1
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Perez-Bertoldi JM, Zhao Y, Thawani A, Yildiz A, Nogales E. Molecular interplay between HURP and Kif18A in mitotic spindle regulation. RESEARCH SQUARE 2024:rs.3.rs-4249615. [PMID: 38854046 PMCID: PMC11160874 DOI: 10.21203/rs.3.rs-4249615/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
During mitosis, microtubule dynamics are regulated to ensure proper alignment and segregation of chromosomes. The dynamics of kinetochore-attached microtubules are regulated by hepatoma-upregulated protein (HURP) and the mitotic kinesin-8 Kif18A, but the underlying mechanism remains elusive. Using single-molecule imaging in vitro, we demonstrate that Kif18A motility is regulated by HURP. While sparse decoration of HURP activates the motor, higher concentrations hinder processive motility. To shed light on this behavior, we determined the binding mode of HURP to microtubules using Cryo-EM. The structure reveals that one HURP motif spans laterally across β-tubulin, while a second motif binds between adjacent protofilaments. HURP partially overlaps with the microtubule-binding site of the Kif18A motor domain, indicating that excess HURP inhibits Kif18A motility by steric exclusion. We also observed that HURP and Kif18A function together to suppress dynamics of the microtubule plus-end, providing a mechanistic basis for how they collectively serve in spindle length control.
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Affiliation(s)
| | - Yuanchang Zhao
- Physics Department, University of California, Berkeley, CA, USA
| | - Akanksha Thawani
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
| | - Ahmet Yildiz
- Biophysics Graduate Group, University of California, Berkeley, CA, USA
- Physics Department, University of California, Berkeley, CA, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
- Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Eva Nogales
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
- Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Howard Hughes Medical Institute, University of California, Berkeley, CA, USA
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2
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Craig EM, Oprea F, Alam S, Grodsky A, Miller KE. A simple active fluid model unites cytokinesis, cell crawling, and axonal outgrowth. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.22.595337. [PMID: 38826455 PMCID: PMC11142150 DOI: 10.1101/2024.05.22.595337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
Axonal outgrowth, cell crawling, and cytokinesis utilize actomyosin, microtubule-based motors, cytoskeletal dynamics, and substrate adhesions to produce traction forces and bulk cellular motion. While it has long been appreciated that growth cones resemble crawling cells and that the mechanisms that drive cytokinesis help power cell crawling, they are typically viewed as unique processes. To better understand the relationship between these modes of motility, here, we developed a unified active fluid model of cytokinesis, amoeboid migration, mesenchymal migration, neuronal migration, and axonal outgrowth in terms of cytoskeletal flow, adhesions, viscosity, and force generation. Using numerical modeling, we fit subcellular velocity profiles of the motions of cytoskeletal structures and docked organelles from previously published studies to infer underlying patterns of force generation and adhesion. Our results indicate that, during cytokinesis, there is a primary converge zone at the cleavage furrow that drives flow towards it; adhesions are symmetric across the cell, and as a result, cells are stationary. In mesenchymal, amoeboid, and neuronal migration, the site of the converge zone shifts, and differences in adhesion between the front and back of the cell drive crawling. During neuronal migration and axonal outgrowth, the primary convergence zone lies within the growth cone, which drives actin retrograde flow in the P-domain and bulk anterograde flow of the axonal shaft. They differ in that during neuronal migration, the cell body is weakly attached to the substrate and thus moves forward at the same velocity as the axon. In contrast, during axonal outgrowth, the cell body strongly adheres to the substrate and remains stationary, resulting in a decrease in flow velocity away from the growth cone. The simplicity with which cytokinesis, cell crawling, and axonal outgrowth can be modeled by varying coefficients in a simple model suggests a deep connection between them.
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Affiliation(s)
- Erin M Craig
- Central Washington University, Department of Physics, 400 E. University Way, Ellensburg, WA 98926-7422, USA
| | - Francesca Oprea
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Sajid Alam
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Ania Grodsky
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Kyle E Miller
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA
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3
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Perez-Bertoldi JM, Zhao Y, Thawani A, Yildiz A, Nogales E. Molecular interplay between HURP and Kif18A in mitotic spindle regulation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.11.589088. [PMID: 38645125 PMCID: PMC11030443 DOI: 10.1101/2024.04.11.589088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
During mitosis, microtubule dynamics are regulated to ensure proper alignment and segregation of chromosomes. The dynamics of kinetochore-attached microtubules are regulated by hepatoma-upregulated protein (HURP) and the mitotic kinesin-8 Kif18A, but the underlying mechanism remains elusive. Using single-molecule imaging in vitro , we demonstrate that Kif18A motility is regulated by HURP. While sparse decoration of HURP activates the motor, higher concentrations hinder processive motility. To shed light on this behavior, we determined the binding mode of HURP to microtubules using Cryo-EM. The structure reveals that one HURP motif spans laterally across β-tubulin, while a second motif binds between adjacent protofilaments. HURP partially overlaps with the microtubule-binding site of the Kif18A motor domain, indicating that excess HURP inhibits Kif18A motility by steric exclusion. We also observed that HURP and Kif18A function together to suppress dynamics of the microtubule plus-end, providing a mechanistic basis for how they collectively serve in spindle length control.
