Dual roles of tropomyosin as an F‐actin stabilizer and a regulator of muscle contraction in <i>Caenorhabditis elegans</i> body wall muscle

Yu, Robinson; Ono, Shoichiro

doi:10.1002/cm.20152

Cited by 31 publications

(29 citation statements)

References 90 publications

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“…This protein has two sevenblade propellers at each end of the protein that interact with the thin filament, and the UNC-60B actin depolymerizing factor/cofilin protein binds to the filament by wedging between the propellers (Ono, 2003;Mohri et al, 2004;Clark et al, 2006). Tropomyosin inhibits actin depolymerizing factor/cofilin activity (Ono and Ono, 2002;Yu and Ono, 2006). Actin depolymerizing factor/cofilin, tropomyosin, and myosin heavy chain are all required for proper muscle arm development (in C. elegans the muscles extend cytoplasmic arms to contact the motor nerves, see third review) (Dixon and Roy, 2005).…”

Section: Thin Filamentmentioning

confidence: 99%

Invertebrate muscles: Thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle

Hooper

Hobbs

Thuma

2008

Progress in Neurobiology

126

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This is the second in a series of canonical reviews on invertebrate muscle. We cover here thin and thick filament structure, the molecular basis of force generation and its regulation, and two special properties of some invertebrate muscle, catch and asynchronous muscle. Invertebrate thin filaments resemble vertebrate thin filaments, although helix structure and tropomyosin arrangement show small differences. Invertebrate thick filaments, alternatively, are very different from vertebrate striated thick filaments and show great variation within invertebrates. Part of this diversity stems from variation in paramyosin content, which is greatly increased in very large diameter invertebrate thick filaments. Other of it arises from relatively small changes in filament backbone structure, which results in filaments with grossly similar myosin head placements (rotating crowns of heads every 14.5 nm) but large changes in detail (distances between heads in azimuthal registration varying from three to thousands of crowns). The lever arm basis of force generation is common to both vetebrates and invertebrates, and in some invertebrates this process is understood on the near atomic level. Invertebrate actomyosin is both thin (tropomyosin:troponin) and thick (primarily via direct Ca ++ binding to myosin) filament regulated, and most invertebrate muscles are dually regulated. These mechanisms are well understood on the molecular level, but the behavioral utility of dual regulation is less so. The phosphorylation state of the thick filament associated giant protein, twitchin, has been recently shown to be the molecular basis of catch. The molecular basis of the stretch activation underlying asynchronous muscle activity, however, remains unresolved.

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Section: Thin Filamentmentioning

confidence: 99%

Invertebrate muscles: Thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle

Hooper

Hobbs

Thuma

2008

Progress in Neurobiology

126

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“…On the other hand, the addition of cofilin to the F-actin-tropomyosin complex at increasing concentrations causes dissociation of tropomyosin from the filament, supporting the competitive nature of tropomyosin and cofilin binding to the filaments [26]. To date, only a few tropomyosin isoforms were demonstrated to enhance cofilin binding to actin microfilaments [27][28][29]. However, details of the mechanisms of regulation of cofilins are poorly understood.…”

Section: Introductionmentioning

confidence: 99%

Tropomyosin isoforms differentially modulate the regulation of actin filament polymerization and depolymerization by cofilins

