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Keen AN, Payne LA, Mehta V, Rice A, Simpson LJ, Pang KL, del Rio Hernandez A, Reader JS, Tzima E. Eukaryotic initiation factor 6 regulates mechanical responses in endothelial cells. J Cell Biol 2022; 221:e202005213. [PMID: 35024764 PMCID: PMC8763864 DOI: 10.1083/jcb.202005213] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 10/11/2021] [Accepted: 12/08/2021] [Indexed: 12/22/2022] Open
Abstract
The repertoire of extratranslational functions of components of the protein synthesis apparatus is expanding to include control of key cell signaling networks. However, very little is known about noncanonical functions of members of the protein synthesis machinery in regulating cellular mechanics. We demonstrate that the eukaryotic initiation factor 6 (eIF6) modulates cellular mechanobiology. eIF6-depleted endothelial cells, under basal conditions, exhibit unchanged nascent protein synthesis, polysome profiles, and cytoskeleton protein expression, with minimal effects on ribosomal biogenesis. In contrast, using traction force and atomic force microscopy, we show that loss of eIF6 leads to reduced stiffness and force generation accompanied by cytoskeletal and focal adhesion defects. Mechanistically, we show that eIF6 is required for the correct spatial mechanoactivation of ERK1/2 via stabilization of an eIF6-RACK1-ERK1/2-FAK mechanocomplex, which is necessary for force-induced remodeling. These results reveal an extratranslational function for eIF6 and a novel paradigm for how mechanotransduction, the cellular cytoskeleton, and protein translation constituents are linked.
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Affiliation(s)
- Adam N. Keen
- Radcliffe Department of Medicine, University of Oxford, Oxford, UK
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Luke A. Payne
- Radcliffe Department of Medicine, University of Oxford, Oxford, UK
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Vedanta Mehta
- Radcliffe Department of Medicine, University of Oxford, Oxford, UK
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Alistair Rice
- Cellular and Molecular Biomechanics Laboratory, Department of Bioengineering, Imperial College London, London, UK
| | - Lisa J. Simpson
- Radcliffe Department of Medicine, University of Oxford, Oxford, UK
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Kar Lai Pang
- Radcliffe Department of Medicine, University of Oxford, Oxford, UK
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Armando del Rio Hernandez
- Cellular and Molecular Biomechanics Laboratory, Department of Bioengineering, Imperial College London, London, UK
| | - John S. Reader
- Radcliffe Department of Medicine, University of Oxford, Oxford, UK
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Ellie Tzima
- Radcliffe Department of Medicine, University of Oxford, Oxford, UK
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
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Singh K, Kim AB, Morgan KG. Non-muscle myosin II regulates aortic stiffness through effects on specific focal adhesion proteins and the non-muscle cortical cytoskeleton. J Cell Mol Med 2021; 25:2471-2483. [PMID: 33547870 PMCID: PMC7933926 DOI: 10.1111/jcmm.16170] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 11/09/2020] [Accepted: 11/13/2020] [Indexed: 12/13/2022] Open
Abstract
Non‐muscle myosin II (NMII) plays a role in many fundamental cellular processes including cell adhesion, migration, and cytokinesis. However, its role in mammalian vascular function is not well understood. Here, we investigated the function of NMII in the biomechanical and signalling properties of mouse aorta. We found that blebbistatin, an inhibitor of NMII, decreases agonist‐induced aortic stress and stiffness in a dose‐dependent manner. We also specifically demonstrate that in freshly isolated, contractile, aortic smooth muscle cells, the non‐muscle myosin IIA (NMIIA) isoform is associated with contractile filaments in the core of the cell as well as those in the non‐muscle cell cortex. However, the non‐muscle myosin IIB (NMIIB) isoform is excluded from the cell cortex and colocalizes only with contractile filaments. Furthermore, both siRNA knockdown of NMIIA and NMIIB isoforms in the differentiated A7r5 smooth muscle cell line and blebbistatin‐mediated inhibition of NM myosin II suppress agonist‐activated increases in phosphorylation of the focal adhesion proteins FAK Y925 and paxillin Y118. Thus, we show in the present study, for the first time that NMII regulates aortic stiffness and stress and that this regulation is mediated through the tension‐dependent phosphorylation of the focal adhesion proteins FAK and paxillin.
