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Badal KK, Zhao Y, Raveendra BL, Lozano-Villada S, Miller KE, Puthanveettil SV. PKA Activity-Driven Modulation of Bidirectional Long-Distance transport of Lysosomal vesicles During Synapse Maintenance. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.28.601272. [PMID: 38979384 PMCID: PMC11230415 DOI: 10.1101/2024.06.28.601272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
The bidirectional long-distance transport of organelles is crucial for cell body-synapse communication. However, the mechanisms by which this transport is modulated for synapse formation, maintenance, and plasticity are not fully understood. Here, we demonstrate through quantitative analyses that maintaining sensory neuron-motor neuron synapses in the Aplysia gill-siphon withdrawal reflex is linked to a sustained reduction in the retrograde transport of lysosomal vesicles in sensory neurons. Interestingly, while mitochondrial transport in the anterograde direction increases within 12 hours of synapse formation, the reduction in lysosomal vesicle retrograde transport appears three days after synapse formation. Moreover, we find that formation of new synapses during learning induced by neuromodulatory neurotransmitter serotonin further reduces lysosomal vesicle transport within 24 hours, whereas mitochondrial transport increases in the anterograde direction within one hour of exposure. Pharmacological inhibition of several signaling pathways pinpoints PKA as a key regulator of retrograde transport of lysosomal vesicles during synapse maintenance. These results demonstrate that synapse formation leads to organelle-specific and direction specific enduring changes in long-distance transport, offering insights into the mechanisms underlying synapse maintenance and plasticity.
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Affiliation(s)
- Kerriann. K. Badal
- Department of Neuroscience, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, 130 Scripps Way, Jupiter, FL 33458, USA
- Integrative Biology PhD Program, Charles E. Schmidt College of Science, Florida Atlantic University, Jupiter, FL 33458, USA
| | - Yibo. Zhao
- Department of Neuroscience, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Bindu L Raveendra
- Department of Neuroscience, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Sebastian Lozano-Villada
- Harriet L. Wilkes Honors College, Florida Atlantic University, 5353 Parkside Drive, Jupiter, FL 33458, USA
| | - Kyle. E. Miller
- Harriet L. Wilkes Honors College, Florida Atlantic University, 5353 Parkside Drive, Jupiter, FL 33458, USA
| | - Sathyanarayanan V. Puthanveettil
- Department of Neuroscience, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, 130 Scripps Way, Jupiter, FL 33458, USA
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AlAbdi L, Desbois M, Rusnac DV, Sulaiman RA, Rosenfeld JA, Lalani S, Murdock DR, Burrage LC, Billie Au PY, Towner S, Wilson WG, Wong L, Brunet T, Strobl-Wildemann G, Burton JE, Hoganson G, McWalter K, Begtrup A, Zarate YA, Christensen EL, Opperman KJ, Giles AC, Helaby R, Kania A, Zheng N, Grill B, Alkuraya FS. Loss-of-function variants in MYCBP2 cause neurobehavioural phenotypes and corpus callosum defects. Brain 2023; 146:1373-1387. [PMID: 36200388 PMCID: PMC10319777 DOI: 10.1093/brain/awac364] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Revised: 08/11/2022] [Accepted: 08/22/2022] [Indexed: 11/14/2022] Open
Abstract
The corpus callosum is a bundle of axon fibres that connects the two hemispheres of the brain. Neurodevelopmental disorders that feature dysgenesis of the corpus callosum as a core phenotype offer a valuable window into pathology derived from abnormal axon development. Here, we describe a cohort of eight patients with a neurodevelopmental disorder characterized by a range of deficits including corpus callosum abnormalities, developmental delay, intellectual disability, epilepsy and autistic features. Each patient harboured a distinct de novo variant in MYCBP2, a gene encoding an atypical really interesting new gene (RING) ubiquitin ligase and signalling hub with evolutionarily conserved functions in axon development. We used CRISPR/Cas9 gene editing to introduce disease-associated variants into conserved residues in the Caenorhabditis elegans MYCBP2 orthologue, RPM-1, and evaluated functional outcomes in vivo. Consistent with variable phenotypes in patients with MYCBP2 variants, C. elegans carrying the corresponding human mutations in rpm-1 displayed axonal and behavioural abnormalities including altered habituation. Furthermore, abnormal axonal accumulation of the autophagy marker LGG-1/LC3 occurred in variants that affect RPM-1 ubiquitin ligase activity. Functional genetic outcomes from anatomical, cell biological and behavioural readouts indicate that MYCBP2 variants are likely to result in loss of function. Collectively, our results from multiple human patients and CRISPR gene editing with an in vivo animal model support a direct link between MYCBP2 and a human neurodevelopmental spectrum disorder that we term, MYCBP2-related developmental delay with corpus callosum defects (MDCD).
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Affiliation(s)
- Lama AlAbdi
- Department of Zoology, College of Science, King Saud University, Riyadh 11362, Saudi Arabia
- Department of Translational Genomics, Center for Genomic Medicine, King Faisal Specialist Hospital and Research Center, Riyadh 11564, Saudi Arabia
| | - Muriel Desbois
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA 98101, USA
| | - Domniţa-Valeria Rusnac
- Department of Pharmacology, University of Washington School of Medicine, Seattle, WA 98195, USA
- Howard Hughes Medical Institute, Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Raashda A Sulaiman
- Department of Medical Genetics, King Faisal Specialist Hospital and Research Center, Riyadh 11564, Saudi Arabia
| | - Jill A Rosenfeld
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Seema Lalani
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - David R Murdock
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Lindsay C Burrage
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | | | - Ping Yee Billie Au
- Department of Medical Genetics, Alberta Children’s Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Shelley Towner
- Pediatric Genetics, University of Virginia, Charlottesville, VA 22903, USA
| | - William G Wilson
- Pediatric Genetics, University of Virginia, Charlottesville, VA 22903, USA
| | - Lawrence Wong
- Department of Genetics, Northern California Kaiser Permanente, Oakland, CA 94611, USA
| | - Theresa Brunet
- Institute of Human Genetics, Klinikum rechts der Isar, School of Medicine, Technical University of Munich, 81675 Munich, Germany
- Institute of Neurogenomics (ING), Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Neuherberg, Germany
| | | | - Jennifer E Burton
- Department of Genetics, University of Illinois College of Medicine at Peoria, Peoria, IL 61605, USA
| | - George Hoganson
- Department of Genetics, University of Illinois College of Medicine at Peoria, Peoria, IL 61605, USA
| | - Kirsty McWalter
- Genedx, Inc., 207 Perry Parkway, Gaithersburg, MD 20877, USA
| | - Amber Begtrup
- Genedx, Inc., 207 Perry Parkway, Gaithersburg, MD 20877, USA
| | - Yuri A Zarate
- Section of Genetics and Metabolism, Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR 72202, USA
| | - Elyse L Christensen
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA 98101, USA
| | - Karla J Opperman
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA 98101, USA
| | - Andrew C Giles
- Division of Medical Sciences, University of Northern British Columbia, Prince George, BC V2N 4Z9, Canada
| | - Rana Helaby
- Department of Translational Genomics, Center for Genomic Medicine, King Faisal Specialist Hospital and Research Center, Riyadh 11564, Saudi Arabia
| | - Artur Kania
- Institut de recherches cliniques de Montréal (IRCM), Montréal, QC H2W 1R7, Canada
- Integrated Program in Neuroscience, McGill University, Montréal, QC H3A 2B4, Canada
- Division of Experimental Medicine, McGill University, Montréal, QC H3A 2B2, Canada
- Department of Anatomy and Cell Biology, McGill University, Montréal, QC H3A 0C7, Canada
| | - Ning Zheng
- Department of Pharmacology, University of Washington School of Medicine, Seattle, WA 98195, USA
- Howard Hughes Medical Institute, Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Brock Grill
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA 98101, USA
- Department of Pharmacology, University of Washington School of Medicine, Seattle, WA 98195, USA
- Department of Pediatrics, University of Washington School of Medicine, Seattle, WA 98101, USA
| | - Fowzan S Alkuraya
- Department of Translational Genomics, Center for Genomic Medicine, King Faisal Specialist Hospital and Research Center, Riyadh 11564, Saudi Arabia
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Synaptic branch stability is mediated by non-enzymatic functions of MEC-17/αTAT1 and ATAT-2. Sci Rep 2022; 12:14003. [PMID: 35977998 PMCID: PMC9385713 DOI: 10.1038/s41598-022-18333-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 08/09/2022] [Indexed: 11/08/2022] Open
Abstract
Microtubules are fundamental elements of neuronal structure and function. They are dynamic structures formed from protofilament chains of α- and β-tubulin heterodimers. Acetylation of the lysine 40 (K40) residue of α-tubulin protects microtubules from mechanical stresses by imparting structural elasticity. The enzyme responsible for this acetylation event is MEC-17/αTAT1. Despite its functional importance, however, the consequences of altered MEC-17/αTAT1 levels on neuronal structure and function are incompletely defined. Here we demonstrate that overexpression or loss of MEC-17, or of its functional paralogue ATAT-2, causes a delay in synaptic branch extension, and defective synaptogenesis in the mechanosensory neurons of Caenorhabditis elegans. Strikingly, by adulthood, the synaptic branches in these animals are lost, while the main axon shaft remains mostly intact. We show that MEC-17 and ATAT-2 regulate the stability of the synaptic branches largely independently from their acetyltransferase domains. Genetic analyses reveals novel interactions between both mec-17 and atat-2 with the focal adhesion gene zyx-1/Zyxin, which has previously been implicated in actin remodelling. Together, our results reveal new, acetylation-independent roles for MEC-17 and ATAT-2 in the development and maintenance of neuronal architecture.
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Desbois M, Opperman KJ, Amezquita J, Gaglio G, Crawley O, Grill B. Ubiquitin ligase activity inhibits Cdk5 to control axon termination. PLoS Genet 2022; 18:e1010152. [PMID: 35421092 PMCID: PMC9041834 DOI: 10.1371/journal.pgen.1010152] [Citation(s) in RCA: 6] [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: 09/10/2021] [Revised: 04/26/2022] [Accepted: 03/17/2022] [Indexed: 01/29/2023] Open
Abstract
The Cdk5 kinase plays prominent roles in nervous system development, plasticity, behavior and disease. It also has important, non-neuronal functions in cancer, the immune system and insulin secretion. At present, we do not fully understand negative regulatory mechanisms that restrict Cdk5. Here, we use Caenorhabditis elegans to show that CDK-5 is inhibited by the RPM-1/FSN-1 ubiquitin ligase complex. This atypical RING ubiquitin ligase is conserved from C. elegans through mammals. Our finding originated from unbiased, in vivo affinity purification proteomics, which identified CDK-5 as a putative RPM-1 substrate. CRISPR-based, native biochemistry showed that CDK-5 interacts with the RPM-1/FSN-1 ubiquitin ligase complex. A CRISPR engineered RPM-1 substrate ‘trap’ enriched CDK-5 binding, which was mediated by the FSN-1 substrate recognition module. To test the functional genetic relationship between the RPM-1/FSN-1 ubiquitin ligase complex and CDK-5, we evaluated axon termination in mechanosensory neurons and motor neurons. Our results indicate that RPM-1/FSN-1 ubiquitin ligase activity restricts CDK-5 to control axon termination. Collectively, these proteomic, biochemical and genetic results increase our understanding of mechanisms that restrain Cdk5 in the nervous system. Cdk5 is an atypical cyclin dependent kinase and an important player in nervous system development, plasticity, and disease. Decades of research has focused on understanding how Cdk5 is activated. In contrast, we know much less about the genetic and molecular mechanisms that restrict Cdk5 activity. Here, we examined how Cdk5 is inhibited in the nervous system using the model organism C. elegans. Our results indicate that the RPM-1/FSN-1 E3 ubiquitin ligase complex inhibits Cdk5 to control termination of axon growth. Our finding that ubiquitin ligase activity restricts Cdk5 in the nervous system in vivo now opens up the interesting possibility that ubiquitin ligase activity might regulate Cdk5 in other cellular contexts and disease settings.