et al. 2015

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The specific functions of actin filaments located in the contractile and cytoskeletal compartments of muscle cells depend on the stability and dynamic polymerization/depolymerization of filaments. Tropomyosins and cofilins control the length and dynamic rearrangement of the filaments, although the mechanisms regulating actin dynamics are not well understood. In the present study, we used in vitro assays to examine the regulation of two cofilin isoforms, constitutive cofilin‐1 and muscle cofilin‐2, by the muscle homodimer Tpm1.1, muscle heterodimer Tpm1.1/Tpm2.2, and the cytoskeletal Tpm3.1. Depolymerization from the pointed end induced by the muscle‐specific cofilin‐2 was inhibited by all tropomyosins, whereas the muscle isoforms were most effective. By contrast, depolymerization by cofilin‐1 was inhibited by Tpm3.1 and Tpm1.1, but not by Tpm1.1/Tpm2.2. Polymerization of G‐actin was inhibited by cofilin‐2, whereas cofilin‐1 had no effect. All three tropomyosins switched on the inhibiting activity of cofilin‐1; however, Tpm3.1 and Tpm1.1 were much more efficient. Cofilin‐2‐induced inhibition of polymerization was affected neither by Tpm1.1, nor by Tpm3.1, but partly relieved by Tpm1.1/Tpm2.2. Cofilins removed tropomyosin isoforms from the filament with different efficiencies, which correlated with the cooperativities of cofilin binding to the F‐actin/tropomyosin complex. Because neither zero‐length, nor long‐arm cross‐linking between tropomyosin and cofilin isoforms was observed, the effects of tropomyosin isoforms on the activities of cofilins were executed allosterically. The results reveal that isoform‐specific interactions with actin filament permit tropomyosins to discriminate between cofilin isoforms and to differentially regulate their activities.

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“…Studies in C. elegans striated muscle show that tropomyosin (LEV-11) (Ono and Ono, 2002;Yu and Ono, 2006) and UNC-87, a calponin-like protein (Yamashiro et al, 2007), protect actin filaments from severing by ADF/cofilin, while actin-interacting protein 1 (AIP1) enhances disassembly of ADF/cofilin-bound actin filaments (Mohri et al, 2006;Mohri and Ono, 2003;Ono, 2001;Ono et al, 2011). Tropomodulin (UNC-94/TMD-1) caps the pointed ends of actin filaments and protects them from ADF/cofilin-mediated depolymerization .…”

Section: Introductionmentioning

confidence: 99%

CAS-1, a C. elegans cyclase-associated protein, is required for sarcomeric actin assembly in striated muscle

Nomura

Ono

2012

Journal of Cell Science

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SummaryAssembly of contractile apparatuses in striated muscle requires precisely regulated reorganization of the actin cytoskeletal proteins into sarcomeric organization. Regulation of actin filament dynamics is one of the essential processes of myofibril assembly, but the mechanism of actin regulation in striated muscle is not clearly understood. Actin depolymerizing factor (ADF)/cofilin is a key enhancer of actin filament dynamics in striated muscle in both vertebrates and nematodes. Here, we report that CAS-1, a cyclase-associated protein in Caenorhabditis elegans, promotes ADF/cofilin-dependent actin filament turnover in vitro and is required for sarcomeric actin organization in striated muscle. CAS-1 is predominantly expressed in striated muscle from embryos to adults. In vitro, CAS-1 binds to actin monomers and enhances exchange of actin-bound ATP/ADP even in the presence of UNC-60B, a muscle-specific ADF/cofilin that inhibits the nucleotide exchange. As a result, CAS-1 and UNC-60B cooperatively enhance actin filament turnover. The two proteins also cooperate to shorten actin filaments. A cas-1 mutation is homozygous lethal with defects in sarcomeric actin organization. cas-1-mutant embryos and worms have aggregates of actin in muscle cells, and UNC-60B is mislocalized to the aggregates. These results provide genetic and biochemical evidence that cyclase-associated protein is a critical regulator of sarcomeric actin organization in striated muscle.

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Dual roles of tropomyosin as an F‐actin stabilizer and a regulator of muscle contraction in Caenorhabditis elegans body wall muscle

Cited by 31 publications

References 90 publications

Invertebrate muscles: Thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle

Invertebrate muscles: Thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle

Tropomyosin isoforms differentially modulate the regulation of actin filament polymerization and depolymerization by cofilins

CAS-1, a C. elegans cyclase-associated protein, is required for sarcomeric actin assembly in striated muscle

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