The Stress-Inducible Protein DRR1 Exerts Distinct Effects on Actin Dynamics

Cytoskeletal dynamics are pivotal to memory, learning, and stress physiology, and thus psychiatric diseases. Downregulated in renal cell carcinoma 1 (DRR1) protein was characterized as the link between stress, actin dynamics, neuronal function, and cognition. To elucidate the underlying molecular mechanisms, we undertook a domain analysis of DRR1 and probed the effects on actin binding, polymerization, and bundling, as well as on actin-dependent cellular processes. Methods: DRR1 domains were cloned and expressed as recombinant proteins to perform in vitro analysis of actin dynamics (binding, bundling, polymerization, and nucleation). Cellular actin-dependent processes were analyzed in transfected HeLa cells with fluorescence recovery after photobleaching (FRAP) and confocal microscopy. Results: DRR1 features an actin binding site at each terminus, separated by a coiled coil domain. DRR1 enhances actin bundling, the cellular F-actin content, and serum response factor (SRF)-dependent transcription, while it diminishes actin filament elongation, cell spreading, and actin treadmilling. We also provide evidence for a nucleation effect of DRR1. Blocking of pointed end elongation by addition of profilin indicates DRR1 as a novel barbed end capping factor. Conclusions: DRR1 impacts actin dynamics in several ways with implications for cytoskeletal dynamics in stress physiology and pathophysiology.

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βcap73-ARF6 Interactions Modulate Cell Shape and Motility after Injury In Vitro

Molecular Biology of the Cell ◽

10.1091/mbc.e02-11-0726 ◽

2003 ◽

Vol 14 (10) ◽

pp. 4155-4161 ◽

Cited By ~ 11

Author(s):

Kathleen N. Riley ◽

Angel E. Maldonado ◽

Patrice Tellier ◽

Crislyn D'Souza-Schorey ◽

Ira M. Herman

Keyword(s):

Western Blot ◽

Molecular Mechanisms ◽

Active Form ◽

Leading Edge ◽

Dominant Negative ◽

Actin Dynamics ◽

Actin Binding ◽

Capping Protein ◽

Actin Capping Protein

To understand the role that ARF6 plays in regulating isoactin dynamics and cell motility, we transfected endothelial cells (EC) with HA-tagged ARF6: the wild-type form (WT), a constitutively-active form unable to hydrolyze GTP (Q67L), and two dominant-negative forms, which are either unable to release GDP (T27N) or fail to bind nucleotide (N122I). Motility was assessed by digital imaging microscopy before Western blot analysis, coimmunoprecipitation, or colocalization studies using ARF6, β-actin, or β-actin-binding protein-specific antibodies. EC expressing ARF6-Q67L spread and close in vitro wounds at twice the control rates. EC expressing dominant-negative ARF6 fail to develop a leading edge, are unable to ruffle their membranes (N122I), and possess arborized processes. Colocalization studies reveal that the Q67L and WT ARF6-HA are enriched at the leading edge with β-actin; but T27N and N122I ARF6-HA are localized on endosomes together with the β-actin capping protein, βcap73. Coimmunoprecipitation and Western blot analyses reveal the direct association of ARF6-HA with βcap73, defining a role for ARF6 in signaling cytoskeletal remodeling during motility. Knowledge of the role that ARF6 plays in orchestrating membrane and β-actin dynamics will help to reveal molecular mechanisms regulating actin-based motility during development and disease.

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Actin-depolymerizing Factor and Cofilin-1 Play Overlapping Roles in Promoting Rapid F-Actin Depolymerization in Mammalian Nonmuscle Cells

Molecular Biology of the Cell ◽

10.1091/mbc.e04-07-0555 ◽

2005 ◽

Vol 16 (2) ◽

pp. 649-664 ◽

Cited By ~ 240

Author(s):

Pirta Hotulainen ◽

Eija Paunola ◽

Maria K. Vartiainen ◽

Pekka Lappalainen

Keyword(s):

