The prion protein unstructured N-terminal region is a broad-spectrum molecular sensor with diverse and contrasting potential functions

The physiological function of the prion protein (PrPC) and its conversion into its infectious form (PrPSc) are central issues to understanding the pathogenesis of prion diseases. The N-terminal moiety of PrPC (NH2-PrPC) is an unstructured region with the characteristic of interacting with a broad range of partners. These interactions endow PrPC with multifunctional and sometimes contrasting capabilities, including neuroprotection and neurotoxicity. Recently, binding of beta-sheet rich conformers to NH2-PrPC demonstrated a probable neurotoxic function for PrPC in Alzheimers disease. NH2-PrPC also enhances the propagation of prions in vivo and is the target of the most potent antiprion compounds. Another level of complexity is provided by endoproteolysis and release of most of NH2-PrPC into the extracellular space. Further studies will be necessary to understand how NH2-PrPC regulates the physiological function of PrPC and how it is involved in the corruption of its normal function in diseases.