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Alsina FC, Lupan BM, Lin LJ, Musso CM, Mosti F, Newman CR, Wood LM, Suzuki A, Agostino M, Moore JK, Silver DL. The RNA-binding protein EIF4A3 promotes axon development by direct control of the cytoskeleton. Cell Rep 2024; 43:114666. [PMID: 39182224 DOI: 10.1016/j.celrep.2024.114666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 02/28/2024] [Accepted: 08/06/2024] [Indexed: 08/27/2024] Open
Abstract
The exon junction complex (EJC), nucleated by EIF4A3, is indispensable for mRNA fate and function throughout eukaryotes. We discover that EIF4A3 directly controls microtubules, independent of RNA, which is critical for neural wiring. While neuronal survival in the developing mouse cerebral cortex depends upon an intact EJC, axonal tract development requires only Eif4a3. Using human cortical organoids, we show that EIF4A3 disease mutations also impair neuronal growth, highlighting conserved functions relevant for neurodevelopmental pathology. Live imaging of growing neurons shows that EIF4A3 is essential for microtubule dynamics. Employing biochemistry and competition experiments, we demonstrate that EIF4A3 directly binds to microtubules, mutually exclusive of the EJC. Finally, in vitro reconstitution assays and rescue experiments demonstrate that EIF4A3 is sufficient to promote microtubule polymerization and that EIF4A3-microtubule association is a major contributor to axon growth. This reveals a fundamental mechanism by which neurons re-utilize core gene expression machinery to directly control the cytoskeleton.
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Affiliation(s)
- Fernando C Alsina
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA.
| | - Bianca M Lupan
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Lydia J Lin
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Camila M Musso
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Federica Mosti
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Carly R Newman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Lisa M Wood
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Denver, CO, USA
| | - Aussie Suzuki
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin-Madison, Madison, WI, USA
| | - Mark Agostino
- Curtin Health Innovation Research Institute, Curtin Medical School, and Curtin Institute for Computation, Curtin University, Bentley, WA 6102, Australia
| | - Jeffrey K Moore
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Denver, CO, USA
| | - Debra L Silver
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA; Departments of Cell Biology and Neurobiology, Duke University Medical Center, Durham, NC 27710, USA; Duke Institute for Brain Sciences and Duke Regeneration Center, Duke University Medical Center, Durham, NC 27710, USA.
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2
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Montgomery AC, Mendoza CS, Garbouchian A, Quinones GB, Bentley M. Polarized transport requires AP-1-mediated recruitment of KIF13A and KIF13B at the trans-Golgi. Mol Biol Cell 2024; 35:ar61. [PMID: 38446634 PMCID: PMC11151104 DOI: 10.1091/mbc.e23-10-0401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2024] Open
Abstract
Neurons are polarized cells that require accurate membrane trafficking to maintain distinct protein complements at dendritic and axonal membranes. The Kinesin-3 family members KIF13A and KIF13B are thought to mediate dendrite-selective transport, but the mechanism by which they are recruited to polarized vesicles and the differences in the specific trafficking role of each KIF13 have not been defined. We performed live-cell imaging in cultured hippocampal neurons and found that KIF13A is a dedicated dendrite-selective kinesin. KIF13B confers two different transport modes, dendrite- and axon-selective transport. Both KIF13s are maintained at the trans-Golgi network by interactions with the heterotetrameric adaptor protein complex AP-1. Interference with KIF13 binding to AP-1 resulted in disruptions to both dendrite- and axon-selective trafficking. We propose that AP-1 is the molecular link between the sorting of polarized cargoes into vesicles and the recruitment of kinesins that confer polarized transport.
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Affiliation(s)
- Andrew C Montgomery
- Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180
| | - Christina S Mendoza
- Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180
| | - Alex Garbouchian
- Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180
| | - Geraldine B Quinones
- Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180
| | - Marvin Bentley
- Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180
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3
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Harley P, Kerins C, Gatt A, Neves G, Riccio F, Machado CB, Cheesbrough A, R'Bibo L, Burrone J, Lieberam I. Aberrant axon initial segment plasticity and intrinsic excitability of ALS hiPSC motor neurons. Cell Rep 2023; 42:113509. [PMID: 38019651 DOI: 10.1016/j.celrep.2023.113509] [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: 05/04/2023] [Revised: 10/06/2023] [Accepted: 11/13/2023] [Indexed: 12/01/2023] Open
Abstract
Dysregulated neuronal excitability is a hallmark of amyotrophic lateral sclerosis (ALS). We sought to investigate how functional changes to the axon initial segment (AIS), the site of action potential generation, could impact neuronal excitability in ALS human induced pluripotent stem cell (hiPSC) motor neurons. We find that early TDP-43 and C9orf72 hiPSC motor neurons show an increase in the length of the AIS and impaired activity-dependent AIS plasticity that is linked to abnormal homeostatic regulation of neuronal activity and intrinsic hyperexcitability. In turn, these hyperactive neurons drive increased spontaneous myofiber contractions of in vitro hiPSC motor units. In contrast, late hiPSC and postmortem ALS motor neurons show AIS shortening, and hiPSC motor neurons progress to hypoexcitability. At a molecular level, aberrant expression of the AIS master scaffolding protein ankyrin-G and AIS-specific voltage-gated sodium channels mirror these dynamic changes in AIS function and excitability. Our results point toward the AIS as an important site of dysfunction in ALS motor neurons.
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Affiliation(s)
- Peter Harley
- Centre for Gene Therapy & Regenerative Medicine, Kings College London, London SE1 9RT, UK; Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK; UCL Queen Square Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, UCL, London, UK
| | - Caoimhe Kerins
- Centre for Gene Therapy & Regenerative Medicine, Kings College London, London SE1 9RT, UK; Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK; Centre for Craniofacial & Regenerative Biology, King's College London, London SE1 9RT, UK
| | - Ariana Gatt
- Queen Square Brain Bank, Department of Neurodegenerative Disease, Institute of Neurology, University College London, London WC1N 1PJ, UK
| | - Guilherme Neves
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK
| | - Federica Riccio
- Centre for Gene Therapy & Regenerative Medicine, Kings College London, London SE1 9RT, UK; Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK
| | - Carolina Barcellos Machado
- Centre for Gene Therapy & Regenerative Medicine, Kings College London, London SE1 9RT, UK; Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK
| | - Aimee Cheesbrough
- Centre for Gene Therapy & Regenerative Medicine, Kings College London, London SE1 9RT, UK; Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK
| | - Lea R'Bibo
- Centre for Gene Therapy & Regenerative Medicine, Kings College London, London SE1 9RT, UK; Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK
| | - Juan Burrone
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK; MRC Centre for Neurodevelopmental Disorders, Kings College London, London SE1 1UL, UK.
| | - Ivo Lieberam
- Centre for Gene Therapy & Regenerative Medicine, Kings College London, London SE1 9RT, UK; Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, UK; MRC Centre for Neurodevelopmental Disorders, Kings College London, London SE1 1UL, UK.
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4
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Iwahashi M, Yoshimura T, Harigai W, Takuma K, Hashimoto H, Katayama T, Hayata-Takano A. Pituitary adenylate cyclase-activating polypeptide deficient mice show length abnormalities of the axon initial segment. J Pharmacol Sci 2023; 153:175-182. [PMID: 37770159 DOI: 10.1016/j.jphs.2023.08.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 08/08/2023] [Accepted: 08/25/2023] [Indexed: 10/03/2023] Open
Abstract
We previously found that pituitary adenylate cyclase-activating polypeptide (PACAP)-deficient (PACAP-/-) mice exhibit dendritic spine morphology impairment and neurodevelopmental disorder (NDD)-like behaviors such as hyperactivity, increased novelty-seeking behavior, and deficient pre-pulse inhibition. Recent studies have indicated that rodent models of NDDs (e.g., attention-deficit hyperactivity disorder (ADHD) and autism spectrum disorder) show abnormalities in the axon initial segment (AIS). Here, we revealed that PACAP-/- mice exhibited a longer AIS length in layer 2/3 pyramidal neurons of the primary somatosensory barrel field compared with wild-type control mice. Further, we previously showed that a single injection of atomoxetine, an ADHD drug, improved hyperactivity in PACAP-/- mice. In this study, we found that repeated treatments of atomoxetine significantly improved AIS abnormality along with hyperactivity in PACAP-/- mice. These results suggest that AIS abnormalities are associated with NDDs-like behaviors in PACAP-/- mice. Thus, improvement in AIS abnormalities will be a novel drug therapy for NDDs.
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Affiliation(s)
- Misaki Iwahashi
- Department of Child Development and Molecular Brain Science, United Graduate School of Child Development, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Takeshi Yoshimura
- Department of Child Development and Molecular Brain Science, United Graduate School of Child Development, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
| | - Wakana Harigai
- Department of Child Development and Molecular Brain Science, United Graduate School of Child Development, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Kazuhiro Takuma
- Department of Pharmacology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan; Molecular Research Center for Children's Mental Development, United Graduate School of Child Development, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Hitoshi Hashimoto
- Molecular Research Center for Children's Mental Development, United Graduate School of Child Development, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan; Laboratory of Molecular Neuropharmacology, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan; Transdimensional Life Imaging Division, Institute for Open and Transdisciplinary Research Initiatives, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan; Division of Bioscience, Institute for Datability Science, Osaka University, 2-8 Yamadaoka, Suita, Osaka, 565-0871, Japan; Department of Molecular Pharmaceutical Science, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Taiichi Katayama
- Department of Child Development and Molecular Brain Science, United Graduate School of Child Development, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Atsuko Hayata-Takano
- Department of Pharmacology, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan; Molecular Research Center for Children's Mental Development, United Graduate School of Child Development, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan; Laboratory of Molecular Neuropharmacology, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan.
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5
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Piguel NH, Yoon S, Gao R, Horan KE, Garza JC, Petryshen TL, Smith KR, Penzes P. Lithium rescues dendritic abnormalities in Ank3 deficiency models through the synergic effects of GSK3β and cyclic AMP signaling pathways. Neuropsychopharmacology 2023; 48:1000-1010. [PMID: 36376465 PMCID: PMC10209204 DOI: 10.1038/s41386-022-01502-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 10/07/2022] [Accepted: 11/01/2022] [Indexed: 11/16/2022]
Abstract
Bipolar disorder (BD) is a highly heritable mood disorder with intermittent episodes of mania and depression. Lithium is the first-in-line medication to treat BD, but it is only effective in a subset of individuals. Large-scale human genomic studies have repeatedly linked the ANK3 gene (encoding ankyrin-G, AnkG) to BD. Ank3 knockout mouse models mimic BD behavioral features and respond positively to lithium treatment. We investigated cellular phenotypes associated with BD, including dendritic arborization of pyramidal neurons and spine morphology in two models: (1) a conditional knockout mouse model which disrupts Ank3 expression in adult forebrain pyramidal neurons, and (2) an AnkG knockdown model in cortical neuron cultures. We observed a decrease in dendrite complexity and a reduction of dendritic spine number in both models, reminiscent of reports in BD. We showed that lithium treatment corrected dendrite and spine deficits in vitro and in vivo. We targeted two signaling pathways known to be affected by lithium using a highly selective GSK3β inhibitor (CHIR99021) and an adenylate cyclase activator (forskolin). In our cortical neuron culture model, CHIR99021 rescues the spine morphology defects caused by AnkG knockdown, whereas forskolin rescued the dendrite complexity deficit. Interestingly, a synergistic action of both drugs was required to rescue dendrite and spine density defects in AnkG knockdown neurons. Altogether, our results suggest that dendritic abnormalities observed in loss of function ANK3 variants and BD patients may be rescued by lithium treatment. Additionally, drugs selectively targeting GSK3β and cAMP pathways could be beneficial in BD.
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Affiliation(s)
- Nicolas H Piguel
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Sehyoun Yoon
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Ruoqi Gao
- University of Texas Southwestern Medical Center, Dallas, TX, 75235, USA
| | - Katherine E Horan
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Jacob C Garza
- Psychiatric and Neurodevelopmental Genetics Unit, Department of Psychiatry and Center for Genomic Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Tracey L Petryshen
- Psychiatric and Neurodevelopmental Genetics Unit, Department of Psychiatry and Center for Genomic Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Katharine R Smith
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO, 80045, USA
| | - Peter Penzes
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA.
- Department of Psychiatry and Behavioral Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA.
- Northwestern University, Center for Autism and Neurodevelopment, Chicago, IL, 60611, USA.
