Assembly and dynamics of the actin filament system in nonmuscle cells

1986 ◽  
Vol 31 (2) ◽  
pp. 87-95 ◽  
Author(s):  
Thomas D. Pollard
Keyword(s):  
Actin Filament ◽  
Filament System ◽  
Nonmuscle Cells

Changes of the actin filament system in the green algaMicrasterias denticulata induced by different cytoskeleton inhibitors

PROTOPLASMA ◽  
2000 ◽  
Vol 212 (3-4) ◽  
pp. 206-216 ◽  
Author(s):  
M. Pfl�gl-Haill ◽  
L. Vidali ◽  
J. W. Vos ◽  
P. K. Hepler ◽  
U. L�tz-Meindl
Keyword(s):  
Actin Filament ◽  
Filament System

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

2005 ◽  
Vol 16 (2) ◽  
pp. 649-664 ◽  
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.

Sorting of actin isoforms in chicken auditory hair cells

1997 ◽  
Vol 110 (6) ◽  
pp. 765-770 ◽  
Author(s):  
D. Hofer ◽  
W. Ness ◽  
D. Drenckhahn
Keyword(s):  
Actin Filament ◽  
Hair Cells ◽  
Auditory Hair Cells ◽  
Actin Isoforms ◽  
Cytoplasmic Actin ◽  
Beta Actin ◽  
Nonmuscle Cells ◽  
Filament Bundles ◽  
Actin Isoform ◽  
Cellular Compartments

Most nonmuscle cells of higher vertebrates contain two different actin isoforms, beta- and gamma-cytoplasmic actin. The beta-isoform is with few exceptions the predominant isoform in nonmuscle cells and tissues. Perturbation of the beta:gamma ratio has been shown to affect the organization of bundled actin filaments indicating that the beta- and gamma-genes encode functionally distinct cytoarchitectural information. In the present study we localized by immunostaining beta- and gamma-actin in chicken auditory hair cells. These highly specialized cells serve as model system for studying certain developmental and structural aspects of a complex actin filament system with high architectural precision. We show that gamma-actin is the predominant actin isoform in auditory hair cells with an apparent beta:gamma ratio of approximately 1:2. gamma-Actin is not sorted and occurs in all three actin assemblies of the hair border, i.e. the cores of sensory hairs (stereocilia), the subjacent gel-like actin filament meshwork (cuticular plate) and the zonula adherens ring. In contrast to gamma-actin, the beta-isoform is specifically sorted to the actin filament core bundle of stereocilia that is extensively crosslinked by fimbrin. In view of recent studies showing that L-plastin, the leukocyte homolog of fimbrin, has a higher binding affinity for beta-actin than for gamma-actin, a mechanism is proposed for how hair cells might restrict formation of actin filament bundles to a single cellular site (i.e. the stereocilia). The limited level of expression of beta-actin in hair cells may help to prevent ectopic bundle formation in other cellular compartments.

scholarly journals The visualization of actin filament polarity in thin sections. Evidence for the uniform polarity of membrane-associated filaments.

1978 ◽  
Vol 79 (3) ◽  
pp. 846-852 ◽  
Author(s):  
D A Begg ◽  
R Rodewald ◽  
L I Rebhun
Keyword(s):  
Actin Filament ◽  
Actin Filaments ◽  
Intestinal Epithelial ◽  
Improved Method ◽  
Thin Sections ◽  
Myosin Subfragment ◽  
Brush Borders ◽  
Nonmuscle Cells ◽  
Myosin Subfragment 1 ◽  
Uniform Polarity

We have developed an improved method for visualizing actin filament polarity in thin sections. Myosin subfragment-1 (S-1)-decorated actin filaments display a dramatically enhanced arrowhead configuration when fixed in a medium which contains 0.2 % tannic acid. With the exception of brush borders from intestinal epithelial cells, the arrowhead periodicity of decorated filaments in a variety of nonmuscle cells is similar to that in isolated myofibrils. The periodicity of decorated filaments in brush borders is significantly smaller. Actin filaments which attach to membranes display a clear, uniform polarity, with the S-1 arrowheads pointing away from the plasma membrane, while those which comprise the stress fibers of myoblasts and CHO cells have antiparallel polarities. These observations are consistent with a sliding filament mechanism of cell motility.

Structure-Function Studies of the Actin Filament System of Acanthamoeba

1989 ◽  
pp. 271-279
Author(s):  
Thomas D. Pollard ◽  
Karen A. Magnus ◽  
Stephen Doberstein ◽  
Pascal Goldschmidt-Clermont ◽  
Donald A. Kaiser ◽  
...  
Keyword(s):  
Structure Function ◽  
Actin Filament ◽  
Filament System

Regulation of adherens junction protein p120ctnby 10 nM CCK precedes actin breakdown in rat pancreatic acini

2000 ◽  
Vol 278 (3) ◽  
pp. G486-G491 ◽  
Author(s):  
J. Leser ◽  
M. F. Beil ◽  
O. A. Musa ◽  
G. Adler ◽  
M. P. Lutz
Keyword(s):  
Tyrosine Phosphorylation ◽  
Actin Filament ◽  
Adherens Junctions ◽  
Adherens Junction ◽  
Acinar Cells ◽  
Pancreatic Acini ◽  
Filament System ◽  
Adherens Junction Protein ◽  
Junction Protein ◽  
E Cadherin

The initial pathophysiological events that characterize CCK-hyperstimulation pancreatitis include the breakdown of the actin filament system and disruption of cadherin-catenin protein complexes. Cadherins and catenins are part of adherens junctions, which may act as anchor for the cellular actin filament system. We examined the composition and regulation of adherens junctions during CCK-induced acinar cell damage. Freshly isolated CCK-stimulated rat pancreatic acini were examined for actin filaments and functional adherens junctions by immunocytology and laser confocal scanning microscopy or by coprecipitation and immunoblotting for E-cadherin, β- and α-catenin, p120ctn, and phosphotyrosine. In addition to E-cadherin and β-catenin, acinar cells express the cadherin-regulatory protein p120ctn and the attachment protein α-catenin. Both colocalize and coimmunoprecipitate with E-cadherin in one complex, and all colocalize with the terminal actin web. Supramaximal secretory CCK concentrations (10 nM) initiated tyrosine phosphorylation of p120ctn but not of β-catenin within 2 min, preceding the breakdown of the terminal actin web by several minutes. Under these conditions, the cadherin-catenin association within the adherens junction complex remained intact. We describe for the first time supramaximal CCK-dependent tyrosine phosphorylation of the adherens junction protein p120ctnand demonstrate the presence of an intact adherens junction protein complex in acinar cells. p120ctn may participate in the actin filament breakdown during experimental conditions mimicking pancreatitis.

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