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Zaninello M, Bean C. Highly Specialized Mechanisms for Mitochondrial Transport in Neurons: From Intracellular Mobility to Intercellular Transfer of Mitochondria. Biomolecules 2023; 13:938. [PMID: 37371518 DOI: 10.3390/biom13060938] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 05/26/2023] [Accepted: 06/01/2023] [Indexed: 06/29/2023] Open
Abstract
The highly specialized structure and function of neurons depend on a sophisticated organization of the cytoskeleton, which supports a similarly sophisticated system to traffic organelles and cargo vesicles. Mitochondria sustain crucial functions by providing energy and buffering calcium where it is needed. Accordingly, the distribution of mitochondria is not even in neurons and is regulated by a dynamic balance between active transport and stable docking events. This system is finely tuned to respond to changes in environmental conditions and neuronal activity. In this review, we summarize the mechanisms by which mitochondria are selectively transported in different compartments, taking into account the structure of the cytoskeleton, the molecular motors and the metabolism of neurons. Remarkably, the motor proteins driving the mitochondrial transport in axons have been shown to also mediate their transfer between cells. This so-named intercellular transport of mitochondria is opening new exciting perspectives in the treatment of multiple diseases.
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Affiliation(s)
- Marta Zaninello
- Institute for Genetics, University of Cologne, 50931 Cologne, Germany
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), 50931 Cologne, Germany
| | - Camilla Bean
- Department of Medicine, University of Udine, 33100 Udine, Italy
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2
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Saxton WM, Lim A, Djagaeva I. Dissection and Direct Imaging of Axonal Transport in Drosophila Segmental Nerves. Methods Mol Biol 2022; 2431:367-384. [PMID: 35412287 DOI: 10.1007/978-1-0716-1990-2_19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
For neurons, especially those with long axons, the forceful transport of mitochondria, vesicles, and other cytoplasmic components by cytoskeletal motors is vital. Defects in cytoplasmic transport machinery cause a degradation of signaling capacity that is most severe for neurons with the longest axons. In humans, with motor axons up to a meter long, even a mild mutation in one copy of the gene that codes for kinesin-1, the primary anterograde axonal transport motor, can cause spastic paraplegia and other distal neuropathies.To address questions about the molecular mechanisms of organelle movement, we turned to Drosophila as a model system, because it offered rigorous genetic and molecular approaches to the identification and inhibition of specific elements of transport machinery. However, methods for direct observation of organelle transport were largely lacking. We describe here an approach that we developed for imaging the transport behaviors of specific organelles in the long motor axons of larvae. It is straightforward, the equipment is commonly available, and it provides a powerful tool for studying the contributions of specific proteins to organelle transport mechanisms.
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Affiliation(s)
- William M Saxton
- Department of Molecular, Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA, USA.
| | - Angeline Lim
- Department of Molecular, Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Inna Djagaeva
- Department of Molecular, Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA, USA
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3
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Assessment of Mitochondrial Trafficking as a Surrogate for Fast Axonal Transport in Human Induced Pluripotent Stem Cell-Derived Spinal Motor Neurons. Methods Mol Biol 2022; 2431:311-322. [PMID: 35412284 DOI: 10.1007/978-1-0716-1990-2_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Axonal transport is essential for the development, function, and survival of the nervous system. In an energy-demanding process, motor proteins act in concert with microtubules to deliver cargoes, such as organelles, from one end of the axon to the other. Perturbations in axonal transport are a prominent phenotype of many neurodegenerative diseases, including amyotrophic lateral sclerosis. Here, we describe a simple method to fluorescently label mitochondrial cargo, a surrogate for fast axonal transport, in human induced pluripotent stem cell-derived motor neurons. This method enables the sparse labeling of axons to track directionality of movement and can be adapted to assess not only the cell autonomous effects of a genetic mutation on axonal transport but also the cell non-autonomous effects, through the use of conditioned medium and/or co-culture systems.
