scholarly journals The alpha and beta subunits of nematode actin capping protein function in yeast.

1993 ◽  
Vol 4 (9) ◽  
pp. 907-917 ◽  
Author(s):  
J A Waddle ◽  
J A Cooper ◽  
R H Waterston
Keyword(s):  
Actin Cytoskeleton ◽  
Protein Function ◽  
Actin Polymerization ◽  
Beta Subunits ◽  
Wild Type ◽  
Capping Protein ◽  
Actin Capping Protein ◽  
Actin Capping ◽  
Chicken Skeletal Muscle ◽  
Null Mutants

We cloned and analyzed two genes, cap-1 and cap-2, which encode the alpha and beta subunits of Caenorhabditis elegans capping protein (CP). The nematode CP subunits are 55% (cap-1) and 66% (cap-2) identical to the chicken CP subunits and 32% (cap-1) and 48% (cap-2) identical to the yeast CP subunits. Purified nematode CP made by expression of both subunits in yeast is functionally similar to chicken skeletal muscle CP in two different actin polymerization assays. The abnormal cell morphology and disorganized actin cytoskeleton of yeast CP null mutants are restored to wild-type by expression of the nematode CP subunits. Expression of the nematode CP alpha or beta subunit is sufficient to restore viability to yeast cap1 sac6 or cap2 sac6 double mutants, respectively. Therefore, despite evolution of the nematode actin cytoskeleton to a state far more complex than that of yeast, one important component can function in both organisms.

scholarly journals Regulation of Sodium Channel Activity by Capping of Actin Filaments

2003 ◽  
Vol 14 (4) ◽  
pp. 1709-1716 ◽  
Author(s):  
Ekaterina V. Shumilina ◽  
Yuri A. Negulyaev ◽  
Elena A. Morachevskaya ◽  
Horst Hinssen ◽  
Sofia Yu Khaitlina
Keyword(s):  
Plasma Membrane ◽  
Sodium Channel ◽  
Actin Filaments ◽  
Actin Polymerization ◽  
Actin Dynamics ◽  
Channel Activity ◽  
Capping Protein ◽  
Channel Inactivation ◽  
Actin Capping Protein ◽  
Actin Capping

Ion transport in various tissues can be regulated by the cortical actin cytoskeleton. Specifically, involvement of actin dynamics in the regulation of nonvoltage-gated sodium channels has been shown. Herein, inside-out patch clamp experiments were performed to study the effect of the heterodimeric actin capping protein CapZ on sodium channel regulation in leukemia K562 cells. The channels were activated by cytochalasin-induced disruption of actin filaments and inactivated by G-actin under ionic conditions promoting rapid actin polymerization. CapZ had no direct effect on channel activity. However, being added together with G-actin, CapZ prevented actin-induced channel inactivation, and this effect occurred at CapZ/actin molar ratios from 1:5 to 1:100. When actin was allowed to polymerize at the plasma membrane to induce partial channel inactivation, subsequent addition of CapZ restored the channel activity. These results can be explained by CapZ-induced inhibition of further assembly of actin filaments at the plasma membrane due to the modification of actin dynamics by CapZ. No effect on the channel activity was observed in response to F-actin, confirming that the mechanism of channel inactivation does not involve interaction of the channel with preformed filaments. Our data show that actin-capping protein can participate in the cytoskeleton-associated regulation of sodium transport in nonexcitable cells.

scholarly journals Actin-capping protein promotes microtubule stability by antagonizing the actin activity of mDia1

2012 ◽  
Vol 23 (20) ◽  
pp. 4032-4040 ◽  
Author(s):  
Francesca Bartolini ◽  
Nagendran Ramalingam ◽  
Gregg G. Gundersen
Keyword(s):  
Actin Filaments ◽  
Actin Polymerization ◽  
Dependent Manner ◽  
Proliferating Cells ◽  
Capping Protein ◽  
Microtubule Stability ◽  
Selective Stabilization ◽  
Actin Capping Protein ◽  
Actin Capping ◽  
Interfering Rna

In migrating fibroblasts, RhoA and its effector mDia1 regulate the selective stabilization of microtubules (MTs) polarized in the direction of migration. The conserved formin homology 2 domain of mDia1 is involved both in actin polymerization and MT stabilization, and the relationship between these two activities is unknown. We found that latrunculin A (LatA) and jasplakinolide, actin drugs that release mDia1 from actin filament barbed ends, stimulated stable MT formation in serum-starved fibroblasts and caused a redistribution of mDia1 onto MTs. Knockdown of mDia1 by small interfering RNA (siRNA) prevented stable MT induction by LatA, whereas blocking upstream Rho or integrin signaling had no effect. In search of physiological regulators of mDia1, we found that actin-capping protein induced stable MTs in an mDia1-dependent manner and inhibited the translocation of mDia on the ends of growing actin filaments. Knockdown of capping protein by siRNA reduced stable MT levels in proliferating cells and in starved cells stimulated with lysophosphatidic acid. These results show that actin-capping protein is a novel regulator of MT stability that functions by antagonizing mDia1 activity toward actin filaments and suggest a novel form of actin–MT cross-talk in which a single factor acts sequentially on actin and MTs.

