scholarly journals Modulation of the extracellular matrix patterning of thrombospondins by actin dynamics and thrombospondin oligomer state

2015 ◽  
Vol 35 (3) ◽  
Author(s):  
Andrew L. Hellewell ◽  
Xianyun Gong ◽  
Karsten Schärich ◽  
Elena D. Christofidou ◽  
Josephine C. Adams
Keyword(s):  
Extracellular Matrix ◽  
Actin Filament ◽  
Actin Dynamics ◽  
Filament Dynamics ◽  
Evolutionarily Conserved

We report that the patterning of thrombospondin (TSP) deposition into the extracellular matrix (ECM) is modulated by actin filament dynamics. Whereas actin-dependence of patterning is evolutionarily conserved, the extent of modulation correlates inversely with the oligomer state of the TSP.

scholarly journals Tropomyosin inhibits ADF/cofilin-dependent actin filament dynamics

2002 ◽  
Vol 156 (6) ◽  
pp. 1065-1076 ◽  
Author(s):  
Shoichiro Ono ◽  
Kanako Ono
Keyword(s):  
Actin Filament ◽  
Actin Filaments ◽  
Actin Polymerization ◽  
Biological Properties ◽  
Actin Dynamics ◽  
Background Suppression ◽  
Thin Filaments ◽  
Actin Organization ◽  
C Elegans ◽  
Filament Dynamics

Tropomyosin binds to actin filaments and is implicated in stabilization of actin cytoskeleton. We examined biochemical and cell biological properties of Caenorhabditis elegans tropomyosin (CeTM) and obtained evidence that CeTM is antagonistic to ADF/cofilin-dependent actin filament dynamics. We purified CeTM, actin, and UNC-60B (a muscle-specific ADF/cofilin isoform), all of which are derived from C. elegans, and showed that CeTM and UNC-60B bound to F-actin in a mutually exclusive manner. CeTM inhibited UNC-60B–induced actin depolymerization and enhancement of actin polymerization. Within isolated native thin filaments, actin and CeTM were detected as major components, whereas UNC-60B was present at a trace amount. Purified UNC-60B was unable to interact with the native thin filaments unless CeTM and other associated proteins were removed by high-salt extraction. Purified CeTM was sufficient to restore the resistance of the salt-extracted filaments from UNC-60B. In muscle cells, CeTM and UNC-60B were localized in different patterns. Suppression of CeTM by RNA interference resulted in disorganized actin filaments and paralyzed worms in wild-type background. However, in an ADF/cofilin mutant background, suppression of CeTM did not worsen actin organization and worm motility. These results suggest that tropomyosin is a physiological inhibitor of ADF/cofilin-dependent actin dynamics.

scholarly journals Side-binding proteins modulate actin filament dynamics

2014 ◽  
Author(s):  
Alvaro H. Crevenna ◽  
Marcelino Arciniega ◽  
Aurelie Dupont ◽  
Kaja Kowalska ◽  
Oliver Lange ◽  
...  
Keyword(s):  
Actin Filament ◽  
Brownian Dynamics ◽  
Actin Polymerization ◽  
Actin Dynamics ◽  
Central Feature ◽  
Filament Dynamics ◽  
Filament Structure ◽  
The Rich ◽  
Dynamics Simulations ◽  
Pointed End

Actin filament dynamics govern many key physiological processes from cell motility to tissue morphogenesis. A central feature of actin dynamics is the capacity of the filament to polymerize and depolymerize at its ends in response to cellular conditions. It is currently thought that filament kinetics can be described by a single rate constant for each end. Here, using direct visualization of single actin filament elongation, we show that actin polymerization kinetics at both filament ends are strongly influenced by proteins that bind to the lateral filament surface. We also show that the less dynamic end, called the pointed-end, has a non-elongating state that dominates the observed filament kinetic asymmetry. Estimates of filament flexibility and Brownian dynamics simulations suggest that the observed kinetic diversity arises from structural alteration. Tuning filament kinetics by exploiting the natural malleability of the actin filament structure may be a ubiquitous mechanism to generate the rich variety of observed cellular actin dynamics.