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4
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Leung TCN, Lu SN, Chu CN, Lee J, Liu X, Ngai SM. Temporal Quantitative Proteomic and Phosphoproteomic Profiling of SH-SY5Y and IMR-32 Neuroblastoma Cells during All- Trans-Retinoic Acid-Induced Neuronal Differentiation. Int J Mol Sci 2024; 25:1047. [PMID: 38256121 PMCID: PMC10816102 DOI: 10.3390/ijms25021047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 01/05/2024] [Accepted: 01/13/2024] [Indexed: 01/24/2024] Open
Abstract
The human neuroblastoma cell lines SH-SY5Y and IMR-32 can be differentiated into neuron-like phenotypes through treatment with all-trans-retinoic acid (ATRA). After differentiation, these cell lines are extensively utilized as in vitro models to study various aspects of neuronal cell biology. However, temporal and quantitative profiling of the proteome and phosphoproteome of SH-SY5Y and IMR-32 cells throughout ATRA-induced differentiation has been limited. Here, we performed relative quantification of the proteomes and phosphoproteomes of SH-SY5Y and IMR-32 cells at multiple time points during ATRA-induced differentiation. Relative quantification of proteins and phosphopeptides with subsequent gene ontology analysis revealed that several biological processes, including cytoskeleton organization, cell division, chaperone function and protein folding, and one-carbon metabolism, were associated with ATRA-induced differentiation in both cell lines. Furthermore, kinase-substrate enrichment analysis predicted altered activities of several kinases during differentiation. Among these, CDK5 exhibited increased activity, while CDK2 displayed reduced activity. The data presented serve as a valuable resource for investigating temporal protein and phosphoprotein abundance changes in SH-SY5Y and IMR-32 cells during ATRA-induced differentiation.
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Affiliation(s)
- Thomas C. N. Leung
- State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Hong Kong, China
| | - Scott Ninghai Lu
- School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China; (S.N.L.); (C.N.C.); (J.L.); (X.L.)
| | - Cheuk Ning Chu
- School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China; (S.N.L.); (C.N.C.); (J.L.); (X.L.)
| | - Joy Lee
- School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China; (S.N.L.); (C.N.C.); (J.L.); (X.L.)
| | - Xingyu Liu
- School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China; (S.N.L.); (C.N.C.); (J.L.); (X.L.)
| | - Sai Ming Ngai
- State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Hong Kong, China
- School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China; (S.N.L.); (C.N.C.); (J.L.); (X.L.)
- AoE Centre for Genomic Studies on Plant-Environment Interaction for Sustainable Agriculture and Food Security, The Chinese University of Hong Kong, Hong Kong, China
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5
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Lucero EM, Freund RK, Smith A, Johnson NR, Dooling B, Sullivan E, Prikhodko O, Ahmed MM, Bennett DA, Hohman TJ, Dell’Acqua ML, Chial HJ, Potter H. Increased KIF11/ kinesin-5 expression offsets Alzheimer Aβ-mediated toxicity and cognitive dysfunction. iScience 2022; 25:105288. [PMID: 36304124 PMCID: PMC9593841 DOI: 10.1016/j.isci.2022.105288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 08/08/2022] [Accepted: 10/04/2022] [Indexed: 11/28/2022] Open
Abstract
Previously, we found that amyloid-beta (Aβ) competitively inhibits the kinesin motor protein KIF11 (Kinesin-5/Eg5), leading to defects in the microtubule network and in neurotransmitter and neurotrophin receptor localization and function. These biochemical and cell biological mechanisms for Aβ-induced neuronal dysfunction may underlie learning and memory defects in Alzheimer's disease (AD). Here, we show that KIF11 overexpression rescues Aβ-mediated decreases in dendritic spine density in cultured neurons and in long-term potentiation in hippocampal slices. Furthermore, Kif11 overexpression from a transgene prevented spatial learning deficits in the 5xFAD mouse model of AD. Finally, increased KIF11 expression in neuritic plaque-positive AD patients' brains was associated with better cognitive performance and higher expression of synaptic protein mRNAs. Taken together, these mechanistic biochemical, cell biological, electrophysiological, animal model, and human data identify KIF11 as a key target of Aβ-mediated toxicity in AD, which damages synaptic structures and functions critical for learning and memory in AD.