The Role of Tropomodulin in Cardiac Function and Remodeling

2004 ◽  
Author(s):  
Andrea Bryan ◽  
Amy Sung ◽  
Ian Lian ◽  
Jeffrey Omens
Keyword(s):  
Cardiac Function ◽  
Knockout Mice ◽  
Surface Strain ◽  
Loading Conditions ◽  
Wild Type ◽  
Capping Protein ◽  
Actin Capping Protein ◽  
Actin Capping ◽  
Rv Function

Tropomodulin is an actin-capping protein in cardiac muscle, and is associated with both sarcomeric and cytoskeletal actin filaments. Homozygous knockout of erythrocyte tropomodulin (E-Tmod) is embryonically lethal, but heterozygous knockout (+/-) mice survive. Heterozygous E-Tmod knockout resulted in smaller right ventricle (RV) cavities and free walls compared to wild type. To investigate the effect of heterozygous tropomodulin knockout on mouse cardiac function and remodeling, mice (n=6 to 9) were subjected to 5 weeks of hypoxia to increase loading conditions on the RV via pulmonary hypertension. The effect of loading was determined by measuring the volume of RV anatomical features, and surface strain during the cardiac cycle. Although there was no significant change due to loading on RV cavity or free wall volume for wild type, geometrical measurements suggest that tissue had been redistributed. Under equal loading conditions, knockout mice exhibited a significant increase in volume for both RV features. RV epicardial function showed an increase in surface area strain at peak systole for hypoxic knockout mice. Thus it appears that heterozygous knockout of E-Tmod affects RV volume under normal and adverse loading conditions, as well as RV function.

scholarly journals Capping protein regulates actin dynamics during cytokinetic midbody maturation

2018 ◽  
Vol 115 (9) ◽  
pp. 2138-2143 ◽  
Author(s):  
Stephen J. Terry ◽  
Federico Donà ◽  
Paul Osenberg ◽  
Jeremy G. Carlton ◽  
Ulrike S. Eggert
Keyword(s):  
Actin Filaments ◽  
Actin Polymerization ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Capping Protein ◽  
Cytoskeletal Remodeling ◽  
Daughter Cells ◽  
Actin Capping Protein ◽  
Activity Loss ◽  
Actin Capping

During cytokinesis, a cleavage furrow generated by actomyosin ring contraction is restructured into the midbody, a platform for the assembly of the abscission machinery that controls the final separation of daughter cells. The polymerization state of F-actin is important during assembly, ingression, disassembly, and closure of the contractile ring and for the cytoskeletal remodeling that accompanies midbody formation and progression to abscission. Actin filaments must be cleared from the abscission sites before the final cut can take place. Although many conserved proteins interact with and influence the polymerization state of actin filaments, it is poorly understood how they regulate cytokinesis in higher eukaryotes. We report here that the actin capping protein (CP), a barbed end actin binding protein, participates in the control of actin polymerization during later stages of cytokinesis in human cells. Cells depleted of CP furrow and form early midbodies, but they fail cytokinesis. Appropriate recruitment of the ESCRT-III abscission machinery to the midbody is impaired, preventing the cell from progressing to the abscission stage. To generate actin filaments of optimal length, different actin nucleators, such as formins, balance CP’s activity. Loss of actin capping activity leads to excessive accumulation of formin-based linear actin filaments. Depletion of the formin FHOD1 results in partial rescue of CP-induced cytokinesis failure, suggesting that it can antagonize CP activity during midbody maturation. Our work suggests that the actin cytoskeleton is remodeled in a stepwise manner during cytokinesis, with different regulators at different stages required for successful progression to abscission.

scholarly journals Variants in CAPZA2, a member of an F-actin capping complex, cause intellectual disability and developmental delay

2020 ◽  
Vol 29 (9) ◽  
pp. 1537-1546
Author(s):  
Yan Huang ◽  
Xiao Mao ◽  
Richard H van Jaarsveld ◽  
Li Shu ◽  
Paulien A Terhal ◽  
...  
Keyword(s):  
Intellectual Disability ◽  
Motor Development ◽  
Actin Polymerization ◽  
De Novo ◽  
Neurodevelopmental Disorder ◽  
De Novo Mutations ◽  
Lower Efficiency ◽  
Capping Protein ◽  
Actin Capping Protein ◽  
Actin Capping

