title: SNX9 regulates dynamin assembly and is required for efficient clathrin-mediated endocytosis.
abstract: Dynamin, a central player in clathrin-mediated endocytosis, interacts with several functionally diverse SH3 domain-containing proteins. However, the role of these interactions with regard to dynamin function is poorly defined. We have investigated a recently identified protein partner of dynamin, SNX9, sorting nexin 9. SNX9 binds directly to both dynamin-1 and dynamin-2. Moreover by stimulating dynamin assembly, SNX9 stimulates dynamin's basal GTPase activity and potentiates assembly-stimulated GTPase activity on liposomes. In fixed cells, we observe that SNX9 partially localizes to clathrin-coated pits. Using total internal reflection fluorescence microscopy in living cells, we detect a transient burst of EGFP-SNX9 recruitment to clathrin-coated pits that occurs during the late stages of vesicle formation and coincides spatially and temporally with a burst of dynamin-mRFP fluorescence. Transferrin internalization is inhibited in HeLa cells after siRNA-mediated knockdown of SNX9. Thus, our results establish that SNX9 is required for efficient clathrin-mediated endocytosis and suggest that it functions to regulate dynamin activity.
authors.affiliation: Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Soulet
authors.forename: Defne
authors.initials: D
authors.lastname: Yarar
authors.forename: Marilyn
authors.initials: M
authors.lastname: Leonard
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Schmid
mesh_terms: D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002966:Clathrin / Q000378:metabolism*; D003034:Coated Pits, Cell-Membrane / Q000378:metabolism; D034284:Dynamin I / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D034285:Dynamin II / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004705:Endocytosis; D020558:GTP Phosphohydrolases / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008081:Liposomes / Q000378:metabolism; D011485:Protein Binding; D011990:Receptors, Transferrin / Q000378:metabolism; D058305:Sorting Nexins; D033921:Vesicular Transport Proteins
chemical_list: D002352:Carrier Proteins; D002966:Clathrin; D008081:Liposomes; D011990:Receptors, Transferrin; C400533:SNX9 protein, human; D058305:Sorting Nexins; D033921:Vesicular Transport Proteins; D034284:Dynamin I; D020558:GTP Phosphohydrolases; D034285:Dynamin II