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Affiliation(s)
- Kuldeep Singh
- Department of Health Sciences, Boston University, Boston, MA, USA.,CSIR-Institute of Himalayan Bioresource Technology, Palampur, India
| | - Anne B Kim
- Department of Health Sciences, Boston University, Boston, MA, USA
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Vetterkind S, Lin QQ, Morgan KG. A novel mechanism of ERK1/2 regulation in smooth muscle involving acetylation of the ERK1/2 scaffold IQGAP1. Sci Rep 2017; 7:9302. [PMID: 28839270 PMCID: PMC5571205 DOI: 10.1038/s41598-017-09434-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 07/26/2017] [Indexed: 02/07/2023] Open
Abstract
Ceramide, a bioactive lipid and signaling molecule associated with cardiovascular disease, is known to activate extracellular signal regulated kinases 1 and 2 (ERK1/2). Here, we determined that the effect of ceramide on ERK1/2 is mediated by ceramide signaling on an ERK scaffold protein, IQ motif containing GTPase activating protein 1 (IQGAP1). Experiments were performed with aortic smooth muscle cells using inhibitor screening, small interfering RNA (siRNA), immunoprecipitation (IP), immunoblots and bioinformatics. We report here that C6 ceramide increases serum-stimulated ERK1/2 activation in a manner dependent on the ERK1/2 scaffold IQGAP1. C6 ceramide increases IQGAP1 protein levels by preventing its cleavage. Bioinformatic analysis of the IQGAP1 amino acid sequence revealed potential cleavage sites for proteases of the proprotein convertase family that match the cleavage products. These potential cleavage sites overlap with known motifs for lysine acetylation. Deacetylase inhibitor treatment increased IQGAP1 acetylation and reduced IQGAP1 cleavage. These data are consistent with a model in which IQGAP1 cleavage is regulated by acetylation of the cleavage sites. Activation of ERK1/2 by ceramide, known to increase lysine acetylation, appears to be mediated by acetylation-dependent stabilization of IQGAP1. This novel mechanism could open new possibilities for therapeutic intervention in cardiovascular diseases.
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Affiliation(s)
- Susanne Vetterkind
- Department of Health Sciences, Boston University, 635 Commonwealth Ave., Boston, 02215, USA
| | - Qian Qian Lin
- Department of Health Sciences, Boston University, 635 Commonwealth Ave., Boston, 02215, USA
| | - Kathleen G Morgan
- Department of Health Sciences, Boston University, 635 Commonwealth Ave., Boston, 02215, USA.
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Multi-Compartmentalisation in the MAPK Signalling Pathway Contributes to the Emergence of Oscillatory Behaviour and to Ultrasensitivity. PLoS One 2016; 11:e0156139. [PMID: 27243235 PMCID: PMC4887093 DOI: 10.1371/journal.pone.0156139] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 05/10/2016] [Indexed: 12/20/2022] Open
Abstract
Signal transduction through the Mitogen Activated Protein Kinase (MAPK) pathways is evolutionarily highly conserved. Many cells use these pathways to interpret changes to their environment and respond accordingly. The pathways are central to triggering diverse cellular responses such as survival, apoptosis, differentiation and proliferation. Though the interactions between the different MAPK pathways are complex, nevertheless, they maintain a high level of fidelity and specificity to the original signal. There are numerous theories explaining how fidelity and specificity arise within this complex context; spatio-temporal regulation of the pathways and feedback loops are thought to be very important. This paper presents an agent based computational model addressing multi-compartmentalisation and how this influences the dynamics of MAPK cascade activation. The model suggests that multi-compartmentalisation coupled with periodic MAPK kinase (MAPKK) activation may be critical factors for the emergence of oscillation and ultrasensitivity in the system. Finally, the model also establishes a link between the spatial arrangements of the cascade components and temporal activation mechanisms, and how both contribute to fidelity and specificity of MAPK mediated signalling.
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Hirata H, Gupta M, Vedula SRK, Lim CT, Ladoux B, Sokabe M. Actomyosin bundles serve as a tension sensor and a platform for ERK activation. EMBO Rep 2014; 16:250-7. [PMID: 25550404 DOI: 10.15252/embr.201439140] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Tensile forces generated by stress fibers drive signal transduction events at focal adhesions. Here, we report that stress fibers per se act as a platform for tension-induced activation of biochemical signals. The MAP kinase, ERK is activated on stress fibers in a myosin II-dependent manner. In myosin II-inhibited cells, uniaxial stretching of cell adhesion substrates restores ERK activation on stress fibers. By quantifying myosin II- or mechanical stretch-mediated tensile forces in individual stress fibers, we show that ERK activation on stress fibers correlates positively with tensile forces acting on the fibers, indicating stress fibers as a tension sensor in ERK activation. Myosin II-dependent ERK activation is also observed on actomyosin bundles connecting E-cadherin clusters, thus suggesting that actomyosin bundles, in general, work as a platform for tension-dependent ERK activation.