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4
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Bodakuntla S, Yuan X, Genova M, Gadadhar S, Leboucher S, Birling MC, Klein D, Martini R, Janke C, Magiera MM. Distinct roles of α- and β-tubulin polyglutamylation in controlling axonal transport and in neurodegeneration. EMBO J 2021; 40:e108498. [PMID: 34309047 DOI: 10.15252/embj.2021108498] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 06/25/2021] [Accepted: 06/29/2021] [Indexed: 12/19/2022] Open
Abstract
Tubulin polyglutamylation is a post-translational modification of the microtubule cytoskeleton, which is generated by a variety of enzymes with different specificities. The "tubulin code" hypothesis predicts that modifications generated by specific enzymes selectively control microtubule functions. Our recent finding that excessive accumulation of polyglutamylation in neurons causes their degeneration and perturbs axonal transport provides an opportunity for testing this hypothesis. By developing novel mouse models and a new glutamylation-specific antibody, we demonstrate here that the glutamylases TTLL1 and TTLL7 generate unique and distinct glutamylation patterns on neuronal microtubules. We find that under physiological conditions, TTLL1 polyglutamylates α-tubulin, while TTLL7 modifies β-tubulin. TTLL1, but not TTLL7, catalyses the excessive hyperglutamylation found in mice lacking the deglutamylase CCP1. Consequently, deletion of TTLL1, but not of TTLL7, prevents degeneration of Purkinje cells and of myelinated axons in peripheral nerves in these mice. Moreover, loss of TTLL1 leads to increased mitochondria motility in neurons, while loss of TTLL7 has no such effect. By revealing how specific patterns of tubulin glutamylation, generated by distinct enzymes, translate into specific physiological and pathological readouts, we demonstrate the relevance of the tubulin code for homeostasis.
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Affiliation(s)
- Satish Bodakuntla
- Institut Curie, Université PSL, CNRS UMR3348, Orsay, France.,Université Paris-Saclay, CNRS UMR3348, Orsay, France
| | - Xidi Yuan
- Department of Neurology, Developmental Neurobiology, University Hospital Würzburg, Würzburg, Germany
| | - Mariya Genova
- Institut Curie, Université PSL, CNRS UMR3348, Orsay, France.,Université Paris-Saclay, CNRS UMR3348, Orsay, France
| | - Sudarshan Gadadhar
- Institut Curie, Université PSL, CNRS UMR3348, Orsay, France.,Université Paris-Saclay, CNRS UMR3348, Orsay, France
| | - Sophie Leboucher
- Institut Curie, Université PSL, CNRS UMR3348, Orsay, France.,Université Paris-Saclay, CNRS UMR3348, Orsay, France
| | - Marie-Christine Birling
- CELPHEDIA, PHENOMIN, Institut Clinique de la Souris (ICS), CNRS, INSERM, University of Strasbourg, Illkirch, France
| | - Dennis Klein
- Department of Neurology, Developmental Neurobiology, University Hospital Würzburg, Würzburg, Germany
| | - Rudolf Martini
- Department of Neurology, Developmental Neurobiology, University Hospital Würzburg, Würzburg, Germany
| | - Carsten Janke
- Institut Curie, Université PSL, CNRS UMR3348, Orsay, France.,Université Paris-Saclay, CNRS UMR3348, Orsay, France
| | - Maria M Magiera
- Institut Curie, Université PSL, CNRS UMR3348, Orsay, France.,Université Paris-Saclay, CNRS UMR3348, Orsay, France
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Waites C, Qu X, Bartolini F. The synaptic life of microtubules. Curr Opin Neurobiol 2021; 69:113-123. [PMID: 33873059 DOI: 10.1016/j.conb.2021.03.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2021] [Revised: 03/03/2021] [Accepted: 03/08/2021] [Indexed: 12/21/2022]
Abstract
In neurons, control of microtubule dynamics is required for multiple homeostatic and regulated activities. Over the past few decades, a great deal has been learned about the role of the microtubule cytoskeleton in axonal and dendritic transport, with a broad impact on neuronal health and disease. However, significantly less attention has been paid to the importance of microtubule dynamics in directly regulating synaptic function. Here, we review emerging literature demonstrating that microtubules enter synapses and control central aspects of synaptic activity, including neurotransmitter release and synaptic plasticity. The pleiotropic effects caused by a dysfunctional synaptic microtubule cytoskeleton may thus represent a key point of vulnerability for neurons and a primary driver of neurological disease.
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Affiliation(s)
- Clarissa Waites
- Department of Neuroscience, Columbia University, 3227 Broadway, New York, NY 10027, USA
| | - Xiaoyi Qu
- Department of Pathology & Cell Biology, Columbia University Medical Center, 630 W. 168th Street, New York, NY 10032, USA
| | - Francesca Bartolini
- Department of Pathology & Cell Biology, Columbia University Medical Center, 630 W. 168th Street, New York, NY 10032, USA.
