LDLRAP1

The LDLRAP1 gene (also known as autosomal recessive hypercholesterolemia or ARH) provides instructions for making a protein that helps remove cholesterol from the bloodstream. Cholesterol is a waxy, fat-like substance that is produced in the body and obtained from foods that come from animals. The function of the LDLRAP1 protein is particularly important in the liver, which is the organ responsible for clearing most excess cholesterol from the body.

The LDLRAP1 protein interacts with a protein called a low-density lipoprotein receptor. This type of receptor binds to particles called low-density lipoproteins (LDLs), which are the primary carriers of cholesterol in the blood. The receptors sit on the outer surface of cells, where they pick up low-density lipoproteins circulating in the bloodstream. The LDLRAP1 protein appears to play a critical role in moving these receptors, together with their attached low-density lipoproteins, from the cell surface to the interior of the cell. Once inside the cell, low-density lipoproteins are broken down to release cholesterol. The cholesterol is then used by the cell, stored, or removed from the body.

hypercholesterolemia - caused by mutations in the LDLRAP1 gene

More than 10 mutations in the LDLRAP1 gene have been shown to cause a form of inherited high cholesterol called autosomal recessive hypercholesterolemia. These mutations lead to the production of an abnormally small, nonfunctional version of the LDLRAP1 protein or prevent cells from making any of this protein. Without the LDLRAP1 protein, low-density lipoprotein receptors are unable to remove low-density lipoproteins from the bloodstream effectively. Although the receptors can still bind normally to low-density lipoproteins, these molecules are not properly transported into cells (particularly liver cells). As a result, many extra low-density lipoproteins remain in the blood.

Because low-density lipoproteins are major carriers of cholesterol in the blood, people with mutations in the LDLRAP1 gene have very high blood levels of cholesterol. As the excess cholesterol circulates through the bloodstream, it is deposited abnormally in tissues such as the skin, tendons, and arteries that supply blood to the heart (coronary arteries). A buildup of cholesterol in the walls of coronary arteries greatly increases a person's risk of having a heart attack.