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Affiliation(s)
- Hiroaki Hirata
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore
| | - Mukund Gupta
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore
| | | | - Chwee Teck Lim
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore Department of Mechanical Engineering, National University of Singapore, Singapore, Singapore
| | - Benoit Ladoux
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore Institut Jacques Monod (IJM), CNRS UMR 7592 Université Paris Diderot, Paris, France
| | - Masahiro Sokabe
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore Mechanobiology Laboratory, Nagoya University Graduate School of Medicine, Nagoya, Japan
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Vetterkind S, Poythress RH, Lin QQ, Morgan KG. Hierarchical scaffolding of an ERK1/2 activation pathway. Cell Commun Signal 2013; 11:65. [PMID: 23987506 PMCID: PMC3846746 DOI: 10.1186/1478-811x-11-65] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 08/27/2013] [Indexed: 12/30/2022] Open
Abstract
Background Scaffold proteins modulate cellular signaling by facilitating assembly of specific signaling pathways. However, there is at present little information if and how scaffold proteins functionally interact with each other. Results Here, we show that two scaffold proteins, caveolin-1 and IQGAP1, are required for phosphorylation of the actin associated pool of extracellular signal regulated kinase 1 and 2 (ERK1/2) in response to protein kinase C activation. We show by immunofluorescence and proximity ligation assays, that IQGAP1 tethers ERK1/2 to actin filaments. Moreover, siRNA experiments demonstrate that IQGAP1 is required for activation of actin-bound ERK1/2. Caveolin-1 is also necessary for phosphorylation of actin-bound ERK1/2 in response to protein kinase C, but is dispensible for ERK1/2 association with actin. Simultaneous knock down of caveolin-1 and IQGAP1 decreases total phorbol ester-induced ERK1/2 phosphorylation to the same degree as single knock down of either caveolin-1 or IQGAP1, indicating that caveolin-1 and IQGAP1 operate in the same ERK activation pathway. We further show that caveolin-1 knock down, but not IQGAP1 knock down, reduces C-Raf phosphorylation in response to phorbol ester stimulation. Conclusions Based on our data, we suggest that caveolin-1 and IQGAP1 assemble distinct signaling modules, which are then linked in a hierarchical arrangement to generate a functional ERK1/2 activation pathway.
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Affiliation(s)
- Susanne Vetterkind
- Department of Health Sciences, Boston University, Boston, MA 02215, USA.
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Saphirstein RJ, Gao YZ, Jensen MH, Gallant CM, Vetterkind S, Moore JR, Morgan KG. The focal adhesion: a regulated component of aortic stiffness. PLoS One 2013; 8:e62461. [PMID: 23626821 PMCID: PMC3633884 DOI: 10.1371/journal.pone.0062461] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 03/21/2013] [Indexed: 01/16/2023] Open
Abstract
Increased aortic stiffness is an acknowledged predictor and cause of cardiovascular disease. The sources and mechanisms of vascular stiffness are not well understood, although the extracellular matrix (ECM) has been assumed to be a major component. We tested here the hypothesis that the focal adhesions (FAs) connecting the cortical cytoskeleton of vascular smooth muscle cells (VSMCs) to the matrix in the aortic wall are a component of aortic stiffness and that this component is dynamically regulated. First, we examined a model system in which magnetic tweezers could be used to monitor cellular cortical stiffness, serum-starved A7r5 aortic smooth muscle cells. Lysophosphatidic acid (LPA), an activator of myosin that increases cell contractility, increased cortical stiffness. A small molecule inhibitor of Src-dependent FA recycling, PP2, was found to significantly inhibit LPA-induced increases in cortical stiffness, as well as tension-induced increases in FA size. To directly test the applicability of these results to force and stiffness development at the level of vascular tissue, we monitored mouse aorta ring stiffness with small sinusoidal length oscillations during agonist-induced contraction. The alpha-agonist phenylephrine, which also increases myosin activation and contractility, increased tissue stress and stiffness in a PP2- and FAK inhibitor 14-attenuated manner. Subsequent phosphotyrosine screening and follow-up with phosphosite-specific antibodies confirmed that the effects of PP2 and FAK inhibitor 14 in vascular tissue involve FA proteins, including FAK, CAS, and paxillin. Thus, in the present study we identify, for the first time, the FA of the VSMC, in particular the FAK-Src signaling complex, as a significant subcellular regulator of aortic stiffness and stress.
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Affiliation(s)
- Robert J. Saphirstein
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States of America
- Department of Health Sciences, Boston University, Boston, Massachusetts, United States of America
| | - Yuan Z. Gao
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States of America
- Department of Health Sciences, Boston University, Boston, Massachusetts, United States of America
| | - Mikkel H. Jensen
- Department of Physics, Boston University, Boston, Massachusetts, United States of America
- Department of Physiology and Biophysics, Boston University Medical School, Boston, Massachusetts, United States of America
| | - Cynthia M. Gallant
- Department of Health Sciences, Boston University, Boston, Massachusetts, United States of America
| | - Susanne Vetterkind
- Department of Health Sciences, Boston University, Boston, Massachusetts, United States of America
| | - Jeffrey R. Moore
- Department of Physiology and Biophysics, Boston University Medical School, Boston, Massachusetts, United States of America
| | - Kathleen G. Morgan
- Department of Health Sciences, Boston University, Boston, Massachusetts, United States of America
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