Association Study of the M132L Single Nucleotide Polymorphism With Susceptibility to Chronic Wasting Disease in Korean Elk: A Meta-Analysis

Chronic wasting disease (CWD) is a deleterious brain proteinopathy caused by a pathogenic form of prion protein (PrPSc), which is converted from a benign form of prion protein (PrPC) encoded by the prion protein gene (PRNP). In elk, the M132L single nucleotide polymorphism (SNP) of the PRNP gene likely plays a pivotal role in susceptibility to CWD. However, the association of the M132L SNP with susceptibility to CWD has not been evaluated in Korean elk to date. To estimate the association of the M132L SNP with susceptibility to CWD in Korean elk, we investigated the genotype and allele frequencies of the M132L SNP by amplicon sequencing and performed association analysis between CWD-positive and CWD-negative elk. In addition, we performed a meta-analysis to evaluate the association between the M132L SNP and susceptibility to CWD in quantitatively synthesized elk populations. Furthermore, we estimated the effect of the M132L SNP on elk PrP using in silico programs, including PolyPhen-2, PROVEAN, AMYCO and Swiss-PdbViewer. We did not identify a significant association between the M132L SNP of PRNP and susceptibility to CWD in Korean elk. The meta-analysis also did not identify a strong association between the M132L SNP of PRNP and susceptibility to CWD in quantitatively synthesized elk populations. Furthermore, we did not observe significant changes in structure, amyloid propensity or electrostatic potential based on the M132L SNP in elk PrP. To the best of our knowledge, this was the first report of an association analysis and meta-analysis in Korean elk and quantitatively synthesized elk populations, respectively.

Analysis of co-isogenic prion protein deficient mice reveals behavioral deficits, learning impairment, and enhanced hippocampal excitability

Background Cellular prion protein (PrPC) is a cell surface GPI-anchored protein, usually known for its role in the pathogenesis of human and animal prionopathies. However, increasing knowledge about the participation of PrPC in prion pathogenesis contrasts with puzzling data regarding its natural physiological role. PrPC is expressed in a number of tissues, including at high levels in the nervous system, especially in neurons and glial cells, and while previous studies have established a neuroprotective role, conflicting evidence for a synaptic function has revealed both reduced and enhanced long-term potentiation, and variable observations on memory, learning, and behavior. Such evidence has been confounded by the absence of an appropriate knock-out mouse model to dissect the biological relevance of PrPC, with some functions recently shown to be misattributed to PrPC due to the presence of genetic artifacts in mouse models. Here we elucidate the role of PrPC in the hippocampal circuitry and its related functions, such as learning and memory, using a recently available strictly co-isogenic Prnp0/0 mouse model (PrnpZH3/ZH3). Results We performed behavioral and operant conditioning tests to evaluate memory and learning capabilities, with results showing decreased motility, impaired operant conditioning learning, and anxiety-related behavior in PrnpZH3/ZH3 animals. We also carried in vivo electrophysiological recordings on CA3-CA1 synapses in living behaving mice and monitored spontaneous neuronal firing and network formation in primary neuronal cultures of PrnpZH3/ZH3 vs wildtype mice. PrPC absence enhanced susceptibility to high-intensity stimulations and kainate-induced seizures. However, long-term potentiation (LTP) was not enhanced in the PrnpZH3/ZH3 hippocampus. In addition, we observed a delay in neuronal maturation and network formation in PrnpZH3/ZH3 cultures. Conclusion Our results demonstrate that PrPC promotes neuronal network formation and connectivity. PrPC mediates synaptic function and protects the synapse from excitotoxic insults. Its deletion may underlie an epileptogenic-susceptible brain that fails to perform highly cognitive-demanding tasks such as associative learning and anxiety-like behaviors.

The channel activities of the full-length prion and truncated proteins

Prion disease is a fatal neurodegenerative disorder, in which the cellular prion protein PrPC is converted to a misfolded prion which in turn is hypothesized to permeabilize cellular membranes. The pathways leading to toxicity in prion disease are not yet completely elucidated and whether it also includes formation of membrane pores remains to be answered. Prion protein consists of two domains: a globular domain (GD) and a flexible N-terminus (FT) domain. Although a proximal nine polybasic amino acid (FT(23-31)) sequence of FT is a prerequisite for cellular membrane permeabilization, other functional domain regions may influence FT(23-31) and its permeabilization. By using single-channel electrical recordings, we reveal that FT(23-50) dominates the membrane permeabilization within the full-length mouse PrP (mPrP(23-230)). The other domain of FT(51-110) or C-terminal domain down-regulates the channel activity of FT(23-50) and the full-length mouse PrP (mPrP(23-230)). The addition of prion mimetic antibody, POM1 significantly enhances mPrP(23-230) membrane permeabilization, whereas POM1-Y104A, a POM1 mutant that binds to PrP but cannot elicit toxicity has negligible effect on membrane permeabilization. Additionally, anti-N-terminal antibody POM2 or Cu2+ stabilizes FT domain, thus provoking FT(23-110) channel activity. Furthermore, our setup provides a more direct method without an external fused protein to study the channel activity of truncated PrP in the lipid membranes. We therefore hypothesize that the primary N-terminal residues are essential for membranes permeabilization and other functional segments play a vital role to modulate the pathological effects of PrP-medicated neurotoxicity. This may yield essential insights into molecular mechanisms of prion neurotoxicity to cellular membranes in prion disease.

Effects of the Pathological E200K Mutation on Human Prion Protein: A Computational screening and Molecular Dynamic approach

The Human Prion protein gene (PRNP) is mapped to short arm of chromosome 20 (20pter-12). Prion disease is associated with mutations in the Prion Protein encoding gene sequence. The mutations that occur in the prion protein could be divided into two types based on their influence on pathogenic potential: 1. Mutations that cause disease. 2. Disease-resistance mutations. Earlier studies found that the mutation G127V in the PRNP increases protein stability, whereas the mutation E200K, which has the highest mutation rate in the Prion protein, causes Creutzfeldt–Jakob disease (CJD) in humans and induces protein aggregation. We used a variety of bioinformatic algorithms, including SIFT, PolyPhen, I-Mutant, PhD-SNP, and SNP&GO, to predict the association of the E200K mutation with Prion disease. MD simulation is performed and graphs for RMSD, RMSF, Rg, DSSP, PCA, porcupine and FEL are generated to confirm and prove the stability of the wild type and mutant protein structures. The protein is analyzed for aggregation, and the results indicates more fluctuations in the protein structure during the simulation by the E200K mutation, however the G127V mutation makes protein structure stable against aggregation during the simulation.