Apolipoprotein E: a review of its roles in lipoprotein metabolism, neuronal growth and repair and as a risk factor for Alzheimer's disease.

Apolipoprotein E (Apo E) is a polymorphic secretory glycoprotein expressed by a wide variety of tissues in mammals, particularly the liver and the brain (Mahley, 1988). Apo E recently attracted considerable attention when it was found that one of its alleles, apo E4, was associated with an increased risk for Alzheimer's disease (Strittmatter et al. 1993 a). This protein has been well studied with respect to its roles in lipoprotein metabolism in the peripheral circulation and in the nervous system. Accordingly, this protein's structure and function will be reviewed in order to place the potential roles of apo E in Alzheimer's disease into perspective.