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Affiliation(s)
- Esteban M. Lucero
- Department of Neurology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- University of Colorado Alzheimer’s and Cognition Center, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- Linda Crnic Institute for Down Syndrome, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- University of Colorado Program for Human Medical Genetics and Genomics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Ronald K. Freund
- University of Colorado Alzheimer’s and Cognition Center, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Alexandra Smith
- Vanderbilt Memory and Alzheimer’s Center, Vanderbilt University Medical Center, Nashville, TN, USA
- Vanderbilt Genetics Institute, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Noah R. Johnson
- Department of Neurology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- University of Colorado Alzheimer’s and Cognition Center, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- Linda Crnic Institute for Down Syndrome, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Breanna Dooling
- Department of Neurology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- University of Colorado Alzheimer’s and Cognition Center, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- Linda Crnic Institute for Down Syndrome, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- University of Colorado Program for Human Medical Genetics and Genomics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Emily Sullivan
- Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Olga Prikhodko
- Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Md. Mahiuddin Ahmed
- Department of Neurology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- University of Colorado Alzheimer’s and Cognition Center, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- Linda Crnic Institute for Down Syndrome, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - David A. Bennett
- Rush Alzheimer’s Disease Center, Rush University Medical Center, Chicago, IL, USA
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL, USA
| | - Timothy J. Hohman
- Vanderbilt Memory and Alzheimer’s Center, Vanderbilt University Medical Center, Nashville, TN, USA
- Vanderbilt Genetics Institute, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Mark L. Dell’Acqua
- University of Colorado Alzheimer’s and Cognition Center, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- Linda Crnic Institute for Down Syndrome, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Heidi J. Chial
- Department of Neurology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- University of Colorado Alzheimer’s and Cognition Center, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- Linda Crnic Institute for Down Syndrome, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Huntington Potter
- Department of Neurology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- University of Colorado Alzheimer’s and Cognition Center, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- Linda Crnic Institute for Down Syndrome, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
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Zeppillo T, Schulmann A, Macciardi F, Hjelm BE, Föcking M, Sequeira PA, Guella I, Cotter D, Bunney WE, Limon A, Vawter MP. Functional impairment of cortical AMPA receptors in schizophrenia. Schizophr Res 2022; 249:25-37. [PMID: 32513544 PMCID: PMC7718399 DOI: 10.1016/j.schres.2020.03.037] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 03/19/2020] [Accepted: 03/20/2020] [Indexed: 12/14/2022]
Abstract
Clinical and preclinical studies suggest that some of the behavioral alterations observed in schizophrenia (SZ) may be mechanistically linked to synaptic dysfunction of glutamatergic signaling. Recent genetic and proteomic studies suggest alterations of cortical glutamate receptors of the AMPA-type (AMPARs), which are the predominant ligand-gated ionic channels of fast transmission at excitatory synapses. The impact of gene and protein alterations on the electrophysiological activity of AMPARs is not known in SZ. In this proof of principle work, using human postmortem brain synaptic membranes isolated from the dorsolateral prefrontal cortex (DLPFC), we combined electrophysiological analysis from microtransplanted synaptic membranes (MSM) with transcriptomic (RNA-Seq) and label-free proteomics data in 10 control and 10 subjects diagnosed with SZ. We observed in SZ a reduction in the amplitude of AMPARs currents elicited by kainate, an agonist of AMPARs that blocks the desensitization of the receptor. This reduction was not associated with protein abundance but with a reduction in kainate's potency to activate AMPARs. Electrophysiologically-anchored dataset analysis (EDA) was used to identify synaptosomal proteins that linearly correlate with the amplitude of the AMPARs responses, gene ontology functional annotations were then used to determine protein-protein interactions. Protein modules associated with positive AMPARs current increases were downregulated in SZ, while protein modules that were upregulated in SZ were associated with decreased AMPARs currents. Our results indicate that transcriptomic and proteomic alterations, frequently observed in the DLPFC in SZ, converge at the synaptic level producing a functional electrophysiological impairment of AMPARs.
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Affiliation(s)
- Tommaso Zeppillo
- Department of Neurology, Mitchell Center for Neurodegenerative Diseases, School of Medicine, University of Texas Medical Branch at Galveston, USA; Department of Life Sciences, University of Trieste, B.R.A.I.N., Centre for Neuroscience, Trieste, Italy
| | - Anton Schulmann
- Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, VA, USA; Current address: National Institute of Mental Health, Human Genetics Branch, Bethesda, MD, USA
| | - Fabio Macciardi
- Department of Psychiatry & Human Behavior, University of California Irvine, CA 92697, USA
| | - Brooke E Hjelm
- Department of Translational Genomics, Keck School of Medicine of USC, University of Southern California (USC), Los Angeles, CA, USA
| | | | - P Adolfo Sequeira
- Department of Psychiatry & Human Behavior, University of California Irvine, CA 92697, USA
| | - Ilaria Guella
- Department of Psychiatry & Human Behavior, University of California Irvine, CA 92697, USA
| | - David Cotter
- Royal College of Surgeons in Ireland, Dublin, Ireland
| | - William E Bunney
- Department of Psychiatry & Human Behavior, University of California Irvine, CA 92697, USA
| | - Agenor Limon
- Department of Neurology, Mitchell Center for Neurodegenerative Diseases, School of Medicine, University of Texas Medical Branch at Galveston, USA.
| | - Marquis P Vawter
- Department of Psychiatry & Human Behavior, University of California Irvine, CA 92697, USA.