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6
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Piguel NH, Sanders SS, De Simone FI, Martin-de-Saavedra MD, McCoig E, Dionisio LE, Smith KR, Thomas GM, Penzes P. Palmitoylation controls the stability of 190 kDa ankyrin-G in dendritic spines and is regulated by ZDHHC8 and lithium. Front Mol Neurosci 2023; 16:1144066. [PMID: 36969554 PMCID: PMC10031057 DOI: 10.3389/fnmol.2023.1144066] [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: 01/13/2023] [Accepted: 02/14/2023] [Indexed: 03/10/2023] Open
Abstract
Introduction AnkG, encoded by the ANK3 gene, is a multifunctional scaffold protein with complex isoform expression: the 480 and 270 kDa isoforms have roles at the axon initial segment and node of Ranvier, whereas the 190 kDa isoform (AnkG-190) has an emerging role in the dendritic shaft and spine heads. All isoforms of AnkG undergo palmitoylation, a post-translational modification regulating protein attachment to lipid membranes. However, palmitoylation of AnkG-190 has not been investigated in dendritic spines. The ANK3 gene and altered expression of AnkG proteins are associated with a variety of neuropsychiatric and neurodevelopmental disorders including bipolar disorder and are implicated in the lithium response, a commonly used mood stabilizer for bipolar disorder patients, although the precise mechanisms involved are unknown. Result Here, we showed that Cys70 palmitoylation stabilizes the localization of AnkG-190 in spine heads and at dendritic plasma membrane nanodomains. Mutation of Cys70 impairs AnkG-190 function in dendritic spines and alters PSD-95 scaffolding. Interestingly, we find that lithium reduces AnkG-190 palmitoylation thereby increasing its mobility in dendritic spines. Finally, we demonstrate that the palmitoyl acyl transferase ZDHHC8, but not ZDHHC5, increases AnkG-190 stability in spine heads and is inhibited by lithium. Discussion Together, our data reveal that palmitoylation is critical for AnkG-190 localization and function and a potential ZDHHC8/AnkG-190 mechanism linking AnkG-190 mobility to the neuronal effects of lithium.
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Affiliation(s)
- Nicolas H. Piguel
- Department of Neuroscience, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Shaun S. Sanders
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, United States
| | - Francesca I. De Simone
- Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, United States
| | - Maria D. Martin-de-Saavedra
- Department of Neuroscience, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
- Department of Biochemistry and Molecular Biology, School of Pharmacy, Instituto Universitario de Investigación en Neuroquímica, Complutense University of Madrid, Madrid, Spain
| | - Emmarose McCoig
- Department of Neuroscience, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Leonardo E. Dionisio
- Department of Neuroscience, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Katharine R. Smith
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO, United States
| | - Gareth M. Thomas
- Department of Anatomy and Cell Biology, Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, United States
| | - Peter Penzes
- Department of Neuroscience, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
- Department of Psychiatry and Behavioral Sciences, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
- Northwestern University Center for Autism and Neurodevelopment, Chicago, IL, United States
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7
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Su Y, Zeng L, Deng R, Ye B, Tang S, Xiong Z, Sun T, Ding Q, Su W, Jing X, Gao Q, Wang X, Qiu Z, Chen K, Quan D, Guo X. Endogenous Electric Field-Coupled PD@BP Biomimetic Periosteum Promotes Bone Regeneration through Sensory Nerve via Fanconi Anemia Signaling Pathway. Adv Healthc Mater 2023; 12:e2203027. [PMID: 36652677 DOI: 10.1002/adhm.202203027] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Revised: 01/15/2023] [Indexed: 01/20/2023]
Abstract
To treat bone defects, repairing the nerve-rich periosteum is critical for repairing the local electric field. In this study, an endogenous electric field is coupled with 2D black phosphorus electroactive periosteum to explore its role in promoting bone regeneration through nerves. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are used to characterize the electrically active biomimetic periosteum. Here, the in vitro effects exerted by the electrically active periosteum on the transformation of Schwann cells into the repair phenotype, axon initial segment (AIS) and dense core vesicle (DCV) of sensory neurons, and bone marrow mesenchymal stem cells are assessed using SEM, immunofluorescence, RNA-sequencing, and calcium ion probes. The electrically active periosteum stimulates Schwann cells into a neuroprotective phenotype via the Fanconi anemia pathway, enhances the AIS effect of sensory neurons, regulates DCV transport, and releases neurotransmitters, promoting the osteogenic transformation of bone marrow mesenchymal stem cells. Microcomputed tomography and other in vivo techniques are used to study the effects of the electrically active periosteum on bone regeneration. The results show that the electrically active periosteum promotes nerve-induced osteogenic repair, providing a potential clinical strategy for bone regeneration.
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Affiliation(s)
- Yanlin Su
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
| | - Lian Zeng
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
| | - Rongli Deng
- PCFM Lab, School of Chemistry and School of Materials Science and Engineering, Sun Yat-sen University, Guangzhou, Guangdong, 510000, China
| | - Bing Ye
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
| | - Shuo Tang
- Department of Orthopedics, The Eighth Affiliated Hospital, Sun Yat-sen University, Shenzhen, Guangdong, 510127, China
| | - Zekang Xiong
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
| | - Tingfang Sun
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
| | - Qiuyue Ding
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
| | - Weijie Su
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
| | - Xirui Jing
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
| | - Qing Gao
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
| | - Xiumei Wang
- School of Materials Science and Engineering, Tsinghua University, Beijing, 100000, China
| | - Zhiye Qiu
- Allgens Medical Technology Co., Ltd., Beijing, 100000, China
| | - Kaifang Chen
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
| | - Daping Quan
- PCFM Lab, School of Chemistry and School of Materials Science and Engineering, Sun Yat-sen University, Guangzhou, Guangdong, 510000, China
| | - Xiaodong Guo
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
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8
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Teliska LH, Dalla Costa I, Sert O, Twiss JL, Rasband MN. Axon Initial Segments Are Required for Efficient Motor Neuron Axon Regeneration and Functional Recovery of Synapses. J Neurosci 2022; 42:8054-8065. [PMID: 36096668 PMCID: PMC9636994 DOI: 10.1523/jneurosci.1261-22.2022] [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: 06/27/2022] [Accepted: 08/02/2022] [Indexed: 11/21/2022] Open
Abstract
The axon initial segment (AIS) generates action potentials and maintains neuronal polarity by regulating the differential trafficking and distribution of proteins, transport vesicles, and organelles. Injury and disease can disrupt the AIS, and the subsequent loss of clustered ion channels and polarity mechanisms may alter neuronal excitability and function. However, the impact of AIS disruption on axon regeneration after injury is unknown. We generated male and female mice with AIS-deficient multipolar motor neurons by deleting AnkyrinG, the master scaffolding protein required for AIS assembly and maintenance. We found that after nerve crush, neuromuscular junction reinnervation was significantly delayed in AIS-deficient motor neurons compared with control mice. In contrast, loss of AnkyrinG from pseudo-unipolar sensory neurons did not impair axon regeneration into the intraepidermal nerve fiber layer. Even after AIS-deficient motor neurons reinnervated the neuromuscular junction, they failed to functionally recover because of reduced synaptic vesicle protein 2 at presynaptic terminals. In addition, mRNA trafficking was disrupted in AIS-deficient axons. Our results show that, after nerve injury, an intact AIS is essential for efficient regeneration and functional recovery of axons in multipolar motor neurons. Our results also suggest that loss of polarity in AIS-deficient motor neurons impairs the delivery of axonal proteins, mRNAs, and other cargoes necessary for regeneration. Thus, therapeutic strategies for axon regeneration must consider preservation or reassembly of the AIS.SIGNIFICANCE STATEMENT Disruption of the axon initial segment is a common event after nervous system injury. For multipolar motor neurons, we show that axon initial segments are essential for axon regeneration and functional recovery after injury. Our results may help explain injuries where axon regeneration fails, and suggest strategies to promote more efficient axon regeneration.
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Affiliation(s)
- Lindsay H Teliska
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030
| | - Irene Dalla Costa
- Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208
| | - Ozlem Sert
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030
| | - Jeffery L Twiss
- Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208
| | - Matthew N Rasband
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030
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9
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Alexandrov YI, Pletnikov MV. Neuronal metabolism in learning and memory: The anticipatory activity perspective. Neurosci Biobehav Rev 2022; 137:104664. [PMID: 35439520 DOI: 10.1016/j.neubiorev.2022.104664] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 03/30/2022] [Accepted: 04/10/2022] [Indexed: 12/20/2022]
Abstract
Current research on the molecular mechanisms of learning and memory is based on the "stimulus-response" paradigm, in which the neural circuits connecting environmental events with behavioral responses are strengthened. By contrast, cognitive and systems neuroscience emphasize the intrinsic activity of the brain that integrates information, establishes anticipatory actions, executes adaptive actions, and assesses the outcome via regulatory feedback mechanisms. We believe that the difference in the perspectives of systems and molecular studies is a major roadblock to further progress toward understanding the mechanisms of learning and memory. Here, we briefly overview the current studies in molecular mechanisms of learning and memory and propose that studying the predictive properties of neuronal metabolism will significantly advance our knowledge of how intrinsic, predictive activity of neurons shapes a new learning event. We further suggest that predictive metabolic changes in the brain may also take place in non-neuronal cells, including those of peripheral tissues. Finally, we present a path forward toward more in-depth studies of the role of cell metabolism in learning and memory.
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Affiliation(s)
- Yuri I Alexandrov
- V. B. Shvyrkov Laboratory for the Neural Bases of the Mind, Institute of Psychology, the Russian Academy of Sciences, Moscow, Russia; Department of Psychology, Institute for Cognitive Neuroscience, HSE University, Moscow, Russia.
| | - Mikhail V Pletnikov
- Department of Physiology and Biophysics, Jacobs School of Medicine and Biomedical Sciences, State University of New York, University at Buffalo, Buffalo, NY 14203, USA; Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA; Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
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10
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Tymanskyj SR, Curran BM, Ma L. Selective axonal transport through branch junctions is directed by growth cone signaling and mediated by KIF1/kinesin-3 motors. Cell Rep 2022; 39:110748. [PMID: 35476993 PMCID: PMC9097860 DOI: 10.1016/j.celrep.2022.110748] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 01/27/2022] [Accepted: 04/06/2022] [Indexed: 11/16/2022] Open
Abstract
Development and function of nerve cells rely on the orchestration of microtubule-based transport from the cell body into distal axonal terminals. Neurons often have highly elaborate branches innervating multiple targets, but how protein or membrane cargos navigate through branch junctions to specific branch targets is unknown. Here, we demonstrate that anterograde transport of membrane vesicles through axonal branch junctions is highly selective, which is influenced by branch length and more strongly by growth cone motility. Using an optogenetic tool, we demonstrate that signaling from the growth cone can rapidly direct transport through branch junctions. We further demonstrate that such transport selectivity is differentially regulated for different vesicles and mediated by the KIF1/kinesin-3 family motors. We propose that this transport regulation through branch junctions could broadly impact neuronal development, function, and regeneration.
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Affiliation(s)
- Stephen R Tymanskyj
- Department of Neuroscience, Jefferson Center for Synaptic Biology, Vickie and Jack Farber Institute for Neuroscience, Sydney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Bridget M Curran
- Department of Neuroscience, Jefferson Center for Synaptic Biology, Vickie and Jack Farber Institute for Neuroscience, Sydney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Le Ma
- Department of Neuroscience, Jefferson Center for Synaptic Biology, Vickie and Jack Farber Institute for Neuroscience, Sydney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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11
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Wang Y, Guan M, Zhang Y, Zhanghao K, Xi P. Glucose increases the length and spacing of the lattice structure of the axon initial segment. Microsc Res Tech 2022; 85:2679-2691. [PMID: 35411984 DOI: 10.1002/jemt.24122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 03/01/2022] [Accepted: 03/31/2022] [Indexed: 11/12/2022]
Abstract
The axon initial segment (AIS) plays an important role in maintaining neuronal polarity and initiating action potentials (APs). The AIS adapts to its environment by changing its length and distance from the cell body, resulting in modulation of neuronal excitability, which is referred to as AIS plasticity. Previous studies found an ~200 nm single periodic distribution of the key AIS components ankyrinG (AnkG), Nav 1.2, and βIV-spectrin, while it remains unclear how the lattice structure is altered by AIS plasticity. In this study, we found that the length of the AIS significantly increased, resulting in increased neuronal excitability, with high-concentration glucose treatment. Structured illumination microscopy (SIM) images of the lattice structure showed a dual-spacing periodic distribution (~200 nm and ~260 nm) of AnkG, Nav 1.2, and βIV-spectrin. Moreover, 480-kDa AnkG was crucial for AIS plasticity and increased lattice structure spacing. The discovery of new regulators for modulating AIS plasticity will help us to understand and manipulate the structure and function of the AIS.
