101
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Suzuki J, Imanishi E, Nagata S. Exposure of phosphatidylserine by Xk-related protein family members during apoptosis. J Biol Chem 2014; 289:30257-30267. [PMID: 25231987 DOI: 10.1074/jbc.m114.583419] [Citation(s) in RCA: 120] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Apoptotic cells expose phosphatidylserine (PtdSer) on their surface as an "eat me" signal. Mammalian Xk-related (Xkr) protein 8, which is predicted to contain six transmembrane regions, and its Caenorhabditis elegans homolog CED-8 promote apoptotic PtdSer exposure. The mouse and human Xkr families consist of eight and nine members, respectively. Here, we found that mouse Xkr family members, with the exception of Xkr2, are localized to the plasma membrane. When Xkr8-deficient cells, which do not expose PtdSer during apoptosis, were transformed by Xkr family members, the transformants expressing Xkr4, Xkr8, or Xkr9 responded to apoptotic stimuli by exposing cell surface PtdSer and were efficiently engulfed by macrophages. Like Xkr8, Xkr4 and Xkr9 were found to possess a caspase recognition site in the C-terminal region and to require its direct cleavage by caspases for their function. Site-directed mutagenesis of the amino acid residues conserved among CED-8, Xkr4, Xkr8, and Xkr9 identified several essential residues in the second transmembrane and second cytoplasmic regions. Real time PCR analysis indicated that unlike Xkr8, which is ubiquitously expressed, Xkr4 and Xkr9 expression is tissue-specific.
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Affiliation(s)
- Jun Suzuki
- Department of Medical Chemistry, Graduate School of Medicine, Kyoto University, Yoshida-Konoe, Sakyo-ku, Kyoto, Kyoto 606-8501, Japan
| | - Eiichi Imanishi
- Department of Medical Chemistry, Graduate School of Medicine, Kyoto University, Yoshida-Konoe, Sakyo-ku, Kyoto, Kyoto 606-8501, Japan
| | - Shigekazu Nagata
- Department of Medical Chemistry, Graduate School of Medicine, Kyoto University, Yoshida-Konoe, Sakyo-ku, Kyoto, Kyoto 606-8501, Japan.
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102
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Schuldiner O, Yaron A. Mechanisms of developmental neurite pruning. Cell Mol Life Sci 2014; 72:101-19. [PMID: 25213356 DOI: 10.1007/s00018-014-1729-6] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 09/02/2014] [Accepted: 09/04/2014] [Indexed: 12/19/2022]
Abstract
The precise wiring of the nervous system is a combined outcome of progressive and regressive events during development. Axon guidance and synapse formation intertwined with cell death and neurite pruning sculpt the mature circuitry. It is now well recognized that pruning of dendrites and axons as means to refine neuronal networks, is a wide spread phenomena required for the normal development of vertebrate and invertebrate nervous systems. Here we will review the arising principles of cellular and molecular mechanisms of neurite pruning. We will discuss these principles in light of studies in multiple neuronal systems, and speculate on potential explanations for the emergence of neurite pruning as a mechanism to sculpt the nervous system.
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Affiliation(s)
- Oren Schuldiner
- Department of Molecular Cell Biology, Weizmann Institute of Sciences, 7610001, Rehovot, Israel,
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103
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Pease SE, Segal RA. Preserve and protect: maintaining axons within functional circuits. Trends Neurosci 2014; 37:572-82. [PMID: 25167775 DOI: 10.1016/j.tins.2014.07.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 07/21/2014] [Accepted: 07/27/2014] [Indexed: 12/14/2022]
Abstract
During development, neural circuits are initially generated by exuberant innervation and are rapidly refined by selective preservation and elimination of axons. The establishment and maintenance of functional circuits therefore requires coordination of axon survival and degeneration pathways. Both developing and mature circuits rely on interdependent mitochondrial and cytoskeletal components to maintain axonal health and homeostasis; injury or diseases that impinge on these components frequently cause pathologic axon loss. Here, we review recent findings that identify mechanisms of axonal preservation in the contexts of development, injury, and disease.
