The Saccharomyces cerevisiae Calponin/Transgelin Homolog Scp1 Functions with Fimbrin to Regulate Stability and Organization of the Actin Cytoskeleton

Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA.
Molecular Biology of the Cell (Impact Factor: 4.47). 08/2003; 14(7):2617-29. DOI: 10.1091/mbc.E03-01-0028
Source: PubMed


Calponins and transgelins are members of a conserved family of actin-associated proteins widely expressed from yeast to humans. Although a role for calponin in muscle cells has been described, the biochemical activities and in vivo functions of nonmuscle calponins and transgelins are largely unknown. Herein, we have used genetic and biochemical analyses to characterize the budding yeast member of this family, Scp1, which most closely resembles transgelin and contains one calponin homology (CH) domain. We show that Scp1 is a novel component of yeast cortical actin patches and shares in vivo functions and biochemical activities with Sac6/fimbrin, the one other actin patch component that contains CH domains. Purified Scp1 binds directly to filamentous actin, cross-links actin filaments, and stabilizes filaments against disassembly. Sequences in Scp1 sufficient for actin binding and cross-linking reside in its carboxy terminus, outside the CH domain. Overexpression of SCP1 suppresses sac6Delta defects, and deletion of SCP1 enhances sac6Delta defects. Together, these data show that Scp1 and Sac6/fimbrin cooperate to stabilize and organize the yeast actin cytoskeleton.


