General Description
Apolipoprotein E (ApoE) is present in the brain and is mainly produced by astrocytes. It is a 299 amino acid glycoprotein of 34kDa. It is present in all classes of lipoproteins except LDL (low-density lipoprotein). APOE?gene has three alleles, such as APOE?ε
3, APOE?ε
4?and APOE?ε
2. It is located on human chromosome 19q13.
Biochem/physiol Actions
Apolipoprotein E4 is a member of the apolipoprotein E family of plasma lipoproteins that bind reversibly with lipoprotein and play an important role in lipid metabolism. ApoE4 regulates plasma lipid levels by increasing the degradation of particles rich in triglycerides and cholesterol. In addition to facilitating solubilization of lipids, these proteins help to maintain the structural integrity of lipoproteins, serve as ligands for lipoprotein receptors, regulate the activity of enzymes involved in lipid metabolism and bind amyloid-β protein, the major component of plaques in Alzheimer′s disease, which it delivers to the microglia, the major scavenger cells of brain. Individuals heterozygous for the ApoE4 allele are at higher risk of late-onset Alzheimer′s disease. ApoE exists in three major isoforms: E2, E3, and E4, which differ from one another by a single amino-acid substitution. Recombinant human ApoE4 is a 34.4 kDa protein containing 300 amino acid residues.