Cell Motility ◽

Actin Filament ◽

Actin Filaments ◽

Actin Dynamics ◽

Actin Binding ◽

Actin Depolymerizing Factor ◽

Cytoskeletal Dynamics ◽

Nonmuscle Cells ◽

In Cells

Actin-depolymerizing factor (ADF)/cofilins are small actin-binding proteins found in all eukaryotes. In vitro, ADF/cofilins promote actin dynamics by depolymerizing and severing actin filaments. However, whether ADF/cofilins contribute to actin dynamics in cells by disassembling “old” actin filaments or by promoting actin filament assembly through their severing activity is a matter of controversy. Analysis of mammalian ADF/cofilins is further complicated by the presence of multiple isoforms, which may contribute to actin dynamics by different mechanisms. We show that two isoforms, ADF and cofilin-1, are expressed in mouse NIH 3T3, B16F1, and Neuro 2A cells. Depleting cofilin-1 and/or ADF by siRNA leads to an accumulation of F-actin and to an increase in cell size. Cofilin-1 and ADF seem to play overlapping roles in cells, because the knockdown phenotype of either protein could be rescued by overexpression of the other one. Cofilin-1 and ADF knockdown cells also had defects in cell motility and cytokinesis, and these defects were most pronounced when both ADF and cofilin-1 were depleted. Fluorescence recovery after photobleaching analysis and studies with an actin monomer-sequestering drug, latrunculin-A, demonstrated that these phenotypes arose from diminished actin filament depolymerization rates. These data suggest that mammalian ADF and cofilin-1 promote cytoskeletal dynamics by depolymerizing actin filaments and that this activity is critical for several processes such as cytokinesis and cell motility.

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Myocardin-Related Transcription Factor A Activation by Competition with WH2 Domain Proteins for Actin Binding

Molecular and Cellular Biology ◽

10.1128/mcb.01097-15 ◽

2016 ◽

Vol 36 (10) ◽

pp. 1526-1539 ◽

Cited By ~ 9

Author(s):

Julia Weissbach ◽

Franziska Schikora ◽

Anja Weber ◽

Michael Kessels ◽

Guido Posern

Keyword(s):

Serum Response Factor ◽

De Novo ◽

Actin Dynamics ◽

Actin Binding ◽

Serum Stimulation ◽

Competitive Mechanism ◽

Related Transcription Factor ◽

Simultaneous Inhibition ◽

Serum Response

The myocardin-related transcription factors (MRTFs) are coactivators of serum response factor (SRF)-mediated gene expression. Activation of MRTF-A occurs in response to alterations in actin dynamics and critically requires the dissociation of repressive G-actin–MRTF-A complexes. However, the mechanism leading to the release of MRTF-A remains unclear. Here we show that WH2 domains compete directly with MRTF-A for actin binding. Actin nucleation-promoting factors, such as N-WASP and WAVE2, as well as isolated WH2 domains, including those of Spire2 and Cobl, activate MRTF-A independently of changes in actin dynamics. Simultaneous inhibition of Arp2-Arp3 or mutation of the CA region only partially reduces MRTF-A activation by N-WASP and WAVE2. Recombinant WH2 domains and the RPEL domain of MRTF-A bind mutually exclusively to cellular and purified G-actinin vitro. The competition by different WH2 domains correlates with MRTF-SRF activation. Following serum stimulation, nonpolymerizable actin dissociates from MRTF-A, andde novoformation of the G-actin–RPEL complex is impaired by a transferable factor. Our work demonstrates that WH2 domains activate MRTF-A and contribute to target gene regulation by a competitive mechanism, independently of their role in actin filament formation.

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Villin Severing Activity Enhances Actin-based Motility In Vivo

Molecular Biology of the Cell ◽

10.1091/mbc.e06-05-0423 ◽

2007 ◽

Vol 18 (3) ◽

pp. 827-838 ◽

Cited By ~ 22

Author(s):

Céline Revenu ◽

Matthieu Courtois ◽

Alphée Michelot ◽

Cécile Sykes ◽

Daniel Louvard ◽

...

