Ca2+ influx through distinct routes controls exocytosis and endocytosis at drosophila presynaptic terminals.
Endocytosis of synaptic vesicles follows exocytosis, and both processes require external Ca(2+). However, it is not known whether Ca(2+) influx through one route initiates both processes. At larval Drosophila neuromuscular junctions, we separately measured exocytosis and endocytosis using FM1-43. In a temperature-sensitive Ca(2+) channel mutant, cacophony(TS2), exocytosis induced by high K(+) decreased at nonpermissive temperatures, while endocytosis remained unchanged. In wild-type larvae, a spider toxin, PLTXII, preferentially inhibited exocytosis, whereas the Ca(2+) channel blockers flunarizine and La(3+) selectively depressed endocytosis. None of these blockers affected exocytosis or endocytosis induced by a Ca(2+) ionophore. Evoked synaptic potentials were depressed regardless of stimulus frequency in cacophony(TS2) at nonpermissive temperatures and in wild-type by PLTXII, whereas flunarizine or La(3+) gradually depressed synaptic potentials only during high-frequency stimulation, suggesting depletion of synaptic vesicles due to blockade of endocytosis. In shibire(ts1), a dynamin mutant, flunarizine or La(3+) inhibited assembly of clathrin at the plasma membrane during stimulation without affecting dynamin function.
Kuromi
Hiroshi
H
Institute for Behavioral Sciences, Gunma University School of Medicine, Maebashi, Japan. kuromi@med.gunna-u.ac.jp
Honda
Atsuko
A
Kidokoro
Yoshiaki
Y
D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000235:genetics; D004331:Drosophila melanogaster; D004558:Electric Stimulation; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D005444:Flunarizine / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D007811:Lanthanum / Q000494:pharmacology; D007814:Larva; D009154:Mutation / Q000502:physiology; D011188:Potassium / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000502:physiology*; D013111:Spider Venoms / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects; D013572:Synaptic Vesicles / Q000502:physiology*; D013696:Temperature
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D007476:Ionophores; C083634:PLTX-II; D013111:Spider Venoms; D002104:Cadmium; D000001:Calcimycin; D007811:Lanthanum; D005444:Flunarizine; D011188:Potassium; D002118:Calcium