101
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Lyons JS, Joca HC, Law RA, Williams KM, Kerr JP, Shi G, Khairallah RJ, Martin SS, Konstantopoulos K, Ward CW, Stains JP. Microtubules tune mechanotransduction through NOX2 and TRPV4 to decrease sclerostin abundance in osteocytes. Sci Signal 2017; 10:10/506/eaan5748. [PMID: 29162742 DOI: 10.1126/scisignal.aan5748] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The adaptation of the skeleton to its mechanical environment is orchestrated by mechanosensitive osteocytes, largely by regulating the abundance of sclerostin, a secreted inhibitor of bone formation. We defined a microtubule-dependent mechanotransduction pathway that linked fluid shear stress to reactive oxygen species (ROS) and calcium (Ca2+) signals that led to a reduction in sclerostin abundance in cultured osteocytes. We demonstrated that microtubules stabilized by detyrosination, a reversible posttranslational modification of polymerized α-tubulin, determined the stiffness of the cytoskeleton, which set the mechanoresponsive range of cultured osteocytes to fluid shear stress. We showed that fluid shear stress through the microtubule network activated NADPH oxidase 2 (NOX2)-generated ROS that target the Ca2+ channel TRPV4 to elicit Ca2+ influx. Furthermore, tuning the abundance of detyrosinated tubulin affected cytoskeletal stiffness to define the mechanoresponsive range of cultured osteocytes to fluid shear stress. Finally, we demonstrated that NOX2-ROS elicited Ca2+ signals that activated the kinase CaMKII to decrease the abundance of sclerostin protein. Together, these discoveries may identify potentially druggable targets for regulating osteocyte mechanotransduction to affect bone quality.
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Affiliation(s)
- James S Lyons
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Humberto C Joca
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Robert A Law
- Department of Chemical & Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Katrina M Williams
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Jaclyn P Kerr
- Department of Orthopaedics, University of Maryland School of Nursing, Baltimore, MD 21201, USA
| | - Guoli Shi
- Department of Orthopaedics, University of Maryland School of Nursing, Baltimore, MD 21201, USA
| | | | - Stuart S Martin
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | | | - Christopher W Ward
- Department of Orthopaedics, University of Maryland School of Nursing, Baltimore, MD 21201, USA.
| | - Joseph P Stains
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
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102
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Bernabé-Rubio M, Alonso MA. Routes and machinery of primary cilium biogenesis. Cell Mol Life Sci 2017; 74:4077-4095. [PMID: 28624967 PMCID: PMC11107551 DOI: 10.1007/s00018-017-2570-5] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 06/01/2017] [Accepted: 06/13/2017] [Indexed: 02/06/2023]
Abstract
Primary cilia are solitary, microtubule-based protrusions of the cell surface that play fundamental roles as photosensors, mechanosensors and biochemical sensors. Primary cilia dysfunction results in a long list of developmental and degenerative disorders that combine to give rise to a large spectrum of human diseases affecting almost any major body organ. Depending on the cell type, primary ciliogenesis is initiated intracellularly, as in fibroblasts, or at the cell surface, as in renal polarized epithelial cells. In this review, we have focused on the routes of primary ciliogenesis placing particular emphasis on the recently described pathway in renal polarized epithelial cells by which the midbody remnant resulting from a previous cell division event enables the centrosome for initiation of primary cilium assembly. The protein machinery implicated in primary cilium formation in epithelial cells, including the machinery best known for its involvement in establishing cell polarity and polarized membrane trafficking, is also discussed.
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Affiliation(s)
- Miguel Bernabé-Rubio
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Nicolás Cabrera 1, Cantoblanco, 28049, Madrid, Spain
| | - Miguel A Alonso
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Nicolás Cabrera 1, Cantoblanco, 28049, Madrid, Spain.
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103
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Wloga D, Joachimiak E, Fabczak H. Tubulin Post-Translational Modifications and Microtubule Dynamics. Int J Mol Sci 2017; 18:ijms18102207. [PMID: 29065455 PMCID: PMC5666887 DOI: 10.3390/ijms18102207] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 10/12/2017] [Accepted: 10/19/2017] [Indexed: 11/24/2022] Open
Abstract
Microtubules are hollow tube-like polymeric structures composed of α,β-tubulin heterodimers. They play an important role in numerous cellular processes, including intracellular transport, cell motility and segregation of the chromosomes during cell division. Moreover, microtubule doublets or triplets form a scaffold of a cilium, centriole and basal body, respectively. To perform such diverse functions microtubules have to differ in their properties. Post-translational modifications are one of the factors that affect the properties of the tubulin polymer. Here we focus on the direct and indirect effects of post-translational modifications of tubulin on microtubule dynamics.
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Affiliation(s)
- Dorota Wloga
- Laboratory of Cytoskeleton and Cilia Biology, Department of Cell Biology, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Str., 02-093 Warsaw, Poland.
| | - Ewa Joachimiak
- Laboratory of Cytoskeleton and Cilia Biology, Department of Cell Biology, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Str., 02-093 Warsaw, Poland.
| | - Hanna Fabczak
- Laboratory of Cytoskeleton and Cilia Biology, Department of Cell Biology, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur Str., 02-093 Warsaw, Poland.
