Severing of F-actin by yeast cofilin is pH-independent

Pavlov, Dmitry; Mühlrád, András; Cooper, John A.; Wear, Martin A.; Reisler, Emil

doi:10.1002/cm.20142

Cited by 22 publications

(20 citation statements)

References 51 publications

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“…We previously demonstrated that, by themselves, all of the mutant actins polymerized to the same extent as WT actin (13), so cofilin-dependent changes involving these actins could be easily compared. Consistent with a previous study (45), stoichiometric amounts of cofilin caused an average 42% increase in the light scattering shown by F-actin alone (Fig. 2) based on 21 different trials involving more than 5 different actin prepara-tions.…”

Section: Effects Of Mutations On Filament Sensitivity To Cofilin-cofi-supporting

confidence: 90%

“…As a result, it is possible to measure the ability of mammalian cofilin to bind to muscle actin filaments by lowering the pH of the solution to pH 6.5 (20), as this condition eliminates/greatly reduces cofilin filament severing activity. However, we could not use this approach because yeast cofilin severing is pHindependent (45). As a result, we have no insight into whether these mutations directly alter either the cofilin binding site and/or alter the inherent topology of the monomer-monomer interface which changes the accessibility of cofilin for its F-actin binding site.…”

Section: Discussionmentioning

confidence: 99%

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Allele-specific Effects of Human Deafness γ-Actin Mutations (DFNA20/26) on the Actin/Cofilin Interaction

Bryan

Rubenstein

2009

Journal of Biological Chemistry

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Auditory hair cell function requires proper assembly and regulation of the nonmuscle gamma isoactin-rich cytoskeleton, and six point mutations in this isoactin cause a type of delayed onset autosomal dominant nonsyndromic progressive hearing loss, DFNA20/26. The molecular basis underlying this actin-dependent hearing loss is unknown. To address this problem, the mutations have been introduced into yeast actin, and their effects on actin function were assessed in vivo and in vitro. Because we previously showed that polymerization was unaffected in five of the six mutants, we have focused on proteins that regulate actin, in particular cofilin, which severs F-actin and sequesters actin monomers. The mutations do not affect the interaction of cofilin with G-actin. However, T89I and V370A mutant F-actins are much more susceptible to cofilin disassembly than WT filaments in vitro. Conversely, P332A filaments demonstrate enhanced resistance. Wild type actin solutions containing T89I, K118M, or P332A mutant actins at mole fractions similar to those found in the hair cell respond in vitro toward cofilin in a manner proportional to the level of the mutant present. Finally, depression of cofilin action in vivo by elimination of the cofilin-activating protein, Aip1p, rescues the inability to grow on glycerol caused by K118M, T278I, P332A, and V370A. These results suggest that a filament instability caused by these mutations can be balanced by decreasing a system in vivo that promotes increased filament turnover. Such mutant-dependent filament destabilization could easily result in hair cell malfunction leading to the late-onset hearing loss observed in these patients.Our ability to perceive sounds hinges on the proper functioning of a highly specialized group of cells, called hair cells, which are housed in the cochlea of the inner ear. Their actin cytoskeleton plays a vital role in the ability of these cells to transduce mechanical stimuli into electrical responses (1). The columnar auditory hair cell consists of three actin-rich components (2). First are the three graded rows of finger-like projections from the apical surface of the cell referred to as stereocilia. These protrusions, comprised predominantly of bundles of actin filaments, are surrounded by the cellular membrane (3, 4). Soundgenerated pressure waves in the cochlear fluid displace the basilar membrane, which in turn forces the stereocilia into the overlaying tectorial membrane, resulting in their mechanical deformation. Deflection of the stereocilia results in the opening of mechanoelectrical transduction ion channels residing on the stereocilia and ultimately triggers the initiation of a nerve impulse, which is relayed by the auditory nerve to the brain for interpretation (5).Normal development, functioning, and maintenance of hair cell structures depend on tight regulation of the hair cell cytoskeleton as it controls the height and width of the stereociliary bundles. Each stereocilium inserts into the second actinrich structure, the cuticular plate, a web-...

