The Modular Adaptor Protein Autosomal Recessive Hypercholesterolemia (ARH) Promotes Low Density Lipoprotein Receptor Clustering into Clathrin-coated Pits

• Published in: The Journal of biological chemistry Vol. 280; no. 49; pp. 40996 - 41004
• Main Authors: Garuti, Rita, Jones, Christopher, Li, Wei-Ping, Michaely, Peter, Herz, Joachim, Gerard, Robert D., Cohen, Jonathan C., Hobbs, Helen H.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 09.12.2005; American Society for Biochemistry and Molecular Biology
• Subjects: Adaptor Protein Complex 2 - metabolism; Adaptor Proteins, Signal Transducing - chemistry; Adaptor Proteins, Signal Transducing - deficiency; Adaptor Proteins, Signal Transducing - genetics; Adaptor Proteins, Signal Transducing - physiology; Animals; Binding Sites; Cell Fusion; Cell Line, Transformed; Cell Membrane - chemistry; Clathrin - metabolism; Clathrin-Coated Vesicles - metabolism; Cytoplasm - chemistry; Fibroblasts; Fluorescent Antibody Technique; Gene Expression; Hepatocytes; Humans; Mice; Mice, Knockout; Microscopy, Fluorescence; Microscopy, Immunoelectron; Mutation; Rats; Receptors, LDL - chemistry; Receptors, LDL - genetics; Receptors, LDL - metabolism; Recombinant Proteins - analysis; Structure-Activity Relationship; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M509394200

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.