Heart disease caused by damage to blood vessels is the leading cause of death worldwide. Arteries become clogged with fats and cholesterol when certain proteins in the body, known as lipoproteins, combine with and transport fats in the blood to cells. Scientists have long believed that the LDL receptor molecule was responsible for the intracellular transport of LDL. But given that some individuals lacking the LDL receptor still have high levels of LDL, questions remain about the mechanism.