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Section: Effects Of Mutations On Filament Sensitivity To Cofilin-cofi-supporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Allele-specific Effects of Human Deafness γ-Actin Mutations (DFNA20/26) on the Actin/Cofilin Interaction

Bryan

Rubenstein

2009

Journal of Biological Chemistry

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“…Cofilin, an actin filament severing and depolymerization promoting protein [28, 40, 41] was found to disassemble lysozyme- and polylysine-induced bundles. Its effect is maximal at equimolar concentration of cofilin to actin.…”

Section: Discussionmentioning

confidence: 99%

Polycation induced actin bundles

Mühlrád

Grintsevich

Reisler

2011

Biophysical Chemistry

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Three polycations, polylysine, the polyamine spermine and the polycationic protein lysozyme were used to study the formation, structure, ionic strength sensitivity and dissociation of polycation-induced actin bundles. Bundles form fast, simultaneously with the polymerization of MgATP-G-actins, upon addition of polycations to solutions of actins at low ionic strength conditions. This indicates that nuclei and/or nascent filaments bundle due to attractive, electrostatic effect of polycations and the neutralization of repulsive interactions of negative charges on actin. The attractive forces between the filaments are strong, as shown by the low (in nanomolar range) critical concentration of their bundling at low ionic strength. These bundles are sensitive to ionic strength and disassemble partially in 100mM NaCl, but both the dissociation and ionic strength sensitivity can be countered by higher polycation concentrations. Cys374 residues of actin monomers residing on neighboring filaments in the bundles can be cross-linked by the short span (5.4 Å) MTS-1 (1,1-Methanedyl Bismethanethiosulfonate) cross-linker, which indicates a tight packing of filaments in the bundles. The interfilament cross-links, which connect monomers located on oppositely oriented filaments, prevent disassembly of bundles at high ionic strength. Cofilin and the polysaccharide polyanion heparin disassemble lysozyme induced actin bundles more effectively than the polylysine-induced bundles. The actin-lysozyme bundles are pathologically significant as both proteins are found in the pulmonary airways of cystic fibrosis patients. Their bundles contribute to the formation of viscous mucus, which is the main cause of breathing difficulties and eventual death in this disorder.

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“…In addition release of Pi is increased ~10-fold by cofilin binding [86]. Cofilin’s ability to depolymerize faster at higher pH is thought to result from the pH dependence of Pi release [87] because the binding of Pi is stronger at low pH (6.5) than high pH (8.0) [85]. …”

Section: Functions Of Cofilinmentioning

confidence: 99%

ADF/Cofilin: a functional node in cell biology

Bernstein

Bamburg

2010

Trends in Cell Biology

625

630

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Recent findings have significantly expanded our understanding of the regulation of actin depolymerizing factor (ADF)/cofilin proteins and the profound multifaceted impact that these well-established regulators of actin dynamics have on cell biology. In this review we discuss new aspects of previously documented regulation, such as phosphorylation, but also cover novel recently established modes of regulation and new functions of ADF (also known as destrin)/cofilin. We now understand that their activity responds to a vast array of inputs far greater than previously appreciated and that these proteins not only feed back to the crucially important dynamics of actin, but also to apoptosis cascades, phospholipid metabolism, and gene expression. We argue that this ability to respond to physiological changes by modulating those same changes makes the ADF/cofilin protein family a homeostatic regulator or ‘functional node’ in cell biology.

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Severing of F-actin by yeast cofilin is pH-independent

Cited by 22 publications

References 51 publications

Allele-specific Effects of Human Deafness γ-Actin Mutations (DFNA20/26) on the Actin/Cofilin Interaction

Allele-specific Effects of Human Deafness γ-Actin Mutations (DFNA20/26) on the Actin/Cofilin Interaction

Polycation induced actin bundles

ADF/Cofilin: a functional node in cell biology

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