PKC modulation of transmitter release by SNAP-25 at sensory-to-motor synapses in aplysia.
Activation of phosphokinase C (PKC) can increase transmitter release at sensory-motor neuron synapses in Aplysia, but the target of PKC phosphorylation has not been determined. One putative target of PKC at synapses is the synaptosomal-associated protein of 25 kDa (SNAP-25), a member of the SNARE protein complex implicated in synaptic vesicle docking and fusion. To determine whether PKC regulated transmitter release through phosphorylation of SNAP-25, we cloned Aplysia SNAP-25 and expressed enhanced green fluorescent protein (EGFP)-coupled SNAP-25 constructs mutated at the PKC phosphorylation site Ser198 in Aplysia sensory neurons. We found several distinct effects of expression of EGFP-SNAP-25 constructs. First, the rates of synaptic depression were slowed when cells contained SNAP-25 with phosphomimetic residues Glu or Asp. Second, PDBu-mediated increases in transmitter release at naïve synapses were blocked in cells expressing nonphosphorylated-state SNAP-25. Finally, expression of EGFP-coupled SNAP-25 but not uncoupled SNAP-25 inhibited 5-HT-mediated reversal of depression and the ability of EGFP-coupled SNAP-25 to inhibit the reversal of depression was affected by changes at Ser198. These results suggest SNAP-25 and phosphorylation of SNAP-25 by PKC can regulate transmitter release at Aplysia sensory-motor neuron synapses by a number of distinct processes.
Houeland
Gry
G
Department of Physiology, University of Montreal, Montreal, Quebec, Canada.
Nakhost
Arash
A
Sossin
Wayne S
WS
Castellucci
Vincent F
VF
D000818:Animals; D001048:Aplysia; D002478:Cells, Cultured; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D009046:Motor Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009475:Neurons, Afferent / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D050825:Synaptosomal-Associated Protein 25 / Q000235:genetics / Q000378:metabolism*
D018377:Neurotransmitter Agents; D011993:Recombinant Fusion Proteins; D050825:Synaptosomal-Associated Protein 25; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D012701:Serotonin; D011493:Protein Kinase C