scholarly journals Faculty Opinions recommendation of Tropomyosin isoforms differentially tune actin filament length and disassembly.

2019 ◽  
Author(s):  
Robert Insall
Keyword(s):  
Actin Filament ◽  
Filament Length ◽  
Tropomyosin Isoforms

scholarly journals Tropomyosin isoforms differentially tune actin filament length and disassembly

2019 ◽  
Vol 30 (5) ◽  
pp. 671-679 ◽  
Author(s):  
Silvia Jansen ◽  
Bruce L. Goode
Keyword(s):  
Fluorescence Microscopy ◽  
Actin Filament ◽  
Actin Filaments ◽  
Total Internal Reflection ◽  
Internal Reflection ◽  
Total Internal Reflection Fluorescence ◽  
Filament Length ◽  
Actin Networks ◽  
Tropomyosin Isoforms ◽  
Specific Effects

Cellular actin networks exhibit diverse filamentous architectures and turnover dynamics, but how these differences are specified remains poorly understood. Here, we used multicolor total internal reflection fluorescence microscopy to ask how decoration of actin filaments by five biologically prominent Tropomyosin (TPM) isoforms influences disassembly induced by Cofilin alone, or by the collaborative effects of Cofilin, Coronin, and AIP1 (CCA). TPM decoration restricted Cofilin binding to pointed ends, while not interfering with Coronin binding to filament sides. Different isoforms of TPM provided variable levels of protection against disassembly, with the strongest protection by Tpm3.1 and the weakest by Tpm1.6. In biomimetic assays in which filaments were simultaneously assembled by formins and disassembled by CCA, these TPM isoform–specific effects persisted, giving rise to filaments with different lengths and treadmilling behavior. Together, our data reveal that TPM isoforms have quantitatively distinct abilities to tune actin filament length and turnover.

scholarly journals Specification of Actin Filament Function and Molecular Composition by Tropomyosin Isoforms

2003 ◽  
Vol 14 (3) ◽  
pp. 1002-1016 ◽  
Author(s):  
Nicole S. Bryce ◽  
Galina Schevzov ◽  
Vicki Ferguson ◽  
Justin M. Percival ◽  
Jim J.-C. Lin ◽  
...  
Keyword(s):  
Cell Size ◽  
Functional Properties ◽  
Actin Filament ◽  
Actin Filaments ◽  
Myosin Ii ◽  
Molecular Composition ◽  
Cellular Migration ◽  
Stress Fibers ◽  
Human Homologue ◽  
Tropomyosin Isoforms

The specific functions of greater than 40 vertebrate nonmuscle tropomyosins (Tms) are poorly understood. In this article we have tested the ability of two Tm isoforms, TmBr3 and the human homologue of Tm5 (hTM5NM1), to regulate actin filament function. We found that these Tms can differentially alter actin filament organization, cell size, and shape. hTm5NM1was able to recruit myosin II into stress fibers, which resulted in decreased lamellipodia and cellular migration. In contrast, TmBr3 transfection induced lamellipodial formation, increased cellular migration, and reduced stress fibers. Based on coimmunoprecipitation and colocalization studies, TmBr3 appeared to be associated with actin-depolymerizing factor/cofilin (ADF)-bound actin filaments. Additionally, the Tms can specifically regulate the incorporation of other Tms into actin filaments, suggesting that selective dimerization may also be involved in the control of actin filament organization. We conclude that Tm isoforms can be used to specify the functional properties and molecular composition of actin filaments and that spatial segregation of isoforms may lead to localized specialization of actin filament function.

Requirement of pointed-end capping by tropomodulin to maintain actin filament length in embryonic chick cardiac myocytes

Nature ◽  
1995 ◽  
Vol 377 (6544) ◽  
pp. 83-86 ◽  
Author(s):  
Carol C. Gregorio ◽  
Annemarie Weber ◽  
Meredith Bondad ◽  
Cynthia R. Pennise ◽  
Velia M. Fowler
Keyword(s):  
Cardiac Myocytes ◽  
Actin Filament ◽  
Embryonic Chick ◽  
Filament Length ◽  
End Capping ◽  
Pointed End

scholarly journals Tropomyosin Isoforms Specify Functionally Distinct Actin Filament Populations In Vitro

2017 ◽  
Vol 27 (5) ◽  
pp. 705-713 ◽  
Author(s):  
Gergana Gateva ◽  
Elena Kremneva ◽  
Theresia Reindl ◽  
Tommi Kotila ◽  
Konstantin Kogan ◽  
...  
Keyword(s):  
Actin Filament ◽  
Tropomyosin Isoforms

scholarly journals Emergence and maintenance of different sized actin filaments in a common pool of building blocks

2021 ◽  
Author(s):  
Deb Sankar Banerjee ◽  
Shiladitya Banerjee
Keyword(s):  
Growth Inhibition ◽  
Actin Filament ◽  
Actin Filaments ◽  
Length Distribution ◽  
Building Blocks ◽  
Nucleation And Growth ◽  
Actin Binding ◽  
Filament Length ◽  
Growth Promoters ◽  
Spontaneous Nucleation

