Tropomyosin binding to F‐actin protects the F‐actin from disassembly by brain actin‐depolymerizing factor (ADF)

Bernstein, Ben C.; Bamburg, James R.

doi:10.1002/cm.970020102

Cited by 242 publications

(179 citation statements)

References 34 publications

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“…For example, one possibility is that TM may stabilize actin filaments in noumuscle cells. This function has also been inferred from in vitro experiments which have shown that TM protects actin filaments against the severing action of gelsolin (Fattoum et al, 1983;Ishikawa et al, 1989) or the activities of brain depolymerizing factor (Bernstein and Bamburg, 1982). Other experiments have shown that the nonmuscle TMs prevent villin induced severing (Mooseker et al, 1982) or bundling of F-actin (Burgess et al, 1987), but they were unable to prevent bundling caused by 55-kD protein (Matsumura and YamashiroMatsumura, 1986).…”

mentioning

confidence: 87%

In vitro and in vivo characterization of four fibroblast tropomyosins produced in bacteria: TM-2, TM-3, TM-5a, and TM-5b are co-localized in interphase fibroblasts.

Pittenger

Helfman

1992

The Journal of Cell Biology

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Abstract. Most cell types express several tropomyosin isoforms, the individual functions of which are poorly understood. In rat fibroblasts there are at least six isoforms; TM-1, TM-2, TM-3, TM-4, TM-5a, and TM-5b. TM-1 is the product of the/5 gene. TM-4 is produced from the TM-4 gene, and TMs 2, 3, 5a, and 5b are the products of the oe gene. To begin to study the localization and function of the isoforms in fibroblasts, cDNAs for TM isoforms 2, 3, 5a, and 5b were placed into bacterial expression vectors and used to produce TM isoforms. The bacterially produced TMs were determined to be full length by sequencing the amino-and carboxy termini. These TMs were found to bind to F-actin in vitro, with properties similar to that of skeletal muscle TM. In addition, competition experiments demonstrated that TM-5b was better than TM-5a in displacing other TM isoforms from F-actin in vitro. To investigate the intracellular localization of these fibroblast isoforms, each was derivatized with a fluorescent chromophore and microinjected into rat fibroblasts. TM-2, TM-3, TM-5a, and TM-5b were each found to associate along actin filaments. There was no preferred cellular location or subset of actin filaments for these isoforms. Furthermore, coinjection of two isoforms labeled with different fluorochromes showed identical staining. At the level of the light microscope, these isoforms from the ct gene do not appear to achieve different functions by binding to particular subsets of actin filaments or locations in cells. Some alternative possibilities are discussed. The results show that bacterially produced TMs can be used to study in vitro and in vivo properties of the isoforms.

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confidence: 87%

In vitro and in vivo characterization of four fibroblast tropomyosins produced in bacteria: TM-2, TM-3, TM-5a, and TM-5b are co-localized in interphase fibroblasts.

Pittenger

Helfman

1992

The Journal of Cell Biology

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“…Tropomyosins are coiled-coiled dimers that bind along the length of actin filaments and stabilize their structures by regulating access of the filament to other actin regulatory proteins such as gelsolin [7], Arp2/3 [8], and ADF/cofilin [9,10]. Approximately forty isoforms of tropomyosins now have been identified in rodents, and most of these are expressed in nonmuscle cells [11].…”

Section: Introductionmentioning

confidence: 99%

Tropomyosin 4 regulates adhesion structures and resorptive capacity in osteoclasts

McMichael

Lee

2008

Experimental Cell Research

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Tropomyosins (Tms) are α-helical dimers that bind and stabilize actin microfilaments while regulating their accessibility to other actin-associated proteins. Four genes encode expression of over forty Tms, most of which are expressed in nonmuscle cells. In recent years, it has become clear that individual Tm isoforms may regulate specific actin pools within cells. In this study, we examined how osteoclast function may be regulated by the tropomyosin isoform Tm-4, which we previously showed to be highly localized to podosomes and sealing zones of osteoclasts. RNAi-mediated knockdown of Tm-4, both in RAW264.7-and mouse marrow-derived osteoclasts, resulted in thinning of the actin ring of the sealing zone. Knockdown of Tm-4 also resulted in diminished bone resorptive capacity and altered resorption pit shape. In contrast, osteoclasts overexpressing Tm-4 demonstrated thickened podosomes on glass as well as thickened, aberrant actin structures on bone, and diminished motility and resorptive capacity. These results indicate that Tm-4 plays a role in regulating adhesion structures of osteoclasts, most likely by stabilizing the actin microfilaments present in podosomes and the sealing zone.

