors.lastname: Lauranzano
authors.forename: Pietro
authors.initials: P
authors.lastname: Veglianese
authors.forename: Mauro
authors.initials: M
authors.lastname: Pignataro
authors.forename: Luana
authors.initials: L
authors.lastname: Fioriti
authors.forename: David A
authors.initials: DA
authors.lastname: Harris
authors.forename: Mario
authors.initials: M
authors.lastname: Salmona
authors.forename: Roberto
authors.initials: R
authors.lastname: Chiesa
authors.forename: Valentina
authors.initials: V
authors.lastname: Bonetto
mesh_terms: D000818:Animals; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D051379:Mice; D050505:Mutant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D011328:Prions / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D021381:Protein Transport / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D040901:Proteomics; D034741:RNA, Small Interfering / Q000494:pharmacology; D055571:Secretory Pathway / Q000187:drug effects / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D014407:Tumor Cells, Cultured; D020691:rab GTP-Binding Proteins / Q000378:metabolism* / Q000502:physiology; D000099193:rab11 GTP-Binding Proteins
chemical_list: D020730:Guanine Nucleotide Dissociation Inhibitors; D050505:Mutant Proteins; D011328:Prions; D034741:RNA, Small Interfering; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C086796:GDP dissociation inhibitor 1