Keyword(s):

Shigella Flexneri ◽

Actin Dynamics ◽

Actin Binding ◽

Loss Of Function ◽

Mesenchymal Transition ◽

Capping Protein ◽

Function Strategy ◽

In Cells

Villin, an actin-binding protein associated with the actin bundles that support microvilli, bundles, caps, nucleates, and severs actin in a calcium-dependant manner in vitro. We hypothesized that the severing activity of villin is responsible for its reported role in enhancing cell plasticity and motility. To test this hypothesis, we chose a loss of function strategy and introduced mutations in villin based on sequence comparison with CapG. By pyrene-actin assays, we demonstrate that this mutant has a strongly reduced severing activity, whereas nucleation and capping remain unaffected. The bundling activity and the morphogenic effects of villin in cells are also preserved in this mutant. We thus succeeded in dissociating the severing from the three other activities of villin. The contribution of villin severing to actin dynamics is analyzed in vivo through the actin-based movement of the intracellular bacteria Shigella flexneri in cells expressing villin and its severing variant. The severing mutations abolish the gain of velocity induced by villin. To further analyze this effect, we reconstituted an in vitro actin-based bead movement in which the usual capping protein is replaced by either the wild type or the severing mutant of villin. Confirming the in vivo results, villin-severing activity enhances the velocity of beads by more than two-fold and reduces the density of actin in the comets. We propose a model in which, by severing actin filaments and capping their barbed ends, villin increases the concentration of actin monomers available for polymerization, a mechanism that might be paralleled in vivo when an enterocyte undergoes an epithelio-mesenchymal transition.

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A Coiled-Coil Domain of Melanophilin Is Essential for Myosin Va Recruitment and Melanosome Transport in Melanocytes

Molecular Biology of the Cell ◽

10.1091/mbc.e06-05-0457 ◽

2006 ◽

Vol 17 (11) ◽

pp. 4720-4735 ◽

Cited By ~ 61

Author(s):

Alistair N. Hume ◽

Abul K. Tarafder ◽

José S. Ramalho ◽

Elena V. Sviderskaya ◽

Miguel C. Seabra

Keyword(s):

Coiled Coil ◽

Binding Domain ◽

Actin Binding ◽

Binding Studies ◽

Null Cell ◽

Coiled Coil Region ◽

Actin Binding Domain ◽

Transport Assay ◽

Myosin Va

Melanophilin (Mlph) regulates retention of melanosomes at the peripheral actin cytoskeleton of melanocytes, a process essential for normal mammalian pigmentation. Mlph is proposed to be a modular protein binding the melanosome-associated protein Rab27a, Myosin Va (MyoVa), actin, and microtubule end-binding protein (EB1), via distinct N-terminal Rab27a-binding domain (R27BD), medial MyoVa-binding domain (MBD), and C-terminal actin-binding domain (ABD), respectively. We developed a novel melanosome transport assay using a Mlph-null cell line to study formation of the active Rab27a:Mlph:MyoVa complex. Recruitment of MyoVa to melanosomes correlated with rescue of melanosome transport and required intact R27BD together with MBD exon F–binding region (EFBD) and unexpectedly a potential coiled-coil forming sequence within ABD. In vitro binding studies indicate that the coiled-coil region enhances binding of MyoVa by Mlph MBD. Other regions of Mlph reported to interact with MyoVa globular tail, actin, or EB1 are not essential for melanosome transport rescue. The strict correlation between melanosomal MyoVa recruitment and rescue of melanosome distribution suggests that stable interaction with Mlph and MyoVa activation are nondissociable events. Our results highlight the importance of the coiled-coil region together with R27BD and EFBD regions of Mlph in the formation of the active melanosomal Rab27a-Mlph-MyoVa complex.

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Microtubule Actin Cross-Linking Factor (Macf)

The Journal of Cell Biology ◽

10.1083/jcb.147.6.1275 ◽

1999 ◽

Vol 147 (6) ◽

pp. 1275-1286 ◽

Cited By ~ 150

Author(s):

Conrad L. Leung ◽

Dongming Sun ◽

Min Zheng ◽

David R. Knowles ◽

Ronald K.H. Liem

Keyword(s):

