Calmodulin increases the initial rate of exocytosis in adrenal chromaffin cells
The effect of calmodulin on exocytosis in bovine adrenal medullary chromaffin cells was examined by the use of patch-clamp capacitance recording. Calmodulin was dialysed into cells via the patch-pipette and cells stimulated by depolarisation. Following a test stimulation, cells were dialysed with a control or with a calmodulin containing buffer for 10mins and then were stimulated at 2min intervals thereafter. The inclusion of calmodulin in the pipette did not increase Ca2+ currents which instead decreased during dialysis. The presence of calmodulin, however, resulted in a 2-fold increase in the initial rate of exocytosis during the 10min depolarisation step. These results demonstrate the utility of the patch-clamp capacitance technique for the examination of the effect of soluble proteins on exocytosis and in conjunction with previous work on permeabilised chromaffin cells suggest that calmodulin regulates late steps in Ca2+-dependent exocytosis.
Key wordsExocytosis Calcium Calmodulin Chromaffin
Unable to display preview. Download preview PDF.
- 6.Fournier S, Trifaro J-M (1988) A similar calmodulin-binding protein expressed in chromaffin, synaptic, and neurohypophyseal secretory vesicles. J Neurochem 50: 20–37Google Scholar
- 9.Burgoyne RD (1992) Investigation of the intracellular regulators and components of the exocytotic pathway. In: Boulton A, Baker G, Taylor C (eds) Neuromethods, Volume 20: Intracellular Messengers. Humana Press Inc, New Jersey, pp 433–470Google Scholar