Actin is one of the key structural components of the eukaryotic cytoskeleton that regulates cellular architecture and mechanical properties. Dynamic regulation of actin filament length and organization is essential for the control of many physiological processes including cell adhesion, motility and division. While previous studies have mostly focused on the mechanisms controlling the mean length of individual actin filaments, it remains poorly understood how distinct actin filament populations in cells maintain different size using the same set of molecular building blocks. Here we develop a theoretical model for the length regulation of multiple actin filaments by nucleation and growth rate modulation by actin binding proteins in a limiting pool of monomers. We first show that spontaneous nucleation of actin filaments naturally leads to heterogeneities in filament length distribution. We then investigate the effects of filament growth inhibition by capping proteins and growth promotion by formin proteins on filament length distribution. We find that filament length heterogeneity can be increased by growth inhibition, whereas growth promoters do not significantly affect length heterogeneities. Interestingly, a competition between filament growth inhibitors and growth promoters can give rise to bimodal filament length distribution as well as a highly heterogeneous length distribution with large statistical dispersion. We quantitatively predict how heterogeneity in actin filament length can be modulated by tuning F-actin nucleation and growth rates in order to create distinct filament subpopulations with different lengths.

scholarly journals Tropomodulin 1-null mice have a mild spherocytic elliptocytosis with appearance of Tropomodulin 3 in red blood cells and disruption of the membrane skeleton

Blood ◽  
2010 ◽  
Vol 116 (14) ◽  
pp. 2590-2599 ◽  
Author(s):  
Jeannette D. Moyer ◽  
Roberta B. Nowak ◽  
Nancy E. Kim ◽  
Sandra K. Larkin ◽  
Luanne L. Peters ◽  
...  
Keyword(s):  
Actin Filament ◽  
Actin Filaments ◽  
Membrane Skeleton ◽  
Actin Dynamics ◽  
Filament Length ◽  
Western Blots ◽  
Rbc Membrane ◽  
Cellular Dehydration ◽  
Rbc Membrane Skeleton

Abstract The short actin filaments in the red blood cell (RBC) membrane skeleton are capped at their pointed ends by tropomodulin 1 (Tmod1) and coated with tropomyosin (TM) along their length. Tmod1-TM control of actin filament length is hypothesized to regulate spectrin-actin lattice organization and membrane stability. We used a Tmod1 knockout mouse to investigate the in vivo role of Tmod1 in the RBC membrane skeleton. Western blots of Tmod1-null RBCs confirm the absence of Tmod1 and show the presence of Tmod3, which is normally not present in RBCs. Tmod3 is present at only one-fifth levels of Tmod1 present on wild-type membranes, but levels of actin, TMs, adducins, and other membrane skeleton proteins remain unchanged. Electron microscopy shows that actin filament lengths are more variable with spectrin-actin lattices displaying abnormally large and more variable pore sizes. Tmod1-null mice display a mild anemia with features resembling hereditary spherocytic elliptocytosis, including decreased RBC mean corpuscular volume, cellular dehydration, increased osmotic fragility, reduced deformability, and heterogeneity in osmotic ektacytometry. Insufficient capping of actin filaments by Tmod3 may allow greater actin dynamics at pointed ends, resulting in filament length redistribution, leading to irregular and attenuated spectrin-actin lattice connectivity, and concomitant RBC membrane instability.

Latrunculin B increases force fluctuation-induced relengthening of ACh-contracted, isotonically shortened canine tracheal smooth muscle

2005 ◽  
Vol 98 (2) ◽  
pp. 489-497 ◽  
Author(s):  
M. L. Dowell ◽  
O. J. Lakser ◽  
W. T. Gerthoffer ◽  
J. J. Fredberg ◽  
G. L. Stelmack ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Actin Filament ◽  
Isometric Force ◽  
Muscle Length ◽  
Tracheal Smooth Muscle ◽  
Filament Length ◽  
Latrunculin B ◽  
Force Fluctuation ◽  
Reference Length

We hypothesized that differences in actin filament length could influence force fluctuation-induced relengthening (FFIR) of contracted airway smooth muscle and tested this hypothesis as follows. One-hundred micromolar ACh-stimulated canine tracheal smooth muscle (TSM) strips set at optimal reference length ( Lref) were allowed to shorten against 32% maximal isometric force (Fmax) steady preload, after which force oscillations of ±16% Fmax were superimposed. Strips relengthened during force oscillations. We measured hysteresivity and calculated FFIR as the difference between muscle length before and after 20-min imposed force oscillations. Strips were relaxed by ACh removal and treated for 1 h with 30 nM latrunculin B (sequesters G-actin and promotes depolymerization) or 500 nM jasplakinolide (stabilizes actin filaments and opposes depolymerization). A second isotonic contraction protocol was then performed; FFIR and hysteresivity were again measured. Latrunculin B increased FFIR by 92.2 ± 27.6% Lref and hysteresivity by 31.8 ± 13.5% vs. pretreatment values. In contrast, jasplakinolide had little influence on relengthening by itself; neither FFIR nor hysteresivity was significantly affected. However, when jasplakinolide-treated tissues were then incubated with latrunculin B in the continued presence of jasplakinolide for 1 more h and a third contraction protocol performed, latrunculin B no longer substantially enhanced TSM relengthening. In TSM treated with latrunculin B + jasplakinolide, FFIR increased by only 3.03 ± 5.2% Lref and hysteresivity by 4.14 ± 4.9% compared with its first (pre-jasplakinolide or latrunculin B) value. These results suggest that actin filament length, in part, determines the relengthening of contracted airway smooth muscle.

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