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 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 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.

scholarly journals GJA1-20k, an internally translated isoform of Connexin 43, is an actin capping protein

2022 ◽  
Author(s):  
Robin Mark Shaw ◽  
Rachel Baum ◽  
Joseph Alexander Palatinus ◽  
Miriam Waghalter ◽  
Daisuke Shimura ◽  
...  
Keyword(s):  
Actin Filaments ◽  
Connexin 43 ◽  
Ischemia Reperfusion ◽  
Mitochondrial Fission ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Binding Motif ◽  
Capping Protein ◽  
Actin Capping Protein ◽  
Actin Capping

Previously, we identified that GJA1-20k, an internally translated isoform of Connexin 43, mediates an actin-dependent protective form of mitochondrial fission (Shimura, Nuebel et al. 2021). We found that when GJA1-20k is present, bands of actin surround mitochondria at locations enriched with GJA1-20k, inducing mitochondrial fission which generates less oxygen free radicals, protecting hearts subjected to ischemia-reperfusion injury. Here, we report that GJA1-20k is a direct actin binding protein and thereby identify the mechanism by which GJA1-20k is able to recruit and stabilize actin filaments around the mitochondria. Surprisingly, GJA1-20k functions as a canonical actin capping protein, producing both truncated actin puncta and stabilized actin filaments. GJA1-20k contains an RPEL-like actin binding motif, and we confirm with both computational modeling and biochemistry, that this domain is crucial for actin capping. The actin capping functionality of GJA1-20k adds GJA1-20k to the family of proteins that regulate actin dynamics. As a stress responsive protein, GJA1-20k can help explain cytoskeletal dependent responses to cellular stress, from delivery of channels to affecting mitochondrial size and function.

scholarly journals Actin capping protein regulates actomyosin contractility to maintain germline architecture in C. elegans

2021 ◽  
Author(s):  
Shinjini Ray ◽  
Priti Agarwal ◽  
Ronen Zaidel-Bar
Keyword(s):  
Physiological Role ◽  
Fold Increase ◽  
Actin Dynamics ◽  
Structural Defects ◽  
Capping Protein ◽  
C Elegans ◽  
Actomyosin Contractility ◽  
Actin Capping Protein ◽  
Actin Capping

Actin dynamics play an important role in the morphogenesis of cells and tissues, yet the control of actin filament growth takes place at the molecular level. A challenge in the field is to link the molecular function of actin regulators with their physiological function. Here, we report the in vivo role of the actin capping protein CAP-1 in the C. elegans germline. We show that CAP-1 is associated with actomyosin structures in the cortex and rachis, where it keeps the level of contractility in check. A 60% reduction in the level of CAP-1 leads to a 2-fold increase in F-actin and non-muscle myosin II and only a 30% increase in Arp2/3. CAP-1 depletion leads to severe structural defects in the syncytial germline and oocytes, which can be rescued by reducing myosin activity. Thus, we uncover a physiological role for actin capping protein in maintaining C. elegans fertility by regulating the level of actomyosin contractility.

scholarly journals Cap Z(36/32), a barbed end actin-capping protein, is a component of the Z-line of skeletal muscle.

1987 ◽  
Vol 105 (1) ◽  
pp. 371-379 ◽  
Author(s):  
J F Casella ◽  
S W Craig ◽  
D J Maack ◽  
A E Brown
Keyword(s):  
Electron Microscopy ◽  
Skeletal Muscle ◽  
Actin Filaments ◽  
Biological Activities ◽  
Capping Protein ◽  
Actin Capping Protein ◽  
In Vitro Effects ◽  
Actin Capping

Various biological activities have been attributed to actin-capping proteins based on their in vitro effects on actin filaments. However, there is little direct evidence for their in vivo activities. In this paper, we show that Cap Z(36/32), a barbed end, actin-capping protein isolated from muscle (Casella, J. F., D. J. Maack, and S. Lin, 1986, J. Biol. Chem., 261:10915-10921) is localized to the barbed ends of actin filaments by electron microscopy and to the Z-line of chicken skeletal muscle by indirect immunofluorescence and electron microscopy. Since actin filaments associate with the Z-line at their barbed ends, these findings suggest that Cap Z(36/32) may play a role in regulating length, orienting, or attaching actin filaments to Z-discs.

scholarly journals Vertebrate Isoforms of Actin Capping Protein β Have Distinct Functions in Vivo

1999 ◽  
Vol 147 (6) ◽  
pp. 1287-1298 ◽  
Author(s):  
Marilyn C. Hart ◽  
John A. Cooper
Keyword(s):  
Actin Filaments ◽  
Cell Periphery ◽  
Actin Assembly ◽  
Severe Phenotype ◽  
Intercalated Disc ◽  
Capping Protein ◽  
Intercalated Discs ◽  
Actin Capping Protein ◽  
Actin Capping