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Li J, Snyder EY, Tang FHF, Pasqualini R, Arap W, Sidman RL. Nna1 gene deficiency triggers Purkinje neuron death by tubulin hyperglutamylation and ER dysfunction. JCI Insight 2020; 5:136078. [PMID: 33004692 PMCID: PMC7566705 DOI: 10.1172/jci.insight.136078] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 08/26/2020] [Indexed: 02/06/2023] Open
Abstract
Posttranslational glutamylation/deglutamylation balance in tubulins influences dendritic maturation and neuronal survival of cerebellar Purkinje neurons (PNs). PNs and some additional neuronal types degenerate in several spontaneous, independently occurring Purkinje cell degeneration (pcd) mice featuring mutant neuronal nuclear protein induced by axotomy (Nna1), a deglutamylase gene. This defective deglutamylase allows glutamylases to form hyperglutamylated tubulins. In pcd, all PNs die during postnatal “adolescence.” Neurons in some additional brain regions also die, mostly later than PNs. We show in laser capture microdissected single PNs, in cerebellar granule cell neuronal clusters, and in dissected hippocampus and substantia nigra that deglutamase mRNA and protein were virtually absent before pcd PNs degenerated, whereas glutaminase mRNA and protein remained normal. Hyperglutamylated microtubules and dimeric tubulins accumulated in pcd PNs and were involved in pcd PN death by glutamylase/deglutamylase imbalance. Importantly, treatment with a microtubule depolymerizer corrected the glutamylation/deglutamylation ratio, increasing PN survival. Further, before onset of neuronal death, pcd PNs displayed prominent basal polylisosomal masses rich in ER. We propose a “seesaw” metamorphic model summarizing mutant Nna1-induced tubulin hyperglutamylation, the pcd’s PN phenotype, and report that the neuronal disorder involved ER stress, unfolded protein response, and protein synthesis inhibition preceding PN death by apoptosis/necroptosis. Purkinje cell degeneration is due to ER stress, unfolded protein response, and protein synthesis inhibition preceding Purkinje neuron death by apoptosis/necroptosis.
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Affiliation(s)
- Jianxue Li
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Evan Y Snyder
- Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Fenny HF Tang
- Rutgers Cancer Institute of New Jersey and Division of Cancer Biology, Department of Radiation Oncology, Rutgers New Jersey Medical School, Newark, New Jersey, USA
| | - Renata Pasqualini
- Rutgers Cancer Institute of New Jersey and Division of Cancer Biology, Department of Radiation Oncology, Rutgers New Jersey Medical School, Newark, New Jersey, USA
| | - Wadih Arap
- Rutgers Cancer Institute of New Jersey and Division of Hematology/Oncology, Department of Medicine, Rutgers New Jersey Medical School, Newark, New Jersey, USA
| | - Richard L Sidman
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
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7
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Rajaee A, Geisen ME, Sellers AK, Stirling DP. Repeat intravital imaging of the murine spinal cord reveals degenerative and reparative responses of spinal axons in real-time following a contusive SCI. Exp Neurol 2020; 327:113258. [PMID: 32105708 DOI: 10.1016/j.expneurol.2020.113258] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 02/06/2020] [Accepted: 02/22/2020] [Indexed: 12/18/2022]
Abstract
Spinal cord injury (SCI) induces a secondary degenerative response that causes the loss of spared axons and worsens neurological outcome. The complex molecular mechanisms that mediate secondary axonal degeneration remain poorly understood. To further our understanding of secondary axonal degeneration following SCI, we assessed the spatiotemporal dynamics of axonal spheroid and terminal bulb formation following a contusive SCI in real-time in vivo. Adult 6-8 week old Thy1YFP transgenic mice underwent a T12 laminectomy for acute imaging sessions or were implanted with a custom spinal cord imaging chamber for chronic imaging of the spinal cord. Two-photon excitation time-lapse microscopy was performed prior to a mild contusion SCI (30 kilodyne, IH Impactor) and at 1-4 h and 1-14 days post-SCI. We quantified the number of axonal spheroids, their size and distribution, the number of endbulbs, and axonal survival from 1 h to 14 days post-SCI. Our data reveal that the majority of axons underwent swelling and axonal spheroid formation acutely after SCI resulting in the loss of ~70% of axons by 1 day after injury. In agreement, the number of axonal spheroids rapidly increased at 1 h after SCI and remained significantly elevated up to 14 days after SCI. Furthermore, the distribution of axonal spheroids spread mediolaterally over time indicative of delayed secondary degenerative processes. In contrast, axonal endbulbs were relatively sparse and their numbers peaked at 1 day after injury. Intriguingly, axonal survival significantly increased at 7 and 14 days compared to 3 days after SCI revealing a potential endogenous axonal repair process that mirrors the known spontaneous functional recovery after SCI. In support, ~43% of tracked axonal spheroids resolved over the course of observation revealing their dynamic nature. Furthermore, axonal spheroids and endbulbs accumulated mitochondria and excessive tubulin polyglutamylation suggestive of disrupted axonal transport as a shared mechanism. Collectively, this study provides important insight into both degenerative and recoverable responses of axons following contusive SCI in real-time. Understanding how axons spontaneously recover after SCI will be an important avenue for future SCI research and may help guide future clinical trials.
