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Summary: Endoplasmic reticulum localization of the low density
lipoprotein receptor mediates presecretory
degradation of apolipoprotein B
Donald L. Gillian-Daniel*, Paul W. Bates
, Angie Tebon*, and Alan D. Attie*
Departments of *Biochemistry and Nutritional Sciences, University of Wisconsin, Madison, WI 53706-1544
Edited by Michael S. Brown, University of Texas Southwestern Medical Center, Dallas, TX, and approved January 29, 2002 (received for review
October 18, 2001)
Mutations in the low density lipoprotein (LDL) receptor (LDLR)
cause hypercholesterolemia because of inefficient LDL clearance
from the circulation. In addition, there is a paradoxical oversecre-
tion of the metabolic precursor of LDL, very low density lipoprotein
(VLDL). We recently demonstrated that the LDLR mediates pre-
secretory degradation of the major VLDL protein, apolipoprotein B
(apoB). Kinetic studies suggested that the degradation process is
initiated in the secretory pathway. Here, we evaluated the ability
of several LDLR variants that are stalled within the secretory
pathway to regulate apoB secretion. Both a naturally occurring
mutant LDLR and an LDLR consisting of only the ligand-binding
domains and a C-terminal endoplasmic reticulum (ER) retention
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