Key result
The basic mechanism of stimulus-secretion coupling for catecholamine release in PC-12 cells does not absolutely require a regulated protein phosphorylation- or calmodulin-dependent step.
The basic mechanism of stimulus-secretion coupling in PC-12 cells does not absolutely require protein phosphorylation or calmodulin-dependent steps.
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Questions necessity of phosphorylation- and calmodulin-dependent steps in exocytosis; leaves open applicability beyond PC-12 cells.
Catecholamine secretion from PC-12 cells can be triggered by agents that increase intracellular Ca2+ and is enhanced by phorbol esters and agents that elevate intracellular cAMP concentrations. In mutant PC-12 cells lacking cAMP-dependent protein kinase (PK-A) in which protein kinase C (PK-C) was down-regulated, Ca2+-dependent secretion occurred normally but was no longer enhanced by cAMP or phorbol esters. In digitonin-permeabilized PC-12 cells that lacked PK-C and PK-A, a range of calmodulin (CaM) inhibitors failed to block Ca2+-triggered catecholamine release. Moreover, Mn2+, a CaM activator, failed to trigger catecholamine release whereas Ba2+, which does not activate CaM, supported secretion. These results indicate that the basic mechanism of stimulus/secretion coupling in PC-12 cells does not absolutely require a regulated protein phosphorylation- or calmodulin-dependent step.
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Matthies et al. (1988) studied this question. Intracellular Ca2+ elevating agents, cAMP, phorbol esters, and CaM inhibitors was evaluated on Catecholamine release. The basic mechanism of stimulus-secretion coupling for catecholamine release in PC-12 cells does not absolutely require a regulated protein phosphorylation- or calmodulin-dependent step.
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