Abstract
Application of Clostridium difficile toxin B, an inhibitor of the Rho family of GTPases, at the Aplysia sensory to motor neuron synapse blocks long-term facilitation and the associated growth of new sensory neuron varicosities induced by repeated pulses of serotonin (5-HT). We have isolated cDNAs encoding Aplysia Rho, Rac, and Cdc42 and found that Rho and Rac had no effect but that overexpression in sensory neurons of a dominant-negative mutant of ApCdc42 or the CRIB domains of its downstream effectors PAK and N-WASP selectively reduces the long-term changes in synaptic strength and structure. FRET analysis indicates that 5-HT activates ApCdc42 in a subset of varicosities contacting the postsynaptic motor neuron and that this activation is dependent on the PI3K and PLC signaling pathways. The 5-HT-induced activation of ApCdc42 initiates reorganization of the presynaptic actin network leading to the outgrowth of filopodia, some of which are morphological precursors for the learning-related formation of new sensory neuron varicosities.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Actin Cytoskeleton / metabolism
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Actins / drug effects
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Actins / metabolism*
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Amino Acid Sequence
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Animals
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Aplysia
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Cells, Cultured
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Conserved Sequence / genetics
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Learning / drug effects
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Learning / physiology*
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Molecular Sequence Data
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Motor Neurons / cytology
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Motor Neurons / physiology
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Mutation / genetics
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Nerve Tissue Proteins / genetics
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Nerve Tissue Proteins / isolation & purification
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Nerve Tissue Proteins / metabolism
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Neuronal Plasticity / drug effects
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Neuronal Plasticity / physiology*
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Neurons, Afferent / cytology
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Neurons, Afferent / drug effects
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Neurons, Afferent / metabolism*
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Phosphatidylinositol 3-Kinases / metabolism
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Presynaptic Terminals / drug effects
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Presynaptic Terminals / metabolism
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Presynaptic Terminals / ultrastructure
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / isolation & purification
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Protein Structure, Tertiary / genetics
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Pseudopodia / metabolism
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Serotonin / metabolism*
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Serotonin / pharmacology
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Synapses / drug effects
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Synapses / metabolism*
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Type C Phospholipases / metabolism
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Wiskott-Aldrich Syndrome Protein, Neuronal
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cdc42 GTP-Binding Protein / genetics
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cdc42 GTP-Binding Protein / isolation & purification
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cdc42 GTP-Binding Protein / metabolism
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p21-Activated Kinases
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rac GTP-Binding Proteins / genetics
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rac GTP-Binding Proteins / isolation & purification
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rac GTP-Binding Proteins / metabolism
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rho GTP-Binding Proteins / genetics
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rho GTP-Binding Proteins / isolation & purification
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rho GTP-Binding Proteins / metabolism
Substances
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Actins
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Nerve Tissue Proteins
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Wiskott-Aldrich Syndrome Protein, Neuronal
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Serotonin
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Protein Serine-Threonine Kinases
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p21-Activated Kinases
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Type C Phospholipases
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cdc42 GTP-Binding Protein
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rac GTP-Binding Proteins
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rho GTP-Binding Proteins