Scavenger, transducer, RNA chaperone? What ligands of the prion protein teach us about its function

Prion protein, a misfolded isoform of which is the essential component of the agent of prion diseases, still remains an enigmatic protein whose physiological functions are at best hypothetical. To gain a better insight into its putative role, many studies were undertaken to look for molecules that bind prion protein, and have notably identified divalent metal ions, several proteins, and nucleic acids. At first sight, the diversity of prion protein's ligands seems of little help to infer a plausible function. However, the intrinsically disordered property of its N-terminal tail and the potential of the protein to adopt a transmembrane topology, can both be taken into account to predict its different states during its cellular cycle and its possible functions, of which the most promising correspond to a general scavenger, a sensor or adaptor in a signaling cascade, and an RNA chaperone.