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“…In nonmuscle cells (which do not contain troponin), TM is associated with actin in microfilaments (28,36,50) and, although the function of TM in these filaments is not known, there is evidence suggesting that one function resides in its ability to stabilize F-actin polymers (3,13). TMs from a variety of nonmuscle sources have been characterized (9,10,14,15,17), and a distinctive feature of these nonmuscle species has been their apparent molecular weight of 30,000, significantly less than that of skeletal muscle TM, which has a molecular weight range of 34,000 to 36,000.…”

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confidence: 99%

Multiple tropomyosin polypeptides in chicken embryo fibroblasts: differential repression of transcription by Rous sarcoma virus transformation.

Hendricks¹,

Weintraub²

1984

Mol. Cell. Biol.

130

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We have found that cytoskeletal extracts of cultured chicken embryo fibroblasts contain at least seven distinct polypeptides (two major and five minor) which cross-react with antiserum to chicken smooth muscle tropomyosin. These polypeptides range in apparent molecular weight from 31,000 to 47,000, and each is encoded by mRNAs which specifically hybridize to cloned muscle tropomyosin cDNAs. These nonmuscle tropomyosin species and their respective mRNAs are electrophoretically distinct from those of chicken skeletal muscle and appear by genomic DNA blotting to comprise a part of a multigene tropomyosin family. In Rous sarcoma virus-transformed chicken embryo fibroblasts, synthesis of the tropomyosins is differentially repressed such that the synthesis of the major species (cp35 and cp33, cytoskeletal proteins of molecular weight 35,000 and 33,000, respectively) and three minor species is drastically reduced, whereas the synthesis of two of the minor species (cp32 and cp3l) remains essentially unchanged. Analysis of cellular mRNA and runoff nuclear transcription experiments indicate that the repression of tropomyosin synthesis by Rous sarcoma virus transformation occurs at the level of transcription. This repression of tropomyosin synthesis is partially mimicked in normal chicken embryo fibroblasts during incubation in high-NaCI medium, a condition in which chicken embryo fibroblasts acquire many characteristics of transformed cells.Tropomyosin (TM) is a protein which has been best studied in skeletal muscle, where it is associated with actin in thin filaments and, together with the troponin complex, is responsible for mediating the effect of calcium on the contraction-generating interaction of actin and myosin (11,24). In nonmuscle cells (which do not contain troponin), TM is associated with actin in microfilaments (28,36,50) and, although the function of TM in these filaments is not known, there is evidence suggesting that one function resides in its ability to stabilize F-actin polymers (3,13). TMs from a variety of nonmuscle sources have been characterized (9,10,14,15,17), and a distinctive feature of these nonmuscle species has been their apparent molecular weight of 30,000, significantly less than that of skeletal muscle TM, which has a molecular weight range of 34,000 to 36,000. However, two forms of nonmuscle TM with significantly larger apparent molecular weights of 35,000 and 33,000 were identified in the cytoskeleton of cultured chicken embryo fibroblasts (25). More recently, multiple forms of TM having a broad range of molecular weights have been identified in the cytoskeleton of human fibroblasts (44) and in microfilaments of a variety of other cultured mammalian cells (35,36).It is commonly believed that microfilaments play a major role in cell motility and cell shape changes (7,18,27). A general feature of oncogenic transformation is the morphological alteration of the cell (for reviews, see references 23 and 45). Correlated with this change in cell morphology is a dramatic change in the organizatio...

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Tropomyosin binding to F‐actin protects the F‐actin from disassembly by brain actin‐depolymerizing factor (ADF)

Cited by 242 publications

References 34 publications

In vitro and in vivo characterization of four fibroblast tropomyosins produced in bacteria: TM-2, TM-3, TM-5a, and TM-5b are co-localized in interphase fibroblasts.

In vitro and in vivo characterization of four fibroblast tropomyosins produced in bacteria: TM-2, TM-3, TM-5a, and TM-5b are co-localized in interphase fibroblasts.

Tropomyosin 4 regulates adhesion structures and resorptive capacity in osteoclasts

Multiple tropomyosin polypeptides in chicken embryo fibroblasts: differential repression of transcription by Rous sarcoma virus transformation.

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