Apolipoprotein E in the brain and its role in Alzheimer's disease.

Recent evidence indicates that apolipoprotein E (apoE) plays a central role in the brain response to injury. The coordinated expression of apoE and its main receptor, the apoE/apoB (LDL) receptor, appears to regulate the transport of cholesterol and phospholipids during the different phases of the reinnervation process. The recent discovery that a peculiar form of apoE, the apoE4, is strongly linked to both sporadic and familial late onset Alzheimer's disease (AD) raises the possibility that a dysfunction of the lipid transport system associated with compensatory sprouting and synaptic remodelling could be central to the AD process. The role of apoE in the central nervous system (CNS) is particularly important in relation to the function of the cholinergic system which relies to a certain extent on the integrity of phospholipid homeostasis in neurons. Recent evidence suggests that apoE4 allele has a direct impact on cholinergic function in AD.