Ca(2+)-dependent phosphorylation of myosin light chain kinase decreases the Ca2+ sensitivity of light chain phosphorylation within smooth muscle cells.
Ca(2+)-dependent phosphorylation of myosin light chain kinase decreases the Ca2+ sensitivity of light chain phosphorylation within smooth muscle cells.
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DOI：
10.1016/s0021-9258(17)36969-7
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发表时间：
1994
期刊：
影响因子：
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通讯作者：
M. Tansey;K. Luby‐Phelps;K. Kamm;J. Stull
中科院分区：
文献类型：
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作者：
M. Tansey;K. Luby‐Phelps;K. Kamm;J. Stull
肌球蛋白轻链激酶（MLCK）在收缩平滑肌时被磷酸化。MLCK的磷酸化速率慢于培养的完整气管平滑肌细胞中胞浆Ca 2+浓度和肌球蛋白调节轻链磷酸化的增加速率。在渗透性细胞中，增加Ca 2+浓度增加肌球蛋白轻链和MLCK磷酸化的程度。对于MLCK和肌球蛋白轻链，半数最大磷酸化所需的Ca 2+浓度分别为500 nM和250 nM。添加KN-62或合成肽CK II，多功能Ca 2 +/钙调蛋白依赖性蛋白激酶II活性的抑制剂，废除MLCK磷酸化。在这些条件下，半数最大轻链磷酸化所需的Ca 2+浓度降至170 nM。因此，MLCK磷酸化所需的Ca 2+浓度大于平滑肌细胞中轻链磷酸化所需的Ca 2+浓度。此外，MLCK的磷酸化降低了轻链磷酸化的Ca 2+敏感性。这些结果可以解释的调节方案，其中钙调蛋白可用于肌球蛋白轻链激酶激活是有限的。当气管平滑肌细胞和组织在松弛溶液中透化时，钙调蛋白的保留以及罗丹明-钙调蛋白在完整气管平滑肌细胞中的低流动性支持了这一点。
Myosin light chain kinase (MLCK) is phosphorylated in contracting smooth muscle. The rate of phosphorylation of MLCK is slower than the rates of increase in cytosolic Ca2+ concentrations and phosphorylation of the regulatory light chain of myosin in intact tracheal smooth muscle cells in culture. In permeable cells, increasing the Ca2+ concentration increased the extent of myosin light chain and MLCK phosphorylation. The Ca2+ concentration required for half-maximal phosphorylation was 500 nM for MLCK and 250 nM for myosin light chain. Addition of KN-62 or a synthetic peptide CK II, inhibitors of multifunctional Ca2+/calmodulin-dependent protein kinase II activity, abolished MLCK phosphorylation. Under these conditions, the Ca2+ concentration required for half-maximal light chain phosphorylation decreased to 170 nM. Thus, the Ca2+ concentrations required for MLCK phosphorylation are greater than those required for light chain phosphorylation in smooth muscle cells. Furthermore, phosphorylation of MLCK decreases the Ca2+ sensitivity of light chain phosphorylation. These results can be explained by a regulatory scheme in which calmodulin available for myosin light chain kinase activation is limiting. This is supported by the retention of calmodulin when tracheal smooth muscle cells and tissues are permeabilized in relaxing solution and by the low mobility of rhodamine-calmodulin in intact tracheal smooth muscle cells.