title: Dynamin 2 mediates fluid-phase micropinocytosis in epithelial cells.
abstract: It is well-known that dynamin 2 (Dyn2) participates in clathrin- and caveolae-mediated endocytosis; however, the role of Dyn2 in coat-independent endocytic processes remains controversial. Here we demonstrate a role for specific spliced variants of Dyn2 in the micropinocytosis of fluid in epithelial cells, independent of coat-mediated endocytic pathways. A general inhibition of Dyn2 was first performed using either microinjection of anti-dynamin antibodies or Dyn2-siRNA treatment. Both of these methods resulted in reduced uptake of transferrin, a marker for clathrin-mediated endocytosis, and, under unstimulated conditions, reduced the uptake of the fluid-phase markers dextran and horseradish peroxidase (HRP). By contrast, cells treated similarly but stimulated with serum or EGF internalized substantial amounts of dextran or HRP, indicating that Dyn2 is not required for stimulated fluid uptake via macropinocytosis. We next tested whether a specific spliced variant might selectively affect fluid-phase endocytosis. Mutation of specific Dyn2 spliced variants resulted in a differential attenuation of transferrin and dextran internalization. Furthermore, the reduction in fluid uptake in Dyn2-siRNA-treated cells was only rescued upon re-expression of select spliced variants. These findings suggest that Dyn2 function is required for the coat-independent internalization of fluid through endocytic pathways distinct from macropinocytosis and, in addition, implicate different Dyn2 spliced variants in specific endocytic functions.
authors.affiliation: Mayo Clinic, Department of Biochemistry and Molecular Biology and the Miles and Shirley Fiterman Center for Digestive Diseases, Rochester, MN 55905, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Cao
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Muyiwa
authors.initials: M
authors.lastname: Awoniyi
authors.forename: John R
authors.initials: JR
authors.lastname: Henley
authors.forename: Mark A
authors.initials: MA
authors.lastname: McNiven
mesh_terms: D000818:Animals; D018929:Cell Culture Techniques; D002460:Cell Line; D002999:Clone Cells; D004285:Dogs; D034285:Dynamin II / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006735:Horseradish Peroxidase / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D007668:Kidney / Q000166:cytology; D008099:Liver / Q000166:cytology; D051379:Mice; D009154:Mutation; D009841:Oligonucleotides / Q000378:metabolism; D010873:Pinocytosis / Q000502:physiology*; D010957:Plasmids; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D013997:Time Factors; D014162:Transfection
chemical_list: D009841:Oligonucleotides; D034741:RNA, Small Interfering; D049452:Green Fluorescent Proteins; D006735:Horseradish Peroxidase; D034285:Dynamin II