title: A Hip1R-cortactin complex negatively regulates actin assembly associated with endocytosis.
abstract: Actin polymerization plays a critical role in clathrin-mediated endocytosis in many cell types, but how polymerization is regulated is not known. Hip1R may negatively regulate actin assembly during endocytosis because its depletion increases actin assembly at endocytic sites. Here, we show that the C-terminal proline-rich domain of Hip1R binds to the SH3 domain of cortactin, a protein that binds to dynamin, actin filaments and the Arp2/3 complex. We demonstrate that Hip1R deleted for the cortactin-binding site loses its ability to rescue fully the formation of abnormal actin structures at endocytic sites induced by Hip1R siRNA. To determine when this complex might function during endocytosis, we performed live cell imaging. The maximum in vivo recruitment of Hip1R, clathrin and cortactin to endocytic sites was coincident, and all three proteins disappeared together upon formation of a clathrin-coated vesicle. Finally, we showed that Hip1R inhibits actin assembly by forming a complex with cortactin that blocks actin filament barbed end elongation.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, USA.
authors.forename: Christophe
authors.initials: C
authors.lastname: Le Clainche
authors.forename: Barbara S
authors.initials: BS
authors.lastname: Pauly
authors.forename: Claire X
authors.initials: CX
authors.lastname: Zhang
authors.forename: Asa E Y
authors.initials: AE
authors.lastname: Engqvist-Goldstein
authors.forename: Kimberley
authors.initials: K
authors.lastname: Cunningham
authors.forename: David G
authors.initials: DG
authors.lastname: Drubin
mesh_terms: D000199:Actins / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D001665:Binding Sites; D051356:Cortactin / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D034281:Dynamins / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D000071058:Huntingtin Protein; D008840:Microfilament Proteins; D008954:Models, Biological; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D011485:Protein Binding; D034622:RNA Interference; D015398:Signal Transduction / Q000187:drug effects; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; C495868:CTTN protein, human; D051356:Cortactin; C489537:HIP1R protein, human; C086055:HTT protein, human; D000071058:Huntingtin Protein; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D033921:Vesicular Transport Proteins; D034281:Dynamins