Heat shock proteins and amateur chaperones in amyloid-beta accumulation and clearance in Alzheimer's disease

The pathologic lesions of Alzheimer's disease ( AD) are characterized by accumulation of protein aggregates consisting of intracellular or extracellular misfolded proteins. The amyloid-beta ( A beta) protein accumulates extracellularly in senile plaques and cerebral amyloid angiopathy, whereas the hyperphosphorylated tau protein accumulates intracellularly as neurofibrillary tangles. Professional chaperones, such as the heat shock protein family, have a function in the prevention of protein misfolding and subsequent aggregation. Amateur chaperones, such as apolipoproteins and heparan sulfate proteoglycans, bind amyloidogenic proteins and may affect their aggregation process. Professional and amateur chaperones not only colocalize with the pathological lesions of AD, but may also be involved in conformational changes of A beta, and in the clearance of A beta from the brain via phagocytosis or active transport across the blood-brain barrier. Thus, both professional and amateur chaperones may be involved in the aggregation, accumulation, persistence, and clearance of A beta and tau and in other A beta-associated reactions such as inflammation associated with AD lesions, and may, therefore, serve as potential targets for therapeutic intervention.