Actin polymerization and its regulation by proteins from nonmuscle cells.

Korn, Edward D.

doi:10.1152/physrev.1982.62.2.672

Cited by 738 publications

(381 citation statements)

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“…One way to study the increase in the number of filament ends caused by fragmentation is to use cytochalasins that bind actin filaments by preferentially capping the barbed end (review [19]). This binding is reported to depolymerize actin filaments under conditions where the filaments have polarity, i.e.…”

Section: Resultsmentioning

confidence: 99%

Effect of spectrin dimer on actin polymerization

1985

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Spectrin dimer is shown to influence the polymerization behaviour of actin. The polymerization of both Mg2+-and Caz+-actin is regulated by an enhancement in the rate of nucleation and a fragmentation of preformed actin filaments. In addition, spectrin decreases the critical concentration of Ca2+-actin but not that of Mg2+-actin. This suggests that the two types of actin may differ in their interaction with spectrin dimer probably due to the different ~nfo~ations.Band 4.1 elevates the effects of spectrin under non-equilib~~ conditions but its cont~bution is less at steady state.

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Section: Resultsmentioning

confidence: 99%

Effect of spectrin dimer on actin polymerization

1985

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“…Approximations for the concentrations of actin and profilin in yeast are 60 and 20 M, respectively (Magdolen et al, 1993). Presuming that the Factin/G-actin ratio in yeast is at least 1:1, as has been stated for other organisms (Korn, 1982;Hug et al, 1995), then the G-actin/profilin ratio would be expected to be ϳ3:2. Therefore, because the majority of actin monomers within the cell could be profilin bound, cofilin gating of barbed ends is a feasible hypothesis for a novel mode of barbed-end regulation.…”

Section: Is Aip1p a Capping Protein?mentioning

confidence: 91%

A Genetic Dissection of Aip1p's Interactions Leads to a Model for Aip1p-Cofilin Cooperative Activities

Clark

Teply

Haarer

et al. 2006

MBoC

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Actin interacting protein 1 (Aip1p) and cofilin cooperate to disassemble actin filaments in vitro and are thought to promote rapid turnover of actin networks in vivo. The precise method by which Aip1p participates in these activities has not been defined, although severing and barbed-end capping of actin filaments have been proposed. To better describe the mechanisms and biological consequences of Aip1p activities, we undertook an extensive mutagenesis of AIP1 aimed at disrupting and mapping Aip1p interactions. Site-directed mutagenesis suggested that Aip1p has two actin binding sites, the primary actin binding site lies on the edge of its N-terminal ␤-propeller and a secondary actin binding site lies in a comparable location on its C-terminal ␤-propeller. Random mutagenesis followed by screening for separation of function mutants led to the identification of several mutants specifically defective for interacting with cofilin but still able to interact with actin. These mutants suggested that cofilin binds across the cleft between the two propeller domains, leaving the actin binding sites exposed and flanking the cofilin binding site. Biochemical, genetic, and cell biological analyses confirmed that the actin binding-and cofilin binding-specific mutants are functionally defective, whereas the genetic analyses further suggested a role for Aip1p in an early, internalization step of endocytosis. A complementary, unbiased molecular modeling approach was used to derive putative structures for the Aip1p-cofilin complex, the most stable of which is completely consistent with the mutagenesis data. We theorize that Aip1p-severing activity may involve simultaneous binding to two actin subunits with cofilin wedged between the two actin binding sites of the N-and C-terminal propeller domains.

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“…Fluorescent G-actin, which is generated either via attachment of a chemical fluorophore or by fluorescent protein fusions, can alter actin assembly and processes dependent on actin assembly [Hird, 1996;Aizawa et al, 1997;Wu and Pollard, 2005] and, moreover, may not incorporate into all pools of F-actin [Kovar et al, 2006]. Further, because only a fraction of actin is in polymer form at any given time [Korn, 1982], imaging with fluorescent G-actin entails high background signal, unless specialized techniques such as speckling are employed [Waterman-Storer et al, 1998]. Phalloidin must be microinjected, and stabilizes actin filaments [Dancker et al, 1975], and thus changes the balance of actin assembly/ disassembly in vivo [Planques et al, 1991;Dancker et al, 1975;Wehland et al, 1977].…”

Section: Introductionmentioning

confidence: 99%

Versatile fluorescent probes for actin filaments based on the actin‐binding domain of utrophin

Burkel

Dassow

Bement

2007

Cell Motil. Cytoskeleton

448

485

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Actin filaments (F-actin) are protein polymers that undergo rapid assembly and disassembly and control an enormous variety of cellular processes ranging from force production to regulation of signal transduction. Consequently, imaging of F-actin has become an increasingly important goal for biologists seeking to understand how cells and tissues function. However, most of the available means for imaging F-actin in living cells suffer from one or more biological or experimental shortcomings. Here we describe fluorescent F-actin probes based on the calponin homology domain of utrophin (Utr-CH), which binds F-actin without stabilizing it in vitro. We show that these probes faithfully report the distribution of F-actin in living and fixed cells, distinguish between stable and dynamic F-actin, and have no obvious effects on processes that depend critically on the balance of actin assembly and disassembly.

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Actin polymerization and its regulation by proteins from nonmuscle cells.

Cited by 738 publications

References 0 publications

Effect of spectrin dimer on actin polymerization

Effect of spectrin dimer on actin polymerization

A Genetic Dissection of Aip1p's Interactions Leads to a Model for Aip1p-Cofilin Cooperative Activities

Versatile fluorescent probes for actin filaments based on the actin‐binding domain of utrophin

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