title: Endosomal Na+/H+ exchanger NHE5 influences MET recycling and cell migration.
abstract: Increased recycling and elevated cell surface expression of receptors serve as a mechanism for persistent receptor-mediated signaling. We show that the neuron-enriched Na(+)/H(+) exchanger NHE5 is abundantly expressed in C6 glioma cells and plays an important part in regulating cell surface expression of the receptor tyrosine kinases MET and EGF receptor. NHE5 is associated with transferrin receptor (TfR)- and Rab11-positive recycling endosomal membranes, and NHE5 knockdown by short hairpin RNA significantly elevates pH of TfR-positive recycling endosomes. We present evidence that NHE5 facilitates MET recycling to the plasma membrane, protects MET from degradation, and modulates HGF-induced phosphatidylinositol-3-kinase and mitogen-activated protein kinase signaling. Moreover, NHE5 depletion abrogates Rac1 and Cdc42 signaling and actin cytoskeletal remodeling. We further show that NHE5 knockdown impairs directed cell migration and causes loss of cell polarity. Our study highlights a possible role of recycling endosomal pH in regulating receptor-mediated signaling through vesicular trafficking.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
authors.forename: Steven Hung-Yi
authors.initials: SH
authors.lastname: Fan
authors.affiliation: Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Numata
authors.affiliation: Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada mnumata@mail.ubc.ca.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Numata
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000201:enzymology; D002465:Cell Movement; D003599:Cytoskeleton / Q000378:metabolism; D011992:Endosomes / Q000201:enzymology*; D066246:ErbB Receptors / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006863:Hydrogen-Ion Concentration; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D021381:Protein Transport; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D011990:Receptors, Transferrin / Q000378:metabolism; D015398:Signal Transduction; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: D000199:Actins; D034741:RNA, Small Interfering; D011990:Receptors, Transferrin; D017923:Sodium-Hydrogen Exchangers; C117561:sodium-hydrogen exchanger 5; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D019859:Proto-Oncogene Proteins c-met; D020928:Mitogen-Activated Protein Kinases; C499134:Rac1 protein, rat; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein