151
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Tondeleir D, Lambrechts A, Müller M, Jonckheere V, Doll T, Vandamme D, Bakkali K, Waterschoot D, Lemaistre M, Debeir O, Decaestecker C, Hinz B, Staes A, Timmerman E, Colaert N, Gevaert K, Vandekerckhove J, Ampe C. Cells lacking β-actin are genetically reprogrammed and maintain conditional migratory capacity. Mol Cell Proteomics 2012; 11:255-71. [PMID: 22448045 DOI: 10.1074/mcp.m111.015099] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Vertebrate nonmuscle cells express two actin isoforms: cytoplasmic β- and γ-actin. Because of the presence and localized translation of β-actin at the leading edge, this isoform is generally accepted to specifically generate protrusive forces for cell migration. Recent evidence also implicates β-actin in gene regulation. Cell migration without β-actin has remained unstudied until recently and it is unclear whether other actin isoforms can compensate for this cytoplasmic function and/or for its nuclear role. Primary mouse embryonic fibroblasts lacking β-actin display compensatory expression of other actin isoforms. Consistent with this preservation of polymerization capacity, β-actin knockout cells have unchanged lamellipodial protrusion rates despite a severe migration defect. To solve this paradox we applied quantitative proteomics revealing a broad genetic reprogramming of β-actin knockout cells. This also explains why reintroducing β-actin in knockout cells does not restore the affected cell migration. Pathway analysis suggested increased Rho-ROCK signaling, consistent with observed phenotypic changes. We therefore developed and tested a model explaining the phenotypes in β-actin knockout cells based on increased Rho-ROCK signaling and increased TGFβ production resulting in increased adhesion and contractility in the knockout cells. Inhibiting ROCK or myosin restores migration of β-actin knockout cells indicating that other actins compensate for β-actin in this process. Consequently, isoactins act redundantly in providing propulsive forces for cell migration, but β-actin has a unique nuclear function, regulating expression on transcriptional and post-translational levels, thereby preventing myogenic differentiation.
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152
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Cheever TR, Li B, Ervasti JM. Restricted morphological and behavioral abnormalities following ablation of β-actin in the brain. PLoS One 2012; 7:e32970. [PMID: 22403730 PMCID: PMC3293915 DOI: 10.1371/journal.pone.0032970] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Accepted: 02/08/2012] [Indexed: 01/12/2023] Open
Abstract
The local translation of β-actin is one mechanism proposed to regulate spatially-restricted actin polymerization crucial for nearly all aspects of neuronal development and function. However, the physiological significance of localized β-actin translation in neurons has not yet been demonstrated in vivo. To investigate the role of β-actin in the mammalian central nervous system (CNS), we characterized brain structure and function in a CNS-specific β-actin knock-out mouse (CNS-ActbKO). β-actin was rapidly ablated in the embryonic mouse brain, but total actin levels were maintained through upregulation of other actin isoforms during development. CNS-ActbKO mice exhibited partial perinatal lethality while survivors presented with surprisingly restricted histological abnormalities localized to the hippocampus and cerebellum. These tissue morphology defects correlated with profound hyperactivity as well as cognitive and maternal behavior impairments. Finally, we also identified localized defects in axonal crossing of the corpus callosum in CNS-ActbKO mice. These restricted defects occurred despite the fact that primary neurons lacking β-actin in culture were morphologically normal. Altogether, we identified novel roles for β-actin in promoting complex CNS tissue architecture while also demonstrating that distinct functions for the ubiquitously expressed β-actin are surprisingly restricted in vivo.
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Affiliation(s)
| | | | - James M. Ervasti
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
- * E-mail:
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153
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Rivière JB, van Bon BWM, Hoischen A, Kholmanskikh SS, O'Roak BJ, Gilissen C, Gijsen S, Sullivan CT, Christian SL, Abdul-Rahman OA, Atkin JF, Chassaing N, Drouin-Garraud V, Fry AE, Fryns JP, Gripp KW, Kempers M, Kleefstra T, Mancini GMS, Nowaczyk MJM, van Ravenswaaij-Arts CMA, Roscioli T, Marble M, Rosenfeld JA, Siu VM, de Vries BBA, Shendure J, Verloes A, Veltman JA, Brunner HG, Ross ME, Pilz DT, Dobyns WB. De novo mutations in the actin genes ACTB and ACTG1 cause Baraitser-Winter syndrome. Nat Genet 2012; 44:440-4, S1-2. [PMID: 22366783 PMCID: PMC3677859 DOI: 10.1038/ng.1091] [Citation(s) in RCA: 204] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Accepted: 01/06/2012] [Indexed: 12/16/2022]
Abstract
Brain malformations are individually rare but collectively common causes of developmental disabilities1–3. Many forms occur sporadically and have reduced reproductive fitness, pointing towards a causative role for de novo mutations4,5. Here we report our studies of Baraitser-Winter syndrome, a well-defined syndrome characterized by distinct craniofacial features, ocular colobomata and a neuronal migration defect6,7. By using whole-exome sequencing in three proband-parent trios, we identified de novo missense changes in the cytoplasmic actin genes ACTB and ACTG1 in one and two probands, respectively. Sequencing of both genes in fifteen additional patients revealed disease-causing mutations in all probands, including two recurrent de novo mutations (ACTB p.Arg196His and ACTG1 p.Ser155Phe). Our results confirm that trio-based exome sequencing is a powerful approach to discover the genes causing sporadic developmental disorders, emphasize the overlapping roles of cytoplasmic actins in development, and suggest that Baraitser-Winter syndrome is the predominant phenotype associated with mutations of these two genes.
