Membrane Environment Alters the Conformational Structure of the Recombinant Human Prion Protein

Manuel Morillas,Wieslaw Swietnicki,Pierluigi Gambetti,Witold K Surewicz

doi:10.1074/jbc.274.52.36859

Manuel Morillas, Wieslaw Swietnicki + Show 2 more

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https://doi.org/10.1074/jbc.274.52.36859

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Abstract

The prion protein (PrP) in a living cell is associated with cellular membranes. However, all previous biophysical studies with the recombinant prion protein have been performed in an aqueous solution. To determine the effect of a membrane environment on the conformational structure of PrP, we studied the interaction of the recombinant human prion protein with model lipid membranes. The protein was found to bind to acidic lipid-containing membrane vesicles. This interaction is pH-dependent and becomes particularly strong under acidic conditions. Spectroscopic data show that membrane binding of PrP results in a significant ordering of the N-terminal part of the molecule. The folded C-terminal domain, on the other hand, becomes destabilized upon binding to the membrane surface, especially at low pH. Overall, these results show that the conformational structure and stability of the recombinant human PrP in a membrane environment are substantially different from those of the free protein in solution. These observations have important implications for understanding the mechanism of the conversion between the normal (PrP(C)) and pathogenic (PrP(Sc)) forms of prion protein.

Highlights

Prion diseases, known as spongiform encephalopathies, are fatal neurodegenerative diseases that can be sporadic, genetically determined, or acquired by infection [1,2,3]
It is believed that the conversion of PrPC into PrPSc constitutes the key molecular event in the pathogenesis of prion diseases
A critical limitation of all these studies is that they have been performed in an aqueous solution, whereas PrPC in a living cell is associated with cellular membranes [24]

Summary

Introduction

Known as spongiform encephalopathies, are fatal neurodegenerative diseases that can be sporadic, genetically determined, or acquired by infection [1,2,3]. PrPC is monomeric and readily degradable by proteinase K, whereas PrPSc forms highly insoluble aggregates and shows a remarkable resistance to proteolytic digestion [6, 7] These characteristics most likely reflect different conformations of the two protein isoforms. To bridge the gap between the cellular studies with the authentic PrPC and the experiments with the recombinant PrP in an aqueous solution, we have characterized the biophysical properties of the recombinant prion protein associated with model lipid membranes. We provide evidence that the membrane environment strongly affects, in a pH-dependent manner, the conformational structure and stability of the protein These findings have important implications for understanding the conversion of PrPC to PrPSc

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