Abstract
Prions are known to be involved in neurodegenerative pathologies such as Creutzfeld-Jakob disease. Current models point to a molecular event which rely on a transmissible structural change that leads to the production of β-sheet-rich prion conformer (PrPSc). PrPSc itself has the capability to trigger the structural rearrangement of the ubiquitously present prion (PrPc) substrate in a self-perpetuating cascade. In this article, we demonstrate that recombinant PrPc exists in a conformational equilibrium. The conformers’ abundances were shown to be dependent on PrPc concentration through the formation of transient multimers leading to conformational selection. The study of PrPc mutants that follow dedicated oligomerization pathways demonstrated that the conformers’ relative abundances are modified, thus reinforcing the assertion that the nature of conformers’ interactions orient the oligomerization pathways. Further this result can be viewed as the “signature” of an aborted oligomerization process. This discovery sheds a new light on the possible origin of prion protein diseases, namely that a change in prion protein structure could be transmitted through the formation of transient multimers having different conformer compositions. This could explain the selection of a transient multimeric type that could be viewed as the precursor of PrPSc responsible for structural information transmission, and strain apparition.
Highlights
A few analytical methods, such as NMR1 or molecular dynamic simulation[2] allow the study of the conformational landscape of proteins[1,2]
We observed that in size-exclusion chromatography (SEC) coupled to ion mobility and mass spectrometry (IMS-Mass spectrometry (MS)), the charge state distribution (CSD) of I208M mutant recorded under “native” conditions evolves within the chromatographic peak. Under these conditions the bimodal charge state distributions (CSD) (+5 - +7 and +8 - +16) shows changes in their respective charge states (CS) intensities with the observation of an increase in the (+8 - +16) CSD at the middle of the chromatographic peak while (+5 - +7) CSD is predominant on the front and tail edges
Litterature has shown that charge state distribution can be used as an indicator of the folded nature of a protein[8,21], this behavior could indicate a change in conformation in the course of the chromatographic peak elution
Summary
A few analytical methods, such as NMR1 or molecular dynamic simulation[2] allow the study of the conformational landscape of proteins[1,2] An alternative to these techniques relies on “native” electrospray ionization mass spectrometry that has become a valuable tool for the study of protein assemblies in the past years[3]. On ion mobility is a method of choice to describe the native conformational properties of proteins[4,5,6] This approach allowed the study of Syrian (golden) hamster prion protein (PrP) conformers[7] and more recently our group deeply described the ovine prion protein structural features[8]. This article will describe our initial observations as well as other “native” mass spectrometry experiments that confirm this hypothesis and demonstrate this effect both for wild-type (wt) Prion protein (PrP) monomer as for some mutants which have specific oligomerization pathways. Our data demonstrate that protein concentration affect the conformer family abundances for wild-type (wt) Prion protein monomer as well as for mutants leading to specific oligomerization pathways
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