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PMID: 23242996 Published · ppublish English Journal Article Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't

Caenorhabditis elegans reveals a FxNPxY-independent low-density lipoprotein receptor internalization mechanism mediated by epsin1.

Molecular biology of the cell ·Vol. 24 ·No. 3 ·2013-02-00 ·Pages 308-18

Kang YL, Yochem J, Bell L, Sorensen EB, Chen L, Conner SD

Abstract

Low-density lipoprotein receptor (LDLR) internalization clears cholesterol-laden LDL particles from circulation in humans. Defects in clathrin-dependent LDLR endocytosis promote elevated serum cholesterol levels and can lead to atherosclerosis. However, our understanding of the mechanisms that control LDLR uptake remains incomplete. To identify factors critical to LDLR uptake, we pursued a genome-wide RNA interference screen using Caenorhabditis elegans LRP-1/megalin as a model for LDLR transport. In doing so, we discovered an unanticipated requirement for the clathrin-binding endocytic adaptor epsin1 in LDLR endocytosis. Epsin1 depletion reduced LDLR internalization rates in mammalian cells, similar to the reduction observed following clathrin depletion. Genetic and biochemical analyses of epsin in C. elegans and mammalian cells uncovered a requirement for the ubiquitin-interaction motif (UIM) as critical for receptor transport. As the epsin UIM promotes the internalization of some ubiquitinated receptors, we predicted LDLR ubiquitination as necessary for endocytosis. However, engineered ubiquitination-impaired LDLR mutants showed modest internalization defects that were further enhanced with epsin1 depletion, demonstrating epsin1-mediated LDLR endocytosis is independent of receptor ubiquitination. Finally, we provide evidence that epsin1-mediated LDLR uptake occurs independently of either of the two documented internalization motifs (FxNPxY or HIC) encoded within the LDLR cytoplasmic tail, indicating an additional internalization mechanism for LDLR.

MeSH Terms
Adaptor Proteins, Vesicular Transport/genetics,metabolism Amino Acid Motifs Amino Acid Substitution Animals Caenorhabditis elegans/genetics,metabolism Caenorhabditis elegans Proteins/genetics,metabolism Endocytosis Gene Knockdown Techniques HeLa Cells Humans Low Density Lipoprotein Receptor-Related Protein-1/chemistry,genetics,metabolism Molecular Sequence Data Protein Stability Protein Transport RNA Interference Ubiquitination
Chemicals
Adaptor Proteins, Vesicular Transport Caenorhabditis elegans Proteins DAB-1 protein, C elegans Low Density Lipoprotein Receptor-Related Protein-1 epsin
Authors & Affiliations
6 authors, click to expand affiliations / ORCID
Kang Yuan-Lin
Department of Genetics, Cell Biology, and Development and the Developmental Biology Center, University of Minnesota, Minneapolis, MN 55455, USA.
Yochem John
Bell Leslie
Sorensen Erika B
Chen Lihsia
Conner Sean D
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Article Info
Journal
Molecular biology of the cell
Abbr.
Mol Biol Cell
ISSN
1939-4586
DOI
10.1091/mbc.E12-02-0163
Published
2013-02-00
Epub
2012-00-14
Pages
308-18
Language
English
Region
United States
NLM ID
9201390
PMCID
PMC3564534
Subset
IM
Grants
NIGMS NIH HHS · R01 GM085029 · United States
NICHD NIH HHS · T32 HD007480 · United States
NINDS NIH HHS · R01 NS045873 · United States
NINDS NIH HHS · NS045873 · United States
NIGMS NIH HHS · GM085029 · United States
NICHD NIH HHS · 2T32-HD007480-11A1 · United States
External Links
PubMed source DOI: 10.1091/mbc.E12-02-0163 PMC Full Text View journal details
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