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Affiliation(s)
- Jean-Baptiste Rivière
- Center for Integrative Brain Research, Seattle Children's Hospital, Seattle, Washington, USA
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154
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Guidi F, Landini I, Puglia M, Magherini F, Gabbiani C, Cinellu MA, Nobili S, Fiaschi T, Bini L, Mini E, Messori L, Modesti A. Proteomic analysis of ovarian cancer cell responses to cytotoxic gold compounds. Metallomics 2012; 4:307-14. [PMID: 22322463 DOI: 10.1039/c2mt00083k] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Platinum-based chemotherapy is the primary treatment for human ovarian cancer. Overcoming platinum resistance has become a critical issue in the current chemotherapeutic strategies of ovarian cancer as drug resistance is the main reason for treatment failure. Cytotoxic gold compounds hold great promise to reach this goal; however, their modes of action are still largely unknown. To shed light on the underlying molecular mechanisms, we performed 2-DE and MS analysis to identify differential protein expression in a cisplatin-resistant human ovarian cancer cell line (A2780/R) following treatment with two representative gold compounds, namely Auranofin and Auoxo6. It is shown that Auranofin mainly acts by altering the expression of Proteasome proteins while Auoxo6 mostly modifies proteins related to mRNA splicing, trafficking and stability. We also found that Thioredoxin-like protein 1 expression is greatly reduced after treatment with both gold compounds. These results are highly indicative of the likely sites of action of the two tested gold drugs and of the affected cellular functions. The implications of the obtained results are thoroughly discussed in the frame of current knowledge on cytotoxic gold agents.
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Affiliation(s)
- Francesca Guidi
- Department of Biochemical Sciences, University of Florence, viale G. Morgagni, 50, 50134 Firenze, Italy
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155
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Dwyer J, Iskratsch T, Ehler E. Actin in striated muscle: recent insights into assembly and maintenance. Biophys Rev 2011; 4:17-25. [PMID: 28510000 DOI: 10.1007/s12551-011-0062-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Accepted: 11/17/2011] [Indexed: 01/28/2023] Open
Abstract
Striated muscle cells are characterised by a para-crystalline arrangement of their contractile proteins actin and myosin in sarcomeres, the basic unit of the myofibrils. A multitude of proteins is required to build and maintain the structure of this regular arrangement as well as to ensure regulation of contraction and to respond to alterations in demand. This review focuses on the actin filaments (also called thin filaments) of the sarcomere and will discuss how they are assembled during myofibrillogenesis and in hypertrophy and how their integrity is maintained in the working myocardium.
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Affiliation(s)
- Joseph Dwyer
- The Randall Division of Cell and Molecular Biophysics and The Cardiovascular Division, King's College London, British Heart Foundation Centre of Research Excellence, New Hunt's House, Guy's Campus, London, SE1 1UL, UK
| | - Thomas Iskratsch
- The Randall Division of Cell and Molecular Biophysics and The Cardiovascular Division, King's College London, British Heart Foundation Centre of Research Excellence, New Hunt's House, Guy's Campus, London, SE1 1UL, UK.,Biological Sciences, Columbia University, 713 Fairchild Center, New York, NY, 10027, USA
| | - Elisabeth Ehler
- The Randall Division of Cell and Molecular Biophysics and The Cardiovascular Division, King's College London, British Heart Foundation Centre of Research Excellence, New Hunt's House, Guy's Campus, London, SE1 1UL, UK.
