ApoE protein. Computer model of an apoE molecule. ApoE is classed as an apolipoprotein, a type of protein that binds to lipid (fat) particles. It is linked to Alzheimer's disease because one form of the gene that makes it increases the risk of developing the condition. Alzheimer's is an incurable condition involving the loss of brain tissue, producing memory loss and disorientation. ApoE is known to be involved in lipid transport, but is involved in many other functions in the body, including regulating hormone production and the immune system.