The modular adaptor protein autosomal recessive hypercholesterolemia (ARH) promotes low density lipoprotein receptor clustering into clathrin-coated pits.
Autosomal recessive hypercholesterolemia is characterized by a cell type-specific defect in low density lipoprotein receptor (LDLR) endocytosis. LDLR-mediated uptake of LDL is impaired in the liver, but not in fibroblasts of subjects with this disorder. The disease is caused by mutations in ARH, which encodes a putative adaptor protein that interacts with the cytoplasmic tail of the LDLR, phospholipids, and two components of the clathrin endocytic machinery, clathrin and adaptor protein-2 (AP-2) in vitro. To determine the physiological relevance of these interactions, we examined the effect of mutations in the ARH on LDLR location and function in polarized hepatocytes (WIF-B). The integrity of the FDNPVY sequence in the LDLR cytoplasmic tail was required for ARH-associated LDLR clustering into clathrin-coated pits. The phosphotyrosine binding domain of ARH plus either the clathrin box or the AP-2 binding region were required for both clustering and internalization of the LDLR. Parallel studies performed in vivo with the same recombinant forms of ARH in livers of Arh(-/-) mice confirmed the relevance of the cell culture findings. These results demonstrate that ARH must bind the LDLR tail and either clathrin or AP-2 to promote receptor clustering and internalization of LDL.
Garuti
Rita
R
Department of Molecular Genetics, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-8591, USA.
Jones
Christopher
C
Li
Wei-Ping
WP
Michaely
Peter
P
Herz
Joachim
J
Gerard
Robert D
RD
Cohen
Jonathan C
JC
Hobbs
Helen H
HH
D033962:Adaptor Protein Complex 2 / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D000818:Animals; D001665:Binding Sites; D002459:Cell Fusion; D002461:Cell Line, Transformed; D002462:Cell Membrane / Q000737:chemistry; D002966:Clathrin / Q000378:metabolism; D022163:Clathrin-Coated Vesicles / Q000378:metabolism*; D003593:Cytoplasm / Q000737:chemistry; D005347:Fibroblasts; D005455:Fluorescent Antibody Technique; D015870:Gene Expression; D022781:Hepatocytes; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D016253:Microscopy, Immunoelectron; D009154:Mutation; D051381:Rats; D011973:Receptors, LDL / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000032:analysis; D013329:Structure-Activity Relationship; D014162:Transfection
D033962:Adaptor Protein Complex 2; D048868:Adaptor Proteins, Signal Transducing; D002966:Clathrin; C469745:LDLRAP1 protein, human; C500241:Ldlrap1 protein, mouse; D011973:Receptors, LDL; D011994:Recombinant Proteins