Mutations Alter RNA-Mediated Conversion of Human Prions

Abstract

Prion diseases are connected with self-replication and self-propagation of misfolded proteins. The rate-limiting factor is the formation of the initial seed. We have recently studied the early stages in the conversion between functional PrPC and the infectious scrapie PrPSC form, triggered by the binding of RNA. Here, we study how this process is modulated by the prion sequence. We focus on residues 129 and 178, which are connected to the hereditary neurodegenerative disease fatal familial insomnia.

pH-Induced Misfolding Mechanism of Prion Protein: Insights from Microsecond-Accelerated Molecular Dynamics Simulations

“…Similarly, Bjorndahl et al have also reported that the N- and C-termini of α2 are the first regions to experience conformational conversion upon a reduction in pH by using NMR spectroscopy and other biophysical techniques. Except for the large structural change of the α2 C-terminus, we also observed that α1 in AMD1 and AMD6 is partially unfolded, indicating that α1 may also play an important role in the pH-induced PrP misfolding, since previous studies have shown that α1 can act as a gate-keeper , by preventing the α2-α3 subdomain from becoming hydrated, and it tends to unravel under the RNA-induced PrP misfolding. , Meanwhile, as we observed in run 3, we also find that in the trajectories AMD2 and AMD4, typical β-structures are newly formed at the β2-α2 loop, which was not observed in the works of Kamp/Daggett. , This finding further supports that the β2-α2 loop can also serve as an important site for PrP misfolding, since single residue substitution of this region in mouse PrP Sc can reduce or prevent prion conversion in vitro. , …”

Early Stages of RNA-Mediated Conversion of Human Prions

“…The 10 highest scoring docked systems for each of the four targets were collected and examined for common regions of protein–RNA interaction. As in our previous studies , we found three main binding sites: binding site 1 (residues 21–31), binding site 2 (residues 111–121), and binding site 3 (residues 144–155). For the wild type 129M-178D and the mutant 129V-178N, all three binding sites were found, while in the wild-type variant 129V-178D binding site 3 is lost, and in the mutant 129M-178N the binding sites 1 and 2 are lost.…”

“…The four variants of human prions are simulated both with and without presence of poly-A-RNA, i.e., eight different systems. While connecting in this way to our earlier work, the use the coarse-grained simulations allows us to cover 600 μs, i.e., a time span that is 2000 times longer than the one considered by us in ref . Comparing the various systems, we find that both the D178N mutation and interacting with polyadenosine RNA reduce the helicity of the protein and encourage formation of transient β-strands.As was already conjectured in earlier studies, , such strands are likely the seed for the conversion into the β-sheet-rich PrP SC form.…”

“…Nucleation of the initial seed may also be enhanced by environmental conditions or interaction with other molecules. For instance, various studies by us and other groups point to the possibility that polyadenosine RNA (poly-A-RNA) catalyzes conversion of the native PrP C form into PrP SC . − …”

Melatonin: Regulation of Prion Protein Phase Separation in Cancer Multidrug Resistance

“…PrP C replication environment depleted of RNA gave rise to a completely new strain of PrP Sc without changing PrP primary structure [ 278 ]. Mutations in residues can increase binding of RNA to specific sites in PrP C , facilitating the formation of a pincer motif that leads to the decay of the N-terminal α-helix, which is a requisite step in the hastened conversion of PrP C to the toxic, infectious PrP Sc isoform [ 279 , 280 ]. Experimental studies showed that mutant peptides may exhibit greater resistance to cancer drugs such as cisplatin as a result of weakened adduct binding affinity.…”