Identifying a role of the actin capping protein CapZ in β-adrenergic receptor signalling

2012 ◽  
Vol 207 (1) ◽  
pp. 173-182 ◽  
Author(s):  
L. Gaikis ◽  
D. Stewart ◽  
R. Johnson ◽  
W. G. Pyle
Keyword(s):  
Adrenergic Receptor ◽  
Capping Protein ◽  
Receptor Signalling ◽  
Actin Capping Protein ◽  
Actin Capping

scholarly journals The actin-capping protein alpha-adducin is required for T-cell costimulation

2019 ◽  
Author(s):  
Timothy J. Thauland ◽  
Manish J. Butte
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cell Activation ◽  
Conditional Knockout ◽  
Capping Protein ◽  
Actin Capping Protein ◽  
Actin Capping ◽  
Spectrin Network

AbstractAlpha-adducin (Add1) is a critical component of the actin-spectrin network in erythrocytes, acting to cap the fast-growing, barbed ends of actin filaments, and recruiting spectrin to these junctions. Add1 is highly expressed in T cells, but its role in T-cell activation has not been examined. Using a conditional knockout model, we show that Add1 is necessary for complete activation of CD4+ T cells in response to low levels of antigen but is dispensable for CD8+ T cell activation and response to infection. Surprisingly, costimulatory signals through CD28 were completely abrogated in the absence of Add1. This study is the first to examine the role of actin-capping in T cells, and it reveals a previously unappreciated role for the actin cytoskeleton in regulating costimulation.

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.

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 The Role of CKIP-1 in Cell Morphology Depends on Its Interaction with Actin-capping Protein

2006 ◽  
Vol 281 (47) ◽  
pp. 36347-36359 ◽  
Author(s):  
David A. Canton ◽  
Mary Ellen K. Olsten ◽  
Hanspeter Niederstrasser ◽  
John A. Cooper ◽  
David W. Litchfield
Keyword(s):  
Cell Morphology ◽  
Capping Protein ◽  
Actin Capping Protein ◽  
Actin Capping

scholarly journals Flightless I interacts with NMMIIA to promote cell extension formation, which enables collagen remodeling

2015 ◽  
Vol 26 (12) ◽  
pp. 2279-2297 ◽  
Author(s):  
Pamma D. Arora ◽  
Yongqiang Wang ◽  
Anne Bresnick ◽  
Paul A. Janmey ◽  
Christopher A. McCulloch
Keyword(s):  
Mass Spectrometry Analysis ◽  
Binding Assays ◽  
Cell Extension ◽  
Spectrometry Analysis ◽  
Collagen Remodeling ◽  
Capping Protein ◽  
Coated Membranes ◽  
Actin Capping Protein ◽  
Actin Capping

We examined the role of the actin-capping protein flightless I (FliI) in collagen remodeling by mouse fibroblasts. FliI-overexpressing cells exhibited reduced spreading on collagen but formed elongated protrusions that stained for myosin10 and fascin and penetrated pores of collagen-coated membranes. Inhibition of Cdc42 blocked formation of cell protrusions. In FliI-knockdown cells, transfection with constitutively active Cdc42 did not enable protrusion formation. FliI-overexpressing cells displayed increased uptake and degradation of exogenous collagen and strongly compacted collagen fibrils, which was blocked by blebbistatin. Mass spectrometry analysis of FliI immunoprecipitates showed that FliI associated with nonmuscle myosin IIA (NMMIIA), which was confirmed by immunoprecipitation. GFP-FliI colocalized with NMMIIA at cell protrusions. Purified FliI containing gelsolin-like domains (GLDs) 1–6 capped actin filaments efficiently, whereas FliI GLD 2–6 did not. Binding assays showed strong interaction of purified FliI protein (GLD 1–6) with the rod domain of NMMIIA ( kD = 0.146 μM), whereas FliI GLD 2–6 showed lower binding affinity ( kD = 0.8584 μM). Cells expressing FliI GLD 2–6 exhibited fewer cell extensions, did not colocalize with NMMIIA, and showed reduced collagen uptake compared with cells expressing FliI GLD 1–6. We conclude that FliI interacts with NMMIIA to promote cell extension formation, which enables collagen remodeling in fibroblasts.

