Abstract : Spongiform encephalopathies are fatal neurodegenerative diseases involving a highly protease resistant protein referred to as prion scrapie (PrPsc). Human prion diseases include Creutzfeldt-Jakob disease and some iatrogenic transmission cases. PrPsc corresponds to the abnormal conformation of the ubiquitous cellular prion (PrPc) mainly synthesized in the central nervous system. PrPc is endoproteolyzed mainly at the 110/111 peptide bond, leading to a secreted product referred to as N1. ADAM10 and TACE are identified as the main enzymes responsible for constitutive and regulated production of N1. Of most interest was demonstration that the most infectious innoculates of PrPsc remained innocuous in absence of PrPc. Thus, PrPc null mice resist toxicity and infection by scrapie homogenates. Therefore, strategies aimed at depleting endogenous PrPc has the potential of slowing down or preventing disease transmission. During my thesis I demonstrated that PKC-coupled muscarinic receptors are involved in the regulation of PrPc physiological cleavage and identified the PKC isoforms implicated in this mechanism.