The physiological functions of prion protein.

Prion proteins are mentioned predominantly as unprecedented infectious pathogens in the context of transmissible spongiform encephalopathies. Since prions are devoid of nucleic acids, disease transmission must be mediated by an entirely novel mechanism. The general accepted theory proposes the conversion of cellular prion protein (PrP(C)) into the pathological isoform solely through conformational changes. This process favors the development of insoluble protein aggregates in the central nervous system typical for prion diseases. However, progress to elucidate the physiological functions of PrP(C) is still slow besides recent indications of a multifaceted network, in which PrP(C) seems to play a fundamental role. Possible contributions of interrupted or disturbed physiological signaling events due to the pathological prion protein isoform are presented in terms of recent findings.