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7
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Rabadan MA, De La Cruz ED, Rao SB, Chen Y, Gong C, Crabtree G, Xu B, Markx S, Gogos JA, Yuste R, Tomer R. An in vitro model of neuronal ensembles. Nat Commun 2022; 13:3340. [PMID: 35680927 PMCID: PMC9184643 DOI: 10.1038/s41467-022-31073-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 06/01/2022] [Indexed: 11/28/2022] Open
Abstract
Advances in 3D neuronal cultures, such as brain spheroids and organoids, are allowing unprecedented in vitro access to some of the molecular, cellular and developmental mechanisms underlying brain diseases. However, their efficacy in recapitulating brain network properties that encode brain function remains limited, thereby precluding development of effective in vitro models of complex brain disorders like schizophrenia. Here, we develop and characterize a Modular Neuronal Network (MoNNet) approach that recapitulates specific features of neuronal ensemble dynamics, segregated local-global network activities and a hierarchical modular organization. We utilized MoNNets for quantitative in vitro modelling of schizophrenia-related network dysfunctions caused by highly penetrant mutations in SETD1A and 22q11.2 risk loci. Furthermore, we demonstrate its utility for drug discovery by performing pharmacological rescue of alterations in neuronal ensembles stability and global network synchrony. MoNNets allow in vitro modelling of brain diseases for investigating the underlying neuronal network mechanisms and systematic drug discovery.
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Affiliation(s)
- M Angeles Rabadan
- Department of Biological Sciences, Columbia University, New York, NY, USA
| | | | - Sneha B Rao
- Mortimer B. Zuckerman Mind Brain and Behavior Institute, Columbia University, New York, NY, USA
| | - Yannan Chen
- Department of Biological Sciences, Columbia University, New York, NY, USA
- Department of Biomedical Engineering, Columbia University, New York, NY, USA
| | - Cheng Gong
- Department of Biological Sciences, Columbia University, New York, NY, USA
- Department of Biomedical Engineering, Columbia University, New York, NY, USA
| | - Gregg Crabtree
- Mortimer B. Zuckerman Mind Brain and Behavior Institute, Columbia University, New York, NY, USA
| | - Bin Xu
- Department of Psychiatry, Vagelos College of Physicians & Surgeons, Columbia University, New York, NY, USA
| | - Sander Markx
- Department of Psychiatry, Vagelos College of Physicians & Surgeons, Columbia University, New York, NY, USA
| | - Joseph A Gogos
- Mortimer B. Zuckerman Mind Brain and Behavior Institute, Columbia University, New York, NY, USA
- Department of Physiology, Columbia University, New York, NY, USA
- Department of Neuroscience, Columbia University, New York, NY, USA
- Department of Psychiatry, Columbia University, New York, NY, USA
| | - Rafael Yuste
- Department of Biological Sciences, Columbia University, New York, NY, USA
- NeuroTechnology Center, Columbia University, New York, NY, USA
| | - Raju Tomer
- Department of Biological Sciences, Columbia University, New York, NY, USA.
- Mortimer B. Zuckerman Mind Brain and Behavior Institute, Columbia University, New York, NY, USA.
- Department of Biomedical Engineering, Columbia University, New York, NY, USA.
- NeuroTechnology Center, Columbia University, New York, NY, USA.
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8
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Wu C, Zhao L, Li X, Xu Y, Guo H, Huang Z, Wang Q, Liu H, Chen D, Zhu M. Integrated Bioinformatics Analysis of Potential mRNA and miRNA Regulatory Networks in Mice With Ischemic Stroke Treated by Electroacupuncture. Front Neurol 2021; 12:719354. [PMID: 34566862 PMCID: PMC8461332 DOI: 10.3389/fneur.2021.719354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Accepted: 07/22/2021] [Indexed: 12/02/2022] Open
Abstract
Background: The complicated molecular mechanisms underlying the therapeutic effect of electroacupuncture (EA) on ischemic stroke are still unclear. Recently, more evidence has revealed the essential role of the microRNA (miRNA)–mRNA networks in ischemic stroke. However, a systematic analysis of novel key genes, miRNAs, and miRNA–mRNA networks regulated by EA in ischemic stroke is still absent. Methods: We established a middle cerebral artery occlusion (MCAO) mouse model and performed EA therapy on ischemic stroke mice. Behavior tests and measurement of infarction area were applied to measure the effect of EA treatment. Then, we performed RNA sequencing to analyze differentially expressed genes (DEGs) and functional enrichment between the EA and control groups. In addition, a protein–protein interaction (PPI) network was built, and hub genes were screened by Cytoscape. Upstream miRNAs were predicted by miRTarBase. Then hub genes and predicted miRNAs were verified as key biomarkers by RT-qPCR. Finally, miRNA–mRNA networks were constructed to explore the potential mechanisms of EA in ischemic stroke. Results: Our analysis revealed that EA treatment could significantly alleviate neurological deficits in the affected limbs and reduce infarct area of the MCAO model mice. A total of 174 significant DEGs, including 53 upregulated genes and 121 downregulated genes, were identified between the EA and control groups. Functional enrichment analysis showed that these DEGs were associated with the FOXO signaling pathway, NF-kappa B signaling pathway, T-cell receptor signaling pathway, and other vital pathways. The top 10 genes with the highest degree scores were identified as hub genes based on the degree method, but only seven genes were verified as key genes according to RT-qPCR. Twelve upstream miRNAs were predicted to target the seven key genes. However, only four miRNAs were significantly upregulated and indicated favorable effects of EA treatment. Finally, comprehensive analysis of the results identified the miR-425-5p-Cdk1, mmu-miR-1186b-Prc1, mmu-miR-434-3p-Prc1, and mmu-miR-453-Prc1 miRNA–mRNA networks as key networks that are regulated by EA and linked to ischemic stroke. These networks might mainly take place in neuronal cells regulated by EA in ischemic stroke. Conclusion: In summary, our study identified key DEGs, miRNAs, and miRNA–mRNA regulatory networks that may help to facilitate the understanding of the molecular mechanism underlying the effect of EA treatment on ischemic stroke.