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Affiliation(s)
- Sarah E Pease
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA; Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Rosalind A Segal
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA; Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA 02215, USA.
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104
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Boulanger A, Dura JM. Nuclear receptors and Drosophila neuronal remodeling. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1849:187-95. [PMID: 24882358 DOI: 10.1016/j.bbagrm.2014.05.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 04/25/2014] [Accepted: 05/26/2014] [Indexed: 11/30/2022]
Abstract
During the development of both vertebrates and invertebrates, neurons undergo a crucial remodeling process that is necessary for their new function. Neuronal remodeling is composed of two stages: first, axons and dendrites are pruned without the loss of the cell body; later, this process is most commonly followed by a regrowth step. Holometabolous insects like the fruitfly Drosophila exhibit striking differences between their larval and adult stages. These neuronal remodeling processes occur during metamorphosis, the period of transformation from a larva to an adult. All axon and dendrite pruning events ultimately depend on the EcR nuclear receptor. Its ligand, the steroid molting hormone ecdysone, binds to heteromeric receptors comprising the nuclear receptor ECR and USP, and this complex regulates target genes involved in neuronal remodeling. Here we review the nuclear receptor-mediated genetic control of the main neuronal remodeling events described so far in Drosophila. These events consist of neurite degeneration in the mushroom bodies (MBs: the brain memory center) and in the dendritic arborizing sensory neurons, of neurite retraction or small scale elimination in the thoracic ventral neurosecretory cells, in the olfactory circuits and in the neuromuscular junction. MB axon regrowth after pruning and the role of MB neuron remodeling in memory formation are also reviewed. This article is part of a Special Issue entitled: Nuclear receptors in animal development.
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Affiliation(s)
- Ana Boulanger
- Institute of Human Genetics, UPR 1142, CNRS, 141, rue de la Cardonille, 34396 Montpellier, France.
| | - Jean-Maurice Dura
- Institute of Human Genetics, UPR 1142, CNRS, 141, rue de la Cardonille, 34396 Montpellier, France.
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105
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Drosophila Valosin-Containing Protein is required for dendrite pruning through a regulatory role in mRNA metabolism. Proc Natl Acad Sci U S A 2014; 111:7331-6. [PMID: 24799714 DOI: 10.1073/pnas.1406898111] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The dendritic arbors of the larval Drosophila peripheral class IV dendritic arborization neurons degenerate during metamorphosis in an ecdysone-dependent manner. This process-also known as dendrite pruning-depends on the ubiquitin-proteasome system (UPS), but the specific processes regulated by the UPS during pruning have been largely elusive. Here, we show that mutation or inhibition of Valosin-Containing Protein (VCP), a ubiquitin-dependent ATPase whose human homolog is linked to neurodegenerative disease, leads to specific defects in mRNA metabolism and that this role of VCP is linked to dendrite pruning. Specifically, we find that VCP inhibition causes an altered splicing pattern of the large pruning gene molecule interacting with CasL and mislocalization of the Drosophila homolog of the human RNA-binding protein TAR-DNA-binding protein of 43 kilo-Dalton (TDP-43). Our data suggest that VCP inactivation might lead to specific gain-of-function of TDP-43 and other RNA-binding proteins. A similar combination of defects is also seen in a mutant in the ubiquitin-conjugating enzyme ubcD1 and a mutant in the 19S regulatory particle of the proteasome, but not in a 20S proteasome mutant. Thus, our results highlight a proteolysis-independent function of the UPS during class IV dendritic arborization neuron dendrite pruning and link the UPS to the control of mRNA metabolism.