scholarly journals Actin filament dynamics are dominated by rapid growth and severing activity in the Arabidopsis cortical array

2009 ◽  
Vol 184 (2) ◽  
pp. 269-280 ◽  
Author(s):  
Christopher J. Staiger ◽  
Michael B. Sheahan ◽  
Parul Khurana ◽  
Xia Wang ◽  
David W. McCurdy ◽  
...  
Keyword(s):  
Actin Filament ◽  
Actin Filaments ◽  
Stochastic Dynamics ◽  
Actin Dynamics ◽  
Epifluorescence Microscopy ◽  
Actin Assembly ◽  
Cortical Actin ◽  
Filament Dynamics ◽  
Cortical Array

Metazoan cells harness the power of actin dynamics to create cytoskeletal arrays that stimulate protrusions and drive intracellular organelle movements. In plant cells, the actin cytoskeleton is understood to participate in cell elongation; however, a detailed description and molecular mechanism(s) underpinning filament nucleation, growth, and turnover are lacking. Here, we use variable-angle epifluorescence microscopy (VAEM) to examine the organization and dynamics of the cortical cytoskeleton in growing and nongrowing epidermal cells. One population of filaments in the cortical array, which most likely represent single actin filaments, is randomly oriented and highly dynamic. These filaments grow at rates of 1.7 µm/s, but are generally short-lived. Instead of depolymerization at their ends, actin filaments are disassembled by severing activity. Remodeling of the cortical actin array also features filament buckling and straightening events. These observations indicate a mechanism inconsistent with treadmilling. Instead, cortical actin filament dynamics resemble the stochastic dynamics of an in vitro biomimetic system for actin assembly.

Single-molecule imaging of IQGAP1 regulating actin filament dynamics

2021 ◽  
Author(s):  
Gregory J. Hoeprich ◽  
Amy N. Sinclair ◽  
Shashank Shekhar ◽  
Bruce L. Goode
Keyword(s):  
Cell Adhesion ◽  
Actin Filament ◽  
Single Molecule ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Functional Effect ◽  
Single Filament ◽  
Filament Dynamics ◽  
Do So

IQGAP is a conserved family of actin-binding proteins with essential roles in cell motility, cytokinesis, and cell adhesion, yet there remains a limited understanding of how IQGAP proteins directly influence actin filament dynamics. To close this gap, we used single-molecule and single-filament TIRF microscopy to observe IQGAP regulating actin dynamics in real time. To our knowledge, this is the first study to do so. Our results demonstrate that full-length human IQGAP1 forms dimers that stably bind to actin filament sides and transiently cap barbed ends. These interactions organize filaments into thin bundles, suppress barbed end growth, and inhibit filament disassembly. Surprisingly, each activity depends on distinct combinations of IQGAP1 domains and/or dimerization, suggesting that different mechanisms underlie each functional effect on actin. These observations have important implications for how IQGAP functions as an actin regulator in vivo, and how it may be regulated in different biological settings. [Media: see text] [Media: see text] [Media: see text]

scholarly journals Actin Depolymerizing Factor (ADF/Cofilin) Enhances the Rate of Filament Turnover: Implication in Actin-based Motility

1997 ◽  
Vol 136 (6) ◽  
pp. 1307-1322 ◽  
Author(s):  
Marie-France Carlier ◽  
Valérie Laurent ◽  
Jérôme Santolini ◽  
Ronald Melki ◽  
Dominique Didry ◽  
...  
Keyword(s):  
Actin Filament ◽  
Atp Hydrolysis ◽  
Fold Increase ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Actin Depolymerizing Factor ◽  
Filament Dynamics ◽  
Relevant Effect

