Prion protein functions and dysfunction in prion diseases.

Prion diseases are zoonotic infectious diseases caused by infectious particles, termed prions. Main component of prions is presumably a misfolded, partially protease-resistant conformer (PrP(Sc)) of a normal cell surface protein, the cellular prion protein (PrP(C)), whose anti-oxidative role is presumed by studies using prion protein (PrP)-knockout mice and cell lines. Major common features of prion diseases are PrP(Sc) deposition, astrocytosis, and vacuolation, but the presence of these features and transmission route are dependent on the combination of prion strain and host species. Generally, prions replicate first in the lymphoreticular system, although the presence of PrP(Sc) within lymphoid tissues seems to be dependent on factors such as route of prion exposure or type of prion strain. After that, prions travel to the brain via neuronal pathways along peripheral nerves, where their conversion leads to the accumulation of PrP(Sc) and a deficiency of PrP(C), contributing etiologically to the death of neurons including apoptosis and autophagy. In this review, we provide an overview of current information on PrP(C) and PrP(Sc) as well as their involvement in the pathogenesis of prion diseases.