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Affiliation(s)
- Yiming Wang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing, China
| | - Meiling Guan
- Department of Biomedical Engineering, College of Future Technology, Peking University, Beijing, China
| | - Yan Zhang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing, China.,PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing, China
| | - Karl Zhanghao
- UTS-SUStech Joint Research Centre for Biomedical Materials & Devices, Department of Biomedical Engineering, College of Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, China
| | - Peng Xi
- Department of Biomedical Engineering, College of Future Technology, Peking University, Beijing, China.,UTS-SUStech Joint Research Centre for Biomedical Materials & Devices, Department of Biomedical Engineering, College of Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, China.,National Biomedical Imaging Center, Peking University, Beijing, China
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12
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Steele-Nicholson LJ, Andrews MR. Axon-Targeting Motifs: Mechanisms and Applications of Enhancing Axonal Localisation of Transmembrane Proteins. Cells 2022; 11:cells11060937. [PMID: 35326388 PMCID: PMC8946247 DOI: 10.3390/cells11060937] [Citation(s) in RCA: 2] [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: 02/15/2022] [Revised: 03/04/2022] [Accepted: 03/07/2022] [Indexed: 11/16/2022] Open
Abstract
Neuronal polarity established in developing neurons ensures proper function in the mature nervous system. As functionally distinct cellular compartments, axons and dendrites often require different subsets of proteins to maintain synaptic transmission and overall order. Although neurons in the mature CNS do not regenerate throughout life, their interactions with their extracellular environment are dynamic. The axon remains an overall protected area of the neuron where only certain proteins have access throughout the lifespan of the cell. This is in comparison to the somatodendritic compartment, where although it too has a specialised subset of proteins required for its maintenance, many proteins destined for the axonal compartment must first be trafficked through the former. Recent research has shown that axonal proteins contain specific axon-targeting motifs that permit access to the axonal compartment as well as downstream targeting to the axonal membrane. These motifs target proteins to the axonal compartment by a variety of mechanisms including: promoting segregation into axon-targeted secretory vesicles, increasing interaction with axonal kinesins and enhancing somatodendritic endocytosis. In this review, we will discuss axon-targeting motifs within the context of established neuron trafficking mechanisms. We will also include examples of how these motifs have been applied to target proteins to the axonal compartment to improve both tools for the study of axon biology, and for use as potential therapeutics for axonopathies.
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Affiliation(s)
- Lloyd J. Steele-Nicholson
- Faculty of Environmental and Life Sciences, University of Southampton, Southampton SO17 1BJ, UK;
- Centre for Human Development, Stem Cells and Regeneration, School of Biological Sciences, University of Southampton, Southampton SO17 1BJ, UK
| | - Melissa R. Andrews
- Faculty of Environmental and Life Sciences, University of Southampton, Southampton SO17 1BJ, UK;
- Centre for Human Development, Stem Cells and Regeneration, School of Biological Sciences, University of Southampton, Southampton SO17 1BJ, UK
- Correspondence:
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13
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Nabb AT, Bentley M. NgCAM and VAMP2 reveal that direct delivery and dendritic degradation maintain axonal polarity. Mol Biol Cell 2022; 33:ar3. [PMID: 34731031 PMCID: PMC8886818 DOI: 10.1091/mbc.e21-08-0425] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Neurons are polarized cells of extreme scale and compartmentalization. To fulfill their role in electrochemical signaling, axons must maintain a specific complement of membrane proteins. Despite being the subject of considerable attention, the trafficking pathway of axonal membrane proteins is not well understood. Two pathways, direct delivery and transcytosis, have been proposed. Previous studies reached contradictory conclusions about which of these mediates delivery of axonal membrane proteins to their destination, in part because they evaluated long-term distribution changes and not vesicle transport. We developed a novel strategy to selectively label vesicles in different trafficking pathways and determined the trafficking of two canonical axonal membrane proteins, neuron-glia cell adhesion molecule and vesicle-associated membrane protein-2. Results from detailed quantitative analyses of transporting vesicles differed substantially from previous studies and found that axonal membrane proteins overwhelmingly undergo direct delivery. Transcytosis plays only a minor role in axonal delivery of these proteins. In addition, we identified a novel pathway by which wayward axonal proteins that reach the dendritic plasma membrane are targeted to lysosomes. These results redefine how axonal proteins achieve their polarized distribution, a crucial requirement for elucidating the underlying molecular mechanisms.
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Affiliation(s)
- Alec T. Nabb
- Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180
| | - Marvin Bentley
- Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180,*Address correspondence to: Marvin Bentley ()
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14
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Usui N, Tian X, Harigai W, Togawa S, Utsunomiya R, Doi T, Miyoshi K, Shinoda K, Tanaka J, Shimada S, Katayama T, Yoshimura T. Length impairments of the axon initial segment in rodent models of attention-deficit hyperactivity disorder and autism spectrum disorder. Neurochem Int 2021; 153:105273. [PMID: 34971749 DOI: 10.1016/j.neuint.2021.105273] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 12/22/2021] [Accepted: 12/24/2021] [Indexed: 11/25/2022]
Abstract
The axon initial segment (AIS) is a structural neuronal compartment of the proximal axon that plays key roles in sodium channel clustering, action potential initiation, and signal propagation of neuronal outputs. Mutations in constitutive genes of the AIS, such as ANK3, have been identified in patients with neurodevelopmental disorders. Nevertheless, morphological changes in the AIS in neurodevelopmental disorders have not been characterized. In this study, we investigated the length of the AIS in rodent models of attention-deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). We observed abnormalities in AIS length in both animal models. In ADHD model rodents, we observed shorter AIS length in layer 2/3 (L2/3) neurons of the medial prefrontal cortex (mPFC) and primary somatosensory barrel field (S1BF). Further, we observed shorter AIS length in S1BF L5 neurons. In ASD model mice, we observed shorter AIS length in L2/3 and L5 neurons of the S1BF. These results suggest that impairments in AIS length are common phenomena in neurodevelopmental disorders such as ADHD and ASD and may be conserved across species. Our findings provide novel insight into the potential contribution of the AIS to the pathophysiology and pathogenesis of neurodevelopmental disorders.
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Affiliation(s)
- Noriyoshi Usui
- Department of Neuroscience and Cell Biology, Graduate School of Medicine, Osaka University, Suita, 565-0871, Japan; United Graduate School of Child Development, Osaka University, Suita, 565-0871, Japan; Global Center for Medical Engineering and Informatics, Osaka University, Suita, 565-0871, Japan; Addiction Research Unit, Osaka Psychiatric Research Center, Osaka Psychiatric Medical Center, Hirakata, 573-0022, Japan.
| | - Xiaoye Tian
- Department of Child Development and Molecular Brain Science, United Graduate School of Child Development, Osaka University, Suita, 565-0871, Japan
| | - Wakana Harigai
- Department of Child Development and Molecular Brain Science, United Graduate School of Child Development, Osaka University, Suita, 565-0871, Japan
| | - Shogo Togawa
- Department of Neuroscience and Cell Biology, Graduate School of Medicine, Osaka University, Suita, 565-0871, Japan; Division of Neuroanatomy, Department of Neuroscience, Yamaguchi University Graduate School of Medicine, Yamaguchi, 755-8505, Japan
| | - Ryo Utsunomiya
- Department of Molecular and Cellular Physiology, Graduate School of Medicine, Ehime University, Ehime, 791-0295, Japan
| | - Tomomi Doi
- Department of Molecular and Cellular Physiology, Graduate School of Medicine, Ehime University, Ehime, 791-0295, Japan
| | - Ko Miyoshi
- Department of Child Development and Molecular Brain Science, United Graduate School of Child Development, Osaka University, Suita, 565-0871, Japan
| | - Koh Shinoda
- Division of Neuroanatomy, Department of Neuroscience, Yamaguchi University Graduate School of Medicine, Yamaguchi, 755-8505, Japan
| | - Junya Tanaka
- Department of Molecular and Cellular Physiology, Graduate School of Medicine, Ehime University, Ehime, 791-0295, Japan
| | - Shoichi Shimada
- Department of Neuroscience and Cell Biology, Graduate School of Medicine, Osaka University, Suita, 565-0871, Japan; United Graduate School of Child Development, Osaka University, Suita, 565-0871, Japan; Addiction Research Unit, Osaka Psychiatric Research Center, Osaka Psychiatric Medical Center, Hirakata, 573-0022, Japan
| | - Taiichi Katayama
- Department of Child Development and Molecular Brain Science, United Graduate School of Child Development, Osaka University, Suita, 565-0871, Japan
| | - Takeshi Yoshimura
- Department of Child Development and Molecular Brain Science, United Graduate School of Child Development, Osaka University, Suita, 565-0871, Japan.
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15
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Petropavlovskiy A, Kogut J, Leekha A, Townsend C, Sanders S. A sticky situation: regulation and function of protein palmitoylation with a spotlight on the axon and axon initial segment. Neuronal Signal 2021; 5:NS20210005. [PMID: 34659801 PMCID: PMC8495546 DOI: 10.1042/ns20210005] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 09/19/2021] [Accepted: 09/21/2021] [Indexed: 11/17/2022] Open
Abstract
In neurons, the axon and axon initial segment (AIS) are critical structures for action potential initiation and propagation. Their formation and function rely on tight compartmentalisation, a process where specific proteins are trafficked to and retained at distinct subcellular locations. One mechanism which regulates protein trafficking and association with lipid membranes is the modification of protein cysteine residues with the 16-carbon palmitic acid, known as S-acylation or palmitoylation. Palmitoylation, akin to phosphorylation, is reversible, with palmitate cycling being mediated by substrate-specific enzymes. Palmitoylation is well-known to be highly prevalent among neuronal proteins and is well studied in the context of the synapse. Comparatively, how palmitoylation regulates trafficking and clustering of axonal and AIS proteins remains less understood. This review provides an overview of the current understanding of the biochemical regulation of palmitoylation, its involvement in various neurological diseases, and the most up-to-date perspective on axonal palmitoylation. Through a palmitoylation analysis of the AIS proteome, we also report that an overwhelming proportion of AIS proteins are likely palmitoylated. Overall, our review and analysis confirm a central role for palmitoylation in the formation and function of the axon and AIS and provide a resource for further exploration of palmitoylation-dependent protein targeting to and function at the AIS.
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Affiliation(s)
- Andrey A. Petropavlovskiy
- Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Rd E, Guelph N1G 2W1, Ontario, Canada
| | - Jordan A. Kogut
- Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Rd E, Guelph N1G 2W1, Ontario, Canada
| | - Arshia Leekha
- Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Rd E, Guelph N1G 2W1, Ontario, Canada
| | - Charlotte A. Townsend
- Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Rd E, Guelph N1G 2W1, Ontario, Canada
| | - Shaun S. Sanders
- Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Rd E, Guelph N1G 2W1, Ontario, Canada
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16
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Risner ML, Pasini S, Chamling X, McGrady NR, Goldberg JL, Zack DJ, Calkins DJ. Intrinsic Morphologic and Physiologic Development of Human Derived Retinal Ganglion Cells In Vitro. Transl Vis Sci Technol 2021; 10:1. [PMID: 34383881 PMCID: PMC8362626 DOI: 10.1167/tvst.10.10.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Purpose Human retinal ganglion cells (hRGC) derived from human pluripotent stem cells are promising candidates to model, protect, and replace degenerating RGCs. Here, we examined intrinsic morphologic and physiologic development of hRGCs. Methods We used CRISPR-Cas9 to selectively express tdTomato under the RGC-specific promoter, BRN3B. Human pluripotent stem cells were chemically differentiated into hRGCs and cultured up to 7 weeks. We measured soma area, neurite complexity, synaptic protein, axon-related messenger RNA and protein, and voltage-dependent responses. Results Soma area, neurite complexity, and postsynaptic density protein 95 increased over time. Soma area and neurite complexity increased proportionally week to week, and this relationship was dynamic, strengthening between 2 and 3 weeks and diminishing by 4 weeks. Postsynaptic density 95 localization was dependent on culture duration. After 1 to 2 weeks, postsynaptic density 95 localized within somas but redistributed along neurites after 3 to 4 weeks. Axon initial segment scaffolding protein, Ankyrin G, expression also increased over time, and by 7 weeks, Ankyrin G often localized within putative axons. Voltage-gated inward currents progressively developed, but outward currents matured by 4 weeks. Current-induced spike generation increased over time but limited by depolarization block. Conclusions Human RGCs develop up to 7 weeks after culture. Thus, the state of hRGC maturation should be accounted for in designing models and treatments for optic neuropathies. Translational Relevance We characterized hRGC morphologic and physiologic development towards identifying key time points when hRGCs express mechanisms that may be harnessed to enhance the efficacy of neuroprotective and cell replacement therapies.
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Affiliation(s)
- Michael L Risner
- Vanderbilt Eye Institute, Department of Ophthalmology & Visual Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Silvia Pasini
- Vanderbilt Eye Institute, Department of Ophthalmology & Visual Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Xitiz Chamling
- Wilmer Eye Institute, Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Nolan R McGrady
- Vanderbilt Eye Institute, Department of Ophthalmology & Visual Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Jeffrey L Goldberg
- Byers Eye Institute, Department of Ophthalmology, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Donald J Zack
- Wilmer Eye Institute, Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - David J Calkins
- Vanderbilt Eye Institute, Department of Ophthalmology & Visual Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
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17
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Quistgaard EM, Nissen JD, Hansen S, Nissen P. Mind the Gap: Molecular Architecture of the Axon Initial Segment - From Fold Prediction to a Mechanistic Model of Function? J Mol Biol 2021; 433:167176. [PMID: 34303720 DOI: 10.1016/j.jmb.2021.167176] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 07/14/2021] [Accepted: 07/14/2021] [Indexed: 11/28/2022]
Abstract
The axon initial segment (AIS) is a distinct neuronal domain, which is responsible for initiating action potentials, and therefore of key importance to neuronal signaling. To determine how it functions, it is necessary to establish which proteins reside there, how they are organized, and what the dynamic features are. Great strides have been made in recent years, and it is now clear that several AIS cytoskeletal and membrane proteins interact to form a higher-order periodic structure. Here we briefly describe AIS function, protein composition and molecular architecture, and discuss perspectives for future structural characterization, and if structure predictions will be able to model complex higher-order assemblies.
