Citron kinase, a Rho-dependent kinase, induces di-phosphorylation of regulatory light chain of myosin II
Citron kinase, a Rho-dependent kinase, induces di-phosphorylation of regulatory light chain of myosin II
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DOI：
10.1091/mbc.e02-07-0427
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发表时间：
2003-05-01
影响因子：
3.3
通讯作者：
Matsumura, F
中科院分区：
文献类型：
--
作者：
Yamashiro, S;Totsukawa, G;Matsumura, F
Citron激酶是一种Rho效应蛋白激酶，与ROCK/ROK/Rho激酶家族的Rho相关激酶相关。ROCK和Citron激酶都被认为在胞质分裂中起作用。然而，没有已知的柠檬激酶的底物。我们发现，柠檬酸激酶磷酸化的肌球蛋白II的调节轻链（MLC）的Ser-19和Thr-18在体外。然而，与ROCK不同的是，香橼激酶不磷酸化肌球蛋白磷酸酶的肌球蛋白结合亚基，表明它不抑制肌球蛋白磷酸酶。我们发现，柠檬激酶的激酶结构域的表达导致MLC二磷酸化的增加。此外，激酶结构域能够增加二磷酸化和恢复应力纤维组装，即使当ROCK被抑制与一个特定的抑制剂，Y-27632。在胞质分裂过程中，全长柠檬酸激酶的表达也增加了二磷酸化。这些观察结果表明，柠檬激酶磷酸化MLC，以产生二磷酸化MLC在体内。虽然单磷酸化和二磷酸化的MLC被发现在卵裂沟，二磷酸化的MLC表现出更多的限制本地化比单磷酸化的MLC。由于柠檬酸激酶定位于卵裂沟，因此柠檬酸激酶可能参与调节胞质分裂期间MLC的二磷酸化。
Citron kinase is a Rho-effector protein kinase that is related to Rho-associated kinases of ROCK/ROK/Rho-kinase family. Both ROCK and citron kinase are suggested to play a role in cytokinesis. However, no substrates are known for citron kinase. We found that citron kinase phosphorylated regulatory light chain (MLC) of myosin II at both Ser-19 and Thr-18 in vitro. Unlike ROCK, however, citron kinase did not phosphorylate the myosin binding subunit of myosin phosphatase, indicating that it does not inhibit myosin phosphatase. We found that the expression of the kinase domain of citron kinase resulted in an increase in MLC di-phosphorylation. Furthermore, the kinase domain was able to increase di-phosphorylation and restore stress fiber assembly even when ROCK was inhibited with a specific inhibitor, Y-27632. The expression of full-length citron kinase also increased di-phosphorylation during cytokinesis. These observations suggest that citron kinase phosphorylates MLC to generate di-phosphorylated MLC in vivo. Although both mono- and di-phosphorylated MLC were found in cleavage furrows, di-phosphorylated MLC showed more constrained localization than did mono-phosphorylated MLC. Because citron kinase is localized in cleavage furrows, citron kinase may be involved in regulating di-phosphorylation of MLC during cytokinesis.