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156
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Abstract
Hereditary deafness is genetically heterogeneous such that mutations of many different genes can cause hearing loss. This review focuses on the evidence and implications that several of these deafness genes encode actin-interacting proteins or actin itself. There is a growing appreciation of the contribution of the actin interactome in stereocilia development, maintenance, mechanotransduction and malfunction of the auditory system.
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157
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Weymouth N, Shi Z, Rockey DC. Smooth muscle α actin is specifically required for the maintenance of lactation. Dev Biol 2011; 363:1-14. [PMID: 22123032 DOI: 10.1016/j.ydbio.2011.11.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Revised: 11/03/2011] [Accepted: 11/04/2011] [Indexed: 11/30/2022]
Abstract
Smooth muscle α-actin (Acta2) is one of six highly conserved mammalian actin isoforms that appear to exhibit functional redundancy. Nonetheless, we have postulated a specific functional role for the smooth muscle specific isoform. Here, we show that Acta2 deficient mice have a remarkable mammary phenotype such that dams lacking Acta2 are unable to nurse their offspring effectively. The phenotype was rescued in cross fostering experiments with wild type mice, excluding a developmental defect in Acta2 null pups. The mechanism for the underlying phenotype is due to myoepithelial dysfunction postpartum resulting in precocious involution. Further, we demonstrate a specific defect in myoepithelial cell contractility in Acta2 null mammary glands, despite normal expression of cytoplasmic actins. We conclude that Acta2 specifically mediates myoepithelial cell contraction during lactation and that this actin isoform therefore exhibits functional specificity.
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Affiliation(s)
- Nate Weymouth
- University of Texas Southwestern Medical Center, Dallas, TX 75390-8887, USA
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158
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Chiu TT, Jensen TE, Sylow L, Richter EA, Klip A. Rac1 signalling towards GLUT4/glucose uptake in skeletal muscle. Cell Signal 2011; 23:1546-54. [DOI: 10.1016/j.cellsig.2011.05.022] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Accepted: 05/31/2011] [Indexed: 12/27/2022]
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159
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Shum MSY, Pasquier E, Po'uha ST, O'Neill GM, Chaponnier C, Gunning PW, Kavallaris M. γ-Actin regulates cell migration and modulates the ROCK signaling pathway. FASEB J 2011; 25:4423-33. [PMID: 21908715 DOI: 10.1096/fj.11-185447] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Cell migration plays a crucial role in numerous cellular functions, and alterations in the regulation of cell migration are required for invasive transformation of a tumor cell. While the mechanistic process of actin-based migration has been well documented, little is known as to the specific function of the nonmuscle actin isoforms in mammalian cells. Here, we present a comprehensive examination of γ-actin's role in cell migration using an RNAi approach. The partial suppression of γ-actin expression in SH-EP neuroblastoma cells resulted in a significant decrease in wound healing and transwell migration. Similarly, the knockdown of γ-actin significantly reduced speed of motility and severely affected the cell's ability to explore, which was, in part, due to a loss of cell polarity. Moreover, there was a significant increase in the size and number of paxillin-containing focal adhesions, coupled with a significant decrease in phosphorylated paxillin in γ-actin-knockdown cells. In addition, there was a significant increase in the phosphorylation of cofilin and myosin regulatory light chain, suggesting an overactivated Rho-associated kinase (ROCK) signaling pathway in γ-actin-knockdown cells. The alterations in the phosphorylation of paxillin and myosin regulatory light chain were unique to γ-actin and not β-actin knockdown. Inhibition of the ROCK pathway with the inhibitor Y-27632 restored the ability of γ-actin-knockdown cells to migrate. This study demonstrates γ-actin as a potential upstream regulator of ROCK mediated cell migration.
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Affiliation(s)
- Michael S Y Shum
- Children's Cancer Institute Australia, Lowy Cancer Research Centre, UNSW, PO Box 81, Randwick NSW Australia
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160
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Bunnell TM, Burbach BJ, Shimizu Y, Ervasti JM. β-Actin specifically controls cell growth, migration, and the G-actin pool. Mol Biol Cell 2011; 22:4047-58. [PMID: 21900491 PMCID: PMC3204067 DOI: 10.1091/mbc.e11-06-0582] [Citation(s) in RCA: 227] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Targeted deletion of Actb demonstrates that the β-actin gene, in contrast to the γ-actin gene, is an essential gene uniquely required for cell growth and migration. Cell motility and growth defects in β-actin–knockout primary cells are due to a specific role for β-actin in regulating gene expression through control of the cellular G-actin pool. Ubiquitously expressed β-actin and γ-actin isoforms play critical roles in most cellular processes; however, their unique contributions are not well understood. We generated whole-body β-actin–knockout (Actb−/−) mice and demonstrated that β-actin is required for early embryonic development. Lethality of Actb−/− embryos correlated with severe growth impairment and migration defects in β-actin–knockout primary mouse embryonic fibroblasts (MEFs) that were not observed in γ-actin–null MEFs. Migration defects were associated with reduced membrane protrusion dynamics and increased focal adhesions. We also identified migration defects upon conditional ablation of β-actin in highly motile T cells. Of great interest, ablation of β-actin altered the ratio of globular actin (G-actin) to filamentous actin in MEFs, with corresponding changes in expression of genes that regulate the cell cycle and motility. These data support an essential role for β-actin in regulating cell migration and gene expression through control of the cellular G-actin pool.
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Affiliation(s)
- Tina M Bunnell
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
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161
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Brockmann C, Huarte J, Dugina V, Challet L, Rey E, Conne B, Swetloff A, Nef S, Chaponnier C, Vassalli JD. Beta- and gamma-cytoplasmic actins are required for meiosis in mouse oocytes. Biol Reprod 2011; 85:1025-39. [PMID: 21778137 DOI: 10.1095/biolreprod.111.091736] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
In mammals, female meiosis consists of two asymmetric cell divisions, which generate a large haploid oocyte and two small polar bodies. Asymmetric partitioning of the cytoplasm results from migration of the meiotic spindle toward the cortex and requires actin filaments. However, the subcellular localization and the role of the existing two cytoplasmic actin (CYA) isoforms, beta and gamma, have not been characterized. We show that beta- and gamma-CYA are differentially distributed in the maturing oocyte from late metaphase I as well as in preimplantation embryos. Gamma-CYA is preferentially enriched in oocyte cortices and is absent from all cell-cell contact areas from metaphase II until the blastocyst stage. Beta-CYA is enriched in contractile structures, at cytokinesis, at cell-cell contacts, and around the forming blastocoel. Alteration of beta- or gamma-CYA function by isoform-specific antibody microinjection suggests that gamma-CYA holds a major and specific role in the establishment and/or maintenance of asymmetry in meiosis I and in the maintenance of overall cortical integrity. In contrast, beta- and gamma-CYA, together, appear to participate in the formation and the cortical anchorage of the second meiotic spindle in waiting for fertilization. Finally, differences in gamma-CYA expression are amongst the earliest markers of cell fate determination in development.
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Affiliation(s)
- Céline Brockmann
- Departments of Genetic Medicine and Development and Pathology and Immunology, University of Geneva Medical School, Geneva, Switzerland
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162
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Axonal regeneration and neuronal function are preserved in motor neurons lacking ß-actin in vivo. PLoS One 2011; 6:e17768. [PMID: 21445349 PMCID: PMC3062555 DOI: 10.1371/journal.pone.0017768] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Accepted: 02/14/2011] [Indexed: 12/31/2022] Open
Abstract
The proper localization of ß-actin mRNA and protein is essential for growth cone guidance and axon elongation in cultured neurons. In addition, decreased levels of ß-actin mRNA and protein have been identified in the growth cones of motor neurons cultured from a mouse model of Spinal Muscular Atrophy (SMA), suggesting that ß-actin loss-of-function at growth cones or pre-synaptic nerve terminals could contribute to the pathogenesis of this disease. However, the role of ß-actin in motor neurons in vivo and its potential relevance to disease has yet to be examined. We therefore generated motor neuron specific ß-actin knock-out mice (Actb-MNsKO) to investigate the function of ß-actin in motor neurons in vivo. Surprisingly, ß-actin was not required for motor neuron viability or neuromuscular junction maintenance. Skeletal muscle from Actb-MNsKO mice showed no histological indication of denervation and did not significantly differ from controls in several measurements of physiologic function. Finally, motor axon regeneration was unimpaired in Actb-MNsKO mice, suggesting that ß-actin is not required for motor neuron function or regeneration in vivo.
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163
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Prins KW, Call JA, Lowe DA, Ervasti JM. Quadriceps myopathy caused by skeletal muscle-specific ablation of β(cyto)-actin. J Cell Sci 2011; 124:951-7. [PMID: 21325027 PMCID: PMC3048892 DOI: 10.1242/jcs.079848] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/08/2010] [Indexed: 11/20/2022] Open
Abstract
Quadriceps myopathy (QM) is a rare form of muscle disease characterized by pathological changes predominately localized to the quadriceps. Although numerous inheritance patterns have been implicated in QM, several QM patients harbor deletions in dystrophin. Two defined deletions predicted loss of functional spectrin-like repeats 17 and 18. Spectrin-like repeat 17 participates in actin-filament binding, and thus we hypothesized that disruption of a dystrophin-cytoplasmic actin interaction might be one of the mechanisms underlying QM. To test this hypothesis, we generated mice deficient for β(cyto)-actin in skeletal muscles (Actb-msKO). Actb-msKO mice presented with a progressive increase in the proportion of centrally nucleated fibers in the quadriceps, an approximately 50% decrease in dystrophin protein expression without alteration in transcript levels, deficits in repeated maximal treadmill tests, and heightened sensitivity to eccentric contractions. Collectively, these results suggest that perturbing a dystrophin-β(cyto)-actin linkage decreases dystrophin stability, which results in a QM, and implicates β(cyto)-actin as a possible candidate gene in QM pathology.
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Affiliation(s)
- Kurt W. Prins
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Jarrod A. Call
- Department of Physical Medicine and Rehabilitation, University of Minnesota, Minneapolis, MN 55455, USA
| | - Dawn A. Lowe
- Department of Physical Medicine and Rehabilitation, University of Minnesota, Minneapolis, MN 55455, USA
| | - James M. Ervasti
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
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164
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Gallant C, Appel S, Graceffa P, Leavis P, Lin JJC, Gunning PW, Schevzov G, Chaponnier C, DeGnore J, Lehman W, Morgan KG. Tropomyosin variants describe distinct functional subcellular domains in differentiated vascular smooth muscle cells. Am J Physiol Cell Physiol 2011; 300:C1356-65. [PMID: 21289288 DOI: 10.1152/ajpcell.00450.2010] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Tropomyosin (Tm) is known to be an important gatekeeper of actin function. Tm isoforms are encoded by four genes, and each gene produces several variants by alternative splicing, which have been proposed to play roles in motility, proliferation, and apoptosis. Smooth muscle studies have focused on gizzard smooth muscle, where a heterodimer of Tm from the α-gene (Tmsm-α) and from the β-gene (Tmsm-β) is associated with contractile filaments. In this study we examined Tm in differentiated mammalian vascular smooth muscle (dVSM). Liquid chromatography-tandem mass spectrometry (LC MS/MS) analysis and Western blot screening with variant-specific antibodies revealed that at least five different Tm proteins are expressed in this tissue: Tm6 (Tmsm-α) and Tm2 from the α-gene, Tm1 (Tmsm-β) from the β-gene, Tm5NM1 from the γ-gene, and Tm4 from the δ-gene. Tm6 is by far most abundant in dVSM followed by Tm1, Tm2, Tm5NM1, and Tm4. Coimmunoprecipitation and coimmunofluorescence studies demonstrate that Tm1 and Tm6 coassociate with different actin isoforms and display different intracellular localizations. Using an antibody specific for cytoplasmic γ-actin, we report here the presence of a γ-actin cortical cytoskeleton in dVSM cells. Tm1 colocalizes with cortical cytoplasmic γ-actin and coprecipitates with γ-actin. Tm6, on the other hand, is located on contractile bundles. These data indicate that Tm1 and Tm6 do not form a classical heterodimer in dVSM but rather describe different functional cellular compartments.
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Affiliation(s)
- Cynthia Gallant
- Health Sciences Dept., Boston University, 635 Commonwealth Ave., Boston, MA 02215, USA
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165
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Lionnet T, Czaplinski K, Darzacq X, Shav-Tal Y, Wells AL, Chao JA, Park HY, de Turris V, Lopez-Jones M, Singer RH. A transgenic mouse for in vivo detection of endogenous labeled mRNA. Nat Methods 2011; 8:165-70. [PMID: 21240280 PMCID: PMC3076588 DOI: 10.1038/nmeth.1551] [Citation(s) in RCA: 298] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Accepted: 12/10/2010] [Indexed: 01/04/2023]
Abstract
Live-cell single mRNA imaging is a powerful tool but has been restricted in higher eukaryotes to artificial cell lines and reporter genes. We describe an approach that enables live-cell imaging of single endogenous labeled mRNA molecules transcribed in primary mammalian cells and tissue. We generated a knock-in mouse line with an MS2 binding site (MBS) cassette targeted to the 3' untranslated region of the essential β-actin gene. As β-actin-MBS was ubiquitously expressed, we could uniquely address endogenous mRNA regulation in any tissue or cell type. We simultaneously followed transcription from the β-actin alleles in real time and observed transcriptional bursting in response to serum stimulation with precise temporal resolution. We tracked single endogenous labeled mRNA particles being transported in primary hippocampal neurons. The MBS cassette also enabled high-sensitivity fluorescence in situ hybridization (FISH), allowing detection and localization of single β-actin mRNA molecules in various mouse tissues.
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Affiliation(s)
- Timothée Lionnet
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
- Gruss Lipper Biophotonics Center. Albert Einstein College of Medicine
| | - Kevin Czaplinski
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Xavier Darzacq
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS UMR 8197, Paris, France
| | - Yaron Shav-Tal
- The Mina & Everard Goodman Faculty of Life Sciences & Institute of Nanotechnology, Bar-Ilan University, Ramat Gan 52900, Israel
| | - Amber L. Wells
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Jeffrey A. Chao
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Hye Yoon Park
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
- Gruss Lipper Biophotonics Center. Albert Einstein College of Medicine
| | - Valeria de Turris
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Melissa Lopez-Jones
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Robert H. Singer
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
- Gruss Lipper Biophotonics Center. Albert Einstein College of Medicine
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166
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Milli A, Perego P, Beretta GL, Corvo A, Righetti PG, Carenini N, Corna E, Zuco V, Zunino F, Cecconi D. Proteomic Analysis of Cellular Response to Novel Proapoptotic Agents Related to Atypical Retinoids in Human IGROV-1 Ovarian Carcinoma Cells. J Proteome Res 2010; 10:1191-207. [DOI: 10.1021/pr100963n] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Alberto Milli
- Dipartimento di Biotecnologie, Laboratorio di Proteomica e Spettrometria di Massa, University of Verona, Strada le Grazie 15, 37134, Verona, Italy
| | - Paola Perego
- Fondazione IRCCS Istituto Nazionale dei Tumori, via Amadeo 42, 20133, Milano, Italy
| | - Giovanni L. Beretta
- Fondazione IRCCS Istituto Nazionale dei Tumori, via Amadeo 42, 20133, Milano, Italy
| | - Alice Corvo
- Dipartimento di Biotecnologie, Laboratorio di Proteomica e Spettrometria di Massa, University of Verona, Strada le Grazie 15, 37134, Verona, Italy
| | - Pier Giorgio Righetti
- Dipartimento di Chimica, Materiali e Ingegneria Chimica “Giulio Natta”, Politecnico di Milano, Via Mancinelli 7, 20131, Milano, Italy
| | - Nives Carenini
- Fondazione IRCCS Istituto Nazionale dei Tumori, via Amadeo 42, 20133, Milano, Italy
| | - Elisabetta Corna
- Fondazione IRCCS Istituto Nazionale dei Tumori, via Amadeo 42, 20133, Milano, Italy
| | - Valentina Zuco
- Fondazione IRCCS Istituto Nazionale dei Tumori, via Amadeo 42, 20133, Milano, Italy
| | - Franco Zunino
- Fondazione IRCCS Istituto Nazionale dei Tumori, via Amadeo 42, 20133, Milano, Italy
| | - Daniela Cecconi
- Dipartimento di Biotecnologie, Laboratorio di Proteomica e Spettrometria di Massa, University of Verona, Strada le Grazie 15, 37134, Verona, Italy
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167
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Bai Y, Wu C, Zhao J, Liu YH, Ding W, Ling WLW. Role of iron and sodium citrate in animal protein-free CHO cell culture medium on cell growth and monoclonal antibody production. Biotechnol Prog 2010; 27:209-19. [DOI: 10.1002/btpr.513] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Revised: 08/18/2010] [Indexed: 01/04/2023]
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168
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Miazza V, Mottet-Osman G, Startchick S, Chaponnier C, Roux L. Sendai virus induced cytoplasmic actin remodeling correlates with efficient virus particle production. Virology 2010; 410:7-16. [PMID: 21075412 DOI: 10.1016/j.virol.2010.10.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2010] [Revised: 09/27/2010] [Accepted: 10/01/2010] [Indexed: 11/30/2022]
Abstract
Cytoplasmic actins have been found interacting with viral proteins and identified in virus particles. We analyzed by confocal microscopy the cytoplasmic β- and γ-actin patterns during the course of Sendai virus infections in polarized cells. We observed a spectacular remodeling of the β-cytoplasmic actin which correlated with productive viral multiplication. Conversely, suppression of M during the course of a productive infection resulted in the decrease of particle production and the absence of β-actin remodeling. As concomitant suppression of β- and γ-actins resulted as well in reduction of virus particle production, we propose that Sendai virus specifically induces actin remodeling in order to promote efficient virion production. Beta- and γ-cytoplasmic actin recruitment could substitute for that of the endosomal sorting complex required for transport (ESCRT) mobilized by other enveloped viruses but apparently not used by Sendai virus.
