Presenilins: molecular switches between proteolysis and signal transduction

Proteolytic processing and cell biological functions of the amyloid precursor protein

Recent research has identified some key players involved in the proteolytic processing of amyloid precursor protein (APP) to amyloid beta-peptide, the principal component of the amyloid plaques in Alzheimer patients. Interesting parallels exists with the proteolysis of other proteins involved in cell differentiation, cholesterol homeostasis and stress responses. Since the cytoplasmic domain of APP is anchored to a complex protein network that might function in axonal elongation, dendritic arborisation and neuronal cell migration, the proteolysis of APP might be critically involved in intracellular signalling events.

Binding partners of Alzheimer's disease proteins: are they physiologically relevant?

Protein-protein interactions are a molecular basis for the structural and functional organization within cells. They are mediated by a growing number of protein modules that bind peptide targets. Alterations in binding affinities can have serious consequences for some essential cellular processes. The three proteins identified to have mutations in their corresponding genes leading to presenile Alzheimer dementia (AD)-the amyloid precursor protein (APP) and presenilin 1 and 2-all interact with other proteins. The nature and function of these interacting proteins may contribute to elucidating the proper physiological functions of the AD proteins. APP-interacting proteins are pointing toward a function of APP in cell adhesion and neurite outgrowth and signaling. Proteins interacting with the presenilins however are more diverse in nature linking presenilin function to regulation in different signaling pathways including Wnt and Notch but also in apoptosis and Ca(2+) homeostasis. Further research however is still needed to delineate the exact functional relevance of these interactions with respect to the physiological functions of the AD proteins in particular and the contribution of these proteins to AD pathogenesis in general.