title: Actin dynamics counteract membrane tension during clathrin-mediated endocytosis.
abstract: Clathrin-mediated endocytosis is independent of actin dynamics in many circumstances but requires actin polymerization in others. We show that membrane tension determines the actin dependence of clathrin-coat assembly. As found previously, clathrin assembly supports formation of mature coated pits in the absence of actin polymerization on both dorsal and ventral surfaces of non-polarized mammalian cells, and also on basolateral surfaces of polarized cells. Actin engagement is necessary, however, to complete membrane deformation into a coated pit on apical surfaces of polarized cells and, more generally, on the surface of any cell in which the plasma membrane is under tension from osmotic swelling or mechanical stretching. We use these observations to alter actin dependence experimentally and show that resistance of the membrane to propagation of the clathrin lattice determines the distinction between 'actin dependent and 'actin independent'. We also find that light-chain-bound Hip1R mediates actin engagement. These data thus provide a unifying explanation for the role of actin dynamics in coated-pit budding.
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Steeve
authors.initials: S
authors.lastname: Boulant
authors.forename: Comert
authors.initials: C
authors.lastname: Kural
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Zeeh
authors.forename: Florent
authors.initials: F
authors.lastname: Ubelmann
authors.forename: Tomas
authors.initials: T
authors.lastname: Kirchhausen
mesh_terms: D000199:Actins / Q000378:metabolism*; D033962:Adaptor Protein Complex 2 / Q000235:genetics / Q000378:metabolism; D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D016764:Cell Polarity; D002966:Clathrin / Q000378:metabolism*; D022163:Clathrin-Coated Vesicles / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D003034:Coated Pits, Cell-Membrane / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism; D004705:Endocytosis; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D009997:Osmotic Pressure; D010091:Oximes / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D034622:RNA Interference; D013314:Stress, Mechanical; D053778:Thiazolidines / Q000494:pharmacology; D000099149:Ezrin
chemical_list: D000199:Actins; D033962:Adaptor Protein Complex 2; D000634:Aminoquinolines; D001552:Benzazepines; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002966:Clathrin; D003598:Cytoskeletal Proteins; D049452:Green Fluorescent Proteins; D010091:Oximes; D011743:Pyrimidines; D053778:Thiazolidines; D000099149:Ezrin; C487513:NSC 23766; C508970:secramine A; C037067:latrunculin A