title: The Adaptor Protein CD2AP Is a Coordinator of Neurotrophin Signaling-Mediated Axon Arbor Plasticity.
abstract: Growth of intact axons of noninjured neurons, often termed collateral sprouting, contributes to both adaptive and pathological plasticity in the adult nervous system, but the intracellular factors controlling this growth are largely unknown. An automated functional assay of genes regulated in sensory neurons from the rat in vivo spared dermatome model of collateral sprouting identified the adaptor protein CD2-associated protein (CD2AP; human CMS) as a positive regulator of axon growth. In non-neuronal cells, CD2AP, like other adaptor proteins, functions to selectively control the spatial/temporal assembly of multiprotein complexes that transmit intracellular signals. Although CD2AP polymorphisms are associated with increased risk of late-onset Alzheimer's disease, its role in axon growth is unknown. Assessments of neurite arbor structure in vitro revealed CD2AP overexpression, and siRNA-mediated knockdown, modulated (1) neurite length, (2) neurite complexity, and (3) growth cone filopodia number, in accordance with CD2AP expression levels. We show, for the first time, that CD2AP forms a novel multiprotein complex with the NGF receptor TrkA and the PI3K regulatory subunit p85, with the degree of TrkA:p85 association positively regulated by CD2AP levels. CD2AP also regulates NGF signaling through AKT, but not ERK, and regulates long-range signaling though TrkA(+)/RAB5(+) signaling endosomes. CD2AP mRNA and protein levels were increased in neurons during collateral sprouting but decreased following injury, suggesting that, although typically considered together, these two adult axonal growth processes are fundamentally different. These data position CD2AP as a major intracellular signaling molecule coordinating NGF signaling to regulate collateral sprouting and structural plasticity of intact adult axons.
  
  
  CONCLUSIONS
  Growth of noninjured axons in the adult nervous system contributes to adaptive and maladaptive plasticity, and dysfunction of this process may contribute to neurologic pathologies. Functional screening of genes regulated during growth of noninjured axons revealed CD2AP as a positive regulator of axon outgrowth. A novel association of CD2AP with TrkA and p85 suggests a distinct intracellular signaling pathway regulating growth of noninjured axons. This may also represent a novel mechanism of generating specificity in multifunctional NGF signaling. Divergent regulation of CD2AP in different axon growth conditions suggests that separate mechanisms exist for different modes of axon growth. CD2AP is the first signaling molecule associated with adult sensory axonal collateral sprouting, and this association may offer new insights for NGF/TrkA-related Alzheimer's disease mechanisms.
authors.affiliation: Anatomical Sciences and Neurobiology, University of Louisville, Louisville, Kentucky 40202, Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky 40292, Kentucky Biomedical Research Infrastructure Network, University of Louisville, Louisville, Kentucky 40292.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Harrison
authors.affiliation: Anatomical Sciences and Neurobiology, University of Louisville, Louisville, Kentucky 40202, Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky 40292.
authors.forename: Gayathri
authors.initials: G
authors.lastname: Venkat
authors.affiliation: University of Louisville School of Medicine, Louisville, Kentucky 40292.
authors.forename: James L
authors.initials: JL
authors.lastname: Lamb
authors.affiliation: Wolfson Centre for Age Related Diseases, King's College, London SE1 1UL, United Kingdom.
authors.forename: Tom H
authors.initials: TH
authors.lastname: Hutson
authors.affiliation: DuPont Manual High School, Louisville, Kentucky 40205.
authors.forename: Cassa
authors.identifier: http://orcid.org/0000-0003-0467-9615
authors.initials: C
authors.lastname: Drury
authors.affiliation: Anesthesiology and Perioperative Medicine, University of Louisville, Louisville, Kentucky 40202.
authors.forename: Kristofer K
authors.initials: KK
authors.lastname: Rau
authors.affiliation: Miami Project to Cure Paralysis, Department of Neurological Surgery and Neurology, University of Miami Miller School of Medicine, Miami, Florida 33136, Christopher and Dana Reeve Foundation International Consortium on Spinal Cord Injury Research, Short Hills, New Jersey 07078.
authors.forename: Mary Barlett
authors.initials: MB
authors.lastname: Bunge
authors.affiliation: Christopher and Dana Reeve Foundation International Consortium on Spinal Cord Injury Research, Short Hills, New Jersey 07078, Department of Neurobiology and Behavior, State University of New York at Stony Brook, Stony Brook, New York 11794.
authors.forename: Lorne M
authors.initials: LM
authors.lastname: Mendell
authors.affiliation: Christopher and Dana Reeve Foundation International Consortium on Spinal Cord Injury Research, Short Hills, New Jersey 07078, Laboratory of Genetics, The Salk Institute, La Jolla, California 92037.
authors.forename: Fred H
authors.identifier: http://orcid.org/0000-0002-0938-4106
authors.initials: FH
authors.lastname: Gage
authors.affiliation: Department of Physiological Sciences, University of Florida, Gainesville, Florida 32210, McKnight Brain Institute at the University of Florida, Gainesville, Florida 32611.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Johnson
authors.affiliation: Feil Family Burke Medical Research Institute, White Plains, New York 40605, Brain and Mind Research Institute, Weill Cornell Medical College, New York, New York 40065.
authors.forename: Caitlin E
authors.initials: CE
authors.lastname: Hill
authors.affiliation: Kentucky Biomedical Research Infrastructure Network, University of Louisville, Louisville, Kentucky 40292, Department of Computer Engineering and Computer Science, University of Louisville, Louisville, Kentucky 40292, and.
authors.forename: Eric C
authors.initials: EC
authors.lastname: Rouchka
authors.affiliation: Wolfson Centre for Age Related Diseases, King's College, London SE1 1UL, United Kingdom.
authors.forename: Lawrence D F
authors.identifier: http://orcid.org/0000-0001-9622-0312
authors.initials: LD
authors.lastname: Moon
authors.affiliation: Anatomical Sciences and Neurobiology, University of Louisville, Louisville, Kentucky 40202, Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky 40292, Department of Neurosurgery, University of Louisville, Louisville, Kentucky 40202 j.petruska@louisville.edu.
authors.forename: Jeffrey C
authors.identifier: http://orcid.org/0000-0002-3068-2677
authors.initials: JC
authors.lastname: Petruska
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000502:physiology*; D000818:Animals; D001369:Axons / Q000502:physiology*; D002454:Cell Differentiation / Q000235:genetics; D058543:Class Ia Phosphatidylinositol 3-Kinase / Q000502:physiology; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism; D005260:Female; D020935:MAP Kinase Signaling System / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009414:Nerve Growth Factors / Q000502:physiology*; D009473:Neuronal Plasticity / Q000235:genetics / Q000502:physiology*; D011554:Pseudopodia / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D020917:Receptor, trkA / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C114545:CD2-associated protein; D003598:Cytoskeletal Proteins; D009414:Nerve Growth Factors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C000606306:PIK3R2 protein, rat; D058543:Class Ia Phosphatidylinositol 3-Kinase; D020917:Receptor, trkA
keywords: collateral sprouting; nerve growth factor; neural plasticity; signalosome; spared dermatome; transcriptomics