The Role of Formin Tails in Actin Nucleation, Processive Elongation, and Filament Bundling

Vizcarra, Christina L.; Bor, Batbileg; Quinlan, Margot E.

doi:10.1074/jbc.m114.588368

Cited by 48 publications

(67 citation statements)

References 54 publications

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“…(15). We confirm that the very similar FSI of Fmn2 also binds with nanomolar affinity to G-actin in a 1:1 complex at low ionic strength.…”

Section: Table 2 Thermodynamic Parameters Of Formin 2 (Fmn2) and Spirsupporting

confidence: 74%

“…Similar loss of nucleation, however, in the absence of profilin, was reported for the C-terminally truncated Cappuccino formin (15). How removal of FSI affected the association of Fmn2 to barbed ends and processive activity was examined using first a seeded barbed end growth assay.…”

Section: Removal Of the Fsi From Fh1-fh2 Of Fmn2 Facilitates Its Assomentioning

confidence: 53%

“…In contrast to the much better characterized group of Diaphanous-related formins, the Fmn formin family is not regulated by Rho GTPases. Additionally, the C-terminal auto-regulatory DAD region of Diaphanous formins is replaced by a short "tail," also called Formin-Spire-Interaction (FSI) peptide, because it binds the isolated N-terminal KIND domain of the Spire protein (15)(16)(17).Spire is a modular actin-binding protein whose N-terminal constitutively active region (Nt-Spire) consists of an N-terminal KIND domain followed by four consecutive WH2 domains, which confer multifunctional actin assembly activities to Spire. All WH2 domains interact with the barbed face of actin that is exposed on G-actin and on the two terminal subunits of filament barbed ends (1, 4).…”

mentioning

confidence: 99%

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confidence: 99%

“…Recent mutagenesis studies of the Cappuccino tail indicated that this region, although different from other C-terminal regions of formins, binds G-actin and enhances actin nucleation as well as processivity in Cappuccino. These effects were recapitulated by replacing the original tail of Capuccino by the DAD domain of other formins (15).…”

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confidence: 99%

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Role of the C-terminal Extension of Formin 2 in Its Activation by Spire Protein and Processive Assembly of Actin Filaments

Montaville¹,

Kühn²,

Compper

et al. 2016

Journal of Biological Chemistry

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Formin 2 (Fmn2), a member of the FMN family of formins, plays an important role in early development. This formin cooperates with profilin and Spire, a WASP homology domain 2 (WH2) repeat protein, to stimulate assembly of a dynamic cytoplasmic actin meshwork that facilitates translocation of the meiotic spindle in asymmetric division of mouse oocytes. The kinase-like non-catalytic domain (KIND) of Spire directly interacts with the C-terminal extension of the formin homology domain 2 (FH2) domain of Fmn2, called FSI. This direct interaction is required for the synergy between the two proteins in actin assembly. We have recently demonstrated how Spire, which caps barbed ends via its WH2 domains, activates Fmn2. Fmn2 by itself associates very poorly to filament barbed ends but is rapidly recruited to Spire-capped barbed ends via the KIND domain, and it subsequently displaces Spire from the barbed end to elicit rapid processive assembly from profilin⅐actin. Here, we address the mechanism by which Spire and Fmn2 compete at barbed ends and the role of FSI in orchestrating this competition as well as in the processivity of Fmn2. We have combined microcalorimetric, fluorescence, and hydrodynamic binding assays, as well as bulk solution and single filament measurements of actin assembly, to show that removal of FSI converts Fmn2 into a Capping Protein. This activity is mimicked by association of KIND to Fmn2. In addition, FSI binds actin at filament barbed ends as a weak capper and plays a role in displacing the WH2 domains of Spire from actin, thus allowing the association of actin-binding regions of FH2 to the barbed end.Polarized assembly of actin filaments is pivotal in motile processes. It is precisely regulated by proteins that bind the barbed ends of actin filaments and either block or assist filament assembly using various mechanisms (1). Among these regulators, formins are acknowledged to nucleate and track filament barbed ends, mediating rapid processive elongation of filaments (2, 3). In contrast, WASP homology 2 (WH2) 3 repeatcontaining proteins display versatile barbed end capping or tracking and filament severing activities (4). In early oogenesis of Drosophila as well as in mammalian meiosis, a formin (Fmn2/Cappuccino) and a WH2-repeat protein (Spire) synergize in an intriguing fashion to stimulate massive assembly of a dynamic cytoplasmic actin meshwork, required for completion of crucial steps in axis patterning or asymmetric division (5-12). This complexity adds to the known need of profilin for rapid processive assembly of all formins, including Cappuccino (9). Like most formins, Fmn2 harbors conserved C-terminal formin homology 1 (FH1) and formin homology 2 (FH2) domains. The C-terminal FH1-FH2 domain of Fmn2 represents a constitutive active module in which the FH1 domain binds profilin and the FH2 domain to the barbed end of F-actin. The head-to-tail FH2 dimer of formins is thought, from structural data, to encircle the terminal and subterminal actin subunits that constitute the barbed end of the fil...