Actin-binding proteins of the actin depolymerizing factor (ADF)/cofilin family are thought to control actin-based motile processes. ADF1 from Arabidopsis thaliana appears to be a good model that is functionally similar to other members of the family. The function of ADF in actin dynamics has been examined using a combination of physical–chemical methods and actin-based motility assays, under physiological ionic conditions and at pH 7.8. ADF binds the ADPbound forms of G- or F-actin with an affinity two orders of magnitude higher than the ATP- or ADP-Pi– bound forms. A major property of ADF is its ability to enhance the in vitro turnover rate (treadmilling) of actin filaments to a value comparable to that observed in vivo in motile lamellipodia. ADF increases the rate of propulsion of Listeria monocytogenes in highly diluted, ADF-limited platelet extracts and shortens the actin tails. These effects are mediated by the participation of ADF in actin filament assembly, which results in a change in the kinetic parameters at the two ends of the actin filament. The kinetic effects of ADF are end specific and cannot be accounted for by filament severing. The main functionally relevant effect is a 25-fold increase in the rate of actin dissociation from the pointed ends, while the rate of dissociation from the barbed ends is unchanged. This large increase in the rate-limiting step of the monomer-polymer cycle at steady state is responsible for the increase in the rate of actin-based motile processes. In conclusion, the function of ADF is not to sequester G-actin. ADF uses ATP hydrolysis in actin assembly to enhance filament dynamics.

scholarly journals Single-molecule imaging of IQGAP1 regulating actin filament dynamics in real time

2021 ◽  
Author(s):  
Gregory J Hoeprich ◽  
Shashank Shekhar ◽  
Bruce L Goode
Keyword(s):  
Real Time ◽  
Actin Filament ◽  
Single Molecule ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Functional Effect ◽  
Single Filament ◽  
Filament Dynamics ◽  
Do So

IQGAP is a conserved family of actin-binding proteins with essential roles in cell motility, cytokinesis, and cell adhesion, yet it has remained poorly understood how IQGAP proteins directly regulate actin filament dynamics. To close this gap, we used single-molecule and single-filament TIRF microscopy to directly visualize IQGAP regulating actin dynamics in real time. To our knowledge, this is the first study to do so. Our results show that full-length human IQGAP1 forms dimers that stably bind to filament sides and transiently cap barbed ends. These interactions organize actin filaments into thin bundles, suppress barbed end growth, and inhibit filament disassembly. Surprisingly, each activity depends on distinct combinations of IQGAP1 domains and/or dimerization, suggesting that different mechanisms underlie each functional effect on actin. These observations have important implications for how IQGAP functions as a direct actin regulator in vivo, and how it is deployed and regulated in different biological settings.

scholarly journals Two biochemically distinct and tissue-specific twinfilin isoforms are generated from the mouse Twf2 gene by alternative promoter usage

2008 ◽  
Vol 417 (2) ◽  
pp. 593-600 ◽  
Author(s):  
Elisa M. Nevalainen ◽  
Aneta Skwarek-Maruszewska ◽  
Attila Braun ◽  
Markus Moser ◽  
Pekka Lappalainen
Keyword(s):  
Actin Filament ◽  
Alternative Promoter ◽  
Actin Dynamics ◽  
Tissue Specific ◽  
Capping Protein ◽  
Muscle Tissues ◽  
Evolutionarily Conserved ◽  
Cytoskeletal Dynamics ◽  
Promoter Usage ◽  
End Capping

Twf (twinfilin) is an evolutionarily conserved regulator of actin dynamics composed of two ADF-H (actin-depolymerizing factor homology) domains. Twf binds actin monomers and heterodimeric capping protein with high affinity. Previous studies have demonstrated that mammals express two Twf isoforms, Twf1 and Twf2, of which at least Twf1 also regulates cytoskeletal dynamics by capping actin filament barbed-ends. In the present study, we show that alternative promoter usage of the mouse Twf2 gene generates two isoforms, which differ from each other only at their very N-terminal region. Of these isoforms, Twf2a is predominantly expressed in non-muscle tissues, whereas expression of Twf2b is restricted to heart and skeletal muscle. Both proteins bind actin monomers and capping protein, as well as efficiently capping actin filament barbed-ends. However, the N-terminal ADF-H domain of Twf2b interacts with ADP-G-actin with a 5-fold higher affinity than with ATP-G-actin, whereas the corresponding domain of Twf2a binds ADP-G-actin and ATP-G-actin with equal affinities. Taken together, these results show that, like Twf1, mouse Twf2 is a filament barbed-end capping protein, and that two tissue-specific and biochemically distinct isoforms are generated from the Twf2 gene through alternative promoter usage.