Calcium Binding ◽

Coiled Coil ◽

Specific Protein ◽

Binding Domain ◽

Full Length ◽

Actin Binding ◽

Cross Linking ◽

Actin Binding Domain

We cloned and characterized a full-length cDNA of mouse actin cross-linking family 7 (mACF7) by sequential rapid amplification of cDNA ends–PCR. The completed mACF7 cDNA is 17 kb and codes for a 608-kD protein. The closest relative of mACF7 is the Drosophila protein Kakapo, which shares similar architecture with mACF7. mACF7 contains a putative actin-binding domain and a plakin-like domain that are highly homologous to dystonin (BPAG1-n) at its NH2 terminus. However, unlike dystonin, mACF7 does not contain a coiled–coil rod domain; instead, the rod domain of mACF7 is made up of 23 dystrophin-like spectrin repeats. At its COOH terminus, mACF7 contains two putative EF-hand calcium-binding motifs and a segment homologous to the growth arrest–specific protein, Gas2. In this paper, we demonstrate that the NH2-terminal actin-binding domain of mACF7 is functional both in vivo and in vitro. More importantly, we found that the COOH-terminal domain of mACF7 interacts with and stabilizes microtubules. In transfected cells full-length mACF7 can associate not only with actin but also with microtubules. Hence, we suggest a modified name: MACF (microtubule actin cross-linking factor). The properties of MACF are consistent with the observation that mutations in kakapo cause disorganization of microtubules in epidermal muscle attachment cells and some sensory neurons.

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NUANCE, a giant protein connecting the nucleus and actin cytoskeleton

Journal of Cell Science ◽

10.1242/jcs.115.15.3207 ◽

2002 ◽

Vol 115 (15) ◽

pp. 3207-3222 ◽

Cited By ~ 25

Author(s):

Yen-Yi Zhen ◽

Thorsten Libotte ◽

Martina Munck ◽

Angelika A. Noegel ◽

Elena Korenbaum

Keyword(s):

Actin Cytoskeleton ◽

Transmembrane Domain ◽

Coiled Coil ◽

Peripheral Blood Lymphocytes ◽

Binding Domain ◽

Actin Binding ◽

Actin Binding Domain ◽

Microfilament System

NUANCE (NUcleus and ActiN Connecting Element) was identified as a novel protein with an α-actinin-like actin-binding domain. A human 21.8 kb cDNA of NUANCE spreads over 373 kb on chromosome 14q22.1-q22.3. The cDNA sequence predicts a 796 kDa protein with an N-terminal actin-binding domain, a central coiled-coil rod domain and a predicted C-terminal transmembrane domain. High levels of NUANCE mRNA were detected in the kidney, liver,stomach, placenta, spleen, lymphatic nodes and peripheral blood lymphocytes. At the subcellular level NUANCE is present predominantly at the outer nuclear membrane and in the nucleoplasm. Domain analysis shows that the actin-binding domain binds to Factin in vitro and colocalizes with the actin cytoskeleton in vivo as a GFP-fusion protein. The C-terminal transmembrane domain is responsible for the targeting the nuclear envelope. Thus, NUANCE is the firstα-actinin-related protein that has the potential to link the microfilament system with the nucleus.

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Direct regulation of Arp2/3 complex activity and function by the actin binding protein coronin

The Journal of Cell Biology ◽

10.1083/jcb.200206113 ◽

2002 ◽

Vol 159 (6) ◽

pp. 993-1004 ◽

Cited By ~ 126

Author(s):

Christine L. Humphries ◽

Heath I. Balcer ◽

Jessica L. D'Agostino ◽

Barbara Winsor ◽

David G. Drubin ◽

...

Keyword(s):

Binding Protein ◽

Coiled Coil ◽

Actin Binding ◽

Complex Activity ◽

Actin Binding Protein ◽

Coiled Coil Domain ◽

Allele Specific ◽

And Function

Mechanisms for activating the actin-related protein 2/3 (Arp2/3) complex have been the focus of many recent studies. Here, we identify a novel mode of Arp2/3 complex regulation mediated by the highly conserved actin binding protein coronin. Yeast coronin (Crn1) physically associates with the Arp2/3 complex and inhibits WA- and Abp1-activated actin nucleation in vitro. The inhibition occurs specifically in the absence of preformed actin filaments, suggesting that Crn1 may restrict Arp2/3 complex activity to the sides of filaments. The inhibitory activity of Crn1 resides in its coiled coil domain. Localization of Crn1 to actin patches in vivo and association of Crn1 with the Arp2/3 complex also require its coiled coil domain. Genetic studies provide in vivo evidence for these interactions and activities. Overexpression of CRN1 causes growth arrest and redistribution of Arp2 and Crn1p into aberrant actin loops. These defects are suppressed by deletion of the Crn1 coiled coil domain and by arc35-26, an allele of the p35 subunit of the Arp2/3 complex. Further in vivo evidence that coronin regulates the Arp2/3 complex comes from the observation that crn1 and arp2 mutants display an allele-specific synthetic interaction. This work identifies a new form of regulation of the Arp2/3 complex and an important cellular function for coronin.