Abstract The actin cytoskeleton is regulated by many proteins including capping proteins that stabilize actin filaments (F-actin) by inhibiting actin polymerization and depolymerization. Here, we report two pediatric probands who carry damaging heterozygous de novo mutations in CAPZA2 (HGNC: 1490) and exhibit neurological symptoms with shared phenotypes including global motor development delay, speech delay, intellectual disability, hypotonia and a history of seizures. CAPZA2 encodes a subunit of an F-actin-capping protein complex (CapZ). CapZ is an obligate heterodimer consisting of α and β heterodimer conserved from yeast to human. Vertebrate genomes contain three α subunits encoded by three different genes and CAPZA2 encodes the α2 subunit. The single orthologue of CAPZA genes in Drosophila is cpa. Loss of cpa leads to lethality in early development and expression of the human reference; CAPZA2 rescues this lethality. However, the two CAPZA2 variants identified in the probands rescue this lethality at lower efficiency than the reference. Moreover, expression of the CAPZA2 variants affects bristle morphogenesis, a process that requires extensive actin polymerization and bundling during development. Taken together, our findings suggest that variants in CAPZA2 lead to a non-syndromic neurodevelopmental disorder in children.

scholarly journals The Pleckstrin Homology Domain-Containing Protein CKIP-1 Is Involved in Regulation of Cell Morphology and the Actin Cytoskeleton and Interaction with Actin Capping Protein

2005 ◽  
Vol 25 (9) ◽  
pp. 3519-3534 ◽  
Author(s):  
David A. Canton ◽  
Mary Ellen K. Olsten ◽  
Kyoungtae Kim ◽  
Amanda Doherty-Kirby ◽  
Gilles Lajoie ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Actin Cytoskeleton ◽  
Protein Kinase Ck2 ◽  
Mass Spectrometry Analysis ◽  
Pleckstrin Homology Domain ◽  
Pleckstrin Homology ◽  
Capping Protein ◽  
Actin Capping Protein ◽  
Actin Capping ◽  
Kinase Ck2

ABSTRACT CKIP-1 is a pleckstrin homology domain-containing protein that interacts with protein kinase CK2. To elucidate the functions of CKIP-1, we generated human osteosarcoma cell lines with tetracycline-regulated expression of Flag-CKIP-1. Flag-CKIP-1 expression resulted in distinct changes in cellular morphology. Therefore, we examined the actin profile by immunofluorescence, quantitative measurement of phalloidin binding, and immunoblot analysis. These studies demonstrate that Flag-CKIP-1 expression resulted in increases in F-actin staining and protein levels of β-actin. To elucidate the mechanisms behind the observed phenotype, we utilized tandem affinity purification to isolate CKIP-1 interacting proteins. Mass spectrometry analysis led to the identification of the actin capping protein subunits, CPα and CPβ, as novel CKIP-1 interaction partners. Interactions were confirmed by coimmunoprecipitation and by colocalization. Furthermore, we demonstrate that Ser9 of CPα is phosphorylated by protein kinase CK2 in vitro, that CPα is phosphorylated in vivo, and that treatment with a CK2-specific inhibitor results in a decrease in CPα phosphorylation. Finally, we demonstrate that CKIP-1 and CK2 inhibit the activity of actin capping protein at the barbed ends of actin filaments. Overall, our results are consistent with CKIP-1 playing a role in the regulation of the actin cytoskeleton through its interactions with actin capping protein.

Structural insights into the regulation of actin capping protein by twinfilin C-terminal tail

2021 ◽  
pp. 166891
Author(s):  
Shuichi Takeda ◽  
Ryotaro Koike ◽  
Ikuko Fujiwara ◽  
Akihiro Narita ◽  
Makoto Miyata ◽  
...  
Keyword(s):  
Capping Protein ◽  
Actin Capping Protein ◽  
Actin Capping ◽  
Structural Insights

scholarly journals Dynamic cortical actin remodeling by ERM proteins controls BCR microcluster organization and integrity

2011 ◽  
Vol 208 (5) ◽  
pp. 1055-1068 ◽  
Author(s):  
Bebhinn Treanor ◽  
David Depoil ◽  
Andreas Bruckbauer ◽  
Facundo D. Batista
Keyword(s):  
Actin Cytoskeleton ◽  
B Cell ◽  
Protein Function ◽  
Actin Polymerization ◽  
Lymphocyte Activation ◽  
Dominant Negative ◽  
Temporary Increase ◽  
Cortical Actin ◽  
Erm Proteins ◽  
Diffusion Dynamics

Signaling microclusters are a common feature of lymphocyte activation. However, the mechanisms controlling the size and organization of these discrete structures are poorly understood. The Ezrin-Radixin-Moesin (ERM) proteins, which link plasma membrane proteins with the actin cytoskeleton and regulate the steady-state diffusion dynamics of the B cell receptor (BCR), are transiently dephosphorylated upon antigen receptor stimulation. In this study, we show that the ERM proteins ezrin and moesin influence the organization and integrity of BCR microclusters. BCR-driven inactivation of ERM proteins is accompanied by a temporary increase in BCR diffusion, followed by BCR immobilization. Disruption of ERM protein function using dominant-negative or constitutively active ezrin constructs or knockdown of ezrin and moesin expression quantitatively and qualitatively alters BCR microcluster formation, antigen aggregation, and downstream BCR signal transduction. Chemical inhibition of actin polymerization also altered the structure and integrity of BCR microclusters. Together, these findings highlight a crucial role for the cortical actin cytoskeleton during B cell spreading and microcluster formation and function.

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