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Jalilian I, Heu C, Cheng H, Freittag H, Desouza M, Stehn JR, Bryce NS, Whan RM, Hardeman EC, Fath T, Schevzov G, Gunning PW. Cell elasticity is regulated by the tropomyosin isoform composition of the actin cytoskeleton. PLoS One 2015; 10:e0126214. [PMID: 25978408 PMCID: PMC4433179 DOI: 10.1371/journal.pone.0126214] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 03/31/2015] [Indexed: 02/07/2023] Open
Abstract
The actin cytoskeleton is the primary polymer system within cells responsible for regulating cellular stiffness. While various actin binding proteins regulate the organization and dynamics of the actin cytoskeleton, the proteins responsible for regulating the mechanical properties of cells are still not fully understood. In the present study, we have addressed the significance of the actin associated protein, tropomyosin (Tpm), in influencing the mechanical properties of cells. Tpms belong to a multi-gene family that form a co-polymer with actin filaments and differentially regulate actin filament stability, function and organization. Tpm isoform expression is highly regulated and together with the ability to sort to specific intracellular sites, result in the generation of distinct Tpm isoform-containing actin filament populations. Nanomechanical measurements conducted with an Atomic Force Microscope using indentation in Peak Force Tapping in indentation/ramping mode, demonstrated that Tpm impacts on cell stiffness and the observed effect occurred in a Tpm isoform-specific manner. Quantitative analysis of the cellular filamentous actin (F-actin) pool conducted both biochemically and with the use of a linear detection algorithm to evaluate actin structures revealed that an altered F-actin pool does not absolutely predict changes in cell stiffness. Inhibition of non-muscle myosin II revealed that intracellular tension generated by myosin II is required for the observed increase in cell stiffness. Lastly, we show that the observed increase in cell stiffness is partially recapitulated in vivo as detected in epididymal fat pads isolated from a Tpm3.1 transgenic mouse line. Together these data are consistent with a role for Tpm in regulating cell stiffness via the generation of specific populations of Tpm isoform-containing actin filaments.
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Affiliation(s)
- Iman Jalilian
- Oncology Research Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Celine Heu
- Oncology Research Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
- Biomedical Imaging facility, UNSW Australia, Sydney, NSW 2052, Australia
| | - Hong Cheng
- Neurodegeneration and Repair Unit, School of Medical Sciences, UNSW Australia, Sydney NSW 2052, Australia
| | - Hannah Freittag
- Neurodegeneration and Repair Unit, School of Medical Sciences, UNSW Australia, Sydney NSW 2052, Australia
| | - Melissa Desouza
- Oncology Research Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Justine R. Stehn
- Oncology Research Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Nicole S. Bryce
- Oncology Research Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Renee M. Whan
- Biomedical Imaging facility, UNSW Australia, Sydney, NSW 2052, Australia
| | - Edna C. Hardeman
- Neuromuscular and Regenerative Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Thomas Fath
- Neurodegeneration and Repair Unit, School of Medical Sciences, UNSW Australia, Sydney NSW 2052, Australia
| | - Galina Schevzov
- Oncology Research Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Peter W. Gunning
- Oncology Research Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
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Curthoys NM, Freittag H, Connor A, Desouza M, Brettle M, Poljak A, Hall A, Hardeman E, Schevzov G, Gunning PW, Fath T. Tropomyosins induce neuritogenesis and determine neurite branching patterns in B35 neuroblastoma cells. Mol Cell Neurosci 2013; 58:11-21. [PMID: 24211701 DOI: 10.1016/j.mcn.2013.10.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Revised: 10/21/2013] [Accepted: 10/29/2013] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND The actin cytoskeleton is critically involved in the regulation of neurite outgrowth. RESULTS The actin cytoskeleton-associated protein tropomyosin induces neurite outgrowth in B35 neuroblastoma cells and regulates neurite branching in an isoform-dependent manner. CONCLUSIONS Our data indicate that tropomyosins are key regulators of the actin cytoskeleton during neurite outgrowth. SIGNIFICANCE Revealing the molecular machinery that regulates the actin cytoskeleton during neurite outgrowth may provide new therapeutic strategies to promote neurite regeneration after nerve injury. SUMMARY The formation of a branched network of neurites between communicating neurons is required for all higher functions in the nervous system. The dynamics of the actin cytoskeleton is fundamental to morphological changes in cell shape and the establishment of these branched networks. The actin-associated proteins tropomyosins have previously been shown to impact on different aspects of neurite formation. Here we demonstrate that an increased expression of tropomyosins is sufficient to induce the formation of neurites in B35 neuroblastoma cells. Furthermore, our data highlight the functional diversity of different tropomyosin isoforms during neuritogenesis. Tropomyosins differentially impact on the expression levels of the actin filament bundling protein fascin and increase the formation of filopodia along the length of neurites. Our data suggest that tropomyosins are central regulators of actin filament populations which drive distinct aspects of neuronal morphogenesis.
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Affiliation(s)
- Nikki Margarita Curthoys
- Neurodegeneration and Repair Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia; Oncology Research Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Hannah Freittag
- Neurodegeneration and Repair Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia; Neuromuscular and Regenerative Medicine Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Andrea Connor
- Neurodegeneration and Repair Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia; Oncology Research Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Melissa Desouza
- Neurodegeneration and Repair Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia; Oncology Research Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Merryn Brettle
- Neurodegeneration and Repair Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Anne Poljak
- Bioanalytical Mass Spectrometry Facility, Bioanalytical Centre, The University of New South Wales, Sydney, NSW 2052, Australia
| | - Amelia Hall
- Neurodegeneration and Repair Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Edna Hardeman
- Neuromuscular and Regenerative Medicine Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Galina Schevzov
- Oncology Research Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Peter William Gunning
- Oncology Research Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia
| | - Thomas Fath
- Neurodegeneration and Repair Unit, School of Medical Sciences, The University of New South Wales, Sydney NSW 2052, Australia.
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