Formin Is a Processive Motor that Requires Profilin to Accelerate Actin Assembly and Associated ATP Hydrolysis

Roméro, Stéphane; Clainche, Christophe Le; Didry, Dominique; Égile, Coumaran; Pantaloni, Dominique; Carlier, Marie-France

doi:10.1016/j.cell.2004.09.039

Cited by 508 publications

(603 citation statements)

References 54 publications

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“…2. The mDia formins were shown to bind to F-actin barbed-ends but to processively stimulate plus-end assembly [Kovar and Pollard, 2004;Romer et al, 2004;Chhabra and Higgs, 2007]. Within lamellipodia of motile cells the Arp2/3 complex constantly induces actin filament branching by inducing the nucleation of a second filament with its minus-ends sidewise attached to the mother filament [Pollard and Borisy, 2003;Lai et al, 2008].…”

Section: Repolymerization Of Actin From Actin: Tb4 Complexmentioning

confidence: 99%

The β‐thymosins: Intracellular and extracellular activities of a versatile actin binding protein family

Mannherz

Hannappel

2009

Cell Motil. Cytoskeleton

107

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The b-thymosins are N-terminally acetylated peptides of about 5 kDa molecular mass and composed of about 40-44 amino acid residues. The first member of the family, thymosin b4, was initially isolated from thymosin fraction 5, prepared in five steps from calf thymus. Thymosin b4 was supposed to be specifically produced and released by the thymic gland and to possess hormonal activities modulating the immune response. Various paracrine effects have indeed been reported for these peptides such as cardiac protection, angiogenesis, stimulation of wound healing, and hair growth. Besides these paracrine effects, it was noted that b-thymosins occur in high concentration in the cytoplasm of many eukaryotic cells and bind to the cytoskeletal component actin. Subsequently it became apparent from in vitro experiments that they preferentially bind to monomeric (G-)actin and stabilize it in its monomeric form. Due to this ability the b-thymosins are the main intracellular actin sequestering factor, i.e., they posses the ability to remove monomeric actin from the dynamic assembly and disassembly processes of the actin cytoskeleton that constantly occur in activated cells. In this review we will concentrate on the intracellular activity and localization of the b-thymosins, i.e., their modulating effect on the actin cytoskeleton. Cell Motil. Cytoskeleton 66: 839-851, 2009. '

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Section: Repolymerization Of Actin From Actin: Tb4 Complexmentioning

confidence: 99%

The β‐thymosins: Intracellular and extracellular activities of a versatile actin binding protein family

Mannherz

Hannappel

2009

Cell Motil. Cytoskeleton

107

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“…The bundle emergence has been extensively related to specific actin regulators 1-3 in vivo [4][5][6][7] . Such dynamic modulation was also highlighted by biochemical reconstitution of the actin-network assembly, in bulk solution or with biomimetic devices [8][9][10][11][12][13][14][15][16][17][18] . However, the question of how geometrical boundaries, such as those encountered in cells, affect the dynamic formation of highly ordered actin structures remains poorly studied 14,19 .…”

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confidence: 99%

Nucleation geometry governs ordered actin networks structures

et al. 2010

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Actin filaments constitute one of the main components of cell cytoskeleton. Assembled into bundles in filopodia or in stress fibres, they play a pivotal role in eukaryotes during cell morphogenesis, adhesion and motility. The bundle emergence has been extensively related to specific actin regulators 1-3 in vivo [4][5][6][7] . Such dynamic modulation was also highlighted by biochemical reconstitution of the actin-network assembly, in bulk solution or with biomimetic devices [8][9][10][11][12][13][14][15][16][17][18] . However, the question of how geometrical boundaries, such as those encountered in cells, affect the dynamic formation of highly ordered actin structures remains poorly studied 14,19 . Here we demonstrate that the nucleation geometry in itself can be the principal determinant of actin-network architecture. We developed a micropatterning method that enables the spatial control of actin nucleation sites for in vitro assays. Shape, orientation and distance between nucleation regions control filament orientation and length, filament-filament interactions and filopodium-like bundle formation. Modelling of filament growth and interactions demonstrates that basic mechanical and probabilistic laws govern actin assembly in higher-order structures.In cells, actin nucleation occurs at various locations at the plasma membrane, and bundles of parallel actin filaments are initiated at focal adhesion sites 1 or result from the rearrangement of the dynamic branched actin network of the lamellipodium 6 . Here, we modulate the positioning of nucleation sites at scales corresponding to cellular dimensions. As a first step and to precisely regulate the position of actin nucleation sites in vitro, we used a recently developed ultraviolet-based micropatterning approach 20 to create a template for the localization of the nucleation promoting factor pWA (Fig. 1a). pWA comprises the C-terminal domains from the WASP/Scar proteins, a ubiquitous family of proteins that initiate actin polymerization on a pre-existing actin filament in the presence of the Arp2/3 complex and an actin monomer [21][22][23] . A small volume of solution made of a minimal set of purified proteins ensuring actin polymerization 8,10 was placed between the pWA-coated micropatterned slide and a glass support. Functionalized micropatterns specifically initiate actin filament nucleation on their surface and promote two-dimensional growth of actin filaments (Fig. 1b). Real-time visualization of actin-filament nucleation and growth highlighted the autocatalytic process of network formation (see Supplementary Fig. S1). These networks consist of filaments growing from the pWA-coated regions, with their fast-growing, barbed end oriented outwards ( Fig. 1c and Supplementary Fig. S2 and Videos S1-S3). In agreement with actin-filament growth on glass rods 15 , as the nucleation waves propagate, dense and interconnected

