Endosome-lysosomes and neurodegeneration

A number of the major human and animal neurodegenerative diseases, such as Alzheimer's disease and sheep scrapie, are characterised by deposits of amyloid, arising through incomplete breakdown of membrane proteins. Although our knowledge concerning these diseases is increasing, they remain largely untreatable. Recently, attention has focussed on the mechanisms of production of different types of amyloid and the likely involvement within cells of acid compartments called endosome-lysosomes. These organelles may be 'bioreactor' sites for the unfolding and partial degradation of membrane proteins to generate the amyloid materials. These subsequently become expelled from the cell, or are released from dead cells, and accumulate as pathological entities. Common features of the disease processes give new direction to therapeutic intervention.