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104
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Kubo T, Oda T. Electrostatic interaction between polyglutamylated tubulin and the nexin-dynein regulatory complex regulates flagellar motility. Mol Biol Cell 2017. [PMID: 28637765 PMCID: PMC5555654 DOI: 10.1091/mbc.e17-05-0285] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The 3D localization of polyglutamylated tubulin in eukaryotic flagella is identified. Polyglutamylated tubulins are located on the interface between the microtubule and its cross-bridging structure, the N-DRC. Flagellar motility is regulated by electrostatic interaction between negatively charged tubulins and positively charged N-DRC. Tubulins undergo various posttranslational modifications. Among them, polyglutamylation is involved in the motility of eukaryotic flagella and the stability of the axonemal microtubules. However, it remains unclear where polyglutamylated tubulin localizes precisely within the axoneme and how tubulin polyglutamylation affects flagellar motility. In this study, we identified the three-dimensional localization of the polyglutamylated tubulin in Chlamydomonas flagella using antibody labeling and cryo–electron tomography. Polyglutamylated tubulins specifically located in close proximity to a microtubule-cross-bridging structure called the nexin–dynein regulatory complex (N-DRC). Because N-DRC is positively charged, we hypothesized that there is an electrostatic interaction between the polyglutamylated tubulin and the N-DRC, and therefore we mutated the amino acid sequences of DRC4 to modify the charge of the N-DRC. We found that both augmentation and reduction of the positive charge on DRC4 resulted in reduced flagellar motility. Moreover, reduced motility in a mutant with a structurally defective N-DRC was partially restored by increasing the positive charge on DRC4. These results clearly indicate that beating motion of flagella is maintained by the electrostatic cross-bridge formed between the negatively charged polyglutamylated tubulins and the positively charged N-DRC.
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Affiliation(s)
- Tomohiro Kubo
- Department of Anatomy and Structural Biology, Graduate School of Medical Science, University of Yamanashi, Yamanashi 409-3898, Japan
| | - Toshiyuki Oda
- Department of Anatomy and Structural Biology, Graduate School of Medical Science, University of Yamanashi, Yamanashi 409-3898, Japan
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105
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Mooney P, Sulerud T, Pelletier J, Dilsaver M, Tomschik M, Geisler C, Gatlin JC. Tau-based fluorescent protein fusions to visualize microtubules. Cytoskeleton (Hoboken) 2017; 74:221-232. [PMID: 28407416 PMCID: PMC5592782 DOI: 10.1002/cm.21368] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 04/03/2017] [Accepted: 04/10/2017] [Indexed: 01/10/2023]
Abstract
The ability to visualize cytoskeletal proteins and their dynamics in living cells has been critically important in advancing our understanding of numerous cellular processes, including actin- and microtubule (MT)-dependent phenomena such as cell motility, cell division, and mitosis. Here, we describe a novel set of fluorescent protein (FP) fusions designed specifically to visualize MTs in living systems using fluorescence microscopy. Each fusion contains a FP module linked in frame to a modified phospho-deficient version of the MT-binding domain of Tau (mTMBD). We found that expressed and purified constructs containing a single mTMBD decorated Xenopus egg extract spindles more homogenously than similar constructs containing the MT-binding domain of Ensconsin, suggesting that the binding affinity of mTMBD is minimally affected by localized signaling gradients generated during mitosis. Furthermore, MT dynamics were not grossly perturbed by the presence of Tau-based FP fusions. Interestingly, the addition of a second mTMBD to the opposite terminus of our construct caused dramatic changes to the spatial localization of probes within spindles. These results support the use of Tau-based FP fusions as minimally perturbing tools to accurately visualize MTs in living systems.
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Affiliation(s)
- Paul Mooney
- Department of Molecular Biology, University of Wyoming, Laramie, WY,
82071, USA
- Molecular & Cellular Life Sciences Program, University of
Wyoming, Laramie, WY, 82071, USA
- Cell Organization and Division Group, Marine Biological
Laboratories, Woods Hole, MA, 02543, USA
| | - Taylor Sulerud
- Department of Molecular Biology, University of Wyoming, Laramie, WY,
82071, USA
- Molecular & Cellular Life Sciences Program, University of
Wyoming, Laramie, WY, 82071, USA
- Cell Organization and Division Group, Marine Biological
Laboratories, Woods Hole, MA, 02543, USA
| | - James Pelletier
- Cell Organization and Division Group, Marine Biological
Laboratories, Woods Hole, MA, 02543, USA
- Department of Systems Biology, Harvard Medical School, Boston, MA,
02115, USA
| | - Matthew Dilsaver
- Department of Molecular Biology, University of Wyoming, Laramie, WY,
82071, USA
| | - Miroslav Tomschik
- Department of Molecular Biology, University of Wyoming, Laramie, WY,
82071, USA
| | | | - Jesse C. Gatlin
- Department of Molecular Biology, University of Wyoming, Laramie, WY,
82071, USA
- Molecular & Cellular Life Sciences Program, University of
Wyoming, Laramie, WY, 82071, USA
- Cell Organization and Division Group, Marine Biological
Laboratories, Woods Hole, MA, 02543, USA
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