Reduced transmitter release conferred by mutations in the slowpoke-encoded Ca2(+)-activated K+ channel gene of Drosophila.
Potassium channels control the repolarization of nerve terminals and thus play important roles in the control of synaptic transmission. Here we describe the effects of mutations in the slowpoke gene, which is the structural gene for a calcium activated potassium channel, on transmitter release at the neuromuscular junction in Drosophila melanogaster. Surprisingly, we find that the slowpoke mutant exhibits reduced transmitter release compared to normal. Similarly, the slowpoke mutation significantly suppresses the increased transmitter release conferred either by a mutation in Shaker or by application of 4-aminopyridine, which blocks the Shaker-encoded potassium channel at the Drosophila nerve terminal. Furthermore, the slowpoke mutation suppresses the striking increase in transmitter release that occurs following application of 4-aminopyridine to the ether a go-go mutant. This suppression is most likely the result of a reduction of Ca2+ influx into the nerve terminal in the slowpoke mutant. We hypothesize that the effects of the slowpoke mutation are indirect, perhaps resulting from increased Ca2+ channel inactivation, decreased Na+ or Ca2+ channel localization or gene expression, or by increases in the expression or activity of potassium channels distinct from slowpoke.
Warbington
L
L
Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77251, USA.
Hillman
T
T
Adams
C
C
Stern
M
M
D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics*; D004594:Electrophysiology; D051638:Ether-A-Go-Go Potassium Channels; D005260:Female; D017344:Genes, Insect / Q000235:genetics*; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008297:Male; D009154:Mutation / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D009994:Osmolar Concentration; D015221:Potassium Channels / Q000235:genetics*; D024681:Potassium Channels, Calcium-Activated; D051637:Shaker Superfamily of Potassium Channels; D009435:Synaptic Transmission / Q000502:physiology
D029721:Drosophila Proteins; D051638:Ether-A-Go-Go Potassium Channels; D051036:Large-Conductance Calcium-Activated Potassium Channels; D018377:Neurotransmitter Agents; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; C496929:Sh protein, Drosophila; D051637:Shaker Superfamily of Potassium Channels; C496883:eag protein, Drosophila; C494844:slo protein, Drosophila; D015761:4-Aminopyridine; D002118:Calcium