Actin capping protein (CP) binds barbed ends of actin filaments to regulate actin assembly. CP is an α/β heterodimer. Vertebrates have conserved isoforms of each subunit. Muscle cells contain two β isoforms. β1 is at the Z-line; β2 is at the intercalated disc and cell periphery in general. To investigate the functions of the isoforms, we replaced one isoform with another using expression in hearts of transgenic mice. Mice expressing β2 had a severe phenotype with juvenile lethality. Myofibril architecture was severely disrupted. The β2 did not localize to the Z-line. Therefore, β1 has a distinct function that includes interactions at the Z-line. Mice expressing β1 showed altered morphology of the intercalated disc, without the lethality or myofibril disruption of the β2-expressing mice. The in vivo function of CP is presumed to involve binding barbed ends of actin filaments. To test this hypothesis, we expressed a β1 mutant that poorly binds actin. These mice showed both myofibril disruption and intercalated disc remodeling, as predicted. Therefore, CPβ1 and CPβ2 each have a distinct function that cannot be provided by the other isoform. CPβ1 attaches actin filaments to the Z-line, and CPβ2 organizes the actin at the intercalated discs.

scholarly journals The structure of the actin filament uncapping complex mediated by twinfilin

2021 ◽  
Vol 7 (5) ◽  
pp. eabd5271
Author(s):  
Dennis M. Mwangangi ◽  
Edward Manser ◽  
Robert C. Robinson
Keyword(s):  
Actin Filament ◽  
Protein Interactions ◽  
Protein Complex ◽  
Actin Filaments ◽  
Actin Binding ◽  
Capping Protein ◽  
Binding Surface ◽  
Actin Capping Protein ◽  
Actin Capping

Uncapping of actin filaments is essential for driving polymerization and depolymerization dynamics from capping protein–associated filaments; however, the mechanisms of uncapping leading to rapid disassembly are unknown. Here, we elucidated the x-ray crystal structure of the actin/twinfilin/capping protein complex to address the mechanisms of twinfilin uncapping of actin filaments. The twinfilin/capping protein complex binds to two G-actin subunits in an orientation that resembles the actin filament barbed end. This suggests an unanticipated mechanism by which twinfilin disrupts the stable capping of actin filaments by inducing a G-actin conformation in the two terminal actin subunits. Furthermore, twinfilin disorders critical actin-capping protein interactions, which will assist in the dissociation of capping protein, and may promote filament uncapping through a second mechanism involving V-1 competition for an actin-binding surface on capping protein. The extensive interactions with capping protein indicate that the evolutionary conserved role of twinfilin is to uncap actin filaments.

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.

Strong increase in the tyrosine phosphorylation of actin upon inhibition of oxidative phosphorylation: correlation with reversible rearrangements in the actin skeleton of Dictyostelium cells

1994 ◽  
Vol 107 (1) ◽  
pp. 117-125 ◽  
Author(s):  
A. Jungbluth ◽  
V. von Arnim ◽  
E. Biegelmann ◽  
B. Humbel ◽  
A. Schweiger ◽  
...  
Keyword(s):  
Oxidative Phosphorylation ◽  
Tyrosine Phosphorylation ◽  
Actin Filaments ◽  
Cell Shape ◽  
Strong Increase ◽  
Tyrosine Residues ◽  
Capping Protein ◽  
Actin Capping Protein ◽  
Actin Capping ◽  
Shape Changes

When oxidative phosphorylation is inhibited in cells of Dictyostelium discoideum, the phosphorylation of tyrosine residues on actin is strongly increased. This increase is fully reversible. Under the same conditions the amoeboid cells undergo a series of shape changes. Within three minutes the pseudopods are withdrawn and replaced by cell surface blebs. Subsequently, the cells are rounding up to become immobile. In parallel with the changes in cell shape, the distribution of actin filaments is grossly altered within the cells. The cortical network of actin filaments of normal cells is broken down, and the F-actin forms large, irregular clusters deep within the cytoplasm. In these clusters the actin is associated with myosin II and with the heterodimeric F-actin capping protein cap32/34. After restoration of oxidative phosphorylation the actin returns within less than four minutes to its normal cortical position. A causal relationship between tyrosine phosphorylation and changes in the distribution of actin remains to be established. The rearrangements in the actin system that result from the inhibition of oxidative phosphorylation indicate that the organisation of this system and its maintenance in a functional state depend on the continuous supply of energy by ATP.

Sign in / Sign up

Export Citation Format

Share Document