The YXXL Motif, but Not the Two NPXY Motifs, Serves as the Dominant Endocytosis Signal for Low Density Lipoprotein Receptor-related Protein

doi:10.1074/jbc.M000490200

The YXXL Motif, but Not the Two NPXY Motifs, Serves as the Dominant Endocytosis Signal for Low Density Lipoprotein Receptor-related Protein*

From the ^‡Departments of Pediatrics, and Cell Biology and Physiology, Washington University School of Medicine and St. Louis Children's Hospital, St. Louis, Missouri 63110, the ^§Department of Biology, University of Chile, Santiago, Chile, and the ^¶Department of Cell Biology, Utrecht University, Utrecht, The Netherlands

Abstract

All members of the low density lipoprotein (LDL) receptor family contain at least one copy of the NPXY sequence within their cytoplasmic tails. For the LDL receptor, it has been demonstrated that the NPXY motif serves as a signal for rapid endocytosis through coated pits. Thus, it is generally believed that the NPXY sequences function as endocytosis signals for all the LDL receptor family members. The primary aim of this study is to define the endocytosis signal(s) within the cytoplasmic tail of LDL receptor-related protein (LRP). By using LRP minireceptors, which mimic the function and trafficking of full-length endogenous LRP, we demonstrate that the YXXL motif, but not the two NPXY motifs, serves as the dominant signal for LRP endocytosis. We also found that the distal di-leucine motif within the LRP tail contributes to its endocytosis, and its function is independent of the YXXL motif. Although the proximal NPXY motif and the proximal di-leucine motif each play a limited role in LRP endocytosis in the context of the full-length tail, these motifs were functional within the truncated receptor tail. In addition, we show that LRP minireceptor mutants defective in endocytosis signal(s) accumulate at the cell surface and are less efficient in delivery of ligand for degradation.

Footnotes

↵* This work was supported by National Institutes of Health Grants NS37525 and HL59150 (to G. B.) and Fondo Nacional de Ciencia y Technologia Grant 1990600 and Departmento de Investigacion y Desarrollo Grant I007-98/2 (to M. P. M.)The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵‖ To whom correspondence should be addressed: Dept. of Pediatrics, Washington University School of Medicine, Box 8116, One Children's Pl., St. Louis, MO 63110. Tel.: 314-454-2726; Fax: 314-454-2685; E-mail: bu@kids.wustl.edu.
Published, JBC Papers in Press, March 28, 2000, DOI 10.1074/jbc.M000490200
↵2 L. M. Obermoeller, Y. Li, and G. Bu, unpublished results.
Abbreviations:

LDL

low density lipoprotein

CHO

Chinese hamster ovary

LDLR

low density lipoprotein receptor

LRP

low density lipoprotein receptor-related protein

RAP

receptor-associated protein

apoE

apolipoprotein E

apoER2

apolipoprotein E receptor-2

VLDLR

very low density lipoprotein receptor

scuPA

single chain urokinase

PAGE

polyacrylamide gel electrophoresis

HA

hemagglutinin

BSA

bovine serum albumin

ER

endoplasmic reticulum
- Received January 19, 2000.
- Revision received March 21, 2000.
The American Society for Biochemistry and Molecular Biology, Inc.