Mammalian Abp1, a Signal-Responsive F-Actin-Binding Protein, Links the Actin Cytoskeleton to Endocytosis via the Gtpase Dynamin (original) (raw)
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Direct dynamin–actin interactions regulate the actin cytoskeleton
The EMBO Journal, 2010
The large GTPase dynamin assembles into higher order structures that are thought to promote endocytosis. Dynamin also regulates the actin cytoskeleton through an unknown, GTPase-dependent mechanism. Here, we identify a highly conserved site in dynamin that binds directly to actin filaments and aligns them into bundles. Point mutations in the actin-binding domain cause aberrant membrane ruffling and defective actin stress fibre formation in cells. Short actin filaments promote dynamin assembly into higher order structures, which in turn efficiently release the actin-capping protein (CP) gelsolin from barbed actin ends in vitro, allowing for elongation of actin filaments. Together, our results support a model in which assembled dynamin, generated through interactions with short actin filaments, promotes actin polymerization via displacement of actin-CPs.
Journal of Biological Chemistry, 2003
Piccolo is a high molecular weight multi-domain protein shown to be a structural component of the presynaptic CAZ (cytoskeletal matrix assembled at active zones). These features indicate that Piccolo may act to scaffold proteins involved in synaptic vesicle endo-and exocytosis near their site of action. To test this hypothesis, we have utilized a functional cell-based endocytosis assay and identified the N-terminal proline-rich Q domain in Piccolo as a region that interferes with clathrinmediated endocytosis. Utilizing the Piccolo Q domain as bait in a yeast two-hybrid screen, we have identified the F-actin-binding protein Abp1 (also called SH3P7 or HIP-55) as a potential binding partner for this domain. The physiological relevance of this interaction is supported by in vitro binding studies, colocalization in nerve terminals, in vivo recruitment studies, and immunoprecipitation experiments. Intriguingly, Abp1 binds to both Factin and the GTPase dynamin and has been implicated in linking the actin cytoskeleton to clathrin-mediated endocytosis. Our results suggest that Piccolo, as a structural protein of the CAZ, may serve to localize Abp1 at active zones where it can actively participate in creating a functional connection between the dynamic actin cytoskeleton and synaptic vesicle recycling.
Faculty of 1000 evaluation for Direct dynamin-actin interactions regulate the actin cytoskeleton
F1000 - Post-publication peer review of the biomedical literature, 2011
The large GTPase dynamin assembles into higher order structures that are thought to promote endocytosis. Dynamin also regulates the actin cytoskeleton through an unknown, GTPase-dependent mechanism. Here, we identify a highly conserved site in dynamin that binds directly to actin filaments and aligns them into bundles. Point mutations in the actin-binding domain cause aberrant membrane ruffling and defective actin stress fibre formation in cells. Short actin filaments promote dynamin assembly into higher order structures, which in turn efficiently release the actin-capping protein (CP) gelsolin from barbed actin ends in vitro, allowing for elongation of actin filaments. Together, our results support a model in which assembled dynamin, generated through interactions with short actin filaments, promotes actin polymerization via displacement of actin-CPs.
The mechanisms of dynamin-actin interaction
2019
Cell-cell fusion is an indispensable process in the conception, development and physiology of multicellular organisms. Here we demonstrate a direct and noncanonical role for dynamin, best known as a fission GTPase in endocytosis, in cell-cell fusion. Our genetic and cell biological analyses show that dynamin colocalizes within the F-actin-enriched podosome-like structures at the fusogenic synapse, which is required for generating invasive membrane protrusions and myoblast fusion in vivo, in an endocytosis-independent manner. Biochemical, negative stain EM and cryo-electron tomography (cryo-ET) analyses revealed that dynamin forms helices that directly bundles actin filaments by capturing multiple actin filaments at their outer rim via interactions with dynamin’s proline-rich domain. GTP hydrolysis by dynamin triggers disassembly of the dynamin helix, exposes the sides of the actin filaments, promotes dynamic Arp2/3-mediated branched actin polymerization, and generates a mechanically...
A Hip1R–cortactin complex negatively regulates actin assembly associated with endocytosis
The EMBO Journal, 2007
Actin polymerization plays a critical role in clathrinmediated 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.
Actin binding domains direct actin-binding proteins to different cytoskeletal locations
BMC Cell Biology, 2008
Background: Filamin (FLN) and non-muscle α-actinin are members of a family of F-actin crosslinking proteins that utilize Calponin Homology domains (CH-domain) for actin binding. Although these two proteins have been extensively characterized, little is known about what regulates their binding to F-actin filaments in the cell.
Developmental Cell, 2005
Cell membranes undergo continuous curvature changes as a result of membrane trafficking and cell motility. Deformations are achieved both by forces extrinsic to the membrane as well as by structural modifications in the bilayer or at the bilayer surface that favor the acquisition of curvature. We report here that a family of proteins previously implicated in the regulation of the actin cytoskeleton also have powerful lipid bilayerdeforming properties via an N-terminal module (F-BAR) similar to the BAR domain. Several such proteins, like a subset of BAR domain proteins, bind to dynamin, a GTPase implicated in endocytosis and actin dynamics, via SH3 domains. The ability of BAR and F-BAR domain proteins to induce tubular invaginations of the plasma membrane is enhanced by disruption of the actin cytoskeleton and is antagonized by dynamin. These results suggest a close interplay between the mechanisms that control actin dynamics and those that mediate plasma membrane invagination and fission.
F1000 - Post-publication peer review of the biomedical literature, 2000
The GTPase dynamin, a key player in endocytic membrane fission, interacts with numerous proteins that regulate actin dynamics and generate/sense membrane curvature. To determine the functional relationship between these proteins and dynamin, we have analyzed endocytic intermediates that accumulate in cells that lack dynamin (derived from dynamin 1 and 2 double conditional knockout mice). In these cells, actin nucleating proteins, actin and BAR domain proteins accumulate at the base of arrested endocytic clathrin-coated pits where they support the growth of dynamic long tubular necks. These results, which we show reflect the sequence of events in wildtype cells, demonstrate a concerted action of these proteins prior to, and independent of, dynamin, and emphasize similarities between clathrin-mediated endocytosis in yeast and higher eukaryotes. Our data also demonstrate that the relationship between dynamin and actin is intimately connected to dynamin's endocytic role and that dynamin terminates a powerful actin-and BAR protein-dependent tubulating activity.