Cycling of actin assembly in synaptosomes and neurotransmitter release.
We have investigated the regulation of actin assembly in whole mouse brain synaptosomes and how that regulation modulates neurotransmitter release. During a 30 s depolarization with high K+, filamentous actin (F-actin) levels, monitored by staining with rhodamine phalloidin, increase dramatically (up to 300% in 3 s), decrease, and increase once again. This F-actin cycling is regulated by pathways both dependent and independent of Ca2+ influx and is markedly affected by exposing synaptosomes to Li+, tetrodotoxin, and diacylglycerol. Measurement of [3H]norepinephrine release from synaptosomes containing entrapped agents that modulate actin assembly (DNAase I or phalloidin) indicates that actin depolymerization is necessary for normal release and that repolymerization limits release.
Bernstein
B W
BW
Department of Biochemistry, Colorado State University, Fort Collins 80523.
Bamburg
J R
JR
D000199:Actins / Q000378:metabolism*; D000818:Animals; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D009411:Nerve Endings / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D018377:Neurotransmitter Agents / Q000378:metabolism* / Q000502:physiology; D009638:Norepinephrine / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure
D000199:Actins; D018377:Neurotransmitter Agents; D009638:Norepinephrine