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Affiliation(s)
- Chunxiao Wu
- Shenzhen Hospital of Integrated Traditional Chinese and Western Medicine, Guangzhou University of Chinese Medicine, Guangdong, China.,The Research Center of Basic Integrative Medicine, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Lijun Zhao
- Shenzhen Hospital of Integrated Traditional Chinese and Western Medicine, Guangzhou University of Chinese Medicine, Guangdong, China
| | - Xinrong Li
- Shenzhen Hospital of Integrated Traditional Chinese and Western Medicine, Guangzhou University of Chinese Medicine, Guangdong, China
| | - Yingshan Xu
- Clinical Medical of Acupuncture, Moxibustion and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Hongji Guo
- Clinical Medical of Acupuncture, Moxibustion and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Zifeng Huang
- Shenzhen Hospital of Integrated Traditional Chinese and Western Medicine, Guangzhou University of Chinese Medicine, Guangdong, China
| | - Qizhang Wang
- Shenzhen Hospital of Integrated Traditional Chinese and Western Medicine, Guangzhou University of Chinese Medicine, Guangdong, China
| | - Helu Liu
- Shenzhen Hospital of Integrated Traditional Chinese and Western Medicine, Guangzhou University of Chinese Medicine, Guangdong, China
| | - Dongfeng Chen
- The Research Center of Basic Integrative Medicine, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Meiling Zhu
- Shenzhen Hospital of Integrated Traditional Chinese and Western Medicine, Guangzhou University of Chinese Medicine, Guangdong, China
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9
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Mini-review: Microtubule sliding in neurons. Neurosci Lett 2021; 753:135867. [PMID: 33812935 DOI: 10.1016/j.neulet.2021.135867] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 03/22/2021] [Accepted: 03/23/2021] [Indexed: 12/28/2022]
Abstract
Microtubule sliding is an underappreciated mechanism that contributes to the establishment, organization, preservation, and plasticity of neuronal microtubule arrays. Powered by molecular motor proteins and regulated in part by static crosslinker proteins, microtubule sliding is the movement of microtubules relative to other microtubules or to non-microtubule structures such as the actin cytoskeleton. In addition to other important functions, microtubule sliding significantly contributes to the establishment and maintenance of microtubule polarity patterns in different regions of the neuron. The purpose of this article is to review the state of knowledge on microtubule sliding in the neuron, with emphasis on its mechanistic underpinnings as well as its functional significance.
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10
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Joseph NF, Swarnkar S, Puthanveettil SV. Double Duty: Mitotic Kinesins and Their Post-Mitotic Functions in Neurons. Cells 2021; 10:cells10010136. [PMID: 33445569 PMCID: PMC7827351 DOI: 10.3390/cells10010136] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Revised: 01/06/2021] [Accepted: 01/06/2021] [Indexed: 01/23/2023] Open
Abstract
Neurons, regarded as post-mitotic cells, are characterized by their extensive dendritic and axonal arborization. This unique architecture imposes challenges to how to supply materials required at distal neuronal components. Kinesins are molecular motor proteins that mediate the active delivery of cellular materials along the microtubule cytoskeleton for facilitating the local biochemical and structural changes at the synapse. Recent studies have made intriguing observations that some kinesins that function during neuronal mitosis also have a critical role in post-mitotic neurons. However, we know very little about the function and regulation of such kinesins. Here, we summarize the known cellular and biochemical functions of mitotic kinesins in post-mitotic neurons.
