Final answer:
Misfolded prion proteins are toxic to brain cells because they cause other proteins to misfold, leading to neuron death and the accumulation of amyloid plaques, which are characteristic of neurodegenerative diseases such as Alzheimer's and Creutzfeldt-Jakob disease. Prions can induce apoptosis or cellular damage, contributing to the characteristic spongy texture observed in affected brain tissue.
Step-by-step explanation:
Misfolded prion proteins may be toxic to brain cells owing to their capacity to induce other normal proteins to misfold, leading to a cascade of damage that results in brain tissue developing a spongy texture and forming holes. These proteins accumulate and may cause various neurological symptoms, including memory loss and personality changes. Neurodegenerative diseases such as Alzheimer's, Creutzfeldt-Jakob disease, and other forms of transmissible spongiform encephalopathy are linked to the accumulation of rogue prion proteins in the brain.
Upon misfolding, prions change their structure from mostly alpha helices to beta-pleated sheets, which are resistant to proteolysis. This misfolded form, PrPSc, can aggregate and form fibrils within nerve cells, leading to cell death. The exact mechanisms by which misfolded prions cause toxicity are still under investigation. Still, it is known that they can cause the death of neurons either by direct cellular damage or by interfering with normal cellular processes.
Among the proposed mechanisms of prion toxicity include triggering apoptosis or programmed cell death in neurons, leading to neurodegeneration. Additionally, prions might cause the accumulation of amyloid plaques, similar to those found in Alzheimer's disease patients, though their role in such diseases might be more indirect as they are not considered a proximal cause of Alzheimer's.