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Affiliation(s)
- Arezoo Rajaee
- Kentucky Spinal Cord Injury Research Center, University of Louisville, School of Medicine, Louisville, KY 40202, USA; Department of Neurological Surgery, University of Louisville, School of Medicine, Louisville, KY 40202, USA
| | - Mariah E Geisen
- Kentucky Spinal Cord Injury Research Center, University of Louisville, School of Medicine, Louisville, KY 40202, USA; Department of Neurological Surgery, University of Louisville, School of Medicine, Louisville, KY 40202, USA
| | - Alexandra K Sellers
- Department of Bioengineering, University of Louisville, School of Medicine, Louisville, KY 40202, USA
| | - David P Stirling
- Kentucky Spinal Cord Injury Research Center, University of Louisville, School of Medicine, Louisville, KY 40202, USA; Department of Neurological Surgery, University of Louisville, School of Medicine, Louisville, KY 40202, USA; Department of Anatomical Sciences and Neurobiology, University of Louisville, School of Medicine, Louisville, KY 40202, USA; Department of Microbiology and Immunology, University of Louisville, School of Medicine, Louisville, KY 40202, USA.
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Bodakuntla S, Schnitzler A, Villablanca C, Gonzalez-Billault C, Bieche I, Janke C, Magiera MM. Tubulin polyglutamylation is a general traffic-control mechanism in hippocampal neurons. J Cell Sci 2020; 133:jcs241802. [PMID: 31932508 DOI: 10.1242/jcs.241802] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 12/23/2019] [Indexed: 08/31/2023] Open
Abstract
Neurons are highly complex cells that heavily rely on intracellular transport to distribute a range of functionally essential cargoes within the cell. Post-translational modifications of tubulin are emerging as mechanisms for regulating microtubule functions, but their impact on neuronal transport is only marginally understood. Here, we have systematically studied the impact of post-translational polyglutamylation on axonal transport. In cultured hippocampal neurons, deletion of a single deglutamylase, CCP1 (also known as AGTPBP1), is sufficient to induce abnormal accumulation of polyglutamylation, i.e. hyperglutamylation. We next investigated how hyperglutamylation affects axonal transport of a range of functionally different neuronal cargoes: mitochondria, lysosomes, LAMP1 endosomes and BDNF vesicles. Strikingly, we found a reduced motility for all these cargoes, suggesting that polyglutamylation could act as a regulator of cargo transport in neurons. This, together with the recent discovery that hyperglutamylation induces neurodegeneration, makes it likely that perturbed neuronal trafficking could be one of the central molecular causes underlying this novel type of degeneration.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Satish Bodakuntla
- Institut Curie, PSL Research University, CNRS UMR3348, F-91405 Orsay, France
- Université Paris Sud, Université Paris-Saclay, CNRS UMR3348, F-91405 Orsay, France
| | - Anne Schnitzler
- Institut Curie, PSL Research University, Department of Genetics, F-75005 Paris, France
| | - Cristopher Villablanca
- Center for Geroscience, Brain Health and Metabolism (GERO), Santiago 7800003, Chile
- Department of Biology, Faculty of Sciences, University of Chile, Santiago 7800003, Chile
| | - Christian Gonzalez-Billault
- Center for Geroscience, Brain Health and Metabolism (GERO), Santiago 7800003, Chile
- Department of Biology, Faculty of Sciences, University of Chile, Santiago 7800003, Chile
| | - Ivan Bieche
- Institut Curie, PSL Research University, Department of Genetics, F-75005 Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, F-75005 Paris, France
| | - Carsten Janke
- Institut Curie, PSL Research University, CNRS UMR3348, F-91405 Orsay, France
- Université Paris Sud, Université Paris-Saclay, CNRS UMR3348, F-91405 Orsay, France
| | - Maria M Magiera
- Institut Curie, PSL Research University, CNRS UMR3348, F-91405 Orsay, France
- Université Paris Sud, Université Paris-Saclay, CNRS UMR3348, F-91405 Orsay, France
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