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Affiliation(s)
- Nadine F. Joseph
- The Skaggs Graduate School of Chemical and Biological Sciences, Scripps Research Institute, La Jolla, CA 92037, USA;
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA;
| | - Supriya Swarnkar
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA;
| | - Sathyanarayanan V Puthanveettil
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA;
- Correspondence: ; Tel.: +1-561-228-3504; Fax: +1-568-228-2249
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11
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Mégret L, Nair SS, Dancourt J, Aaronson J, Rosinski J, Neri C. Combining feature selection and shape analysis uncovers precise rules for miRNA regulation in Huntington's disease mice. BMC Bioinformatics 2020; 21:75. [PMID: 32093602 PMCID: PMC7041117 DOI: 10.1186/s12859-020-3418-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 02/17/2020] [Indexed: 12/12/2022] Open
Abstract
Background MicroRNA (miRNA) regulation is associated with several diseases, including neurodegenerative diseases. Several approaches can be used for modeling miRNA regulation. However, their precision may be limited for analyzing multidimensional data. Here, we addressed this question by integrating shape analysis and feature selection into miRAMINT, a methodology that we used for analyzing multidimensional RNA-seq and proteomic data from a knock-in mouse model (Hdh mice) of Huntington’s disease (HD), a disease caused by CAG repeat expansion in huntingtin (htt). This dataset covers 6 CAG repeat alleles and 3 age points in the striatum and cortex of Hdh mice. Results Remarkably, compared to previous analyzes of this multidimensional dataset, the miRAMINT approach retained only 31 explanatory striatal miRNA-mRNA pairs that are precisely associated with the shape of CAG repeat dependence over time, among which 5 pairs with a strong change of target expression levels. Several of these pairs were previously associated with neuronal homeostasis or HD pathogenesis, or both. Such miRNA-mRNA pairs were not detected in cortex. Conclusions These data suggest that miRNA regulation has a limited global role in HD while providing accurately-selected miRNA-target pairs to study how the brain may compute molecular responses to HD over time. These data also provide a methodological framework for researchers to explore how shape analysis can enhance multidimensional data analytics in biology and disease.
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Affiliation(s)
- Lucile Mégret
- Sorbonne Université, CNRS UMR8256, INSERM ERL U1164, Brain-C Lab, Paris, France.
| | | | - Julia Dancourt
- Sorbonne Université, CNRS UMR8256, INSERM ERL U1164, Brain-C Lab, Paris, France
| | | | | | - Christian Neri
- Sorbonne Université, CNRS UMR8256, INSERM ERL U1164, Brain-C Lab, Paris, France.
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12
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Del Castillo U, Norkett R, Gelfand VI. Unconventional Roles of Cytoskeletal Mitotic Machinery in Neurodevelopment. Trends Cell Biol 2019; 29:901-911. [PMID: 31597609 DOI: 10.1016/j.tcb.2019.08.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 08/22/2019] [Accepted: 08/23/2019] [Indexed: 12/20/2022]
Abstract
At first look, cell division and neurite formation seem to be two different, essential biological processes. However, both processes require extensive reorganization of the cytoskeleton, and especially microtubules. Remarkably, in recent years, independent work from several groups has shown that multiple cytoskeletal components previously considered specific for the mitotic machinery play important roles in neurite initiation and extension. In this review article, we describe how several cytoplasmic and mitotic microtubule motors, components of mitotic kinetochores, and cortical actin participate in reorganization of the microtubule network required to form and maintain axons and dendrites. The emerging similarities between these two biological processes will certainly generate new insights into the mechanisms generating the unique morphology of neurons.
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Affiliation(s)
- Urko Del Castillo
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Chicago, IL 60611, USA
| | - Rosalind Norkett
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Chicago, IL 60611, USA
| | - Vladimir I Gelfand
- Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Chicago, IL 60611, USA.
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13
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Kelliher MT, Saunders HA, Wildonger J. Microtubule control of functional architecture in neurons. Curr Opin Neurobiol 2019; 57:39-45. [PMID: 30738328 DOI: 10.1016/j.conb.2019.01.003] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 01/04/2019] [Accepted: 01/07/2019] [Indexed: 01/20/2023]
Abstract
Neurons are exquisitely polarized cells whose structure and function relies on microtubules. Microtubules in signal-receiving dendrites and signal-sending axons differ in their organization and microtubule-associated proteins. These differences, coupled with microtubule post-translational modifications, combine to locally regulate intracellular transport, morphology, and function. Recent discoveries provide new insight into the regulation of non-centrosomal microtubule arrays in neurons, the relationship between microtubule acetylation and mechanosensation, and the spatial patterning of microtubules that regulates motor activity and cargo delivery in axons and dendrites. Together, these new studies bring us closer to understanding how microtubule function is locally tuned to match the specialized tasks associated with signal reception and transmission.
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Affiliation(s)
- Michael T Kelliher
- Integrated Program in Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA; Biochemistry Department, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Harriet Aj Saunders
- Integrated Program in Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA; Biochemistry Department, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Jill Wildonger
- Biochemistry Department, University of Wisconsin-Madison, Madison, WI 53706, USA.
