title: Sorting nexin 27 regulates basal and stimulated brush border trafficking of NHE3.
abstract: Sorting nexin 27 (SNX27) contains a PDZ domain that is phylogenetically related to the PDZ domains of the NHERF proteins. Studies on nonepithelial cells have shown that this protein is located in endosomes, where it regulates trafficking of cargo proteins in a PDZ domain-dependent manner. However, the role of SNX27 in trafficking of cargo proteins in epithelial cells has not been adequately explored. Here we show that SNX27 directly interacts with NHE3 (C-terminus) primarily through the SNX27 PDZ domain. A combination of knockdown and reconstitution experiments with wild type and a PDZ domain mutant (GYGF → GAGA) of SNX27 demonstrate that the PDZ domain of SNX27 is required to maintain basal NHE3 activity and surface expression of NHE3 in polarized epithelial cells. Biotinylation-based recycling and degradation studies in intestinal epithelial cells show that SNX27 is required for the exocytosis (not endocytosis) of NHE3 from early endosome to plasma membrane. SNX27 is also required to regulate the retention of NHE3 on the plasma membrane. The findings of the present study extend our understanding of PDZ-mediated recycling of cargo proteins from endosome to plasma membrane in epithelial cells.
authors: Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
authors: Varsha
authors: V
authors: Singh
authors: Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
authors: Jianbo
authors: J
authors: Yang
authors: Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
authors: Boyoung
authors: B
authors: Cha
authors: Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
authors: Tiane-e
authors: TE
authors: Chen
authors: Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
authors: Rafiquel
authors: R
authors: Sarker
authors: Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
authors: Jianyi
authors: J
authors: Yin
authors: Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
authors: Leela Rani
authors: LR
authors: Avula
authors: Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
authors: Ming
authors: M
authors: Tse
authors: Gastroenterology Division, Departments of Physiology and Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205 mdonowit@jhmi.edu.
authors: Mark
authors: M
authors: Donowitz
mesh_terms: D004847:Epithelial Cells / Q000378:metabolism*; D005089:Exocytosis; D006801:Humans; D008871:Microvilli / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D054731:PDZ Domains; D021381:Protein Transport; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
chemical_list: D009419:Nerve Tissue Proteins; C000613385:SLC9A3 protein, human; C000613387:Slc9a3 protein, rat; C477690:Snx27 protein, rat; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers