title: Interaction between Shadoo and PrP Affects the PrP-Folding Pathway.
abstract: Prion diseases are characterized by conformational changes of a cellular prion protein (PrP(C)) into a β-sheet-enriched and aggregated conformer (PrP(Sc)). Shadoo (Sho), a member of the prion protein family, is expressed in the central nervous system (CNS) and is highly conserved among vertebrates. On the basis of histoanatomical colocalization and sequence similarities, it is suspected that Sho and PrP may be functionally related. The downregulation of Sho expression during prion pathology and the direct interaction between Sho and PrP, as revealed by two-hybrid analysis, suggest a relationship between Sho and prion replication. Using biochemical and biophysical approaches, we demonstrate that Sho forms a 1:1 complex with full-length PrP with a dissociation constant in the micromolar range, and this interaction consequently modifies the PrP-folding pathway. Using a truncated PrP that mimics the C-terminal C1 fragment, an allosteric binding behavior with a Hill number of 4 was observed, suggesting that at least a tetramerization state occurs. A cell-based prion titration assay performed with different concentrations of Sho revealed an increase in the PrP(Sc) conversion rate in the presence of Sho. Collectively, our observations suggest that Sho can affect the prion replication process by (i) acting as a holdase and (ii) interfering with the dominant-negative inhibitor effect of the C1 fragment.
  
  
  OBJECTIVE
  Since the inception of the prion theory, the search for a cofactor involved in the conversion process has been an active field of research. Although the PrP interactome presents a broad landscape, candidates corresponding to specific criteria for cofactors are currently missing. Here, we describe for the first time that Sho can affect PrP structural dynamics and therefore increase the prion conversion rate. A biochemical characterization of Sho-PrP indicates that Sho acts as an ATP-independent holdase.
authors: National Institute for Agricultural Research (INRA), Pathological Macro-Assemblies and Prion Pathology Group (MAP), UR892, Virologie Immunologie Moléculaires, Jouy-en-Josas, France.
authors: Danica
authors: D
authors: Ciric
authors: National Institute for Agricultural Research (INRA), Pathological Macro-Assemblies and Prion Pathology Group (MAP), UR892, Virologie Immunologie Moléculaires, Jouy-en-Josas, France.
authors: Charles-Adrien
authors: CA
authors: Richard
authors: National Institute for Agricultural Research (INRA), Pathological Macro-Assemblies and Prion Pathology Group (MAP), UR892, Virologie Immunologie Moléculaires, Jouy-en-Josas, France.
authors: Mohammed
authors: M
authors: Moudjou
authors: National Institute for Agricultural Research (INRA), Pathological Macro-Assemblies and Prion Pathology Group (MAP), UR892, Virologie Immunologie Moléculaires, Jouy-en-Josas, France.
authors: Jérôme
authors: J
authors: Chapuis
authors: National Institute for Agricultural Research (INRA), Pathological Macro-Assemblies and Prion Pathology Group (MAP), UR892, Virologie Immunologie Moléculaires, Jouy-en-Josas, France.
authors: Pierre
authors: P
authors: Sibille
authors: University of Alberta, Centre for Prion and Protein Folding Diseases, Research in Neurodegenerative Diseases, Edmonton, AB, Canada.
authors: Nathalie
authors: N
authors: Daude
authors: University of Alberta, Centre for Prion and Protein Folding Diseases, Research in Neurodegenerative Diseases, Edmonton, AB, Canada.
authors: David
authors: D
authors: Westaway
authors: Institut Universitari d'Investigació en Ciències de la Salut (IUNICS), Departament de Química, Universitat de les Illes Balears, Palma de Mallorca, Spain.
authors: Miguel
authors: M
authors: Adrover
authors: National Institute for Agricultural Research (INRA), Pathological Macro-Assemblies and Prion Pathology Group (MAP), UR892, Virologie Immunologie Moléculaires, Jouy-en-Josas, France.
authors: Vincent
authors: V
authors: Béringue
authors: National Institute for Agricultural Research (INRA), Pathological Macro-Assemblies and Prion Pathology Group (MAP), UR892, Virologie Immunologie Moléculaires, Jouy-en-Josas, France davy.martin@jouy.inra.fr human.rezaei@jouy.inra.fr.
authors: Davy
authors: D
authors: Martin
authors: National Institute for Agricultural Research (INRA), Pathological Macro-Assemblies and Prion Pathology Group (MAP), UR892, Virologie Immunologie Moléculaires, Jouy-en-Josas, France davy.martin@jouy.inra.fr human.rezaei@jouy.inra.fr.
authors: Human
authors: H
authors: Rezaei
mesh_terms: D000818:Animals; D058851:GPI-Linked Proteins; D051379:Mice; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D011328:Prions / Q000378:metabolism*; D011485:Protein Binding; D017510:Protein Folding; D055503:Protein Multimerization; D020798:Two-Hybrid System Techniques
chemical_list: D058851:GPI-Linked Proteins; D009419:Nerve Tissue Proteins; D011328:Prions; C523856:Sprn protein, mouse