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106
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Yu F, Schuldiner O. Axon and dendrite pruning in Drosophila. Curr Opin Neurobiol 2014; 27:192-8. [PMID: 24793180 DOI: 10.1016/j.conb.2014.04.005] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2014] [Revised: 04/04/2014] [Accepted: 04/05/2014] [Indexed: 01/05/2023]
Abstract
Pruning, a process by which neurons selectively remove exuberant or unnecessary processes without causing cell death, is crucial for the establishment of mature neural circuits during animal development. Yet relatively little is known about molecular and cellular mechanisms that govern neuronal pruning. Holometabolous insects, such as Drosophila, undergo complete metamorphosis and their larval nervous systems are replaced with adult-specific ones, thus providing attractive models for studying neuronal pruning. Drosophila mushroom body and dendritic arborization neurons have been utilized as two appealing systems to elucidate the underlying mechanisms of axon and dendrite pruning, respectively. In this review we highlight recent developments and discuss some similarities and differences in the mechanisms that regulate these two distinct modes of neuronal pruning in Drosophila.
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Affiliation(s)
- Fengwei Yu
- Temasek Life Sciences Laboratory and Department of Biological Sciences, 1 Research Link, National University of Singapore, Singapore 117604, Singapore.
| | - Oren Schuldiner
- Department of Molecular Cell Biology, Weizmann Institute of Sciences, Rehovot 7610001, Israel.
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107
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Macrophages gain a partner at the table: epidermal cells digest peripheral dendritic debris in Drosophila. Neuron 2014; 81:465-7. [PMID: 24507184 DOI: 10.1016/j.neuron.2014.01.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In this issue of Neuron, Han et al. (2014) develop powerful methods to visualize phagocytosis of Drosophila peripheral sensory neuron dendrites. Remarkably, epidermal cells rather than professional phagocytes are the primary mediators of debris clearance, using both familiar and new molecular players.
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108
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Lyons GR, Andersen RO, Abdi K, Song WS, Kuo CT. Cysteine proteinase-1 and cut protein isoform control dendritic innervation of two distinct sensory fields by a single neuron. Cell Rep 2014; 6:783-791. [PMID: 24582961 PMCID: PMC4237277 DOI: 10.1016/j.celrep.2014.02.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Revised: 01/21/2014] [Accepted: 02/03/2014] [Indexed: 11/29/2022] Open
Abstract
Dendrites often exhibit structural changes in response to local inputs. Although mechanisms that pattern and maintain dendritic arbors are becoming clearer, processes regulating regrowth, during context-dependent plasticity or after injury, remain poorly understood. We found that a class of Drosophila sensory neurons, through complete pruning and regeneration, can elaborate two distinct dendritic trees, innervating independent sensory fields. An expression screen identified Cysteome proteinase-1 (Cp1) as a critical regulator of this process. Unlike known ecdysone effectors, Cp1-mutant ddaC neurons pruned larval dendrites normally but failed to regrow adult dendrites. Cp1 expression was upregulated/concentrated in the nucleus during metamorphosis, controlling production of a truncated Cut homeodomain transcription factor. This truncated Cut, but not the full-length protein, allowed Cp1-mutant ddaC neurons to regenerate higher-order adult dendrites. These results identify a molecular pathway needed for dendrite regrowth after pruning, which allows the same neuron to innervate distinct sensory fields.
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Affiliation(s)
- Gray R Lyons
- Department of Cell Biology, Duke University School of Medicine, Durham, NC 27710, USA.,Medical Scientist Training Program, Duke University School of Medicine, Durham, NC 27710, USA
| | - Ryan O Andersen
- Department of Cell Biology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Khadar Abdi
- Department of Cell Biology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Won-Seok Song
- Department of Cell Biology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Chay T Kuo
- Department of Cell Biology, Duke University School of Medicine, Durham, NC 27710, USA.,Brumley Neonatal-Perinatal Research Institute, Department of Pediatrics, Duke University School of Medicine, Durham, NC 27710, USA.,Department of Neurobiology, Duke University School of Medicine, Durham, NC 27710, USA.,Preston Robert Tisch Brain Tumor Center, Duke University School of Medicine, Durham, NC 27710, USA.,Duke Institute for Brain Sciences, Duke University School of Medicine, Durham, NC 27710, USA
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109
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Cell biology of the neuron: epidermal cells eat up dendrites. Nat Rev Neurosci 2014; 15:137. [PMID: 24473395 DOI: 10.1038/nrn3688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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