Alzheimer disease (AD) and
Creutzfeldt-Jakob disease (CJD) are sporadic and genetic neurodegenerative conditions characterized by brain accumulation and deposition of
protein aggregates. In AD, the key pathogenic event is linked to the formation of a 4-kDa
amyloid beta (Abeta)
peptide, generated by sequential cleavages of the
amyloid precursor
protein (APP). In CJD and other
prion diseases, the process is initiated by conformational changes of the cellular
prion protein, or PrP(C), into a beta-sheet rich
isoform, named PrP(Sc), which acquires
protease-resistance and
detergent insolubility. Once generated, Abeta and PrP(Sc) are highly prone to misassembly under thermodynamically favourable oligomeric forms and protofibril/fibril structures. The variety of physicochemical states exhibited by Abeta and PrP(Sc) is accounted for by distinct molecular forms with different amino and/or carboxyl termini and alternative conformations. Unlike Abeta, PrP(Sc) is also infectious, and this feature poses public health concerns, as in the case of iatrogenic and variant CJD (vCJD). Several lines of evidence suggest that Abeta and PrP(Sc) are the main factors responsible for death of selected neuronal populations in brains of AD and
prion disease's victims. Therefore, in addition to symptomatic treatment of
dementia, therapeutic efforts are currently aimed at testing the efficacy of disease-modifying, anti-
amyloid therapies. Experimental and clinical therapeutic interventions include passive and active immunization against amyloidogenic
peptides, non immunological strategies, as well as drugs enhancing the nonamyloidogenic
protein processing. In this review, we focus on molecular mechanisms of AD and
prion diseases, and on novel treatment approaches.