Mutant Prion Protein Expression Is Associated with an Alteration of the Rab GDP Dissociation Inhibitor α (GDI)/Rab11 Pathway

Abstract

The prion protein (PrP) is a glycosylphosphatidylinositolanchored 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 ␣ (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. Molecular & Cellular Proteomics 9:611-622, 2010.

Expression of Mutant or Cytosolic PrP in Transgenic Mice and Cells Is Not Associated with Endoplasmic Reticulum Stress or Proteasome Dysfunction

“…Alternatively, intracellular aggregation of mutant PrP might interfere with vesicular traffic impairing delivery of essential cargo molecules to synapses. We did in fact find that D177N PrP expression in N2a cells is associated with an alteration of the GDI/Rab11 pathway governing post-Golgi vesicular traffic [66]. Finally, PG14 and D177N PrP misfolding may affect calcium homeostasis ([67] and A. Senatore and R.C.…”

Mutant PrP Suppresses Glutamatergic Neurotransmission in Cerebellar Granule Neurons by Impairing Membrane Delivery of VGCC α2δ-1 Subunit

“…PrP may participate in cell signaling governing membrane protein transport (Málaga-Trillo et al., 2009) that could be altered by pathogenic mutations. We did in fact find that cells expressing D177N PrP had an impairment in Rab11-dependent trafficking (Massignan et al., 2010), which could potentially affect the endocytic recycling of α 2 δ-1 (Tran-Van-Minh and Dolphin, 2010). …”

Proteomic consequences of expression and pathological conversion of the prion protein in inducible neuroblastoma N2a cells

“…Few proteomics studies have been made in cultured cells for investigating molecular pathogenesis of prion disorders. [5][6][7][8] Proteomic differential protein expression analysis represents however an interesting approach that could complete previous genomic studies. [9][10][11][12] In this article we performed a proteomic investigation in an integrated cellular model where both differential PrP C expression and conversion could be obtained.…”