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14
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Kinesin Family of Proteins Kif11 and Kif21B Act as Inhibitory Constraints of Excitatory Synaptic Transmission Through Distinct Mechanisms. Sci Rep 2018; 8:17419. [PMID: 30479371 PMCID: PMC6258692 DOI: 10.1038/s41598-018-35634-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 11/09/2018] [Indexed: 02/03/2023] Open
Abstract
Despite our understanding of the functions of the kinesin family of motor proteins (Kifs) in neurons, their specific roles in neuronal communication are less understood. To address this, by carrying out RNAi-mediated loss of function studies, we assessed the necessity of 18 Kifs in excitatory synaptic transmission in mouse primary hippocampal neurons prepared from both sexes. Our measurements of excitatory post-synaptic currents (EPSCs) have identified 7 Kifs that were found to be not critical and 11 Kifs that are essential for synaptic transmission by impacting either frequency or amplitude or both components of EPSCs. Intriguingly we found that knockdown of mitotic Kif4A and Kif11 and post-mitotic Kif21B resulted in an increase in EPSCs suggesting that they function as inhibitory constraints on synaptic transmission. Furthermore, Kifs (11, 21B, 13B) with distinct effects on synaptic transmission are expressed in the same hippocampal neuron. Mechanistically, unlike Kif21B, Kif11 requires the activity of pre-synaptic NMDARs. In addition, we find that Kif11 knockdown enhanced dendritic arborization, synapse number, expression of synaptic vesicle proteins synaptophysin and active zone protein Piccolo. Moreover, expression of Piccolo constrained Kif11 function in synaptic transmission. Together these results suggest that neurons are able to utilize specific Kifs as tools for calibrating synaptic function. These studies bring novel insights into the biology of Kifs and functioning of neural circuits.
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15
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NEK7 regulates dendrite morphogenesis in neurons via Eg5-dependent microtubule stabilization. Nat Commun 2018; 9:2330. [PMID: 29899413 PMCID: PMC5997995 DOI: 10.1038/s41467-018-04706-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Accepted: 05/15/2018] [Indexed: 01/22/2023] Open
Abstract
Organization of microtubules into ordered arrays is best understood in mitotic systems, but remains poorly characterized in postmitotic cells such as neurons. By analyzing the cycling cell microtubule cytoskeleton proteome through expression profiling and targeted RNAi screening for candidates with roles in neurons, we have identified the mitotic kinase NEK7. We show that NEK7 regulates dendrite morphogenesis in vitro and in vivo. NEK7 kinase activity is required for dendrite growth and branching, as well as spine formation and morphology. NEK7 regulates these processes in part through phosphorylation of the kinesin Eg5/KIF11, promoting its accumulation on microtubules in distal dendrites. Here, Eg5 limits retrograde microtubule polymerization, which is inhibitory to dendrite growth and branching. Eg5 exerts this effect through microtubule stabilization, independent of its motor activity. This work establishes NEK7 as a general regulator of the microtubule cytoskeleton, controlling essential processes in both mitotic cells and postmitotic neurons. NEK7 is a kinase known for its role in mitotic spindle assembly, driving centrosome separation in prophase through regulation of the kinesin Eg5. Here, the authors show that NEK7 and Eg5 also control dendrite morphogenesis in postmitotic neurons.
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16
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Eibes S, Gallisà-Suñé N, Rosas-Salvans M, Martínez-Delgado P, Vernos I, Roig J. Nek9 Phosphorylation Defines a New Role for TPX2 in Eg5-Dependent Centrosome Separation before Nuclear Envelope Breakdown. Curr Biol 2017; 28:121-129.e4. [PMID: 29276125 DOI: 10.1016/j.cub.2017.11.046] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2017] [Revised: 10/31/2017] [Accepted: 11/21/2017] [Indexed: 11/18/2022]
Abstract
Centrosomes [1, 2] play a central role during spindle assembly in most animal cells [3]. In early mitosis, they organize two symmetrical microtubule arrays that upon separation define the two poles of the forming spindle. Centrosome separation is tightly regulated [4, 5], occurring through partially redundant mechanisms that rely on the action of microtubule-based dynein and kinesin motors and the actomyosin system [6]. While centrosomes can separate in prophase or in prometaphase after nuclear envelope breakdown (NEBD), prophase centrosome separation optimizes spindle assembly and minimizes the occurrence of abnormal chromosome attachments that could end in aneuploidy [7, 8]. Prophase centrosome separation relies on the activity of Eg5/KIF11, a mitotic kinesin [9] that accumulates around centrosomes in early mitosis under the control of CDK1 and the Nek9/Nek6/7 kinase module [10-17]. Here, we show that Eg5 localization and centrosome separation in prophase depend on the nuclear microtubule-associated protein TPX2 [18], a pool of which localizes to the centrosomes before NEBD. This localization involves RHAMM/HMMR [19] and the kinase Nek9 [20], which phosphorylates TPX2 nuclear localization signal (NLS) preventing its interaction with importin and nuclear import. The pool of centrosomal TPX2 in prophase has a critical role for both microtubule aster organization and Eg5 localization, and thereby for centrosome separation. Our results uncover an unsuspected role for TPX2 before NEBD and define a novel regulatory mechanism for centrosome separation in prophase. They furthermore suggest NLS phosphorylation as a novel regulatory mechanism for spindle assembly factors controlled by the importin/Ran system.
