PT  - JOURNAL ARTICLE
AU  - K Kumakura
AU  - K Sasaki
AU  - T Sakurai
AU  - M Ohara-Imaizumi
AU  - H Misonou
AU  - S Nakamura
AU  - Y Matsuda
AU  - Y Nonomura
TI  - Essential role of myosin light chain kinase in the mechanism for MgATP- dependent priming of exocytosis in adrenal chromaffin cells
AID  - 10.1523/JNEUROSCI.14-12-07695.1994
DP  - 1994 Dec 01
TA  - The Journal of Neuroscience
PG  - 7695--7703
VI  - 14
IP  - 12
4099  - http://www.jneurosci.org/content/14/12/7695.short
4100  - http://www.jneurosci.org/content/14/12/7695.full
SO  - J. Neurosci.1994 Dec 01; 14
AB  - Ca(2+)-induced exocytosis in chromaffin cells now seems to consist of at least two distinct steps:MgATP-dependent Ca(2+)-dependent priming of the secretory apparatus, and Ca(2+)-dependent MgATP-independent step that triggers exocytosis (Bittner and Holz, 1992). Recently we found that a specific inhibitor of myosin light chain kinase (MLCK), wortmannin, inhibits Ca(2+)-induced catecholamine release from digitonin-permeabilized chromaffin cells, suggesting an implication of MLCK in the mechanisms of Ca(2+)-induced exocytosis (Imaizumi et al., 1992b). To elucidate further the implication of MLCK in the mechanism of exocytosis, we studied the effects of wortmannin and a peptide inhibitor (SM-1) corresponding to the pseudosubstrate domain of MLCK on MgATP-dependent and MgATP-independent release in digitonin- permeabilized chromaffin cells. Ca(2+)-induced exocytosis from the permeabilized cells in the presence of MgATP was inhibited by both SM-1 and wortmannin. Inhibitory effect of wortmannin on the rate of release induced by 10 microM Ca2+ in the presence of MgATP was much prominent in the later phase (1–10 min), although the initial rate was also decreased. SM-1 strongly inhibited ATP-dependent release without affecting Ca(2+)-dependent ATP-independent release at all. In addition, priming effect of MgATP that underlies Ca(2+)-dependent ATP-independent release was remarkably reduced by both wortmannin and SM-1. These results suggest that MLCK plays an essential role in ATP-dependent priming of Ca(2+)-induced exocytosis in chromaffin cells.