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Affiliation(s)
- Muriel Desbois
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, Washington, United States of America
| | - Karla J. Opperman
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, Washington, United States of America
| | - Jonathan Amezquita
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, Washington, United States of America
- Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, Washington, United States of America
| | - Gabriel Gaglio
- Department of Neuroscience, The Scripps Research Institute, Jupiter, Florida, United States of America
| | - Oliver Crawley
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, San Juan de Alicante, Spain
| | - Brock Grill
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, Washington, United States of America
- Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington, United States of America
- Department of Pharmacology, University of Washington M1-A303/305 Behnke Conference Room, Arnold building, Seattle, Washington, United States of America
- * E-mail:
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Amadeo A, Pizzi S, Comincini A, Modena D, Calogero AM, Madaschi L, Faustini G, Rolando C, Bellucci A, Pezzoli G, Mazzetti S, Cappelletti G. The Association between α-Synuclein and α-Tubulin in Brain Synapses. Int J Mol Sci 2021; 22:ijms22179153. [PMID: 34502063 PMCID: PMC8430732 DOI: 10.3390/ijms22179153] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 08/17/2021] [Accepted: 08/19/2021] [Indexed: 12/14/2022] Open
Abstract
α-synuclein is a small protein that is mainly expressed in the synaptic terminals of nervous tissue. Although its implication in neurodegeneration is well established, the physiological role of α-synuclein remains elusive. Given its involvement in the modulation of synaptic transmission and the emerging role of microtubules at the synapse, the current study aimed at investigating whether α-synuclein becomes involved with this cytoskeletal component at the presynapse. We first analyzed the expression of α-synuclein and its colocalization with α-tubulin in murine brain. Differences were found between cortical and striatal/midbrain areas, with substantia nigra pars compacta and corpus striatum showing the lowest levels of colocalization. Using a proximity ligation assay, we revealed the direct interaction of α-synuclein with α-tubulin in murine and in human brain. Finally, the previously unexplored interaction of the two proteins in vivo at the synapse was disclosed in murine striatal presynaptic boutons through multiple approaches, from confocal spinning disk to electron microscopy. Collectively, our data strongly suggest that the association with tubulin/microtubules might actually be an important physiological function for α-synuclein in the synapse, thus suggesting its potential role in a neuropathological context.
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Affiliation(s)
- Alida Amadeo
- Department of Biosciences, University of Milan, Via Celoria 26, 20126 Milano, Italy; (S.P.); (A.C.); (D.M.); (A.M.C.); (C.R.); (S.M.)
- Center of Excellence on Neurodegenerative Diseases, University of Milan, Via Celoria 26, 20126 Milano, Italy
- Correspondence: (A.A.); (G.C.); Tel.: +39-025-031-4885 (A.A.); +39-025-031-4752 (G.C.)
| | - Sara Pizzi
- Department of Biosciences, University of Milan, Via Celoria 26, 20126 Milano, Italy; (S.P.); (A.C.); (D.M.); (A.M.C.); (C.R.); (S.M.)
| | - Alessandro Comincini
- Department of Biosciences, University of Milan, Via Celoria 26, 20126 Milano, Italy; (S.P.); (A.C.); (D.M.); (A.M.C.); (C.R.); (S.M.)
| | - Debora Modena
- Department of Biosciences, University of Milan, Via Celoria 26, 20126 Milano, Italy; (S.P.); (A.C.); (D.M.); (A.M.C.); (C.R.); (S.M.)
| | - Alessandra Maria Calogero
- Department of Biosciences, University of Milan, Via Celoria 26, 20126 Milano, Italy; (S.P.); (A.C.); (D.M.); (A.M.C.); (C.R.); (S.M.)