Available from: Bruce L Goode, Jul 02, 2014
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    • "Finally, reduced growth rates in sac6Δ and taf14/anc1Δ could be partially suppressed by actin overexpression. Sac6 cross-links and stabilizes actin filaments within the actin cortical patch (Goodman et al. 2002) and we propose that in its absence, an increased actin concentration can partially compensate for the loss of this activity. Anc1/Taf14 is reported to be in a number of protein complexes that are involved in transcription and chromatin remodeling, some of these complexes also contain actin (e.g., the INO80 complex (Shen et al. 2000)). "
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    ABSTRACT: The actin cytoskeleton exists in a dynamic equilibrium with monomeric and filamentous states of its subunit protein actin. The spatial and temporal regulation of actin dynamics is critical to the many functions of actin. Actin levels are remarkably constant, suggesting that cells have evolved to function within a narrow range of actin concentrations. Here we report the results of screens in which we have increased actin levels in strains deleted for the ~4800 nonessential yeast genes using a technical advance called selective ploidy ablation. We detected 83 synthetic dosage interactions with actin, 78 resulted in reduced growth, whereas in 5 cases overexpression of actin suppressed the growth defects caused by the deleted genes. The genes were highly enriched in several classes, including transfer RNA wobble uridine modification, chromosome stability and segregation, cell growth, and cell division. We show that actin overexpression sequesters a limited pool of eEF1A, a bifunctional protein involved in aminoacyl-transfer RNA recruitment to the ribosome and actin filament cross-linking. Surprisingly, the largest class of genes is involved in chromosome stability and segregation. We show that actin mutants have chromosome segregation defects, suggesting a possible role in chromosome structure and function. Monomeric actin is a core component of the INO80 and SWR chromatin remodeling complexes and the NuA4 histone modification complex, and our results suggest these complexes may be sensitive to actin stoichiometry. We propose that the resulting effects on chromatin structure can lead to synergistic effects on chromosome stability in strains lacking genes important for chromosome maintenance.
    G3-Genes Genomes Genetics 03/2013; 3(3):553-61. DOI:10.1534/g3.113.005579 · 3.20 Impact Factor
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    • "Plays an important role in exocytosis by promoting actin cable assembly Imamura et al. 1997; Pruyne et al. 2002; Sagot et al. 2002b; Moseley et al. 2004; Moseley and Goode 2005; Moseley and Goode 2006 Pfy1 Profilin Plays a role in actin organization, endocytosis, and exocytosis Binds to monomeric actin, phosphatidylinositol 4,5-bisphosphate, and polyproline regions Catalyzes ADP/ATP exchange on actin monomers Haarer et al. 1990; Haarer et al. 1996; Moseley and Goode 2006; Sagot et al. 2002b Bud6 Actin-binding protein Formin-binding protein Polarisome component Involved in bipolar bud-site selection, actin cable assembly, and polarized cell growth Binds to monomeric actin and Bni1 Amberg et al. 1997; Evangelista et al. 1997; Moseley et al. 2004; Moseley and Goode 2005 Tpm1 Major isoform of tropomyosin Stabilizes actin filaments in actin cables and actin rings Involved in polarized cell growth and organelle inheritance Binds actin more efficiently upon Tpm1 acetylation by the NatB complex Liu and Bretscher 1989a; Pruyne et al. 1998; Bretscher 2003; Singer and Shaw 2003 (continued) Table 1, continued Name of protein or protein complex a Protein activity Function b (mutant phenotypes and/or key protein interactions) Key references Tpm2 Minor isoform of tropomyosin Stabilizes actin filaments in actin cables and actin rings Shares an essential role with Tpm1 in polarized cell growth and organelle inheritance Plays a role in morphogenesis that is distinct from Tpm1 Liu and Bretscher 1989a; Drees et al. 1995; Pruyne et al. 1998; Bretscher 2003; Singer and Shaw 2003; Yoshida et al. 2006 Sac6 Fimbrin, an actin-bundling protein Acts in concert with Scp1 (transgelin-like protein) for the organization and maintenance of the actin cytoskeleton Adams et al. 1989; Goodman et al. 2003; Winder et al. 2003 Abp140 AdoMet-dependent tRNA methyltransferase and actin-binding protein Binds actin filaments in actin patches and cables Modifies the anti-codon loop of tRNA-Thr and tRNA-Ser Asakura et al. 1998; D'Silva et al. 2011; Noma et al. 2011 Ypt31, Ypt32 Rab GTPases Play important roles in intra-Golgi traffic or vesicle budding from the trans-Golgi Benli et al. 1996; Jedd et al. 1997;Grosshans et al. 2006 Share an essential role in the processes mentioned above Sec4 Rab GTPase Essential for post-Golgi vesicle transport and tethering Interacts with the exocyst subunit Sec15 to promote exocyst assembly at the PM Salminen and Novick 1987; Goud et al. 1988; Guo et al. 1999b Sec2 Rab GEF Essential for post-Golgi vesicle transport and tethering "
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    ABSTRACT: Asymmetric cell division, which includes cell polarization and cytokinesis, is essential for generating cell diversity during development. The budding yeast Saccharomyces cerevisiae reproduces by asymmetric cell division, and has thus served as an attractive model for unraveling the general principles of eukaryotic cell polarization and cytokinesis. Polarity development requires G-protein signaling, cytoskeletal polarization, and exocytosis, whereas cytokinesis requires concerted actions of a contractile actomyosin ring and targeted membrane deposition. In this chapter, we discuss the mechanics and spatial control of polarity development and cytokinesis, emphasizing the key concepts, mechanisms, and emerging questions in the field.
    Genetics 06/2012; 191(2):347-87. DOI:10.1534/genetics.111.132886 · 5.96 Impact Factor
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    • "These changes are consistent with increases or decreases in the overall actin bundling activity in the cell resulting in decreased or increased actin dynamics respectively. Studies in yeast have revealed similar consequences for the effects of Scp1p, the yeast homologue of SM22, in actin dynamics and actin dependent processes such as endocytosis [11,12,28]. The actin binding and bundling activity of SM22 and related proteins is conferred via sequences c-terminal of the calponin homology (CH) domain including a short linker peptide and one to three calponin-like or 'CLIK23' repeats [29]. "
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    ABSTRACT: SM22 has long been studied as an actin-associated protein. Interestingly, levels of SM22 are often reduced in tumour cell lines, while they are increased during senescence possibly indicating a role for SM22 in cell fate decisions via its interaction with actin. In this study we aimed to determine whether reducing levels of SM22 could actively contribute to a tumourigenic phenotype. We demonstrate that in REF52 fibroblasts, decreased levels of SM22 disrupt normal actin organization leading to changes in the motile behaviour of cells. Interestingly, SM22 depletion also led to an increase in the capacity of cells to spontaneously form podosomes with a concomitant increase in the ability to invade Matrigel. In PC3 prostate epithelial cancer cells by contrast, where SM22 is undetectable, re-expression of SM22 reduced the ability to invade Matrigel. Furthermore SM22 depleted cells also had reduced levels of reactive oxygen species when under serum starvation stress. These findings suggest that depletion of SM22 could contribute to tumourigenic properties of cells. Reduction in SM22 levels would tend to promote cell survival when cells are under stress, such as in a hypoxic tumour environment, and may also contribute to increases in actin dynamics that favour metastatic potential.
    BMC Cell Biology 01/2012; 13(1):1. DOI:10.1186/1471-2121-13-1 · 2.34 Impact Factor
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