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Affiliation(s)
- Esben M Quistgaard
- DANDRITE - Nordic EMBL Partnership for Molecular Medicine, Aarhus University, Dept. Molecular Biology and Genetics, DK - 8000 Aarhus C, Denmark
| | - Josephine Dannersø Nissen
- DANDRITE - Nordic EMBL Partnership for Molecular Medicine, Aarhus University, Dept. Molecular Biology and Genetics, DK - 8000 Aarhus C, Denmark
| | - Sean Hansen
- DANDRITE - Nordic EMBL Partnership for Molecular Medicine, Aarhus University, Dept. Molecular Biology and Genetics, DK - 8000 Aarhus C, Denmark
| | - Poul Nissen
- DANDRITE - Nordic EMBL Partnership for Molecular Medicine, Aarhus University, Dept. Molecular Biology and Genetics, DK - 8000 Aarhus C, Denmark.
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18
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Sun Z, Wang B, Chen C, Li C, Zhang Y. 5-HT6R null mutatrion induces synaptic and cognitive defects. Aging Cell 2021; 20:e13369. [PMID: 33960602 PMCID: PMC8208783 DOI: 10.1111/acel.13369] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 03/09/2021] [Accepted: 03/31/2021] [Indexed: 01/01/2023] Open
Abstract
Serotonin 6 receptor (5-HT6R) is a promising target for a variety of human diseases, such as Alzheimer's disease (AD) and schizophrenia. However, the detailed mechanism underlying 5-HT6R activity in the central nervous system (CNS) is not fully understood. In the present study, 5-HT6R null mutant (5-HT6R-/- ) mice were found to exhibit cognitive deficiencies and abnormal anxiety levels. 5-HT6R is considered to be specifically localized on the primary cilia. We found that the loss of 5-HT6R affected the Sonic Hedgehog signaling pathway in the primary cilia. 5-HT6R-/- mice showed remarkable alterations in neuronal morphology, including dendrite complexity and axon initial segment morphology. Neurons lacking 5-HT6R exhibited increased neuronal excitability. Our findings highlight the complexity of 5-HT6R functions in the primary ciliary and neuronal physiology, supporting the theory that this receptor modulates neuronal morphology and transmission, and contributes to cognitive deficits in a variety of human diseases, such as AD, schizophrenia, and ciliopathies.
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Affiliation(s)
- Zehui Sun
- State Key Laboratory of Membrane BiologyCollege of Life SciencesPeking UniversityBeijingChina
| | - Bingjie Wang
- State Key Laboratory of Membrane BiologyCollege of Life SciencesPeking UniversityBeijingChina
| | - Chen Chen
- School of Life SciencesLanzhou UniversityLanzhouChina
| | - Chenjian Li
- State Key Laboratory of Membrane BiologyCollege of Life SciencesPeking UniversityBeijingChina
| | - Yan Zhang
- State Key Laboratory of Membrane BiologyCollege of Life SciencesPeking UniversityBeijingChina,PKU/IDG McGovern Institute for Brain ResearchBeijingChina
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19
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Lipkin AM, Cunniff MM, Spratt PWE, Lemke SM, Bender KJ. Functional Microstructure of Ca V-Mediated Calcium Signaling in the Axon Initial Segment. J Neurosci 2021; 41:3764-3776. [PMID: 33731449 PMCID: PMC8084313 DOI: 10.1523/jneurosci.2843-20.2021] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 02/15/2021] [Accepted: 03/09/2021] [Indexed: 01/12/2023] Open
Abstract
The axon initial segment (AIS) is a specialized neuronal compartment in which synaptic input is converted into action potential (AP) output. This process is supported by a diverse complement of sodium, potassium, and calcium channels (CaV). Different classes of sodium and potassium channels are scaffolded at specific sites within the AIS, conferring unique functions, but how calcium channels are functionally distributed within the AIS is unclear. Here, we use conventional two-photon laser scanning and diffraction-limited, high-speed spot two-photon imaging to resolve AP-evoked calcium dynamics in the AIS with high spatiotemporal resolution. In mouse layer 5 prefrontal pyramidal neurons, calcium influx was mediated by a mix of CaV2 and CaV3 channels that differentially localized to discrete regions. CaV3 functionally localized to produce nanodomain hotspots of calcium influx that coupled to ryanodine-sensitive stores, whereas CaV2 localized to non-hotspot regions. Thus, different pools of CaVs appear to play distinct roles in AIS function.SIGNIFICANCE STATEMENT The axon initial segment (AIS) is the site where synaptic input is transformed into action potential (AP) output. It achieves this function through a diverse complement of sodium, potassium, and calcium channels (CaV). While the localization and function of sodium channels and potassium channels at the AIS is well described, less is known about the functional distribution of CaVs. We used high-speed two-photon imaging to understand activity-dependent calcium dynamics in the AIS of mouse neocortical pyramidal neurons. Surprisingly, we found that calcium influx occurred in two distinct domains: CaV3 generates hotspot regions of calcium influx coupled to calcium stores, whereas CaV2 channels underlie diffuse calcium influx between hotspots. Therefore, different CaV classes localize to distinct AIS subdomains, possibly regulating distinct cellular processes.
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Affiliation(s)
- Anna M Lipkin
- Neuroscience Graduate Program, University of California, San Francisco, California 94158
| | - Margaret M Cunniff
- Neuroscience Graduate Program, University of California, San Francisco, California 94158
| | - Perry W E Spratt
- Neuroscience Graduate Program, University of California, San Francisco, California 94158
| | - Stefan M Lemke
- Neuroscience Graduate Program, University of California, San Francisco, California 94158
| | - Kevin J Bender
- Neuroscience Graduate Program, University of California, San Francisco, California 94158
- Department of Neurology, Kavli Institute for Fundamental Neuroscience, Weill Institute for Neurosciences, University of California, San Francisco, California 94158
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20
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Chen YC, Huang HR, Hsu CH, Ou CY. CRMP/UNC-33 organizes microtubule bundles for KIF5-mediated mitochondrial distribution to axon. PLoS Genet 2021; 17:e1009360. [PMID: 33571181 PMCID: PMC7904166 DOI: 10.1371/journal.pgen.1009360] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 02/24/2021] [Accepted: 11/11/2020] [Indexed: 12/13/2022] Open
Abstract
Neurons are highly specialized cells with polarized cellular processes and subcellular domains. As vital organelles for neuronal functions, mitochondria are distributed by microtubule-based transport systems. Although the essential components of mitochondrial transport including motors and cargo adaptors are identified, it is less clear how mitochondrial distribution among somato-dendritic and axonal compartment is regulated. Here, we systematically study mitochondrial motors, including four kinesins, KIF5, KIF17, KIF1, KLP-6, and dynein, and transport regulators in C. elegans PVD neurons. Among all these motors, we found that mitochondrial export from soma to neurites is mainly mediated by KIF5/UNC-116. Interestingly, UNC-116 is especially important for axonal mitochondria, while dynein removes mitochondria from all plus-end dendrites and the axon. We surprisingly found one mitochondrial transport regulator for minus-end dendritic compartment, TRAK-1, and two mitochondrial transport regulators for axonal compartment, CRMP/UNC-33 and JIP3/UNC-16. While JIP3/UNC-16 suppresses axonal mitochondria, CRMP/UNC-33 is critical for axonal mitochondria; nearly no axonal mitochondria present in unc-33 mutants. We showed that UNC-33 is essential for organizing the population of UNC-116-associated microtubule bundles, which are tracks for mitochondrial trafficking. Disarrangement of these tracks impedes mitochondrial transport to the axon. In summary, we identified a compartment-specific transport regulation of mitochondria by UNC-33 through organizing microtubule tracks for different kinesin motors other than microtubule polarity.
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Affiliation(s)
- Ying-Chun Chen
- Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Hao-Ru Huang
- Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Chia-Hao Hsu
- Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Chan-Yen Ou
- Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, Taipei, Taiwan
- * E-mail:
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21
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Bhardwaj P, Kulasiri D, Samarasinghe S. Modeling protein-protein interactions in axon initial segment to understand their potential impact on action potential initiation. Neural Regen Res 2021; 16:700-706. [PMID: 33063731 PMCID: PMC8067952 DOI: 10.4103/1673-5374.295332] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The axon initial segment (AIS) region is crucial for action potential initiation due to the presence of high-density AIS protein voltage-gated sodium channels (Nav). Nav channels comprise several serine residues responsible for the recruitment of Nav channels into the structure of AIS through interactions with ankyrin-G (AnkG). In this study, a series of computational experiments are performed to understand the role of AIS proteins casein kinase 2 and AnkG on Nav channel recruitment into the AIS. The computational simulation results using Virtual cell software indicate that Nav channels with all serine sites available for phosphorylation bind to AnkG with strong affinity. At the low initial concentration of AnkG and casein kinase 2, the concentration of Nav channels reduces significantly, suggesting the importance of casein kinase 2 and AnkG in the recruitment of Nav channels.
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Affiliation(s)
- Piyush Bhardwaj
- Centre of Advanced Computational Solutions (C-fACS); Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand
| | - Don Kulasiri
- Centre of Advanced Computational Solutions (C-fACS); Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand
| | - Sandhya Samarasinghe
- Centre of Advanced Computational Solutions (C-fACS), Lincoln University, Christchurch, New Zealand
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22
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Assembly and Function of the Juxtaparanodal Kv1 Complex in Health and Disease. Life (Basel) 2020; 11:life11010008. [PMID: 33374190 PMCID: PMC7824554 DOI: 10.3390/life11010008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 12/21/2020] [Accepted: 12/23/2020] [Indexed: 02/07/2023] Open
Abstract
The precise axonal distribution of specific potassium channels is known to secure the shape and frequency of action potentials in myelinated fibers. The low-threshold voltage-gated Kv1 channels located at the axon initial segment have a significant influence on spike initiation and waveform. Their role remains partially understood at the juxtaparanodes where they are trapped under the compact myelin bordering the nodes of Ranvier in physiological conditions. However, the exposure of Kv1 channels in de- or dys-myelinating neuropathy results in alteration of saltatory conduction. Moreover, cell adhesion molecules associated with the Kv1 complex, including Caspr2, Contactin2, and LGI1, are target antigens in autoimmune diseases associated with hyperexcitability such as encephalitis, neuromyotonia, or neuropathic pain. The clustering of Kv1.1/Kv1.2 channels at the axon initial segment and juxtaparanodes is based on interactions with cell adhesion molecules and cytoskeletal linkers. This review will focus on the trafficking and assembly of the axonal Kv1 complex in the peripheral and central nervous system (PNS and CNS), during development, and in health and disease.
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23
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Stone MC, Kothe GO, Rolls MM, Jegla T. Cytoskeletal and synaptic polarity of LWamide-like+ ganglion neurons in the sea anemone Nematostella vectensis. J Exp Biol 2020; 223:jeb233197. [PMID: 32968001 PMCID: PMC7673360 DOI: 10.1242/jeb.233197] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 09/14/2020] [Indexed: 12/22/2022]
Abstract
The centralized nervous systems of bilaterian animals rely on directional signaling facilitated by polarized neurons with specialized axons and dendrites. It is not known whether axo-dendritic polarity is exclusive to bilaterians or was already present in early metazoans. We therefore examined neurite polarity in the starlet sea anemone Nematostella vectensis (Cnidaria). Cnidarians form a sister clade to bilaterians and share many neuronal building blocks characteristic of bilaterians, including channels, receptors and synaptic proteins, but their nervous systems comprise a comparatively simple net distributed throughout the body. We developed a tool kit of fluorescent polarity markers for live imaging analysis of polarity in an identified neuron type, large ganglion cells of the body column nerve net that express the LWamide-like neuropeptide. Microtubule polarity differs in bilaterian axons and dendrites, and this in part underlies polarized distribution of cargo to the two types of processes. However, in LWamide-like+ neurons, all neurites had axon-like microtubule polarity suggesting that they may have similar contents. Indeed, presynaptic and postsynaptic markers trafficked to all neurites and accumulated at varicosities where neurites from different neurons often crossed, suggesting the presence of bidirectional synaptic contacts. Furthermore, we could not identify a diffusion barrier in the plasma membrane of any of the neurites like the axon initial segment barrier that separates the axonal and somatodendritic compartments in bilaterian neurons. We conclude that at least one type of neuron in Nematostella vectensis lacks the axo-dendritic polarity characteristic of bilaterian neurons.