| | - Laura Madaschi
- UNITECH NOLIMITS, University of Milan, Via Celoria 26, 20133 Milan, Italy;
| | - Gaia Faustini
- Division of Pharmacology, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123 Brescia, Italy; (G.F.); (A.B.)
| | - Chiara Rolando
- Department of Biosciences, University of Milan, Via Celoria 26, 20126 Milano, Italy; (S.P.); (A.C.); (D.M.); (A.M.C.); (C.R.); (S.M.)
| | - Arianna Bellucci
- Division of Pharmacology, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123 Brescia, Italy; (G.F.); (A.B.)
| | - Gianni Pezzoli
- Fondazione Grigioni per il Morbo di Parkinson, Via Zuretti 35, 20125 Milano, Italy;
| | - Samanta Mazzetti
- Department of Biosciences, University of Milan, Via Celoria 26, 20126 Milano, Italy; (S.P.); (A.C.); (D.M.); (A.M.C.); (C.R.); (S.M.)
- Fondazione Grigioni per il Morbo di Parkinson, Via Zuretti 35, 20125 Milano, Italy;
| | - Graziella Cappelletti
- Department of Biosciences, University of Milan, Via Celoria 26, 20126 Milano, Italy; (S.P.); (A.C.); (D.M.); (A.M.C.); (C.R.); (S.M.)
- Center of Excellence on Neurodegenerative Diseases, University of Milan, Via Celoria 26, 20126 Milano, Italy
- Correspondence: (A.A.); (G.C.); Tel.: +39-025-031-4885 (A.A.); +39-025-031-4752 (G.C.)
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Crawley O, Grill B. Autophagy in axonal and presynaptic development. Curr Opin Neurobiol 2021; 69:139-148. [PMID: 33940492 DOI: 10.1016/j.conb.2021.03.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 03/17/2021] [Accepted: 03/21/2021] [Indexed: 10/21/2022]
Abstract
The study of autophagy in the nervous system has predominantly centered on degeneration. Evidence is now cementing crucial roles for autophagy in neuronal development and growth, especially in axonal and presynaptic compartments. A picture is emerging that autophagy typically promotes the growth of axons and reduces presynaptic stability. Nonetheless, these are not rigid principles, and it remains unclear why autophagy does not always display these relationships during axonal and presynaptic development. Recent progress has identified mechanisms underlying spatiotemporal control of autophagy in neurons and begun to unravel how autophagy is integrated with other cellular processes, such as proteasomal degradation and axon guidance. Ultimately, understanding how autophagy is regulated and its role in the developing nervous system is key to comprehending how the nervous system assembles its stereotyped yet plastic configuration. It is also likely to inform how we think about neurodevelopmental disorders and neurodegenerative diseases.
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Affiliation(s)
- Oliver Crawley
- Unidad de Neurobiología Celular y de Sistemas, Instituto de Neurociencias (CSIC-UMH), San Juan de Alicante, 03550, Spain.
| | - Brock Grill
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, 98199, USA; Department of Pediatrics, University of Washington School of Medicine, Seattle, WA, USA; Department of Pharmacology, University of Washington School of Medicine, Seattle, WA, USA.
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Cappelletti G, Calogero AM, Rolando C. Microtubule acetylation: A reading key to neural physiology and degeneration. Neurosci Lett 2021; 755:135900. [PMID: 33878428 DOI: 10.1016/j.neulet.2021.135900] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Revised: 04/11/2021] [Accepted: 04/12/2021] [Indexed: 02/02/2023]
Abstract
Neurons are the perfect example of cells where microtubules are essential to achieve an extraordinary degree of morphological and functional complexity. Different tubulin isoforms and associated post-translational modifications are the basis to establish the diversity in biochemical and biophysical properties of microtubules including their stability and the control of intracellular transport. Acetylation is one of the key tubulin modifications and it can influence important structural, mechanical and biological traits of the microtubule network. Here, we present the emerging evidence for the essential role of microtubule acetylation in the control of neuronal and glial function in healthy and degenerative conditions. In particular, we discuss the pathogenic role of tubulin acetylation in neurodegenerative disorders and focus on Parkinson's disease. We also provide a critical analysis about the possibility to target tubulin acetylation as a novel therapeutic intervention for neuroprotective strategies.
