[Role of vesicle fusion mechanism and cell adhesion molecules in growth cone elongation and synaptogenesis].
Growth cones have been regarded to play central roles in forming complex neural network through target tract selection and target cell recognition. We have found that the vesicle fusion molecular system in growth cones is similar to that in synapses. The cleavage of SNAP25, a protein involved in neurotransmitter release in synapse, resulted in inhibition of neurite elongation. Inversely the overexpression of VAMP2/synaptobrevin, another protein involved in neurotransmitter release in synapse, in PC12 cells resulted in promotion of neurite elongation. We have recently isolated a novel components at cadherin-based cell-cell adherens junctions, named neurabin I, neurabin II, and afadin. Neurabin I is specifically expressed in nervous tissues and localized at synapses. Afadin is uviquitously expressed in various tissues and highly concentrated at cell-cell adherens junctions of small intestine epithelial cells, cardiac muscles, synapses. We have identified the transmembrane protein binding to afadin, and named it nectin, which belongs to immunoglobulin superfamily. Nectin, afadin, neurabin I, and neurabin II may be key molecules to find out various unknown guidance cues which can induce regenerating growth cones to repair the functional neuronal connections in central nervous system after injury.
Mizoguchi
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Department of Anatomy and Neurobiology, Faculty of Medicine, Kyoto University, Japan.
D000818:Animals; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000502:physiology; D002490:Central Nervous System / Q000502:physiology; D005089:Exocytosis; D020439:Growth Cones / Q000502:physiology* / Q000648:ultrastructure; D006801:Humans; D016547:Kinesins; D008840:Microfilament Proteins / Q000502:physiology; D009218:Myosins; D009416:Nerve Regeneration; D009419:Nerve Tissue Proteins / Q000502:physiology; D013569:Synapses / Q000502:physiology; D013572:Synaptic Vesicles / Q000502:physiology; D000099273:Neurabins
D015815:Cell Adhesion Molecules; D016547:Kinesins; D008840:Microfilament Proteins; D009218:Myosins; D009419:Nerve Tissue Proteins; D000099273:Neurabins; C095516:AFDN protein, human; C108835:afadin