scholarly journals Side-binding proteins modulate actin filament dynamics

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Alvaro H Crevenna ◽  
Marcelino Arciniega ◽  
Aurélie Dupont ◽  
Naoko Mizuno ◽  
Kaja Kowalska ◽  
...  
Keyword(s):  
Actin Filament ◽  
Actin Polymerization ◽  
Actin Dynamics ◽  
Central Feature ◽  
Filament Dynamics ◽  
Physiological Processes ◽  
Filament Structure ◽  
Pointed End ◽  
Filament Surface ◽  
As Effects

Actin filament dynamics govern many key physiological processes from cell motility to tissue morphogenesis. A central feature of actin dynamics is the capacity of filaments to polymerize and depolymerize at their ends in response to cellular conditions. It is currently thought that filament kinetics can be described by a single rate constant for each end. In this study, using direct visualization of single actin filament elongation, we show that actin polymerization kinetics at both filament ends are strongly influenced by the binding of proteins to the lateral filament surface. We also show that the pointed-end has a non-elongating state that dominates the observed filament kinetic asymmetry. Estimates of flexibility as well as effects on fragmentation and growth suggest that the observed kinetic diversity arises from structural alteration. Tuning elongation kinetics by exploiting the malleability of the filament structure may be a ubiquitous mechanism to generate a rich variety of cellular actin dynamics.

scholarly journals The Three Mouse Actin-depolymerizing Factor/Cofilins Evolved to Fulfill Cell-Type–specific Requirements for Actin Dynamics

2002 ◽  
Vol 13 (1) ◽  
pp. 183-194 ◽  
Author(s):  
Maria K. Vartiainen ◽  
Tuija Mustonen ◽  
Pieta K. Mattila ◽  
Pauli J. Ojala ◽  
Irma Thesleff ◽  
...  
Keyword(s):  
Actin Filament ◽  
Actin Filaments ◽  
Mammalian Species ◽  
Cell Types ◽  
Actin Dynamics ◽  
Actin Depolymerizing Factor ◽  
Filament Dynamics ◽  
Adult Mice ◽  
Multicellular Organisms ◽  
Different Cell Types

Actin-depolymerizing factor (ADF)/cofilins are essential regulators of actin filament turnover. Several ADF/cofilin isoforms are found in multicellular organisms, but their biological differences have remained unclear. Herein, we show that three ADF/cofilins exist in mouse and most likely in all other mammalian species. Northern blot and in situ hybridization analyses demonstrate that cofilin-1 is expressed in most cell types of embryos and adult mice. Cofilin-2 is expressed in muscle cells and ADF is restricted to epithelia and endothelia. Although the three mouse ADF/cofilins do not show actin isoform specificity, they all depolymerize platelet actin filaments more efficiently than muscle actin. Furthermore, these ADF/cofilins are biochemically different. The epithelial-specific ADF is the most efficient in turning over actin filaments and promotes a stronger pH-dependent actin filament disassembly than the two other isoforms. The muscle-specific cofilin-2 has a weaker actin filament depolymerization activity and displays a 5–10-fold higher affinity for ATP-actin monomers than cofilin-1 and ADF. In steady-state assays, cofilin-2 also promotes filament assembly rather than disassembly. Taken together, these data suggest that the three biochemically distinct mammalian ADF/cofilin isoforms evolved to fulfill specific requirements for actin filament dynamics in different cell types.

Sign in / Sign up

Export Citation Format

Share Document