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Affiliation(s)
- Graziella Cappelletti
- Department of Biosciences, Università degli Studi di Milano, Milano, Italy; Center of Excellence on Neurodegenerative Diseases, Università degli Studi di Milano, Milano, Italy.
| | | | - Chiara Rolando
- Department of Biosciences, Università degli Studi di Milano, Milano, Italy
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Microtubule Minus-End Binding Protein CAMSAP2 and Kinesin-14 Motor KIFC3 Control Dendritic Microtubule Organization. Curr Biol 2020; 30:899-908.e6. [PMID: 32084403 PMCID: PMC7063570 DOI: 10.1016/j.cub.2019.12.056] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 10/28/2019] [Accepted: 12/18/2019] [Indexed: 12/21/2022]
Abstract
Neuronal dendrites are characterized by an anti-parallel microtubule organization. The mixed oriented microtubules promote dendrite development and facilitate polarized cargo trafficking; however, the mechanism that regulates dendritic microtubule organization is still unclear. Here, we found that the kinesin-14 motor KIFC3 is important for organizing dendritic microtubules and to control dendrite development. The kinesin-14 motor proteins (Drosophila melanogaster Ncd, Saccharomyces cerevisiae Kar3, Saccharomyces pombe Pkl1, and Xenopus laevis XCTK2) are characterized by a C-terminal motor domain and are well described to organize the spindle microtubule during mitosis using an additional microtubule binding site in the N terminus [1-4]. In mammals, there are three kinesin-14 members, KIFC1, KIFC2, and KIFC3. It was recently shown that KIFC1 is important for organizing axonal microtubules in neurons, a process that depends on the two microtubule-interacting domains [5]. Unlike KIFC1, KIFC2 and KIFC3 lack the N-terminal microtubule binding domain and only have one microtubule-interacting domain, the motor domain [6, 7]. Thus, in order to regulate microtubule-microtubule crosslinking or sliding, KIFC2 and KIFC3 need to interact with additional microtubule binding proteins to connect two microtubules. We found that KIFC3 has a dendrite-specific distribution and interacts with microtubule minus-end binding protein CAMSAP2. Depletion of KIFC3 or CAMSAP2 results in increased microtubule dynamics during dendritic development. We propose a model in which CAMSAP2 anchors KIFC3 at microtubule minus ends and immobilizes microtubule arrays in dendrites.
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Autophagy is inhibited by ubiquitin ligase activity in the nervous system. Nat Commun 2019; 10:5017. [PMID: 31676756 PMCID: PMC6825199 DOI: 10.1038/s41467-019-12804-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 10/01/2019] [Indexed: 12/17/2022] Open
Abstract
Autophagy is an intracellular catabolic process prominent in starvation, aging and disease. Neuronal autophagy is particularly important, as it affects the development and function of the nervous system, and is heavily implicated in neurodegenerative disease. Nonetheless, how autophagy is regulated in neurons remains poorly understood. Using an unbiased proteomics approach, we demonstrate that the primary initiator of autophagy, the UNC-51/ULK kinase, is negatively regulated by the ubiquitin ligase RPM-1. RPM-1 ubiquitin ligase activity restricts UNC-51 and autophagosome formation within specific axonal compartments, and exerts effects broadly across the nervous system. By restraining UNC-51 activity, RPM-1 inhibits autophagosome formation to affect axon termination, synapse maintenance and behavioral habituation. These results demonstrate how UNC-51 and autophagy are regulated subcellularly in axons, and unveils a mechanism for restricting initiation of autophagy across the nervous system. Our findings have important implications beyond nervous system development, given growing links between altered autophagy regulation and neurodegenerative diseases.
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