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Affiliation(s)
- Michelle C Stone
- Department of Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA
| | - Gregory O Kothe
- Department of Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA
| | - Melissa M Rolls
- Department of Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA
| | - Timothy Jegla
- Department of Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA
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24
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Akamine S, Okuzono S, Yamamoto H, Setoyama D, Sagata N, Ohgidani M, Kato TA, Ishitani T, Kato H, Masuda K, Matsushita Y, Ono H, Ishizaki Y, Sanefuji M, Saitsu H, Matsumoto N, Kang D, Kanba S, Nakabeppu Y, Sakai Y, Ohga S. GNAO1 organizes the cytoskeletal remodeling and firing of developing neurons. FASEB J 2020; 34:16601-16621. [PMID: 33107105 DOI: 10.1096/fj.202001113r] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 09/03/2020] [Accepted: 10/13/2020] [Indexed: 01/03/2023]
Abstract
Developmental and epileptic encephalopathy (DEE) represents a group of neurodevelopmental disorders characterized by infantile-onset intractable seizures and unfavorable prognosis of psychomotor development. To date, hundreds of genes have been linked to the onset of DEE. GNAO1 is a DEE-associated gene encoding the alpha-O1 subunit of guanine nucleotide-binding protein (GαO ). Despite the increasing number of reported children with GNAO1 encephalopathy, the molecular mechanisms underlying their neurodevelopmental phenotypes remain elusive. We herein present that co-immunoprecipitation and mass spectrometry analyses identified another DEE-associated protein, SPTAN1, as an interacting partner of GαO . Silencing of endogenous Gnao1 attenuated the neurite outgrowth and calcium-dependent signaling. Inactivation of GNAO1 in human-induced pluripotent stem cells gave rise to anomalous brain organoids that only weakly expressed SPTAN1 and Ankyrin-G. Furthermore, GNAO1-deficient organoids failed to conduct synchronized firing to adjacent neurons. These data indicate that GαO and other DEE-associated proteins organize the cytoskeletal remodeling and functional polarity of neurons in the developing brain.
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Affiliation(s)
- Satoshi Akamine
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Sayaka Okuzono
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Hiroyuki Yamamoto
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Daiki Setoyama
- Department of Clinical Chemistry and Laboratory Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Noriaki Sagata
- Department of Neuropsychiatry, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Masahiro Ohgidani
- Department of Neuropsychiatry, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Takahiro A Kato
- Department of Neuropsychiatry, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Tohru Ishitani
- Division of Integrated Signaling Systems, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan.,Department of Homeostatic Regulation, Division of Cellular and Molecular Biology. Research Institute for Microbial Diseases, Osaka University, Suita, Japan
| | - Hiroki Kato
- Division of Oral Biological Sciences, Department of Molecular Cell Biology and Oral Anatomy, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Keiji Masuda
- Section of Oral Medicine for Children, Division of Oral Health, Growth and Development, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Yuki Matsushita
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Hiroaki Ono
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Yoshito Ishizaki
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Masafumi Sanefuji
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Hirotomo Saitsu
- Department of Biochemistry, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Dongchon Kang
- Department of Clinical Chemistry and Laboratory Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Shigenobu Kanba
- Department of Neuropsychiatry, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Yusaku Nakabeppu
- Division of Neurofunctional Genomics, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan
| | - Yasunari Sakai
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Shouichi Ohga
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
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25
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Nicholson L, Gervasi N, Falières T, Leroy A, Miremont D, Zala D, Hanus C. Whole-Cell Photobleaching Reveals Time-Dependent Compartmentalization of Soluble Proteins by the Axon Initial Segment. Front Cell Neurosci 2020; 14:180. [PMID: 32754013 PMCID: PMC7366827 DOI: 10.3389/fncel.2020.00180] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 05/27/2020] [Indexed: 01/12/2023] Open
Abstract
By limiting protein exchange between the soma and the axon, the axon initial segment (AIS) enables the segregation of specific proteins and hence the differentiation of the somatodendritic compartment and the axonal compartment. Electron microscopy and super-resolution fluorescence imaging have provided important insights in the ultrastructure of the AIS. Yet, the full extent of its filtering properties is not fully delineated. In particular, it is unclear whether and how the AIS opposes the free exchange of soluble proteins. Here we describe a robust framework to combine whole-cell photobleaching and retrospective high-resolution imaging in developing neurons. With this assay, we found that cytoplasmic soluble proteins that are not excluded from the axon upon expression over tens of hours exhibit a strong mobility reduction at the AIS – i.e., are indeed compartmentalized – when monitored over tens of minutes. This form of compartmentalization is developmentally regulated, requires intact F-actin and may be correlated with the composition and ultrastructure of the submembranous spectrin cytoskeleton. Using computational modeling, we provide evidence that both neuronal morphology and the AIS regulate this compartmentalization but act on distinct time scales, with the AIS having a more pronounced effect on fast exchanges. Our results thus suggest that the rate of protein accumulation in the soma may impact to what extent and over which timescales freely moving molecules can be segregated from the axon. This in turn has important implications for our understanding of compartment-specific signaling in neurons.
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Affiliation(s)
- LaShae Nicholson
- Department of Neurology, Yale University School of Medicine, New Haven, CT, United States
| | - Nicolas Gervasi
- Center for Interdisciplinary Research in Biology, College de France, Inserm U1050, CNRS UMR 7241, Labex Memolife, Paris, France
| | - Thibault Falières
- Institute for Psychiatry and Neurosciences of Paris, Inserm UMR 1266, University of Paris, 4 GHU PARIS Psychiatrie & Neurosciences, Paris, France
| | - Adrien Leroy
- Center for Interdisciplinary Research in Biology, College de France, Inserm U1050, CNRS UMR 7241, Labex Memolife, Paris, France
| | - Dorian Miremont
- Institute for Psychiatry and Neurosciences of Paris, Inserm UMR 1266, University of Paris, 4 GHU PARIS Psychiatrie & Neurosciences, Paris, France
| | - Diana Zala
- Institute for Psychiatry and Neurosciences of Paris, Inserm UMR 1266, University of Paris, 4 GHU PARIS Psychiatrie & Neurosciences, Paris, France
| | - Cyril Hanus
- Institute for Psychiatry and Neurosciences of Paris, Inserm UMR 1266, University of Paris, 4 GHU PARIS Psychiatrie & Neurosciences, Paris, France
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26
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Abouelezz A, Stefen H, Segerstråle M, Micinski D, Minkeviciene R, Lahti L, Hardeman EC, Gunning PW, Hoogenraad CC, Taira T, Fath T, Hotulainen P. Tropomyosin Tpm3.1 Is Required to Maintain the Structure and Function of the Axon Initial Segment. iScience 2020; 23:101053. [PMID: 32344377 PMCID: PMC7186529 DOI: 10.1016/j.isci.2020.101053] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Revised: 03/05/2020] [Accepted: 04/06/2020] [Indexed: 12/26/2022] Open
Abstract
The axon initial segment (AIS) is the site of action potential initiation and serves as a cargo transport filter and diffusion barrier that helps maintain neuronal polarity. The AIS actin cytoskeleton comprises actin patches and periodic sub-membranous actin rings. We demonstrate that tropomyosin isoform Tpm3.1 co-localizes with actin patches and that the inhibition of Tpm3.1 led to a reduction in the density of actin patches. Furthermore, Tpm3.1 showed a periodic distribution similar to sub-membranous actin rings but Tpm3.1 was only partially congruent with sub-membranous actin rings. Nevertheless, the inhibition of Tpm3.1 affected the uniformity of the periodicity of actin rings. Furthermore, Tpm3.1 inhibition led to reduced accumulation of AIS structural and functional proteins, disruption in sorting somatodendritic and axonal proteins, and a reduction in firing frequency. These results show that Tpm3.1 is necessary for the structural and functional maintenance of the AIS. Tropomyosin isoform Tpm3.1 co-localizes with the actin cytoskeleton in the AIS Tpm3.1 inhibition led to a less organized AIS actin cytoskeleton Perturbation of Tpm3.1 function reduced the accumulation of AIS scaffolding proteins Tpm3.1 inhibition compromised cargo sorting and rapidly reduced firing frequency
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Affiliation(s)
- Amr Abouelezz
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki 2U, Tukholmankatu 8, 00290 Helsinki, Finland; HiLIFE - Neuroscience Center, University of Helsinki, Haartmaninkatu 8, 00290 Helsinki, Finland
| | - Holly Stefen
- School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia
| | - Mikael Segerstråle
- Faculty of Biological and Environmental Sciences, University of Helsinki, Viikinkaari 1, 00790 Helsinki, Finland
| | - David Micinski
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki 2U, Tukholmankatu 8, 00290 Helsinki, Finland
| | - Rimante Minkeviciene
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki 2U, Tukholmankatu 8, 00290 Helsinki, Finland
| | - Lauri Lahti
- Department of Computer Science, Aalto University School of Science, Espoo, Finland
| | - Edna C Hardeman
- School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia
| | - Peter W Gunning
- School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia
| | - Casper C Hoogenraad
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584CH Utrecht, the Netherlands
| | - Tomi Taira
- Faculty of Veterinary Medicine, University of Helsinki, Agnes Sjöbergin katu 2, 00790 Helsinki, Finland
| | - Thomas Fath
- School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia; Dementia Research Centre, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW 2109, Australia
| | - Pirta Hotulainen
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki 2U, Tukholmankatu 8, 00290 Helsinki, Finland.
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27
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Scherer J, Hogue IB, Yaffe ZA, Tanneti NS, Winer BY, Vershinin M, Enquist LW. A kinesin-3 recruitment complex facilitates axonal sorting of enveloped alpha herpesvirus capsids. PLoS Pathog 2020; 16:e1007985. [PMID: 31995633 PMCID: PMC7010296 DOI: 10.1371/journal.ppat.1007985] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 02/10/2020] [Accepted: 12/15/2019] [Indexed: 12/13/2022] Open
Abstract
Axonal sorting, the controlled passage of specific cargoes from the cell soma into the axon compartment, is critical for establishing and maintaining the polarity of mature neurons. To delineate axonal sorting events, we took advantage of two neuroinvasive alpha-herpesviruses. Human herpes simplex virus 1 (HSV-1) and pseudorabies virus of swine (PRV; suid herpesvirus 1) have evolved as robust cargo of axonal sorting and transport mechanisms. For efficient axonal sorting and subsequent egress from axons and presynaptic termini, progeny capsids depend on three viral membrane proteins (Us7 (gI), Us8 (gE), and Us9), which engage axon-directed kinesin motors. We present evidence that Us7-9 of the veterinary pathogen pseudorabies virus (PRV) form a tripartite complex to recruit Kif1a, a kinesin-3 motor. Based on multi-channel super-resolution and live TIRF microscopy, complex formation and motor recruitment occurs at the trans-Golgi network. Subsequently, progeny virus particles enter axons as enveloped capsids in a transport vesicle. Artificial recruitment of Kif1a using a drug-inducible heterodimerization system was sufficient to rescue axonal sorting and anterograde spread of PRV mutants devoid of Us7-9. Importantly, biophysical evidence suggests that Us9 is able to increase the velocity of Kif1a, a previously undescribed phenomenon. In addition to elucidating mechanisms governing axonal sorting, our results provide further insight into the composition of neuronal transport systems used by alpha-herpesviruses, which will be critical for both inhibiting the spread of infection and the safety of herpesvirus-based oncolytic therapies. Alpha-herpesviruses represent a group of large, enveloped DNA viruses that are capable to establish a quiescent (also called latent) but reactivatable form of infection in the peripheral nervous system of their hosts. Following reactivation of latent genomes, virus progeny is formed in the soma of neuronal cells and depend on sorting into the axon for anterograde spread of infection to mucosal sites and potentially new host. We studied two alpha-herpesviruses (the veterinary pathogen pseudorabies virus (PRV) and human herpes simplex virus 1 (HSV-1)) and found viral membrane proteins Us7, Us8, and Us9 form a complex, which is able to recruit kinsin-3 motors. Motor recruitment facilitates axonal sorting and subsequent transport to distal egress sites. Complex formation occurs at the trans-Golgi network and mediates efficiency of axonal sorting and motility characteristics of egressing capsids. We also used an artificial kinesin-3 recruitment system, which allows controlled induction of axonal sorting and transport of virus mutants lacking Us7, Us8, and Us9. Overall, these data contribute to our understanding of anterograde alpha-herpesvirus spread and kinesin-mediated sorting of vesicular axonal cargoes.
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Affiliation(s)
- Julian Scherer
- Department of Molecular Biology and Princeton Neuroscience Institute, Princeton University, Princeton, New Jersey, United States of America
| | - Ian B. Hogue
- Center for Immunotherapy, Vaccines, and Virotherapy, Biodesign Institute & School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
| | - Zachary A. Yaffe
- University of Washington, Seattle, Washington, United States of America
| | - Nikhila S. Tanneti
- Department of Molecular Biology and Princeton Neuroscience Institute, Princeton University, Princeton, New Jersey, United States of America
| | - Benjamin Y. Winer
- Department of Molecular Biology and Princeton Neuroscience Institute, Princeton University, Princeton, New Jersey, United States of America
| | - Michael Vershinin
- Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah, United States of America
| | - Lynn W. Enquist
- Department of Molecular Biology and Princeton Neuroscience Institute, Princeton University, Princeton, New Jersey, United States of America
- * E-mail:
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28
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Iijima T, Yoshimura T. A Perspective on the Role of Dynamic Alternative RNA Splicing in the Development, Specification, and Function of Axon Initial Segment. Front Mol Neurosci 2019; 12:295. [PMID: 31866821 PMCID: PMC6906172 DOI: 10.3389/fnmol.2019.00295] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Accepted: 11/15/2019] [Indexed: 11/13/2022] Open
Abstract
Alternative splicing is a powerful mechanism for molecular and functional diversification. In neurons, alternative splicing extensively controls various developmental steps as well as the plasticity and remodeling of neuronal activity in the adult brain. The axon initial segment (AIS) is the specialized compartment of proximal axons that initiates action potential (AP). At the AIS, the ion channels and cell adhesion molecules (CAMs) required for AP initiation are densely clustered via the scaffolding and cytoskeletal proteins. Notably, recent studies have elucidated that multiple AIS proteins are controlled by extensive alternative splicing in developing and adult brains. Here, we argue the potential role of dynamic regulation of alternative splicing in the development, specification, and functions of the AIS. In particular, we propose the novel concept that alternative splicing potentially modulates the structural and functional plasticity at the AIS.