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“…(15). We confirm that the very similar FSI of Fmn2 also binds with nanomolar affinity to G-actin in a 1:1 complex at low ionic strength.…”

Section: Table 2 Thermodynamic Parameters Of Formin 2 (Fmn2) and Spirsupporting

confidence: 74%

Section: Removal Of the Fsi From Fh1-fh2 Of Fmn2 Facilitates Its Assomentioning

confidence: 53%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Role of the C-terminal Extension of Formin 2 in Its Activation by Spire Protein and Processive Assembly of Actin Filaments

Montaville¹,

Kühn²,

Compper

et al. 2016

Journal of Biological Chemistry

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Drosophila comes of age as a model system for understanding the function of cytoskeletal proteins in cells, tissues, and organisms

2015

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For the last 100 years, Drosophila melanogaster has been a powerhouse genetic system for understanding mechanisms of inheritance, development, and behavior in animals. In recent years, advances in imaging and genetic tools have led to Drosophila becoming one of the most effective systems for unlocking the subcellular functions of proteins (and particularly cytoskeletal proteins) in complex developmental settings. In this review, written for non‐Drosophila experts, we will discuss critical technical advances that have enabled these cell biological insights, highlighting three examples of cytoskeletal discoveries that have arisen as a result: (1) regulation of Arp2/3 complex in myoblast fusion, (2) cooperation of the actin filament nucleators Spire and Cappuccino in establishment of oocyte polarity, and (3) coordination of supracellular myosin cables. These specific examples illustrate the unique power of Drosophila both to uncover new cytoskeletal structures and functions, and to place these discoveries in a broader in vivo context, providing insights that would have been impossible in a cell culture model or in vitro. Many of the cellular structures identified in Drosophila have clear counterparts in mammalian cells and tissues, and therefore elucidating cytoskeletal functions in Drosophila will be broadly applicable to other organisms. © 2015 Wiley Periodicals, Inc.

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INF2‐ and FHOD‐related formins promote ovulation in the somatic gonad of C. elegans

et al. 2016

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Formins are regulators of actin filament dynamics. We demonstrate here that two formins, FHOD‐1 and EXC‐6, are important in the nematode Caenorhabditis elegans for ovulation, during which actomyosin contractions push a maturing oocyte from the gonad arm into a distensible bag‐like organ, the spermatheca. EXC‐6, a homolog of the disease‐associated mammalian formin INF2, is highly expressed in the spermatheca, where it localizes to cell‐cell junctions and to circumferential actin filament bundles. Loss of EXC‐6 does not noticeably affect the organization the actin filament bundles, and causes only a very modest increase in the population of junction‐associated actin filaments. Despite absence of a strong cytoskeletal phenotype, approximately half of ovulations in exc‐6 mutants exhibit extreme defects, including failure of the oocyte to enter the spermatheca, or breakage of the oocyte as the distal spermatheca entrance constricts during ovulation. Loss of FHOD‐1 alone has little effect, and we cannot detect FHOD‐1 in the spermatheca. However, combined loss of these formins in double fhod‐1;exc‐6 mutants results in profound ovulation defects, with significant slowing of the entry of oocytes into the spermatheca, and failure of nearly 80% of ovulations. We suggest that EXC‐6 plays a role directly in the spermatheca, perhaps by modulating the ability of the spermatheca wall to rapidly accommodate an incoming oocyte, while FHOD‐1 may play an indirect role relating to its known importance in the growth and function of the egg‐laying muscles. © 2016 The Authors. Cytoskeleton Published by Wiley Periodicals, Inc.

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The Role of Formin Tails in Actin Nucleation, Processive Elongation, and Filament Bundling

Cited by 48 publications

References 54 publications

Role of the C-terminal Extension of Formin 2 in Its Activation by Spire Protein and Processive Assembly of Actin Filaments

Role of the C-terminal Extension of Formin 2 in Its Activation by Spire Protein and Processive Assembly of Actin Filaments

Drosophila comes of age as a model system for understanding the function of cytoskeletal proteins in cells, tissues, and organisms

INF2‐ and FHOD‐related formins promote ovulation in the somatic gonad of C. elegans

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