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STIP1/HOP Regulates the Actin Cytoskeleton through Interactions with Actin and Changes in Actin-Binding Proteins Cofilin and Profilin

International Journal of Molecular Sciences ◽

10.3390/ijms21093152 ◽

2020 ◽

Vol 21 (9) ◽

pp. 3152 ◽

Cited By ~ 1

Author(s):

Samantha Joy Beckley ◽

Morgan Campbell Hunter ◽

Sarah Naulikha Kituyi ◽

Ianthe Wingate ◽

Abantika Chakraborty ◽

...

Keyword(s):

Actin Cytoskeleton ◽

Binding Proteins ◽

Major Effect ◽

Vital Role ◽

Actin Dynamics ◽

Actin Binding ◽

Nuclear Accumulation ◽

Actin Binding Proteins ◽

Hsp90 Chaperone

Cell migration plays a vital role in both health and disease. It is driven by reorganization of the actin cytoskeleton, which is regulated by actin-binding proteins cofilin and profilin. Stress-inducible phosphoprotein 1 (STIP1) is a well-described co-chaperone of the Hsp90 chaperone system, and our findings identify a potential regulatory role of STIP1 in actin dynamics. We show that STIP1 can be isolated in complex with actin and Hsp90 from HEK293T cells and directly interacts with actin in vitro via the C-terminal TPR2AB-DP2 domain of STIP1, potentially due to a region spanning two putative actin-binding motifs. We found that STIP1 could stimulate the in vitro ATPase activity of actin, suggesting a potential role in the modulation of F-actin formation. Interestingly, while STIP1 depletion in HEK293T cells had no major effect on total actin levels, it led to increased nuclear accumulation of actin, disorganization of F-actin structures, and an increase and decrease in cofilin and profilin levels, respectively. This study suggests that STIP1 regulates the cytoskeleton by interacting with actin, or via regulating the ratio of proteins known to affect actin dynamics.

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Actin-binding protein G (AbpG) participates in modulating the actin cytoskeleton and cell migration in Dictyostelium discoideum

Molecular Biology of the Cell ◽

10.1091/mbc.e14-05-0972 ◽

2015 ◽

Vol 26 (6) ◽

pp. 1084-1097 ◽

Cited By ~ 3

Author(s):

Wei-Chi Lin ◽

Liang-Chen Wang ◽

Te-Ling Pang ◽

Mei-Yu Chen

Keyword(s):

Cell Migration ◽

Dictyostelium Discoideum ◽

Molecular Mechanisms ◽

Binding Protein ◽

Protein Domain ◽

Actin Dynamics ◽

Actin Binding ◽

Protein G ◽

Wild Type ◽

Actin Binding Protein

Cell migration is involved in various physiological and pathogenic events, and the complex underlying molecular mechanisms have not been fully elucidated. The simple eukaryote Dictyostelium discoideum displays chemotactic locomotion in stages of its life cycle. By characterizing a Dictyostelium mutant defective in chemotactic responses, we identified a novel actin-binding protein serving to modulate cell migration and named it actin-binding protein G (AbpG); this 971–amino acid (aa) protein contains an N-terminal type 2 calponin homology (CH2) domain followed by two large coiled-coil regions. In chemoattractant gradients, abpG− cells display normal directional persistence but migrate significantly more slowly than wild-type cells; expressing Flag-AbpG in mutant cells eliminates the motility defect. AbpG is enriched in cortical/lamellipodial regions and colocalizes well with F-actin; aa 401–600 and aa 501–550 fragments of AbpG show the same distribution as full-length AbpG. The aa 501–550 region of AbpG, which is essential for AbpG to localize to lamellipodia and to rescue the phenotype of abpG− cells, is sufficient for binding to F-actin and represents a novel actin-binding protein domain. Compared with wild-type cells, abpG− cells have significantly higher F-actin levels. Collectively our results suggest that AbpG may participate in modulating actin dynamics to optimize cell locomotion.

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