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Affiliation(s)
- Vincent Miazza
- Department of Microbiology and Molecular Medicine, Faculty of Medicine University of Geneva, CMU, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland
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169
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Perrin BJ, Sonnemann KJ, Ervasti JM. β-actin and γ-actin are each dispensable for auditory hair cell development but required for Stereocilia maintenance. PLoS Genet 2010; 6:e1001158. [PMID: 20976199 PMCID: PMC2954897 DOI: 10.1371/journal.pgen.1001158] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2010] [Accepted: 09/14/2010] [Indexed: 12/02/2022] Open
Abstract
Hair cell stereocilia structure depends on actin filaments composed of cytoplasmic β-actin and γ-actin isoforms. Mutations in either gene can lead to progressive hearing loss in humans. Since β-actin and γ-actin isoforms are 99% identical at the protein level, it is unclear whether each isoform has distinct cellular roles. Here, we compared the functions of β-actin and γ-actin in stereocilia formation and maintenance by generating mice conditionally knocked out for Actb or Actg1 in hair cells. We found that, although cytoplasmic actin is necessary, neither β-actin nor γ-actin is required for normal stereocilia development or auditory function in young animals. However, aging mice with β-actin- or γ-actin-deficient hair cells develop different patterns of progressive hearing loss and distinct pathogenic changes in stereocilia morphology, despite colocalization of the actin isoforms. These results demonstrate overlapping developmental roles but unique post-developmental functions for β-actin and γ-actin in maintaining hair cell stereocilia.
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Affiliation(s)
- Benjamin J. Perrin
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Kevin J. Sonnemann
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - James M. Ervasti
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
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170
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Perrin BJ, Ervasti JM. The actin gene family: function follows isoform. Cytoskeleton (Hoboken) 2010; 67:630-4. [PMID: 20737541 PMCID: PMC2949686 DOI: 10.1002/cm.20475] [Citation(s) in RCA: 234] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2010] [Revised: 07/23/2010] [Accepted: 07/30/2010] [Indexed: 01/07/2023]
Abstract
Although actin is often thought of as a single protein, in mammals it actually consists of six different isoforms encoded by separate genes. Each isoform is remarkably similar to every other isoform, with only slight variations in amino acid sequence. Nevertheless, recent work indicates that actin isoforms carry out unique cellular functions. Here, we review evidence drawn from localization studies, mouse models, and biochemical characterization to suggest a model for how in vivo mixing of actin isoforms may influence cytoskeletal function in cells.
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Affiliation(s)
- Benjamin J Perrin
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA
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171
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Burrows C, Abd Latip N, Lam SJ, Carpenter L, Sawicka K, Tzolovsky G, Gabra H, Bushell M, Glover DM, Willis AE, Blagden SP. The RNA binding protein Larp1 regulates cell division, apoptosis and cell migration. Nucleic Acids Res 2010; 38:5542-53. [PMID: 20430826 PMCID: PMC2938220 DOI: 10.1093/nar/gkq294] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 04/01/2010] [Accepted: 04/07/2010] [Indexed: 01/11/2023] Open
Abstract
The RNA binding protein Larp1 was originally shown to be involved in spermatogenesis, embryogenesis and cell-cycle progression in Drosophila. Our data show that mammalian Larp1 is found in a complex with poly A binding protein and eukaryote initiation factor 4E and is associated with 60S and 80S ribosomal subunits. A reduction in Larp1 expression by siRNA inhibits global protein synthesis rates and results in mitotic arrest and delayed cell migration. Consistent with these data we show that Larp1 protein is present at the leading edge of migrating cells and interacts directly with cytoskeletal components. Taken together, these data suggest a role for Larp1 in facilitating the synthesis of proteins required for cellular remodelling and migration.