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Affiliation(s)
- Takatoshi Iijima
- Department of Molecular Life Science, Division of Basic Medical Science and Molecular Medicine, School of Medicine, Tokai University, Isehara, Japan
| | - Takeshi Yoshimura
- Department of Child Development and Molecular Brain Science, United Graduate School of Child Development, Osaka University, Suita, Japan
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29
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Stucchi R, Plucińska G, Hummel JJA, Zahavi EE, Guerra San Juan I, Klykov O, Scheltema RA, Altelaar AFM, Hoogenraad CC. Regulation of KIF1A-Driven Dense Core Vesicle Transport: Ca 2+/CaM Controls DCV Binding and Liprin-α/TANC2 Recruits DCVs to Postsynaptic Sites. Cell Rep 2019; 24:685-700. [PMID: 30021165 PMCID: PMC6077247 DOI: 10.1016/j.celrep.2018.06.071] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 05/13/2018] [Accepted: 06/15/2018] [Indexed: 01/21/2023] Open
Abstract
Tight regulation of neuronal transport allows for cargo binding and release at specific cellular locations. The mechanisms by which motor proteins are loaded on vesicles and how cargoes are captured at appropriate sites remain unclear. To better understand how KIF1A-driven dense core vesicle (DCV) transport is regulated, we identified the KIF1A interactome and focused on three binding partners, the calcium binding protein calmodulin (CaM) and two synaptic scaffolding proteins: liprin-α and TANC2. We showed that calcium, acting via CaM, enhances KIF1A binding to DCVs and increases vesicle motility. In contrast, liprin-α and TANC2 are not part of the KIF1A-cargo complex but capture DCVs at dendritic spines. Furthermore, we found that specific TANC2 mutations—reported in patients with different neuropsychiatric disorders—abolish the interaction with KIF1A. We propose a model in which Ca2+/CaM regulates cargo binding and liprin-α and TANC2 recruit KIF1A-transported vesicles. KIF1A directly interacts with CaM and with the scaffolds liprin-α and TANC2 KIF1A is regulated by a Ca2+/CaM-dependent mechanism, which allows for DCV loading Liprin-α and TANC2 are static PSD proteins that are not part of the KIF1A-DCV complex KIF1A-driven DCVs are recruited to dendritic spines by liprin-α and TANC2
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Affiliation(s)
- Riccardo Stucchi
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands; Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands; Netherlands Proteomics Centre, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Gabriela Plucińska
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Jessica J A Hummel
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Eitan E Zahavi
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Irune Guerra San Juan
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Oleg Klykov
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands; Netherlands Proteomics Centre, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Richard A Scheltema
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands; Netherlands Proteomics Centre, Padualaan 8, 3584 Utrecht, the Netherlands
| | - A F Maarten Altelaar
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands; Netherlands Proteomics Centre, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Casper C Hoogenraad
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands.
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30
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Kuwako KI, Okano H. The LKB1-SIK Pathway Controls Dendrite Self-Avoidance in Purkinje Cells. Cell Rep 2019; 24:2808-2818.e4. [PMID: 30208308 DOI: 10.1016/j.celrep.2018.08.029] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 06/12/2018] [Accepted: 08/08/2018] [Indexed: 02/08/2023] Open
Abstract
Strictly controlled dendrite patterning underlies precise neural connection. Dendrite self-avoidance is a crucial system preventing self-crossing and clumping of dendrites. Although many cell-surface molecules that regulate self-avoidance have been identified, the signaling pathway that orchestrates it remains poorly understood, particularly in mammals. Here, we demonstrate that the LKB1-SIK kinase pathway plays a pivotal role in the self-avoidance of Purkinje cell (PC) dendrites by ensuring dendritic localization of Robo2, a regulator of self-avoidance. LKB1 is activated in developing PCs, and PC-specific deletion of LKB1 severely disrupts the self-avoidance of PC dendrites without affecting gross morphology. SIK1 and SIK2, downstream kinases of LKB1, mediate LKB1-dependent dendrite self-avoidance. Furthermore, loss of LKB1 leads to significantly decreased Robo2 levels in the dendrite but not in the cell body. Finally, restoration of dendritic Robo2 level via overexpression largely rescues the self-avoidance defect in LKB1-deficient PCs. These findings reveal an LKB1-pathway-mediated developmental program that establishes dendrite self-avoidance.
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Affiliation(s)
- Ken-Ichiro Kuwako
- Department of Physiology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
| | - Hideyuki Okano
- Department of Physiology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
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31
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Khalaf B, Roncador A, Pischedda F, Casini A, Thomas S, Piccoli G, Kiebler M, Macchi P. Ankyrin-G induces nucleoporin Nup358 to associate with the axon initial segment of neurons. J Cell Sci 2019; 132:jcs.222802. [PMID: 31427429 DOI: 10.1242/jcs.222802] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 08/12/2019] [Indexed: 12/11/2022] Open
Abstract
Nup358 (also known as RanBP2) is a member of the large nucleoporin family that constitutes the nuclear pore complex. Depending on the cell type and the physiological state, Nup358 interacts with specific partner proteins and influences distinct mechanisms independent of its role in nucleocytoplasmic transport. Here, we provide evidence that Nup358 associates selectively with the axon initial segment (AIS) of mature neurons, mediated by the AIS scaffold protein ankyrin-G (AnkG, also known as Ank3). The N-terminus of Nup358 is demonstrated to be sufficient for its localization at the AIS. Further, we show that Nup358 is expressed as two isoforms, one full-length and another shorter form of Nup358. These isoforms differ in their subcellular distribution in neurons and expression level during neuronal development. Overall, the present study highlights an unprecedented localization of Nup358 within the AIS and suggests its involvement in neuronal function.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Bouchra Khalaf
- Laboratory of Molecular and Cellular Neurobiology, Department of Cellular, Computational and Integrative Biology-CIBIO, University of Trento, 38123 Trento, Italy
| | - Alessandro Roncador
- Laboratory of Molecular and Cellular Neurobiology, Department of Cellular, Computational and Integrative Biology-CIBIO, University of Trento, 38123 Trento, Italy
| | - Francesca Pischedda
- Dulbecco Telethon Laboratory of Biology of Synapses, Department of Cellular, Computational and Integrative Biology-CIBIO, University of Trento, 38123 Trento, Italy
| | - Antonio Casini
- Laboratory of Molecular Virology, Department of Cellular, Computational and Integrative Biology-CIBIO, University of Trento, 38123 Trento, Italy
| | - Sabine Thomas
- Department for Cell Biology, Biomedical Center, Medical Faculty, Ludwig-Maximilian University of Munich, Großhaderner Straße 9, 82152 Planegg-Martinsried, Germany
| | - Giovanni Piccoli
- Dulbecco Telethon Laboratory of Biology of Synapses, Department of Cellular, Computational and Integrative Biology-CIBIO, University of Trento, 38123 Trento, Italy
| | - Michael Kiebler
- Department for Cell Biology, Biomedical Center, Medical Faculty, Ludwig-Maximilian University of Munich, Großhaderner Straße 9, 82152 Planegg-Martinsried, Germany
| | - Paolo Macchi
- Laboratory of Molecular and Cellular Neurobiology, Department of Cellular, Computational and Integrative Biology-CIBIO, University of Trento, 38123 Trento, Italy
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Liu CH, Rasband MN. Axonal Spectrins: Nanoscale Organization, Functional Domains and Spectrinopathies. Front Cell Neurosci 2019; 13:234. [PMID: 31191255 PMCID: PMC6546920 DOI: 10.3389/fncel.2019.00234] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 05/09/2019] [Indexed: 11/13/2022] Open
Abstract
Spectrin cytoskeletons are found in all metazoan cells, and their physical interactions between actin and ankyrins establish a meshwork that provides cellular structural integrity. With advanced super-resolution microscopy, the intricate spatial organization and associated functional properties of these cytoskeletons can now be analyzed with unprecedented clarity. Long neuronal processes like peripheral sensory and motor axons may be subject to intense mechanical forces including bending, stretching, and torsion. The spectrin-based cytoskeleton is essential to protect axons against these mechanical stresses. Additionally, spectrins are critical for the assembly and maintenance of axonal excitable domains including the axon initial segment and the nodes of Ranvier (NoR). These sites facilitate rapid and efficient action potential initiation and propagation in the nervous system. Recent studies revealed that pathogenic spectrin variants and diseases that protealyze and breakdown spectrins are associated with congenital neurological disorders and nervous system injury. Here, we review recent studies of spectrins in the nervous system and focus on their functions in axonal health and disease.
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Affiliation(s)
- Cheng-Hsin Liu
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, United States
| | - Matthew Neil Rasband
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX, United States.,Department of Neuroscience, Baylor College of Medicine, Houston, TX, United States
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Zhang Y, Tzingounis AV, Lykotrafitis G. Modeling of the axon plasma membrane structure and its effects on protein diffusion. PLoS Comput Biol 2019; 15:e1007003. [PMID: 31048841 PMCID: PMC6497228 DOI: 10.1371/journal.pcbi.1007003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Accepted: 04/03/2019] [Indexed: 11/30/2022] Open
Abstract
The axon plasma membrane consists of the membrane skeleton, which comprises ring-like actin filaments connected to each other by spectrin tetramers, and the lipid bilayer, which is tethered to the skeleton via, at least, ankyrin. Currently it is unknown whether this unique axon plasma membrane skeleton (APMS) sets the diffusion rules of lipids and proteins in the axon. To answer this question, we developed a coarse-grain molecular dynamics model for the axon that includes the APMS, the phospholipid bilayer, transmembrane proteins (TMPs), and integral monotopic proteins (IMPs) in both the inner and outer lipid layers. We first showed that actin rings limit the longitudinal diffusion of TMPs and the IMPs of the inner leaflet but not of the IMPs of the outer leaflet. To reconcile the experimental observations, which show restricted diffusion of IMPs of the outer leaflet, with our simulations, we conjectured the existence of actin-anchored proteins that form a fence which restricts the longitudinal diffusion of IMPs of the outer leaflet. We also showed that spectrin filaments could modify transverse diffusion of TMPs and IMPs of the inner leaflet, depending on the strength of the association between lipids and spectrin. For instance, in areas where spectrin binds to the lipid bilayer, spectrin filaments would restrict diffusion of proteins within the skeleton corrals. In contrast, in areas where spectrin and lipids are not associated, spectrin modifies the diffusion of TMPs and IMPs of the inner leaflet from normal to confined-hop diffusion. Overall, we showed that diffusion of axon plasma membrane proteins is deeply anisotropic, as longitudinal diffusion is of different type than transverse diffusion. Finally, we investigated how accumulation of TMPs affects diffusion of TMPs and IMPs of both the inner and outer leaflets by changing the density of TMPs. We showed that the APMS structure acts as a fence that restricts the diffusion of TMPs and IMPs of the inner leaflet within the membrane skeleton corrals. Our findings provide insight into how the axon skeleton acts as diffusion barrier and maintains neuronal polarity. The axon plasma membrane skeleton consists of repeated periodic actin ring-like structures along its length connected via spectrin tetramers and anchored to the lipid bilayer at least via ankyrin. However, it is currently unclear whether this structure controls diffusion of lipids and proteins in the axon. Here, we developed a coarse-grain molecular dynamics computational model for the axon plasma membrane that comprises minimal representations for the APMS and the lipid bilayer. In a departure from current models, we found that actin rings limit diffusion of proteins only in the inner membrane leaflet. Then, we showed that actin anchored proteins likely act as “fences” confining diffusion of proteins in the outer leaflet. Our simulations, unexpectedly, also revealed that spectrin filaments could impede transverse diffusion in the inner leaflet of the axon and in some conditions modify diffusion from normal to abnormal. We predicted that diffusion of axon plasma membrane proteins is anisotropic as longitudinal diffusion is of different type than transverse (azimuthal) diffusion. We conclude that the periodic structure of the axon plays a critical role in controlling diffusion of proteins and lipids in the axon plasma membrane.
