Brief Communication abstract
Nature Cell Biology 4, 605 - 609 (2002)
Published online: 8 July 2002 | doi:10.1038/ncb827
The epithelial-specific adaptor AP1B mediates post-endocytic recycling to the basolateral membrane
Yunbo Gan1, Timothy E. McGraw2 & Enrique Rodriguez-Boulan1,3
To perform vectorial secretory and transport functions that are critical for the survival of the organism, epithelial cells sort plasma membrane proteins into polarized apical and basolateral domains1, 2. Sorting occurs post-synthetically, in the trans Golgi network (TGN) or after internalization from the cell surface in recycling endosomes, and is mediated by apical and basolateral sorting signals embedded in the protein structure3, 4. Basolateral sorting signals include tyrosine motifs in the cytoplasmic domain that are structurally similar to signals involved in receptor internalization by clathrin-coated pits5, 6. Recently, an epithelial-specific adaptor protein complex, AP1B, was identified7, 8. AP-1B recognizes a subset of basolateral tyrosine motifs through its 
1B subunit7, 8. Here, we characterized the post-synthetic and post-endocytic sorting of the fast recycling low density lipoprotein receptor (LDLR) and transferrin receptor (TfR) in LLC-PK1 cells, which lack 1B and mis-sort both receptors to the apical surface8. Targeting and recycling assays in LLC-PK1 cells, before and after transfection with 1B, and in MDCK cells, which express 1B constitutively, suggest that AP1B sorts basolateral proteins post-endocytically.
- Dyson Vision Research Institute, Weill Medical College of Cornell University, 1300 York Ave., New York, NY 10021, USA
- Department of Biochemistry, Weill Medical College of Cornell University, 1300 York Ave., New York, NY 10021, USA
- Department of Cell Biology, Weill Medical College of Cornell University, 1300 York Ave., New York, NY 10021, USA
Correspondence to: Enrique Rodriguez-Boulan1,3 e-mail: boulan@med.cornell.edu
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