Disabled‐2 Colocalizes with the LDLR in Clathrin‐Coated Pits and Interacts with AP‐2

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Abstract
Disabled‐2 (Dab2) is a widely expressed relative of Disabled‐1, a neuron‐specific signal‐transduction protein that binds to and receives signals from members of the low‐density lipoprotein receptor (LDLR) family. Members of the LDLR family internalize through clathrin‐coated pits and vesicles to endosomes, from where they return to the cell surface through the secretory pathway. In this study, we show that the Dab2 phosphotyrosine‐binding domain binds peptides containing the sequence FXNPXY. This core sequence is found in the intracellular domains of LDLR family members and is important for receptor internalization. Dab2 transiently colocalizes with the LDLR in clathrin‐coated pits, but is absent from endosomes and lysosomes. Dab2 is alternatively spliced and its localization depends on a region of the protein that contains two DPF motifs that are present in the p96 Dab2 protein and absent in the p67 splice variant. This region is sufficient to confer Dab2 binding to the α‐adaptin subunit of the clathrin adaptor protein, AP‐2. Overexpression of p96 but not of p67 Dab2 disrupts the localization of AP‐2. These findings suggest that in addition to previously reported signal‐transduction functions, Dab2 could also act as an adaptor protein that may regulate protein trafficking.