Scientific Results

IDOL Stimulates Clathrin-Independent Endocytosis and Multivesicular Body-Mediated Lysosomal Degradation of the Low-Density Lipoprotein Receptor

Year: 2013

Authors: Scotti E., Calamai M., Goulbourne C.N., Zhang Li, Hong C., Lin R.R., Choi J., Pilch PF., Fong L.G., Zou P., Ting A.Y., Pavone FS., Young S.G., Tontonoza P.

Autors Affiliation: Howard Hughes Medical Institute and Department of Pathology and Laboratory Medicine, University of California, Los Angeles, California, USA;
National Research Council Neuroscience Institute, Pisa, Italy;
Department of Human Genetics,d Department of Medicine, and Department of Chemistry and Biochemistry, University of
California, Los Angeles, California, USA;
Department of Biochemistry, Boston University Medical Center, Boston, Massachusetts, USA;
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA;
University of Florence, European Laboratory for Nonlinear Spectroscopy, Florence, Italy

Abstract: The low-density lipoprotein receptor (LDLR) is a critical determinant of plasma cholesterol levels that internalizes lipoprotein cargo via clathrin-mediated endocytosis. Here, we show that the E3 ubiquitin ligase IDOL stimulates a previously unrecognized, clathrin-independent pathway for LDLR internalization. Real-time single-particle tracking and electron microscopy reveal that IDOL is recruited to the plasma membrane by LDLR, promotes LDLR internalization in the absence of clathrin or caveolae, and facilitates LDLR degradation by shuttling it into the multivesicular body (MVB) protein-sorting pathway. The IDOL-dependent degradation pathway is distinct from that mediated by PCSK9 as only IDOL employs ESCRT (endosomal-sorting complex required for transport) complexes to recognize and traffic LDLR to lysosomes. Small interfering RNA (siRNA)-mediated knockdown of ESCRT-0 (HGS) or ESCRT-I (TSG101) components prevents IDOL-mediated LDLR degradation. We further show that USP8 acts downstream of IDOL to deubiquitinate LDLR and that USP8 is required for LDLR entry into the MVB pathway. These results provide key mechanistic insights into an evolutionarily conserved pathway for the control of lipoprotein receptor expression and cellular lipid uptake.


Volume: 33(8)      Pages from: 1503  to: 1514

More Information: This work was supported by NIH grants HL-066088 and HL-090553, American Heart Association Postdoctoral Fellowship 11POST6600001, the Italian Ministry for Education, Flagship Project NANOMAX, the EU Seventh Framework Programme (FP7/2007-2013, 284464), and the Ente Cassa di Risparmio di Firenze. Confocal laser scanning microscopy was performed at the CNSI Advanced Light Microscopy/Spectroscopy Shared Resource Facility at UCLA, supported with funding from NIH-NCRR shared resources grant (CJX1-443835-WS-29646) and NSF Major Research Instrumentation grant (CHE-0722519).
KeyWords: clathrin; ESCRT protein; low density lipoprotein receptor; small interfering RNA; tumor susceptibility gene 101 protein; ubiquitin protein ligase E3, animal cell; animal experiment; article; caveola; cell membrane; controlled study; degradation; electron microscopy; embryo; endocytosis; human; human cell; internalization; lipid transport; lysosome; mouse; multivesicular body; nonhuman; priority journal; protein expression; protein targeting; ubiquitination, Animals; Cell Cycle Proteins; Cell Line; Clathrin; DNA-Binding Proteins; Endocytosis; Endopeptidases; Endosomal Sorting Complexes Required for Transport; Guanine Nucleotide Exchange Factors; HEK293 Cells; HeLa Cells; Hep G2 Cells; Humans; Lipoproteins, LDL; Lysosomes; Mice; Multivesicular Bodies; Nuclear Proteins; Phosphoproteins; Proprotein Convertases; Protein Transport; Receptors, LDL; RNA Interference; RNA, Small Interfering; Serine Endopeptidases; Transcription Factors; Ubiquitin Thiolesterase; Ubiquitin-Protein Ligases; Ubiquitination
DOI: 10.1128/MCB.01716-12

Citations: 49
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