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Affiliation(s)
- Susana Eibes
- Molecular Biology Institute of Barcelona (IBMB-CSIC) and Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona 08028, Spain
| | - Núria Gallisà-Suñé
- Molecular Biology Institute of Barcelona (IBMB-CSIC) and Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona 08028, Spain
| | - Miquel Rosas-Salvans
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona 08003, Spain; Universitat Pompeu Fabra (UPF), Barcelona 08003, Spain
| | - Paula Martínez-Delgado
- Molecular Biology Institute of Barcelona (IBMB-CSIC) and Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona 08028, Spain
| | - Isabelle Vernos
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona 08003, Spain; Universitat Pompeu Fabra (UPF), Barcelona 08003, Spain; Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona 08010, Spain
| | - Joan Roig
- Molecular Biology Institute of Barcelona (IBMB-CSIC) and Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona 08028, Spain.
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17
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Ran-dependent TPX2 activation promotes acentrosomal microtubule nucleation in neurons. Sci Rep 2017; 7:42297. [PMID: 28205572 PMCID: PMC5304320 DOI: 10.1038/srep42297] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 01/05/2017] [Indexed: 01/07/2023] Open
Abstract
The microtubule (MT) cytoskeleton is essential for the formation of morphologically appropriate neurons. The existence of the acentrosomal MT organizing center in neurons has been proposed but its identity remained elusive. Here we provide evidence showing that TPX2 is an important component of this acentrosomal MT organizing center. First, neurite elongation is compromised in TPX2-depleted neurons. In addition, TPX2 localizes to the centrosome and along the neurite shaft bound to MTs. Depleting TPX2 decreases MT formation frequency specifically at the tip and the base of the neurite, and these correlate precisely with the regions where active GTP-bound Ran proteins are enriched. Furthermore, overexpressing the downstream effector of Ran, importin, compromises MT formation and neuronal morphogenesis. Finally, applying a Ran-importin signaling interfering compound phenocopies the effect of TPX2 depletion on MT dynamics. Together, these data suggest a model in which Ran-dependent TPX2 activation promotes acentrosomal MT nucleation in neurons.
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18
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Kahn OI, Baas PW. Microtubules and Growth Cones: Motors Drive the Turn. Trends Neurosci 2016; 39:433-440. [PMID: 27233682 DOI: 10.1016/j.tins.2016.04.009] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 04/19/2016] [Accepted: 04/21/2016] [Indexed: 01/09/2023]
Abstract
Navigation of the growth cone at the tip of the developing axon is crucial for the proper wiring of the nervous system. Mechanisms of actin-dependent growth cone steering, via signaling cascades, are well documented. Microtubules are also important in growth cone guidance, because their polarized invasion into the peripheral domain on one side of the growth cone is essential for it to turn in that direction. Classically, microtubules have been considered secondary players, invading the peripheral domain only where the actin cytoskeleton permits them to go. Presented here is evidence for an underappreciated mechanism by which signaling cascades can potentially affect growth cone turning, namely through regulatable forces imposed on the microtubules by molecular motor proteins.
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Affiliation(s)
- Olga I Kahn
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA
| | - Peter W Baas
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA.
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19
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Rao AN, Falnikar A, O'Toole ET, Morphew MK, Hoenger A, Davidson MW, Yuan X, Baas PW. Sliding of centrosome-unattached microtubules defines key features of neuronal phenotype. J Cell Biol 2016; 213:329-41. [PMID: 27138250 PMCID: PMC4862329 DOI: 10.1083/jcb.201506140] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 03/28/2016] [Indexed: 12/25/2022] Open
Abstract
Rao et al. show that during migration, neurons contain a small population of centrosome-unattached microtubules in the leading process that are capable of sliding. Increasing the proportion of centrosome-unattached microtubules alters neuronal morphology, migration path, and microtubule behavior in the leading process. Contemporary models for neuronal migration are grounded in the view that virtually all functionally relevant microtubules (MTs) in migrating neurons are attached to the centrosome, which occupies a position between the nucleus and a short leading process. It is assumed that MTs do not undergo independent movements but rather transduce forces that enable movements of the centrosome and nucleus. The present results demonstrate that although this is mostly true, a small fraction of the MTs are centrosome-unattached, and this permits limited sliding of MTs. When this sliding is pharmacologically inhibited, the leading process becomes shorter, migration of the neuron deviates from its normal path, and the MTs within the leading process become buckled. Partial depletion of ninein, a protein that attaches MTs to the centrosome, leads to greater numbers of centrosome-unattached MTs as well as greater sliding of MTs. Concomitantly, the soma becomes less mobile and the leading process acquires an elongated morphology akin to an axon.
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Affiliation(s)
- Anand N Rao
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129
| | - Aditi Falnikar
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129
| | - Eileen T O'Toole
- Boulder Laboratory for 3D Electron Microscopy of Cells, University of Colorado, Boulder, CO 80309
| | - Mary K Morphew
- Boulder Laboratory for 3D Electron Microscopy of Cells, University of Colorado, Boulder, CO 80309
| | - Andreas Hoenger
- Boulder Laboratory for 3D Electron Microscopy of Cells, University of Colorado, Boulder, CO 80309
| | - Michael W Davidson
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310 Department of Biological Science, Florida State University, Tallahassee, FL 32310
| | - Xiaobing Yuan
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129
| | - Peter W Baas
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129
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