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“…This activity occurs through the formin-homology (FH) 2 domain, which dimerizes to form a doughnut-shaped structure containing multiple actin-binding sites in its core Otomo et al, 2005b). This dimer is thought to stabilize otherwise unstable intermediates in the assembly of new actin filaments, and it binds processively to the fast-elongating barbed end of existing actin filaments (Pring et al, 2003;Kovar and Pollard, 2004).The adjacent FH1 domain binds profilin-actin and helps accelerate the elongation of actin filaments (Chang et al, 1997;Evangelista et al, 1997;Watanabe et al, 1997;Romero et al, 2004;Kovar et al, 2006). The budding yeast formin Bni1p also binds the actin monomer-binding protein Bud6p, which, similar to profilin, stimulates the activity of the FH2 domain (Moseley and Goode, 2005).…”

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confidence: 99%

Regulation of the Formin for3p by cdc42p and bud6p

Martin

Rincón

Basu

et al. 2007

MBoC

138

167

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Formins are conserved actin nucleators responsible for the assembly of diverse actin structures. Many formins are controlled through an autoinhibitory mechanism involving the interaction of a C-terminal DAD sequence with an N-terminal DID sequence. Here, we show that the fission yeast formin for3p, which mediates actin cable assembly and polarized cell growth, is regulated by a similar autoinhibitory mechanism in vivo. Multiple sites govern for3p localization to cell tips. The localization and activity of for3p are inhibited by an intramolecular interaction of divergent DAD and DID-like sequences. A for3p DAD mutant expressed at endogenous levels produces more robust actin cables, which appear to have normal organization and dynamics. We identify cdc42p as the primary Rho GTPase involved in actin cable assembly and for3p regulation. Both cdc42p, which binds at the N terminus of for3p, and bud6p, which binds near the C-terminal DAD-like sequence, are needed for for3p localization and full activity, but a mutation in the for3p DAD restores for3p localization and other phenotypes of cdc42 and bud6 mutants. In particular, the for3p DAD mutation suppresses the bipolar growth (NETO) defect of bud6⌬ cells. These findings suggest that cdc42p and bud6p activate for3p by relieving autoinhibition. INTRODUCTIONFormins are key regulators of the actin cytoskeleton and form a large family conserved in all eukaryotes Faix and Grosse, 2006). These proteins are necessary for the formation of numerous actin structures, including stress fibers, filopodia, cytokinetic actin rings, junctional actin structures, or actin cables. The proper regulation of formins is likely to be critical for cellular processes such as cell migration, cytokinesis, cell adhesion, and cell polarity.A well characterized biochemical activity of formins is to nucleate and elongate linear actin filaments Sagot et al., 2002b;Kovar et al., 2003;Li and Higgs, 2003;Moseley et al., 2004). This activity occurs through the formin-homology (FH) 2 domain, which dimerizes to form a doughnut-shaped structure containing multiple actin-binding sites in its core Otomo et al., 2005b). This dimer is thought to stabilize otherwise unstable intermediates in the assembly of new actin filaments, and it binds processively to the fast-elongating barbed end of existing actin filaments (Pring et al., 2003;Kovar and Pollard, 2004).The adjacent FH1 domain binds profilin-actin and helps accelerate the elongation of actin filaments (Chang et al., 1997;Evangelista et al., 1997;Watanabe et al., 1997;Romero et al., 2004;Kovar et al., 2006). The budding yeast formin Bni1p also binds the actin monomer-binding protein Bud6p, which, similar to profilin, stimulates the activity of the FH2 domain (Moseley and Goode, 2005). In addition to their activity in actin filament nucleation and elongation, some formins have been suggested to also function in actin bundling and severing, further contributing to the remodeling of actin structures (Harris et al., 2004Moseley and Goode, 2005;Harris et al., 2006...

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Formin Is a Processive Motor that Requires Profilin to Accelerate Actin Assembly and Associated ATP Hydrolysis

Cited by 508 publications

References 54 publications

The β‐thymosins: Intracellular and extracellular activities of a versatile actin binding protein family

The β‐thymosins: Intracellular and extracellular activities of a versatile actin binding protein family

Nucleation geometry governs ordered actin networks structures

Regulation of the Formin for3p by cdc42p and bud6p

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