Modulation of calcium-evoked [H-3]noradrenaline release from permeabilizedcerebrocortical synaptosomes by the MARCKS protein, calmodulin and the actin cytoskeleton
Si. Walaas et I. Sefland, Modulation of calcium-evoked [H-3]noradrenaline release from permeabilizedcerebrocortical synaptosomes by the MARCKS protein, calmodulin and the actin cytoskeleton, NEUROCHEM I, 36(7), 2000, pp. 581-593
In order to examine intracellular modulation of CNS catecholamine release,
cerebrocortical synaptosomes were prelabeled with [H-3]noradrenaline and pe
rmeabilized with streptolysin-O in the absence or presence of Ca2+. Plasma
membrane permeabilization allowed efflux of cytosol and left a compartmenta
lized pool of [H-3]noradrenaline intact, approximately 10% of which was rel
eased by addition of 10(-5) M Ca2+. Addition of activators or inhibitors of
protein kinase C, as well as inhibitors of Ca2+-calmodulin kinase II or ca
lcineurin, failed to change Ca2+-induced noradrenaline release. Evoked rele
ase from permeabilized synaptosomes deficient in the vesicle-associated pho
sphoprotein synapsin I was also unchanged. In contrast, addition of a synth
etic 'active domain' peptide from the myristoylated, alanine-rich C-kinase
substrate (MARCKS) protein increased, while addition of calmodulin decrease
d Ca2+-induced release from the permeabilized synaptosomes, the latter effe
ct being reversed by a peptide inhibitor of calcineurin. Moreover, addition
of the actin-destabilizing agent DNase I, as well as antibodies to MARCKS,
appeared to increase spontaneous, Ca2+-independent release from noradrener
gic vesicles. These results indicate that the MARCKS protein may modulate r
elease from permeabilized noradrenergic synaptosomes, possibly by modulatin
g calmodulin levels and/or the actin cytoskeleton. (C) 2000 Elsevier Scienc
e Ltd. All rights reserved.