RRC ID 21508
Author Kang YL, Yochem J, Bell L, Sorensen EB, Chen L, Conner SD.
Title Caenorhabditis elegans reveals a FxNPxY-independent low-density lipoprotein receptor internalization mechanism mediated by epsin1.
Journal Mol. Biol. Cell
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.
Volume 24(3)
Pages 308-18
Published 2013-2
DOI 10.1091/mbc.E12-02-0163
PII mbc.E12-02-0163
PMID 23242996
PMC PMC3564534
MeSH Adaptor Proteins, Vesicular Transport / genetics* Adaptor Proteins, Vesicular Transport / metabolism Amino Acid Motifs Amino Acid Substitution Animals Caenorhabditis elegans / genetics Caenorhabditis elegans / metabolism* Caenorhabditis elegans Proteins / genetics Caenorhabditis elegans Proteins / metabolism Endocytosis Gene Knockdown Techniques HeLa Cells Humans Low Density Lipoprotein Receptor-Related Protein-1 / chemistry Low Density Lipoprotein Receptor-Related Protein-1 / genetics Low Density Lipoprotein Receptor-Related Protein-1 / metabolism* Molecular Sequence Data Protein Stability Protein Transport RNA Interference Ubiquitination
IF 3.905
Times Cited 11
C.elegans epn-1(tm3357)