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Molecular cloning and complete sequence of prion protein cDNA from mouse brain infected with the scrapie agent
Abstract:
The prion protein (PrP) is a scrapie-associated fibril protein that accumulates in the brains of hamsters and mice infected with the scrapie agent, and also in the brains of persons affected with kuru or Creutzfeldt-Jakob disease. It has been previously proposed that PrP could be either the primary transmissible agent of scrapie or a secondary component involved in the pathogenesis of scrapie. At present, the second possibility seems more likely, for the PrP-specific mRNA is present in both infected and uninfected brains. We have isolated and sequenced the complete PrP-specific cDNA from mRNA isolated from infected mouse brains. Comparison of the mouse PrP with the hamster PrP reveals a high homology in the amino acid sequence and the presence of a conserved octapeptide repeated four times, whose function is unknown at present. Structural features are discussed and compared with other proteins. Except for its homology with the hamster PrP, mouse PrP has no significant homology to any known protein sequence, including neurofilaments, neuropeptides, and amyloid proteins of Alzheimer disease. Some features of the PrP, however, are similar to structures found in aggregating proteins, such as the wheat glutenin, keratin, and collagen.
Insights
Researchers isolated prion protein (PrP) cDNA from infected mouse brains. Mouse PrP shows high homology to hamster PrP but no significant homology to other known proteins, suggesting a unique role in prion diseases.
Area of Science:
- Neuroscience
- Molecular Biology
- Biochemistry
Background:
- Prion protein (PrP) accumulates in the brains of animals and humans with transmissible spongiform encephalopathies.
- PrP's role in scrapie pathogenesis is debated: it could be the infectious agent or a secondary factor.
- PrP-specific mRNA presence in both infected and uninfected brains suggests PrP is not solely the infectious agent.
Purpose of the Study:
- To isolate and sequence the complete prion protein (PrP)-specific cDNA from infected mouse brains.
- To compare the mouse PrP sequence with hamster PrP and other known protein sequences.
- To analyze structural features of mouse PrP and infer potential functions.
Main Methods:
- Isolation of mRNA from infected mouse brains.
- Reverse transcription to synthesize cDNA.
- Sequencing of the complete PrP-specific cDNA.
- Bioinformatic analysis for sequence homology and structural comparison.
Main Results:
- Complete PrP-specific cDNA was successfully isolated and sequenced from infected mouse brains.
- Mouse PrP exhibits high amino acid sequence homology with hamster PrP.
- Mouse PrP contains a conserved, functionally unknown octapeptide repeat.
- Mouse PrP shows no significant homology to other known proteins, except hamster PrP.
Conclusions:
- The findings support the hypothesis that PrP is a secondary component in scrapie pathogenesis.
- The high homology between mouse and hamster PrP suggests conserved function in prion diseases.
- Structural similarities to aggregating proteins like keratin and collagen warrant further investigation into PrP's aggregation properties.