Walaas SI, Sefland I. Modulation of calcium-evoked [3H]noradrenaline release from permeabilized cerebrocortical synaptosomes by the MARCKS protein, calmodulin and the actin cytoskeleton.
Neurochem Int 2000;
36:581-93. [PMID:
10771116 DOI:
10.1016/s0197-0186(99)00159-x]
[Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In order to examine intracellular modulation of CNS catecholamine release, cerebrocortical synaptosomes were prelabeled with [3H]noradrenaline and permeabilized with streptolysin-O in the absence or presence of Ca(2+). Plasma membrane permeabilization allowed efflux of cytosol and left a compartmentalized pool of [3H]noradrenaline intact, approximately 10% of which was released by addition of 10(-5) M Ca(2+). Addition of activators or inhibitors of protein kinase C, as well as inhibitors of Ca(2+)-calmodulin kinase II or calcineurin, failed to change Ca(2+)-induced noradrenaline release. Evoked release from permeabilized synaptosomes deficient in the vesicle-associated phosphoprotein synapsin I was also unchanged. In contrast, addition of a synthetic 'active domain' peptide from the myristoylated, alanine-rich C-kinase substrate (MARCKS) protein increased, while addition of calmodulin decreased Ca(2+)-induced release from the permeabilized synaptosomes, the latter effect 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, Ca(2+)-independent release from noradrenergic vesicles. These results indicate that the MARCKS protein may modulate release from permeabilized noradrenergic synaptosomes, possibly by modulating calmodulin levels and/or the actin cytoskeleton.
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