Prion acute synaptotoxicity is largely driven by protease-resistant PrPSc species

Area of Science:

• Neuroscience
• Biochemistry
• Molecular Biology

Background:

• Misfolding of normal prion protein (PrPC) into abnormal conformers (PrPSc) is central to prion disease pathogenesis, but the molecular mechanisms remain poorly understood.
• Electrophysiological studies are crucial for understanding synaptic function and dysfunction in neurological disorders.

Purpose of the Study:

• To investigate the acute synaptotoxicity of proteinase K-resistant prion protein (PrPres) species.
• To elucidate the molecular pathophysiology underlying synaptic impairment in prion diseases.

Main Methods:

• Electrophysiology (long-term potentiation [LTP] and post-tetanic potentiation [PTP]) was used to assess synaptic function in hippocampal slices.
• Prion protein (PrPSc) species were prepared from mouse-adapted prion strains and infected cell lysates.
• Immuno-depletion, proteinase K (PK) treatment, and size fractionation chromatography were employed to characterize the synaptotoxic agent.
• Biochemical analyses assessed synaptic protein levels in affected hippocampal slices.

Main Results:

• Proteinase K-resistant PrPSc (PrPres) species demonstrated acute synaptotoxicity, significantly impairing hippocampal CA1 LTP.
• Selective immuno-depletion of PrP rescued LTP, while modestly PK-treated PrPSc retained synaptotoxicity, confirming PrPres as the causative agent.
• Synaptotoxicity was associated with impaired replenishment of the readily releasable pool of vesicles, suggesting pre-synaptic vulnerability.
• Size fractionation indicated that synaptotoxic PrP species were PK-resistant and >100kDa, likely multimeric PrPSc, with levels >6 ng/ml sufficient to induce dysfunction.
• Biochemical analysis revealed reduced levels of key synaptic proteins in slices with acute synaptotoxicity.

Conclusions:

• Proteinase K-resistant PrPSc species are directly responsible for acute synaptic dysfunction in prion diseases.
• The findings provide critical mechanistic insights into prion disease pathophysiology, highlighting pre-synaptic vesicle dynamics.
• This research enhances the prospects for developing targeted and effective therapies for prion-related neurodegenerative disorders.