The pathogenic mechanisms of prion diseases

Prion diseases are rare fatal neurodegenerative disorders that may either occur sporadically, or be inherited or infectiously acquired in humans. Irrespective of etiology, they can be transmitted to other individuals, this fact being responsible for the public attention prion diseases have received especially since the nineteen nineties, when a new variant of Creutzfeldt-Jakob disease linked to the consumption of prion contaminated beef occurred for the first time in Great Britain. The infectious particle, termed prion, is presumably composed exclusively of a misfolded, partially protease-resistant conformer (PrP(Sc)) of a normal cell surface protein, the cellular prion protein (PrP(C)). The pathogenesis of prion diseases comprises entry, spread, and amplification of infectivity in the body periphery in infectiously acquired forms, as well as mechanisms of neuronal cell death in the central nervous system in all disease subtypes. Most experimental therapeutic approaches are either targeted to PrP(C) or PrP(Sc), or to the process of conversion from PrP(C) to PrP(Sc). Neuroprotective strategies aiming at an interruption of central nervous system pathogenesis have also been tested, albeit with only moderate success. In this review, we discuss actual and potential drug targets in the context of the pathogenic mechanisms of prion diseases.