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Affiliation(s)
- Carla Burrows
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - Normala Abd Latip
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - Sarah-Jane Lam
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - Lee Carpenter
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - Kirsty Sawicka
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - George Tzolovsky
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - Hani Gabra
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - Martin Bushell
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - David M. Glover
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - Anne E. Willis
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - Sarah P. Blagden
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
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172
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Bunnell TM, Ervasti JM. Delayed embryonic development and impaired cell growth and survival in Actg1 null mice. Cytoskeleton (Hoboken) 2010; 67:564-72. [PMID: 20662086 PMCID: PMC2989386 DOI: 10.1002/cm.20467] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Accepted: 06/17/2010] [Indexed: 12/24/2022]
Abstract
Actins are among the most highly expressed proteins in eukaryotes and play a central role in nearly all aspects of cell biology. While the intricate process of development undoubtedly requires a properly regulated actin cytoskeleton, little is known about the contributions of different actin isoforms during embryogenesis. Of the six actin isoforms, only the two cytoplasmic actins, beta(cyto)- and gamma(cyto)-actin, are ubiquitously expressed. We found that gamma(cyto)-actin null (Actg1(-/-)) mice were fully viable during embryonic development, but most died within 48 h of birth due to respiratory failure and cannibalization by the parents. While no morphogenetic defects were identified, Actg1(-/-) mice exhibited stunted growth during embryonic and postnatal development as well as delayed cardiac outflow tract formation that resolved by birth. Using primary mouse embryonic fibroblasts, we confirm that gamma(cyto)-actin is not required for cell migration. The Actg1(-/-) cells, however, exhibited growth impairment and reduced cell viability, defects which perhaps contribute to the stunted growth and developmental delays observed in Actg1(-/-) embryos. Since the total amount of actin protein was maintained in Actg1(-/-) cells, our data suggests a distinct requirement for gamma(cyto)-actin in cell growth and survival.
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Affiliation(s)
- Tina M. Bunnell
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455
| | - James M. Ervasti
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455
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173
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Castella LF, Buscemi L, Godbout C, Meister JJ, Hinz B. A new lock-step mechanism of matrix remodelling based on subcellular contractile events. J Cell Sci 2010; 123:1751-60. [PMID: 20427321 DOI: 10.1242/jcs.066795] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Myofibroblasts promote tissue contractures during fibrotic diseases. To understand how spontaneous changes in the intracellular calcium concentration, [Ca(2+)](i), contribute to myofibroblast contraction, we analysed both [Ca(2+)](i) and subcellular contractions. Contractile events were assessed by tracking stress-fibre-linked microbeads and measured by atomic force microscopy. Myofibroblasts exhibit periodic (approximately 100 seconds) [Ca(2+)](i) oscillations that control small (approximately 400 nm) and weak (approximately 100 pN) contractions. Whereas depletion of [Ca(2+)](i) reduces these microcontractions, cell isometric tension is unaffected, as shown by growing cells on deformable substrates. Inhibition of Rho- and ROCK-mediated Ca(2+)-independent contraction has no effect on microcontractions, but abolishes cell tension. On the basis of this two-level regulation of myofibroblast contraction, we propose a single-cell lock-step model. Rho- and ROCK-dependent isometric tension generates slack in extracellular matrix fibrils, which are then accessible for the low-amplitude and high-frequency contractions mediated by [Ca(2+)](i). The joint action of both contraction modes can result in macroscopic tissue contractures of approximately 1 cm per month.
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174
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Bergeron SE, Zhu M, Thiem SM, Friderici KH, Rubenstein PA. Ion-dependent polymerization differences between mammalian beta- and gamma-nonmuscle actin isoforms. J Biol Chem 2010; 285:16087-95. [PMID: 20308063 DOI: 10.1074/jbc.m110.110130] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
beta- and gamma-nonmuscle actins differ by 4 amino acids at or near the N terminus and distant from polymerization interfaces. beta-Actin contains an Asp(1)-Asp(2)-Asp(3) and Val(10) whereas gamma-actin has a Glu(1)-Glu(2)-Glu(3) and Ile(10). Despite these small changes, conserved across mammals, fish, and birds, their differential localization in the same cell suggests they may play different roles reflecting differences in their biochemical properties. To test this hypothesis, we established a baculovirus-driven expression system for producing these actins in isoform-pure populations although contaminated with 20-25% insect actin. Surprisingly, Ca-gamma-actin exhibits a slower monomeric nucleotide exchange rate, a much longer nucleation phase, and a somewhat slower elongation rate than beta-actin. In the Mg-form, this difference between the two is much smaller. Ca-gamma-actin depolymerizes half as fast as does beta-actin. Mixing experiments with Ca-actins reveal the two will readily co-polymerize. In the Ca-form, phosphate release from polymerizing beta-actin occurs much more rapidly and extensively than polymerization, whereas phosphate release lags behind polymerization with gamma-actin. Phosphate release during treadmilling is twice as fast with beta- as with gamma-actin. With Mg-actin in the initial stages, phosphate release for both actins correlates much more closely with polymerization. Calcium bound in the high affinity binding site of gamma-actin may cause a selective energy barrier relative to beta-actin that retards the equilibration between G- and F-monomer conformations resulting in a slower polymerizing actin with greater filament stability. This difference may be particularly important in sites such as the gamma-actin-rich cochlear hair cell stereocilium where local mm calcium concentrations may exist.
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Affiliation(s)
- Sarah E Bergeron
- Department of Biochemistry, Roy A and Lucille A Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
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