It has been discovered that the low density lipoprotein receptor (LDLR) degrades the lipoprotein apoB. Based on this observation, an artificial fusion protein has been designed containing an LDL receptor domain attached to a localization domain which causes retention of the fusion protein inside of a cell. The fusion protein is preferably retained in the endoplasmic reticulum of the cell, where the LDLR can degrade apoB. Data shows that the technique is effective in a mammal to reduce serum LDL cholesterol levels.