Targeting of transmembrane protein shrew-1 to adherens junctions is controlled by cytoplasmic sorting motifs.
We recently identified transmembrane protein shrew-1 and showed that it is able to target to adherens junctions in polarized epithelial cells. This suggested shrew-1 possesses specific basolateral sorting motifs, which we analyzed by mutational analysis. Systematic mutation of amino acids in putative sorting signals in the cytoplasmic domain of shrew-1 revealed three tyrosines and a dileucine motif necessary for basolateral sorting. Substitution of these amino acids leads to apical localization of shrew-1. By applying tannic acid to either the apical or basolateral part of polarized epithelial cells, thereby blocking vesicle fusion with the plasma membrane, we obtained evidence that the apically localized mutants were primarily targeted to the basolateral membrane and were then redistributed to the apical domain. Further support for a postendocytic sorting mechanism of shrew-1 was obtained by demonstrating that mu1B, a subunit of the epithelial cell-specific adaptor complex AP-1B, interacts with shrew-1. In conclusion, our data provide evidence for a scenario where shrew-1 is primarily delivered to the basolateral membrane by a so far unknown mechanism. Once there, adaptor protein complex AP-1B is involved in retaining shrew-1 at the basolateral membrane by postendocytic sorting mechanisms.
Jakob
Viktor
V
Institute of Cell Biology and Neuroscience, Johann-Wolfgang Goethe University of Frankfurt, D-60323 Frankfurt am Main, Germany.
Schreiner
Alexander
A
Tikkanen
Ritva
R
Starzinski-Powitz
Anna
A
D022005:Adherens Junctions / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D015815:Cell Adhesion Molecules; D016764:Cell Polarity / Q000187:drug effects; D002478:Cells, Cultured; D003593:Cytoplasm / Q000737:chemistry*; D004285:Dogs; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects; D005260:Female; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D025941:Protein Interaction Mapping; D021382:Protein Sorting Signals; D021381:Protein Transport / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013552:Swine; D013634:Tannins / Q000494:pharmacology; D014599:Uterus / Q000166:cytology
C483313:AJAP1 protein, human; D015815:Cell Adhesion Molecules; D008565:Membrane Proteins; D050505:Mutant Proteins; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D013634:Tannins