title: Regulation of cortactin/dynamin interaction by actin polymerization during the fission of clathrin-coated pits.
abstract: Separation of clathrin-coated pits from the plasma membrane, a key event during endocytosis, is thought to be driven by dynamin and the actin cytoskeleton. However, the mechanism for the actin-mediated endocytosis remains elusive. RNA interference-mediated suppression of cortactin, an F-actin binding protein that promotes Arp2/3 complex-mediated actin polymerization, effectively blocked transferrin uptake. Depletion of cortactin in brain cytosol inhibited formation of clathrin-coated vesicles by 70% as analyzed in a cell-free system. Interestingly, the interaction between cortactin and dynamin 2 in cells was dependent on actin polymerization and was attenuated upon cell exposure to cytochalasin D as analyzed by immunofluorescence and immunoprecipitation. Moreover, a cortactin mutant deficient in Arp2/3 binding colocalized less efficiently with dynamin 2 and inhibited the uptake of transferrin. The effect of actin polymerization on the interaction between cortactin and the dynamin proline-rich domain (PRD) was further evaluated under a condition for actin polymerization in vitro. Cortactin binds to the dynamin PRD with an equilibrium dissociation constant of 81 nM in the presence of the Arp2/3 complex and actin, and 617 nM in the absence of actin polymerization. Taken together, these data demonstrate that Arp2/3-mediated actin polymerization regulates the accessibility of cortactin to dynamin 2 and imply a novel mechanism by which cortactin and dynamin drive the fission of clathrin-coated pits in an actin polymerization dependent manner.
authors.affiliation: Department of Pathology, Greenebaum Cancer Center, University of Maryland School of Medicine, 15601 Crabbs Branch Way, Rockville, MD 20855, USA.
authors.forename: Jianwei
authors.initials: J
authors.lastname: Zhu
authors.forename: Kang
authors.initials: K
authors.lastname: Zhou
authors.forename: Jian-Jiang
authors.initials: JJ
authors.lastname: Hao
authors.forename: Jiali
authors.initials: J
authors.lastname: Liu
authors.forename: Nicole
authors.initials: N
authors.lastname: Smith
authors.forename: Xi
authors.initials: X
authors.lastname: Zhan
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000595:Amino Acid Sequence; D000818:Animals; D022163:Clathrin-Coated Vesicles / Q000737:chemistry / Q000502:physiology*; D003034:Coated Pits, Cell-Membrane / Q000737:chemistry / Q000502:physiology*; D051356:Cortactin; D003598:Cytoskeletal Proteins / Q000378:metabolism; D034281:Dynamins / Q000737:chemistry / Q000378:metabolism*; D004705:Endocytosis; D006801:Humans; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism* / Q000502:physiology; D008969:Molecular Sequence Data; D051381:Rats
chemical_list: C495926:ACTR2 protein, human; C495928:ACTR3 protein, human; D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; C495927:Actr2 protein, mouse; C495929:Actr3 protein, mouse; C495868:CTTN protein, human; D051356:Cortactin; C495869:Cttn protein, mouse; C495870:Cttn protein, rat; D003598:Cytoskeletal Proteins; D008840:Microfilament Proteins; D034281:Dynamins