Substitutions of PrP N-terminal histidine residues modulate scrapie disease pathogenesis and incubation time in transgenic mice

Abstract

Prion diseases have been linked to impaired copper homeostasis and copper induced-oxidative damage to the brain. Divalent metal ions, such as Cu2+ and Zn2+, bind to cellular prion protein (PrPC) at octapeptide repeat (OR) and non-OR sites within the N-terminal half of the protein but information on the impact of such binding on conversion to the misfolded isoform often derives from studies using either OR and non-OR peptides or bacterially-expressed recombinant PrP. Here we created new transgenic mouse lines expressing PrP with disrupted copper binding sites within all four histidine-containing OR's (sites 1–4, H60G, H68G, H76G, H84G, "TetraH>G" allele) or at site 5 (composed of residues His-95 and His-110; "H95G" allele) and monitored the formation of misfolded PrP in vivo. Novel transgenic mice expressing PrP(TetraH>G) at levels comparable to wild-type (wt) controls were susceptible to mouse-adapted scrapie strain RML but showed significantly prolonged incubation times. In contrast, amino acid replacement at residue 95 accelerated disease progression in corresponding PrP(H95G) mice. Neuropathological lesions in terminally ill transgenic mice were similar to scrapie-infected wt controls, but less severe. The pattern of PrPSc deposition, however, was not synaptic as seen in wt animals, but instead dense globular plaque-like accumulations of PrPSc in TgPrP(TetraH>G) mice and diffuse PrPSc deposition in (TgPrP(H95G) mice), were observed throughout all brain sections. We conclude that OR and site 5 histidine substitutions have divergent phenotypic impacts and that cis interactions between the OR region and the site 5 region modulate pathogenic outcomes by affecting the PrP globular domain.

Strain-Dependent Prion Infection in Mice Expressing Prion Protein with Deletion of Central Residues 91–106

“…Therefore, it is possible that residues 91–106 play an important role in the structural integrity of PrP C . Furthermore, the substitution of copper-binding histidine (H) residue to glycine (G) residue at position 95 in mouse PrP was reported to accelerate prion disease in mice after infection with RML prions [ 28 ], suggesting that copper-binding at H95 might also structurally stabilize PrP C and thereby play an inhibitory role in the conversion of PrP C into PrP Sc .…”

Deciphering copper coordination in the animal prion protein amyloidogenic domain

“…Given the known importance of the region from residues 90 to 231 for prion formation and the proximity of the non-OR region to the palindromic amyloidogenic motif, different studies have addressed the question whether Cu(II)-bound non-OR region has a role in prion generation and disease onset. A recent report showed that transgenic mice, TgPrP(H95G), with an amino acid replacement at residue H96 had shorter disease progression than WT control mice and classical clinical signs of TSE (51). We observed that alteration of Cu(II) coordination due to H96Y mutation causes spontaneous PrP Sc -like formation in neuronal cultured cells and accumulation in the acid compartments (21).…”

N-Terminal Regions of Prion Protein: Functions and Roles in Prion Diseases

“…In contrast, Tg(PrPΔOR)/ Prnp 0/0 mice remained susceptible to RML and 22L scrapie prions, developing the disease without elongated incubation times with slightly less PrP Sc ΔOR in their brains after infection with RML and 22L prions ( Table 2 ) [ 70 ], suggesting that the OR region might be involved in prion pathogenesis in a strain-dependent manner. However, Prnp 0/0 mice expressing PrP with histidine residues in the OR region replaced by glycine residues, termed PrP(TetraH>G), showed significantly prolonged incubation times after infection with RML prions ( Table 2 ) [ 76 ]. Further studies are needed to clarify whether or not the OR region might mediate strain-dependent prion pathogenesis.…”

“…Copper binding to recombinant mouse PrP was reported to cause novel intramolecular interactions, including those between the N-terminal residues 90–120 and the C-terminal residues 144–147 and its nearby residues 139–143, and between the N-terminal region comprising the OR region and the C-terminal residues 174–185 [ 92 ], suggesting that copper binding might also be involved in the unfolding of PrP C . Copper is able to bind to histidine residues located in the OR and post-OR regions [ 76 ]. We have shown that, while Tg(PrP∆OR)/ Prnp 0/0 mice were highly resistant to BSE prions, they still remained susceptible to RML and 22L prions [ 70 ], suggesting that copper binding to histidine residues in the OR region might be irrelevant to the unfolding of PrP C .…”