scholarly journals Crystal structure of human V-1 in the apo form

2021 ◽  
Vol 77 (1) ◽  
pp. 13-21
Author(s):  
Shuichi Takeda ◽  
Ryotaro Koike ◽  
Takayuki Nagae ◽  
Ikuko Fujiwara ◽  
Akihiro Narita ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Actin Dynamics ◽  
Side Chain ◽  
Capping Protein ◽  
Actin Capping Protein ◽  
Large Conformational Change ◽  
Actin Capping ◽  
Atom Motion ◽  
Specific Ligand

V-1, also known as myotrophin, is a 13 kDa ankyrin-repeat protein that binds and inhibits the heterodimeric actin capping protein (CP), which is a key regulator of cytoskeletal actin dynamics. The crystal structure of V-1 in complex with CP revealed that V-1 recognizes CP via residues spanning several ankyrin repeats. Here, the crystal structure of human V-1 is reported in the absence of the specific ligand at 2.3 Å resolution. In the asymmetric unit, the crystal contains two V-1 monomers that exhibit nearly identical structures (Cα r.m.s.d. of 0.47 Å). The overall structures of the two apo V-1 chains are also highly similar to that of CP-bound V-1 (Cα r.m.s.d.s of <0.50 Å), indicating that CP does not induce a large conformational change in V-1. Detailed structural comparisons using the computational program All Atom Motion Tree revealed that CP binding can be accomplished by minor side-chain rearrangements of several residues. These findings are consistent with the known biological role of V-1, in which it globally inhibits CP in the cytoplasm.

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 CapZ integrates several signaling pathways in response to mechanical stiffness

2019 ◽  
Vol 151 (5) ◽  
pp. 660-669 ◽  
Author(s):  
Christopher Solís ◽  
Brenda Russell
Keyword(s):  
Mechanical Load ◽  
Phosphorylation Site ◽  
Tight Binding ◽  
Neonatal Rat ◽  
Actin Binding ◽  
Mechanical Stimuli ◽  
Muscle Adaptation ◽  
Capping Protein ◽  
Actin Capping Protein ◽  
Actin Capping

Muscle adaptation is a response to physiological demand elicited by changes in mechanical load, hormones, or metabolic stress. Cytoskeletal remodeling processes in many cell types are thought to be primarily regulated by thin filament formation due to actin-binding accessory proteins, such as the actin-capping protein. Here, we hypothesize that in muscle, the actin-capping protein (named CapZ) integrates signaling by a variety of pathways, including phosphorylation and phosphatidylinositol 4,5-bisphosphate (PIP2) binding, to regulate muscle fiber growth in response to mechanical load. To test this hypothesis, we assess mechanotransduction signaling that regulates muscle growth using neonatal rat ventricular myocytes cultured on substrates with the stiffness of the healthy myocardium (10 kPa), fibrotic myocardium (100 kPa), or glass. We investigate how PIP2 signaling affects CapZ using the PIP2 sequestering agent neomycin and the effect of PKC-mediated CapZ phosphorylation using the PKC-activating drug phorbol 12-myristate 13-acetate (PMA). Molecular simulations suggest that close interactions between PIP2 and the β-tentacle of CapZ are modified by phosphorylation at T267. Fluorescence recovery after photobleaching (FRAP) demonstrates that the kinetic binding constant of CapZ to sarcomeric thin filaments in living muscle cells increases with stiffness or PMA treatment but is diminished by PIP2 reduction. Furthermore, CapZ with a deletion of the β-tentacle that lacks the phosphorylation site T267 shows increased FRAP kinetics with lack of sensitivity to PMA treatment or PIP2 reduction. Förster resonance energy transfer (FRET) probes the molecular interactions between PIP2 and CapZ, which are decreased by PIP2 availability or by the β-tentacle truncation. These data suggest that CapZ is bound to actin tightly in the idle, locked state, with little phosphorylation or PIP2 binding. However, this tight binding is loosened in growth states triggered by mechanical stimuli such as substrate stiffness, which may have relevance to fibrotic heart disease.

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