Synaptic target contact enhances presynaptic calcium influx by activating cAMP-dependent protein kinase during synaptogenesis.
Individual dissociated supralateral radular tensor (SLT) muscle fibers were manipulated into contact with fura-2-filled neurites of presynaptic buccal motoneuron 19 from Helisoma in cell culture. Within 30 min of contact, action potential-evoked calcium accumulation was reversibly augmented from 228 +/- 82 nM to 803 +/- 212 nM, an action that was blocked by H-7 (40-100 microM). Calcium accumulation was not augmented when buccal motoneuron 19 contacted muscle or neuronal targets with which it does not form chemical synapses. Addition of pCPTcAMP (500 microM) to cultures reversibly enhanced calcium accumulation. Injection of IP20, a peptide inhibitor of cAMP-dependent protein kinase, prevented pCPTcAMP and SLT muscle from enhancing calcium accumulation. These data demonstrate that SLT muscle target retrogradely regulates calcium accumulation in presynaptic nerve terminals by locally activating presynaptic cAMP-dependent protein kinase.
Department of Zoology and Genetics, Iowa State University, Ames 50011.
L R
LR
Funte
P G
PG
Haydon
D000200:Action Potentials; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004789:Enzyme Activation; D016257:Fura-2; D005724:Ganglia / Q000502:physiology; D007700:Kinetics; D008969:Molecular Sequence Data; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology*; D016501:Neurites / Q000502:physiology; D009469:Neuromuscular Junction / Q000502:physiology*; D010455:Peptides / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism*; D012908:Snails; D013050:Spectrometry, Fluorescence; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D013873:Thionucleotides / Q000494:pharmacology; D013997:Time Factors
D010455:Peptides; D013873:Thionucleotides; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D000242:Cyclic AMP; D011494:Protein Kinases; D002118:Calcium; D016257:Fura-2