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ABSTRACT: Slow Wallerian degeneration (Wld(S)) encodes a chimeric Ube4b/nicotinamide mononucleotide adenylyl transferase 1 (Nmnat1) fusion protein that potently suppresses Wallerian degeneration, but the mechanistic action of Wld(S) remains controversial. In this study, we characterize Wld(S)-mediated axon protection in vivo using Drosophila melanogaster. We show that Nmnat1 can protect severed axons from autodestruction but at levels significantly lower than Wld(S), and enzyme-dead versions of Nmnat1 and Wld(S) exhibit severely reduced axon-protective function. Interestingly, a 16-amino acid N-terminal domain of Wld(S) (termed N16) accounts for the differences in axon-sparing activity between Wld(S) and Nmnat1, and N16-dependent enhancement of Nmnat1-protective activity in Wld(S) requires the N16-binding protein valosin-containing protein (VCP)/TER94. Thus, Wld(S)-mediated suppression of Wallerian degeneration results from VCP-N16 interactions and Nmnat1 activity converging in vivo. Surprisingly, mouse Nmnat3, a mitochondrial Nmnat enzyme that localizes to the cytoplasm in Drosophila cells, protects severed axons at levels indistinguishable from Wld(S). Thus, nuclear Nmnat activity does not appear to be essential for Wld(S)-like axon protection.
The Journal of Cell Biology 03/2009; 184(4):501-13. · 10.26 Impact Factor
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ABSTRACT: The cellular machinery promoting phagocytosis of corpses of apoptotic cells is well conserved from worms to mammals. An important component is the Caenorhabditis elegans engulfment receptor CED-1 (ref. 1) and its Drosophila orthologue, Draper. The CED-1/Draper signalling pathway is also essential for the phagocytosis of other types of 'modified self' including necrotic cells, developmentally pruned axons and dendrites, and axons undergoing Wallerian degeneration. Here we show that Drosophila Shark, a non-receptor tyrosine kinase similar to mammalian Syk and Zap-70, binds Draper through an immunoreceptor tyrosine-based activation motif (ITAM) in the Draper intracellular domain. We show that Shark activity is essential for Draper-mediated signalling events in vivo, including the recruitment of glial membranes to severed axons and the phagocytosis of axonal debris and neuronal cell corpses by glia. We also show that the Src family kinase (SFK) Src42A can markedly increase Draper phosphorylation and is essential for glial phagocytic activity. We propose that ligand-dependent Draper receptor activation initiates the Src42A-dependent tyrosine phosphorylation of Draper, the association of Shark and the activation of the Draper pathway. These Draper-Src42A-Shark interactions are strikingly similar to mammalian immunoreceptor-SFK-Syk signalling events in mammalian myeloid and lymphoid cells. Thus, Draper seems to be an ancient immunoreceptor with an extracellular domain tuned to modified self, and an intracellular domain promoting phagocytosis through an ITAM-domain-SFK-Syk-mediated signalling cascade.
Nature 07/2008; 453(7197):935-9. · 36.28 Impact Factor
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ABSTRACT: DRAPER-DEPENDENT GLIAL PHAGOCYTIC ACTIVITY IS MEDIATED BY SRC AND SYK FAMILY KINASE SIGNALING
Jennifer S. Ziegenfuss1, Romi Biswas2, Michelle A. Avery1, Kyoungja Hong2, Amy E. Sheehan1, Yee-Guide Yeung 2 E. Richard Stanley2, and Marc R. Freeman1
1. Department of Neurobiology, University of Massachusetts Medical School, USA. 2. Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, USA.
We are exploring neural injury signaling mechanisms in Drosophila. One of our main goals is to understand how glia sense and respond to neural injury or death and ultimately clear neural debris from the CNS. A central component of the glial phagocytic machinery is Draper, the Drosophila ortholog of the Caenorhabditis elegans engulfment receptor CED-1. Draper is essential for glial engulfment of neuronal cell corpses, developmentally pruned axons and dendrites, and axons undergoing Wallerian degeneration. The Draper/Ced-1 signaling pathway is well conserved from worms to mammals, and has recently been found to be expressed in mammalian glial cells, yet signaling molecules downstream of the Draper receptor remain poorly defined.
We have found that Drosophila Shark, a non-receptor tyrosine kinase similar to mammalian Syk and Zap-70, binds Draper through an immunoreceptor tyrosine-based activation motif (ITAM) in the Draper intracellular domain. We show that Shark activity is essential for Draper-mediated signaling events in vivo, including the recruitment of glial membranes to severed axons and the phagocytosis of axonal debris and neural cell corpses by glia. We also show that the Src family kinase (SFK) Src42A increases Draper phosphorylation and is essential for glial phagocytic activity. We propose that ligand-dependent Draper receptor activation initiates the Src42A-dependent tyrosine phosphorylation of Draper, the association of Shark, and the activation of the Draper pathway. These Draper-Src42A-Shark interactions are strikingly similar to mammalian immunoreceptor-SFK-Syk signaling events in mammalian myeloid and lymphoid cells. Our identification of Shark and Src42A as key regulators of Draper signaling argues that Draper/CED-1 represents an ancient immunoreceptor with an extracellular domain tuned to modified self, and an intracellular domain promoting phagocytosis through an ITAM-domain-SFK-Syk mediated signaling cascade.