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Affiliation(s)
- Yihao Zhang
- Department of Mechanical Engineering, University of Connecticut, Storrs, CT, United States of America
| | - Anastasios V. Tzingounis
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, United States of America
| | - George Lykotrafitis
- Department of Mechanical Engineering, University of Connecticut, Storrs, CT, United States of America
- Department of Biomedical Engineering, University of Connecticut, Storrs, CT, United States of America
- * E-mail:
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34
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Elavl3 regulates neuronal polarity through the alternative splicing of an embryo-specific exon in AnkyrinG. Neurosci Res 2018; 135:13-20. [DOI: 10.1016/j.neures.2018.03.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 03/13/2018] [Accepted: 03/30/2018] [Indexed: 12/12/2022]
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35
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Smith KR, Penzes P. Ankyrins: Roles in synaptic biology and pathology. Mol Cell Neurosci 2018; 91:131-139. [PMID: 29730177 DOI: 10.1016/j.mcn.2018.04.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 04/23/2018] [Accepted: 04/24/2018] [Indexed: 12/27/2022] Open
Abstract
Ankyrins are broadly expressed adaptors that organize diverse membrane proteins into specialized domains and link them to the sub-membranous cytoskeleton. In neurons, ankyrins are known to have essential roles in organizing the axon initial segment and nodes of Ranvier. However, recent studies have revealed novel functions for ankyrins at synapses, where they organize and stabilize neurotransmitter receptors, modulate dendritic spine morphology and control adhesion to the presynaptic site. Ankyrin genes have also been highly associated with a range of neurodevelopmental and psychiatric diseases, including bipolar disorder, schizophrenia and autism, which all demonstrate overlap in their genetics, mechanisms and phenotypes. This review discusses the novel synaptic functions of ankyrin proteins in neurons, and places these exciting findings in the context of ANK genes as key neuropsychiatric disorder risk-factors.
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Affiliation(s)
- Katharine R Smith
- Department of Pharmacology, University of Colorado Denver, 12800 East 19th Avenue, Aurora, CO 80045, USA.
| | - Peter Penzes
- Department of Physiology, Northwestern University Feinberg School of Medicine, 303 E. Chicago Avenue, Chicago, IL 60611, USA; Psychiatry and Behavioral Sciences, Northwestern University Feinberg School of Medicine, 303 E. Chicago Avenue, Chicago, IL 60611, USA.
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36
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Gumy LF, Hoogenraad CC. Local mechanisms regulating selective cargo entry and long-range trafficking in axons. Curr Opin Neurobiol 2018; 51:23-28. [PMID: 29510294 DOI: 10.1016/j.conb.2018.02.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 02/14/2018] [Indexed: 02/02/2023]
Abstract
The polarized long-distance transport of neuronal cargoes depends on the presence of functional and structural axonal subcompartments. Given the heterogeneity of neuronal cargoes, selective sorting and entry occurs in the proximal axon where multiple subcellular specializations such as the axon initial segment, the pre-axonal exclusion zone, the MAP2 pre-axonal filtering zone and the Tau diffusion barrier provide different levels of regulation. Cargoes allowed to pass through the proximal axon spread into the more distal parts. Recent findings show that diverse cargo distributions along the axon depend on the compartmentalized organization of the cytoskeleton and the local regulation of multiple motor proteins by microtubule associated proteins. In this review, we focus on the local mechanisms that control cargo motility and discuss how they play a role in the overall circulation of axonal cargoes.
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Affiliation(s)
- Laura F Gumy
- Department of Anatomy, University of Otago, Dunedin, New Zealand.
| | - Casper C Hoogenraad
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Utrecht, The Netherlands.
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37
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Tortosa E, Hoogenraad CC. Polarized trafficking: the palmitoylation cycle distributes cytoplasmic proteins to distinct neuronal compartments. Curr Opin Cell Biol 2018; 50:64-71. [DOI: 10.1016/j.ceb.2018.02.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Revised: 01/24/2018] [Accepted: 02/07/2018] [Indexed: 12/28/2022]
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38
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The Axon Initial Segment: An Updated Viewpoint. J Neurosci 2018; 38:2135-2145. [PMID: 29378864 DOI: 10.1523/jneurosci.1922-17.2018] [Citation(s) in RCA: 164] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2017] [Revised: 01/20/2018] [Accepted: 01/25/2018] [Indexed: 12/20/2022] Open
Abstract
At the base of axons sits a unique compartment called the axon initial segment (AIS). The AIS generates and shapes the action potential before it is propagated along the axon. Neuronal excitability thus depends crucially on the AIS composition and position, and these adapt to developmental and physiological conditions. The AIS also demarcates the boundary between the somatodendritic and axonal compartments. Recent studies have brought insights into the molecular architecture of the AIS and how it regulates protein trafficking. This Viewpoints article summarizes current knowledge about the AIS and highlights future challenges in understanding this key actor of neuronal physiology.
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39
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Tas RP, Chazeau A, Cloin BMC, Lambers MLA, Hoogenraad CC, Kapitein LC. Differentiation between Oppositely Oriented Microtubules Controls Polarized Neuronal Transport. Neuron 2017; 96:1264-1271.e5. [PMID: 29198755 PMCID: PMC5746200 DOI: 10.1016/j.neuron.2017.11.018] [Citation(s) in RCA: 173] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 10/11/2017] [Accepted: 11/08/2017] [Indexed: 12/21/2022]
Abstract
Microtubules are essential for polarized transport in neurons, but how their organization guides motor proteins to axons or dendrites is unclear. Because different motors recognize distinct microtubule properties, we used optical nanoscopy to examine the relationship between microtubule orientations, stability, and modifications. Nanometric tracking of motors to super-resolve microtubules and determine their polarity revealed that in dendrites, stable and acetylated microtubules are mostly oriented minus-end out, while dynamic and tyrosinated microtubules are oriented oppositely. In addition, microtubules with similar orientations and modifications form bundles that bias transport. Importantly, because the plus-end-directed Kinesin-1 selectively interacts with acetylated microtubules, this organization guides this motor out of dendrites and into axons. In contrast, Kinesin-3 prefers tyrosinated microtubules and can enter both axons and dendrites. This separation of distinct microtubule subsets into oppositely oriented bundles constitutes a key architectural principle of the neuronal microtubule cytoskeleton that enables polarized sorting by different motor proteins. Motor-based nanoscopy enables direct observation of microtubule (MT) polarity In neurons, MTs organize into polarized bundles that locally bias transport In dendrites, bundles of opposite orientation differ in stability and composition Dendritic MTs bias Kinesin-1 transport toward the soma, ensuring axon selectivity
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Affiliation(s)
- Roderick P Tas
- Division of Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Anaël Chazeau
- Division of Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Bas M C Cloin
- Division of Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Maaike L A Lambers
- Division of Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Casper C Hoogenraad
- Division of Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands
| | - Lukas C Kapitein
- Division of Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands.
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40
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M-current inhibition rapidly induces a unique CK2-dependent plasticity of the axon initial segment. Proc Natl Acad Sci U S A 2017; 114:E10234-E10243. [PMID: 29109270 DOI: 10.1073/pnas.1708700114] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Alterations in synaptic input, persisting for hours to days, elicit homeostatic plastic changes in the axon initial segment (AIS), which is pivotal for spike generation. Here, in hippocampal pyramidal neurons of both primary cultures and slices, we triggered a unique form of AIS plasticity by selectively targeting M-type K+ channels, which predominantly localize to the AIS and are essential for tuning neuronal excitability. While acute M-current inhibition via cholinergic activation or direct channel block made neurons more excitable, minutes to hours of sustained M-current depression resulted in a gradual reduction in intrinsic excitability. Dual soma-axon patch-clamp recordings combined with axonal Na+ imaging and immunocytochemistry revealed that these compensatory alterations were associated with a distal shift of the spike trigger zone and distal relocation of FGF14, Na+, and Kv7 channels but not ankyrin G. The concomitant distal redistribution of FGF14 together with Nav and Kv7 segments along the AIS suggests that these channels relocate as a structural and functional unit. These fast homeostatic changes were independent of l-type Ca2+ channel activity but were contingent on the crucial AIS protein, protein kinase CK2. Using compartmental simulations, we examined the effects of varying the AIS position relative to the soma and found that AIS distal relocation of both Nav and Kv7 channels elicited a decrease in neuronal excitability. Thus, alterations in M-channel activity rapidly trigger unique AIS plasticity to stabilize network excitability.
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41
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42
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Nirschl JJ, Ghiretti AE, Holzbaur ELF. The impact of cytoskeletal organization on the local regulation of neuronal transport. Nat Rev Neurosci 2017; 18:585-597. [PMID: 28855741 DOI: 10.1038/nrn.2017.100] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Neurons are akin to modern cities in that both are dependent on robust transport mechanisms. Like the best mass transit systems, trafficking in neurons must be tailored to respond to local requirements. Neurons depend on both high-speed, long-distance transport and localized dynamics to correctly deliver cargoes and to tune synaptic responses. Here, we focus on the mechanisms that provide localized regulation of the transport machinery, including the cytoskeleton and molecular motors, to yield compartment-specific trafficking in the axon initial segment, axon terminal, dendrites and spines. The synthesis of these mechanisms provides a sophisticated and responsive transit system for the cell.
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Affiliation(s)
- Jeffrey J Nirschl
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, 638A Clinical Research Building, 415 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA
| | - Amy E Ghiretti
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, 638A Clinical Research Building, 415 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA
| | - Erika L F Holzbaur
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, 638A Clinical Research Building, 415 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA
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43
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Gumy LF, Katrukha EA, Grigoriev I, Jaarsma D, Kapitein LC, Akhmanova A, Hoogenraad CC. MAP2 Defines a Pre-axonal Filtering Zone to Regulate KIF1- versus KIF5-Dependent Cargo Transport in Sensory Neurons. Neuron 2017; 94:347-362.e7. [PMID: 28426968 DOI: 10.1016/j.neuron.2017.03.046] [Citation(s) in RCA: 109] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2016] [Revised: 01/17/2017] [Accepted: 03/29/2017] [Indexed: 11/15/2022]
Abstract
Polarized cargo transport is essential for neuronal function. However, the minimal basic components required for selective cargo sorting and distribution in neurons remain elusive. We found that in sensory neurons the axon initial segment is largely absent and that microtubule-associated protein 2 (MAP2) defines the cargo-filtering zone in the proximal axon. Here, MAP2 directs axonal cargo entry by coordinating the activities of molecular motors. We show that distinct kinesins differentially regulate cargo velocity: kinesin-3 drives fast axonal cargo trafficking, while kinesin-1 slows down axonal cargo transport. MAP2 inhibits "slow" kinesin-1 motor activity and allows kinesin-3 to drive robust cargo transport from the soma into the axon. In the distal axon, the inhibitory action of MAP2 decreases, leading to regained kinesin-1 activity and vesicle distribution. We propose that selective axonal cargo trafficking requires the MAP2-defined pre-axonal filtering zone and the ability of cargos to switch between distinct kinesin motor activities.
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Affiliation(s)
- Laura F Gumy
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Eugene A Katrukha
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Ilya Grigoriev
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Dick Jaarsma
- Department of Neuroscience, Erasmus Medical Center, 3015 CE Rotterdam, the Netherlands
| | - Lukas C Kapitein
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Anna Akhmanova
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Casper C Hoogenraad
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands.
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44
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Aging Does Not Affect Axon Initial Segment Structure and Somatic Localization of Tau Protein in Hippocampal Neurons of Fischer 344 Rats. eNeuro 2017; 4:eN-NRS-0043-17. [PMID: 28785724 PMCID: PMC5520750 DOI: 10.1523/eneuro.0043-17.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 06/13/2017] [Accepted: 06/29/2017] [Indexed: 11/21/2022] Open
Abstract
Little is known about the specific contributions of aging to the neuron dysfunction and death in Alzheimer’s disease (AD). AD is characterized by the pathological accumulation of abnormal tau (a microtubule-associated protein), and the mislocalization of tau from the axon to the somatodendritic compartment is thought to play an important role in disease pathogenesis. The axon initial segment (AIS) is thought to play a role in the selective localization of tau in the axonal compartment. Thus, disruption in the AIS barrier may allow tau to diffuse freely back into the somatodendritic compartment and potentially lead to neurotoxicity. Here, we analyzed AISs using stereological methods and protein immunoblotting, and the localization of tau was assessed with immunofluorescence optical density measurements and protein immunoblotting. None of the outcome measurements assessed, including AIS structure, AIS protein levels, the distribution of tau in neurons of the hippocampus (HP), and total tau or phospho-tau protein levels were different in young, middle-, and old-age Fischer 344 rats. The outcome measurements assessed, including AIS structure, AIS protein levels, the distribution of tau in neurons of the HP, and total tau or phospho-tau protein levels were not different in young, middle-, and old-age Fischer 344 rats, with the exception of a small reduction in AIS volume and diameter in the CA2 region of aged animals. These data suggest that aging largely has no effect on these properties of the AIS or tau distribution, and thus, may not contribute directly to tau mislocalization.
