title: Sorting nexin 5 is localized to a subdomain of the early endosomes and is recruited to the plasma membrane following EGF stimulation.
abstract: Sorting nexins are a large family of proteins that contain the phosphoinositide-binding Phox homology (PX) domain. A number of sorting nexins are known to bind to PtdIns3P, which mediates their localization to membranes of the endocytic pathway. We show here that sorting nexin 5 (SNX5) can be recruited to two distinct membrane compartments. In non-stimulated cells, the PX domain was independently targeted to endosomal structures and colocalized with full-length SNX5. The membrane binding of the PX domain was inhibited by the PI 3-kinase inhibitor, wortmannin. Although SNX5 colocalized with a fluid-phase marker and was found predominantly within a PtdIns3P-rich endosomal domain, very little colocalization was observed between SNX5 and the PtdIns3P-binding protein, EEA1. Using liposome-based binding assays, we have shown that the PX domain of SNX5 interacts not only with PtdIns3P but also with PtdIns3,4P2. In response to EGF stimulation, either the SNX5-PX domain or full-length SNX5 was rapidly recruited to the plasma membrane. The localization of SNX1, which does not bind PtdIns3,4P2, was unaffected by EGF signalling. Therefore, SNX5 is localized to a subdomain of the early endosome distinct from EEA1 and, following EGF stimulation and elevation of PtdIns3,4P2, is also transiently recruited to the plasma membrane. These results indicate that SNX5 may have functions not only associated with endosomal sorting but also with the phosphoinositide-signalling pathway.
authors.affiliation: The Russell Grimwade School of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Victoria, 3010, Australia.
authors.forename: Ana
authors.initials: A
authors.lastname: Merino-Trigo
authors.forename: Markus C
authors.initials: MC
authors.lastname: Kerr
authors.forename: Fiona
authors.initials: F
authors.lastname: Houghton
authors.forename: Anna
authors.initials: A
authors.lastname: Lindberg
authors.forename: Christina
authors.initials: C
authors.lastname: Mitchell
authors.forename: Rohan D
authors.initials: RD
authors.lastname: Teasdale
authors.forename: Paul A
authors.initials: PA
authors.lastname: Gleeson
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D015703:Antigens, CD / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D003911:Dextrans / Q000378:metabolism; D011992:Endosomes / Q000737:chemistry* / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D019084:Fluorescent Antibody Technique, Indirect; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D008081:Liposomes; D051907:Lysosomal Membrane Proteins; D008565:Membrane Proteins / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D058305:Sorting Nexins; D013997:Time Factors; D014162:Transfection; D020798:Two-Hybrid System Techniques; D033921:Vesicular Transport Proteins / Q000378:metabolism; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D015703:Antigens, CD; D002352:Carrier Proteins; D003911:Dextrans; D004791:Enzyme Inhibitors; D008081:Liposomes; D051907:Lysosomal Membrane Proteins; D008565:Membrane Proteins; D018129:Phosphatidylinositol Phosphates; D011993:Recombinant Fusion Proteins; C402667:SNX5 protein, human; D058305:Sorting Nexins; D033921:Vesicular Transport Proteins; C093846:early endosome antigen 1; C060980:phosphatidylinositol 3,4-diphosphate; D004815:Epidermal Growth Factor; D005982:Glutathione Transferase; D000077191:Wortmannin