Glia in Health & Disease
July 17 - 21, 2008
Abstract Deadline: May 9, 2008
Organizers:
Ben Barres, Stanford University School of Medicine
Beth Stevens, Children's Hospital/Harvard Medical School
We are pleased to announce the second summer conference on Glia in Health & Disease, which will be held at Cold Spring Harbor Laboratory, New York. The meeting will begin at 7:30 p.m. on Thursday, July 17, and will conclude with lunch on Monday, July 21, 2008. The proposed meeting will assemble the leaders in the field, together with junior faculty, postdoctoral fellows and graduate students, to discuss new, cutting-edge developments in the study of all aspects of glial biology in health and disease.
Topics and discussion leaders:
Genetic Analysis of Glial Function
Rob Jackson & Ken McCarthy
Gliovascular Interactions
Brian MacVicar & Maiken Nedergaard
Myelinating Cells
Michael Simons & Wendy Macklin
Glial Development
Christian Klambt & Michael Wegner
Axon-Glial Interactions
Alison Lloyd & Klaus Nave
Astrocyte Function at Synapses
Cagla Eroglu & Shumin Duan
Microglia and Gliosis
Sergei Rivest & Michael Sofrieniew
Glia and Disease
Richard Reynolds & Pedro Lowenstein
The format of the meeting will include eight oral sessions and two poster sessions. Each oral session will include invited speakers and speakers selected from submitted abstracts. For this reason, abstracts from accomplished junior and senior investigators are warmly invited. As usual at Cold Spring Harbor meetings, abstracts of both poster and platform sessions will be published in an abstract book.
Glia in Health and Disease, Cld Spring Harbor; 07/2008
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ABSTRACT: DRAPER- DEPENDENT GLIAL PHAGOCYTIC ACTIVITY IS MEDIATED BY THE NON-RECEPTOR TYROSINE KINASE SHARK
Jennifer S. Ziegenfuss1, Romi Biswas2, Michelle A. Avery1, Amy E. Sheehan1, E. Richard Stanley2, and Marc R. Freeman1
1. Department of Neurobiology, University of Massachusetts Medical School, USA. 2. Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, USA.
We are exploring neural injury signaling mechanisms in Drosophila. One of our main goals is to understand how glial cells sense neural injury or death and clear degenerating neuronal debris from the nervous system. We have recently shown that Draper, the Drosophila ortholog of the C. elegans engulfment receptor CED-1, is a central component of the glial phagocytic machinery. In draper null mutants, developmentally-produced neuronal cell corpses are not efficiently cleared by glia from the embryonic CNS, and in the adult nervous system, glia fail to engulf degenerating axons after injury. While the draper/ced-1 phagocytic signaling pathway is well-conserved from worms to mammals, signaling molecules acting downstream of the Draper/CED-1 receptor have not been defined. We have found that Shark, a non-receptor tyrosine kinase, similar to mammalian Syk and Zap-70, physically interacts with Draper through an immunoreceptor tyrosine-based activation motif (ITAM) domain present in the Draper intracellular domain. We demonstrate that Shark activity is essential for Draper-mediated glial signaling events in vivo, including promotion of glial recruitment to severed axons after nerve injury, glial phagocytosis of degenerating axons, and glial clearance of neuronal cell corpses from the CNS. Genetic analysis shows that shark and draper mutations dominantly suppress glial phagocytosis of severed axons, and shark and draper show strong dominant genetic interactions, consistent with their action in the same genetic pathway. The Draper-Shark interactions we describe are highly reminiscent of mammalian ITAM domain immunoreceptor-Src family kinase/Syk signaling events that mediate, for example, phagocytic activity and activation of mammalian blood cells. Our identification of Shark as a key regulator of Draper signaling therefore argues that CED-1/Draper is an ancient ITAM domain/Syk-mediated phagocytic signaling pathway.
NEUROBIOLOGY OF DROSOPHILA
October 3 - 7, 2007
Abstract Deadline: July 11, 2007
Organizers:
Alex Kolodkin, HHMI/The Johns Hopkins Medical School
Amita Sehgal, HHMI/University of Pennsylvania
Call for nominations for the 2007 Elkins Award
We are pleased to announce the twelfth biennial Neurobiology of Drosophila meeting, which will be held at the Cold Spring Harbor Laboratory. The meeting will begin at 7.30pm on the evening of Wednesday, October 3rd, and will conclude after lunch on Sunday, October 7th.
The goals of this conference are to provide a forum for the presentation of late breaking advances in Drosophila neurobiology, to exchange ideas and techniques, to stimulate future research and collaborations, and to recognize and encourage younger investigators and women working in this field. We strongly encourage all participants to submit an abstract(s) of your most recent work for consideration as oral or poster presentation. In the event of the meeting being oversubscribed, preference to attend will go to those submitting abstracts. The organizers will endeavor to accept for participation at least one representative of every applicant laboratory either engaged in or about to embark on Drosophila neurobiological research. We particularly encourage active participation by younger investigators and minority scientists.
Sessions & Discussion Leaders
Neuronal and Glial Cell Fate
Ulrike Gaul, The Rockefeller University
Neural Circuits and Function
Julie Simpson, HHMI Janelia Farm Research Campus
Cell Biology and Pathology
Linda Restifo, University of Arizona
Sensory Systems
Kristin Scott, University of California, Berkeley
Behavior
F. Rob Jackson, Tufts University School of Medicine
Synaptic Transmission
Chun-Fang Wu, University of Iowa
Process Formation
Kai Zinn, California Institute of Technology
Technology Development
Gero Miesenbock, Yale University School of Medicine
Neurobiology of Drosophila, Cold Spring Harbor; 10/2007