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45
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Nelson AD, Jenkins PM. Axonal Membranes and Their Domains: Assembly and Function of the Axon Initial Segment and Node of Ranvier. Front Cell Neurosci 2017; 11:136. [PMID: 28536506 PMCID: PMC5422562 DOI: 10.3389/fncel.2017.00136] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 04/21/2017] [Indexed: 12/19/2022] Open
Abstract
Neurons are highly specialized cells of the nervous system that receive, process and transmit electrical signals critical for normal brain function. Here, we review the intricate organization of axonal membrane domains that facilitate rapid action potential conduction underlying communication between complex neuronal circuits. Two critical excitable domains of vertebrate axons are the axon initial segment (AIS) and the nodes of Ranvier, which are characterized by the high concentrations of voltage-gated ion channels, cell adhesion molecules and specialized cytoskeletal networks. The AIS is located at the proximal region of the axon and serves as the site of action potential initiation, while nodes of Ranvier, gaps between adjacent myelin sheaths, allow rapid propagation of the action potential through saltatory conduction. The AIS and nodes of Ranvier are assembled by ankyrins, spectrins and their associated binding partners through the clustering of membrane proteins and connection to the underlying cytoskeleton network. Although the AIS and nodes of Ranvier share similar protein composition, their mechanisms of assembly are strikingly different. Here we will cover the mechanisms of formation and maintenance of these axonal excitable membrane domains, specifically highlighting the similarities and differences between them. We will also discuss recent advances in super resolution fluorescence imaging which have elucidated the arrangement of the submembranous axonal cytoskeleton revealing a surprising structural organization necessary to maintain axonal organization and function. Finally, human mutations in axonal domain components have been associated with a growing number of neurological disorders including severe cognitive dysfunction, epilepsy, autism, neurodegenerative diseases and psychiatric disorders. Overall, this review highlights the assembly, maintenance and function of axonal excitable domains, particularly the AIS and nodes of Ranvier, and how abnormalities in these processes may contribute to disease.
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Affiliation(s)
- Andrew D Nelson
- Department of Pharmacology, University of Michigan Medical SchoolAnn Arbor, MI, USA
| | - Paul M Jenkins
- Department of Pharmacology, University of Michigan Medical SchoolAnn Arbor, MI, USA.,Department of Psychiatry, University of Michigan Medical SchoolAnn Arbor, MI, USA
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46
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Cornejo VH, Luarte A, Couve A. Global and local mechanisms sustain axonal proteostasis of transmembrane proteins. Traffic 2017; 18:255-266. [PMID: 28220989 DOI: 10.1111/tra.12472] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 02/02/2017] [Accepted: 02/16/2017] [Indexed: 12/22/2022]
Abstract
The control of neuronal protein homeostasis or proteostasis is tightly regulated both spatially and temporally, assuring accurate and integrated responses to external or intrinsic stimuli. Local or autonomous responses in dendritic and axonal compartments are crucial to sustain function during development, physiology and in response to damage or disease. Axons are responsible for generating and propagating electrical impulses in neurons, and the establishment and maintenance of their molecular composition are subject to extreme constraints exerted by length and size. Proteins that require the secretory pathway, such as receptors, transporters, ion channels or cell adhesion molecules, are fundamental for axonal function, but whether axons regulate their abundance autonomously and how they achieve this is not clear. Evidence supports the role of three complementary mechanisms to maintain proteostasis of these axonal proteins, namely vesicular transport, local translation and trafficking and transfer from supporting cells. Here, we review these mechanisms, their molecular machineries and contribution to neuronal function. We also examine the signaling pathways involved in local translation and their role during development and nerve injury. We discuss the relative contributions of a transport-controlled proteome directed by the soma (global regulation) versus a local-controlled proteome based on local translation or cell transfer (local regulation).
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Affiliation(s)
- Víctor Hugo Cornejo
- Program of Physiology and Biophysics, ICBM, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Biomedical Neuroscience Institute, Universidad de Chile, Santiago, Chile
| | - Alejandro Luarte
- Program of Physiology and Biophysics, ICBM, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Biomedical Neuroscience Institute, Universidad de Chile, Santiago, Chile
| | - Andrés Couve
- Program of Physiology and Biophysics, ICBM, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Biomedical Neuroscience Institute, Universidad de Chile, Santiago, Chile
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47
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Satake T, Yamashita K, Hayashi K, Miyatake S, Tamura-Nakano M, Doi H, Furuta Y, Shioi G, Miura E, Takeo YH, Yoshida K, Yahikozawa H, Matsumoto N, Yuzaki M, Suzuki A. MTCL1 plays an essential role in maintaining Purkinje neuron axon initial segment. EMBO J 2017; 36:1227-1242. [PMID: 28283581 DOI: 10.15252/embj.201695630] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 02/07/2017] [Accepted: 02/10/2017] [Indexed: 11/09/2022] Open
Abstract
The axon initial segment (AIS) is a specialized domain essential for neuronal function, the formation of which begins with localization of an ankyrin-G (AnkG) scaffold. However, the mechanism directing and maintaining AnkG localization is largely unknown. In this study, we demonstrate that in vivo knockdown of microtubule cross-linking factor 1 (MTCL1) in cerebellar Purkinje cells causes loss of axonal polarity coupled with AnkG mislocalization. MTCL1 lacking MT-stabilizing activity failed to restore these defects, and stable MT bundles spanning the AIS were disorganized in knockdown cells. Interestingly, during early postnatal development, colocalization of MTCL1 with these stable MT bundles was observed prominently in the axon hillock and proximal axon. These results indicate that MTCL1-mediated formation of stable MT bundles is crucial for maintenance of AnkG localization. We also demonstrate that Mtcl1 gene disruption results in abnormal motor coordination with Purkinje cell degeneration, and provide evidence suggesting possible involvement of MTCL1 dysfunction in the pathogenesis of spinocerebellar ataxia.
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Affiliation(s)
- Tomoko Satake
- Molecular Cellular Biology Laboratory, Yokohama City University Graduate School of Medical Life Science, Tsurumi-ku Yokohama, Japan
| | - Kazunari Yamashita
- Department of Molecular Biology, Yokohama City University Graduate School of Medical Science, Kanazawa-ku Yokohama, Japan
| | - Kenji Hayashi
- Department of Molecular Biology, Yokohama City University Graduate School of Medical Science, Kanazawa-ku Yokohama, Japan
| | - Satoko Miyatake
- Department of Human Genetics, Yokohama City University Graduate School of Medical Science, Kanazawa-ku Yokohama, Japan
| | - Miwa Tamura-Nakano
- Communal Laboratory, Research Institute, National Center for Global Health and Medicine, Toyama Shinjuku-ku Tokyo, Japan
| | - Hiroshi Doi
- Department of Neurology, Yokohama City University Graduate School of Medical Science, Kanazawa-ku Yokohama, Japan
| | - Yasuhide Furuta
- Animal Resource Development Unit, RIKEN Center for Life Science Technologies, Chuou-ku Kobe, Japan.,Genetic Engineering Team, RIKEN Center for Life Science Technologies, Chuou-ku Kobe, Japan
| | - Go Shioi
- Genetic Engineering Team, RIKEN Center for Life Science Technologies, Chuou-ku Kobe, Japan
| | - Eriko Miura
- Department of Physiology, School of Medicine, Keio University, Shinjuku-ku Tokyo, Japan
| | - Yukari H Takeo
- Department of Physiology, School of Medicine, Keio University, Shinjuku-ku Tokyo, Japan
| | - Kunihiro Yoshida
- Division of Neurogenetics, Department of Brain Disease Research, Shinshu University School of Medicine, Asahi Matsumoto, Japan
| | | | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medical Science, Kanazawa-ku Yokohama, Japan
| | - Michisuke Yuzaki
- Department of Physiology, School of Medicine, Keio University, Shinjuku-ku Tokyo, Japan
| | - Atsushi Suzuki
- Molecular Cellular Biology Laboratory, Yokohama City University Graduate School of Medical Life Science, Tsurumi-ku Yokohama, Japan
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Jegla T, Nguyen MM, Feng C, Goetschius DJ, Luna E, van Rossum DB, Kamel B, Pisupati A, Milner ES, Rolls MM. Bilaterian Giant Ankyrins Have a Common Evolutionary Origin and Play a Conserved Role in Patterning the Axon Initial Segment. PLoS Genet 2016; 12:e1006457. [PMID: 27911898 PMCID: PMC5135030 DOI: 10.1371/journal.pgen.1006457] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 11/03/2016] [Indexed: 12/03/2022] Open
Abstract
In vertebrate neurons, the axon initial segment (AIS) is specialized for action potential initiation. It is organized by a giant 480 Kd variant of ankyrin G (AnkG) that serves as an anchor for ion channels and is required for a plasma membrane diffusion barrier that excludes somatodendritic proteins from the axon. An unusually long exon required to encode this 480Kd variant is thought to have been inserted only recently during vertebrate evolution, so the giant ankyrin-based AIS scaffold has been viewed as a vertebrate adaptation for fast, precise signaling. We re-examined AIS evolution through phylogenomic analysis of ankyrins and by testing the role of ankyrins in proximal axon organization in a model multipolar Drosophila neuron (ddaE). We find giant isoforms of ankyrin in all major bilaterian phyla, and present evidence in favor of a single common origin for giant ankyrins and the corresponding long exon in a bilaterian ancestor. This finding raises the question of whether giant ankyrin isoforms play a conserved role in AIS organization throughout the Bilateria. We examined this possibility by looking for conserved ankyrin-dependent AIS features in Drosophila ddaE neurons via live imaging. We found that ddaE neurons have an axonal diffusion barrier proximal to the cell body that requires a giant isoform of the neuronal ankyrin Ank2. Furthermore, the potassium channel shal concentrates in the proximal axon in an Ank2-dependent manner. Our results indicate that the giant ankyrin-based cytoskeleton of the AIS may have evolved prior to the radiation of extant bilaterian lineages, much earlier than previously thought. The axon initial segment (AIS) is currently thought to be a distinguishing feature of vertebrate neurons that adapts them for rapid, precise signaling. It serves as a hub for the regulation of neuronal excitability as the site of action potential initiation and also acts as the boundary between the highly-specialized axon and the rest of the cell. Here we show that the giant ankyrins that structurally organize the AIS, and were thought to be vertebrate-specific, instead have an ancient origin in a bilaterian ancestor. We further show the presence of a giant ankyrin-dependent AIS-like plasma membrane boundary between the axon and soma in a Drosophila sensory neuron. These results suggest that the cytoskeletal backbone for the AIS is not unique to vertebrates, but instead may be an evolutionarily conserved feature of bilaterian neurons.
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Affiliation(s)
- Timothy Jegla
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- * E-mail: (MMR); (TJ)
| | - Michelle M. Nguyen
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Chengye Feng
- Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Daniel J. Goetschius
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Esteban Luna
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Damian B. van Rossum
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Bishoy Kamel
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Aditya Pisupati
- Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Elliott S. Milner
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Melissa M. Rolls
- Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- * E-mail: (MMR); (TJ)
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49
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Soo Hoo L, Banna CD, Radeke CM, Sharma N, Albertolle ME, Low SH, Weimbs T, Vandenberg CA. The SNARE Protein Syntaxin 3 Confers Specificity for Polarized Axonal Trafficking in Neurons. PLoS One 2016; 11:e0163671. [PMID: 27662481 PMCID: PMC5035089 DOI: 10.1371/journal.pone.0163671] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 09/12/2016] [Indexed: 11/19/2022] Open
Abstract
Cell polarity and precise subcellular protein localization are pivotal to neuronal function. The SNARE machinery underlies intracellular membrane fusion events, but its role in neuronal polarity and selective protein targeting remain unclear. Here we report that syntaxin 3 is involved in orchestrating polarized trafficking in cultured rat hippocampal neurons. We show that syntaxin 3 localizes to the axonal plasma membrane, particularly to axonal tips, whereas syntaxin 4 localizes to the somatodendritic plasma membrane. Disruption of a conserved N-terminal targeting motif, which causes mislocalization of syntaxin 3, results in coincident mistargeting of the axonal cargos neuron-glia cell adhesion molecule (NgCAM) and neurexin, but not transferrin receptor, a somatodendritic cargo. Similarly, RNAi-mediated knockdown of endogenous syntaxin 3 leads to partial mistargeting of NgCAM, demonstrating that syntaxin 3 plays an important role in its targeting. Additionally, overexpression of syntaxin 3 results in increased axonal growth. Our findings suggest an important role for syntaxin 3 in maintaining neuronal polarity and in the critical task of selective trafficking of membrane protein to axons.
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Affiliation(s)
- Linda Soo Hoo
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Chris D. Banna
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Carolyn M. Radeke
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Nikunj Sharma
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Mary E. Albertolle
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Seng Hui Low
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Thomas Weimbs
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Carol A. Vandenberg
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
- Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
- * E-mail:
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50
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Talking to the neighbours: The molecular and physiological mechanisms of clustered synaptic plasticity. Neurosci Biobehav Rev 2016; 71:352-361. [PMID: 27659124 DOI: 10.1016/j.neubiorev.2016.09.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 09/15/2016] [Accepted: 09/18/2016] [Indexed: 11/23/2022]
Abstract
Synaptic connectivity forms the basis for neuronal communication and the storage of information. Experiences and learning of new abilities can drive remodelling of this connectivity and promotes the formation of spine clusters; dendritic segments with a higher spine density. Spines located within these segments are frequently co-activated, undergo different dynamics than synapses located outside of this dendritic compartment and have, in general, a longer lifetime. Several lines of evidence have shown that chemical synapses located close to each other share or compete for intracellular signalling molecules and structural resources. This sharing and competition directly influences spine dynamics. Spines can grow, shrink, increase or decrease the surface expression of receptors, channels and adhesion molecules or remain stable and unchanged over extended periods of time. Here we summarize recent discoveries and provide a closer look at spine clustering, dendritic segment-specific signalling and potential molecular mechanisms underlying associative and heterosynaptic plasticity.
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