title: Semaphorin 3A activates the guanosine triphosphatase Rab5 to promote growth cone collapse and organize callosal axon projections.
abstract: Axon guidance (pathfinding) wires the brain during development and is regulated by various attractive and repulsive cues. Semaphorin 3A (Sema3A) is a repulsive cue, inducing the collapse of axon growth cones. In the mammalian forebrain, the corpus callosum is the major commissure that transmits information flow between the two hemispheres, and contralateral axons assemble into well-defined tracts. We found that the patterning of callosal axon projections in rodent layer II and III (L2/3) cortical neurons in response to Sema3A was mediated by the activation of Rab5, a small guanosine triphosphatase (GTPase) that mediates endocytosis, through the membrane fusion protein Rabaptin-5 and the Rab5 guanine nucleotide exchange factor (GEF) Rabex-5. Rabaptin-5 bound directly to Plexin-A1 in the Sema3A receptor complex [an obligate heterodimer formed by Plexin-A1 and neuropilin 1 (NP1)]; Sema3A enhanced this interaction in cultured neurons. Rabaptin-5 bridged the interaction between Rab5 and Plexin-A1. Sema3A stimulated endocytosis from the cell surface of callosal axon growth cones. In utero electroporation to reduce Rab5 or Rabaptin-5 impaired axon fasciculation or caused mistargeting of L2/3 callosal projections in rats. Overexpression of Rabaptin-5 or Rab5 rescued the defective callosal axon fasciculation or mistargeting of callosal axons caused by the loss of Sema3A-Plexin-A1 signaling in rats expressing dominant-negative Plexin-A1 or in NP1-deficient mice. Thus, our findings suggest that Rab5, its effector Rabaptin-5, and its regulator Rabex-5 mediate Sema3A-induced axon guidance during brain development.
authors.affiliation: Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China.
authors.forename: Kong-Yan
authors.initials: KY
authors.lastname: Wu
authors.affiliation: Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China.
authors.forename: Miao
authors.initials: M
authors.lastname: He
authors.affiliation: Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China.
authors.forename: Qiong-Qiong
authors.initials: QQ
authors.lastname: Hou
authors.affiliation: Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China.
authors.forename: Ai-Li
authors.initials: AL
authors.lastname: Sheng
authors.affiliation: Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Yuan
authors.affiliation: Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Liu
authors.affiliation: Chinese Academy of Sciences Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, National Center for Nanoscience and Technology, 11 Beiyitiao, Zhong Guan Cun, Beijing 100190, China.
authors.forename: Wen-Wen
authors.initials: WW
authors.lastname: Liu
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
authors.forename: Guangpu
authors.initials: G
authors.lastname: Li
authors.affiliation: Chinese Academy of Sciences Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, National Center for Nanoscience and Technology, 11 Beiyitiao, Zhong Guan Cun, Beijing 100190, China.
authors.forename: Xing-Yu
authors.initials: XY
authors.lastname: Jiang
authors.affiliation: Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai 200031, China. zgluo@ion.ac.cn.
authors.forename: Zhen-Ge
authors.initials: ZG
authors.lastname: Luo
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology*; D003337:Corpus Callosum / Q000166:cytology*; D018274:Electroporation; D004789:Enzyme Activation / Q000502:physiology*; D020439:Growth Cones / Q000502:physiology*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D047468:Immunoprecipitation; D051379:Mice; D008817:Mice, Mutant Strains; D044085:Microfluidics; D018613:Microscopy, Confocal; D009419:Nerve Tissue Proteins / Q000378:metabolism; D039942:Neuropilin-1 / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism*; D040121:Semaphorin-3A / Q000235:genetics*; D014162:Transfection; D033921:Vesicular Transport Proteins / Q000378:metabolism; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D009419:Nerve Tissue Proteins; C492114:Plxna1 protein, mouse; D034741:RNA, Small Interfering; C510870:RabGEF1 protein, mouse; C486276:Rabep1 protein, mouse; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; C108639:SEMA3A protein, human; D040121:Semaphorin-3A; D033921:Vesicular Transport Proteins; D039942:Neuropilin-1; D020696:rab5 GTP-Binding Proteins