A 7-kDa Prion Protein (PrP) Fragment, an Integral Component of the PrP Region Required for Infectivity, Is the Major Amyloid Protein in Gerstmann-Sträussler-Scheinker Disease A117V

Fabrizio Tagliavini,Patricia M.-J Lievens,Christine Tranchant,Jean-Marie Warter,Michel Mohr,Giorgio Giaccone,Francesco Perini,Giacomina Rossi,Mario Salmona,Pedro Piccardo,Bernardino Ghetti,Ronald C Beavis,Orso Bugiani,Blas Frangione,Frances Prelli

doi:10.1074/jbc.m007062200

Abstract

Gerstmann-Sträussler-Scheinker disease (GSS) is a cerebral amyloidosis associated with mutations in the prion protein (PrP) gene (PRNP). The aim of this study was to characterize amyloid peptides purified from brain tissue of a patient with the A117V mutation who was Met/Val heterozygous at codon 129, Val(129) being in coupling phase with mutant Val117. The major peptide extracted from amyloid fibrils was a approximately 7-kDa PrP fragment. Sequence analysis and mass spectrometry showed that this fragment had ragged N and C termini, starting mainly at Gly88 and Gly90 and ending with Arg148, Glu152, or Asn153. Only Val was present at positions 117 and 129, indicating that the amyloid protein originated from mutant PrP molecules. In addition to the approximately 7-kDa peptides, the amyloid fraction contained N- and C-terminal PrP fragments corresponding to residues 23-41, 191-205, and 217-228. Fibrillogenesis in vitro with synthetic peptides corresponding to PrP fragments extracted from brain tissue showed that peptide PrP-(85-148) readily assembled into amyloid fibrils. Peptide PrP-(191-205) also formed fibrillary structures although with different morphology, whereas peptides PrP-(23-41) and PrP-(217-228) did not. These findings suggest that the processing of mutant PrP isoforms associated with Gerstmann-Sträussler-Scheinker disease may occur extracellularly. It is conceivable that full-length PrP and/or large PrP peptides are deposited in the extracellular compartment, partially degraded by proteases and further digested by tissue endopeptidases, originating a approximately 7-kDa protease-resistant core that is similar in patients with different mutations. Furthermore, the present data suggest that C-terminal fragments of PrP may participate in amyloid formation.

Highlights

Gerstmann-Straussler-Scheinker disease (GSS) is a cerebral amyloidosis associated with mutations in the prion protein (PrP) gene (PRNP)
Previous studies showed that a common feature of GSS patients with different PRNP mutations is the presence of low molecular weight N- and C-terminal truncated PrP fragments [9, 32, 33]
These fragments can be detected in unprocessed brain homogenates, they are more prominent after proteinase K (PK) digestion, and their relative abundance is not dependent upon the amyloid burden [32]

Summary

Introduction

Gerstmann-Straussler-Scheinker disease (GSS) is a cerebral amyloidosis associated with mutations in the prion protein (PrP) gene (PRNP). The allelic origin of the altered forms of PrP involved in the pathologic process has been investigated in other genetic prion diseases including GSS P102L, fatal familial insomnia, and Creutzfeldt-Jakob disease (CJD) associated with point or insertional mutations (19 –23) These studies showed that only mutant PrP is detergent-insoluble and protease-resistant in GSS P102L [19, 20], fatal familial insomnia, and CJD D178N [21], whereas both the mutant and wild-type proteins have these properties in CJD V210I [22] and CJD with five or six extra copies of the octapeptide repeat [21]. The recruitment of the wild-type protein into the disease process may reflect the effects of conformational changes due to specific mutations, which allow interaction between mutant and normal PrP

Objectives

Results

Conclusion