Phosphatidylinositol 3,4,5-trisphosphate localization in recycling endosomes is necessary for AP-1B-dependent sorting in polarized epithelial cells.
Polarized epithelial cells coexpress two almost identical AP-1 clathrin adaptor complexes: the ubiquitously expressed AP-1A and the epithelial cell-specific AP-1B. The only difference between the two complexes is the incorporation of the respective medium subunits micro1A or micro1B, which are responsible for the different functions of AP-1A and AP-1B in TGN to endosome or endosome to basolateral membrane targeting, respectively. Here we demonstrate that the C-terminus of micro1B is important for AP-1B recruitment onto recycling endosomes. We define a patch of three amino acid residues in micro1B that are necessary for recruitment of AP-1B onto recycling endosomes containing phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P(3)]. We found this lipid enriched in recycling endosomes of epithelial cells only when AP-1B is expressed. Interfering with PI(3,4,5)P(3) formation leads to displacement of AP-1B from recycling endosomes and missorting of AP-1B-dependent cargo to the apical plasma membrane. In conclusion, PI(3,4,5)P(3) formation in recycling endosomes is essential for AP-1B function.
Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, IL 60208, USA.
Ian C
IC
Fields
Shelby M
SM
King
Elina
E
Shteyn
Richard S
RS
Kang
Heike
H
Fölsch
D033983:Adaptor Protein Complex mu Subunits / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D016764:Cell Polarity; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D021381:Protein Transport; D011990:Receptors, Transferrin / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013552:Swine
D033983:Adaptor Protein Complex mu Subunits; D000596:Amino Acids; D018129:Phosphatidylinositol Phosphates; D011990:Receptors, Transferrin; D011993:Recombinant Fusion Proteins; C060974:phosphatidylinositol 3,4,5-triphosphate; D049452:Green Fluorescent Proteins; D017853:Phosphotransferases (Alcohol Group Acceptor)