Diphosphorylated but not monophosphorylated myosin II regulatory light chain localizes to the midzone without its heavy chain during cytokinesis
Diphosphorylated but not monophosphorylated myosin II regulatory light chain localizes to the midzone without its heavy chain during cytokinesis
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DOI：
10.1016/j.bbrc.2011.11.151
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发表时间：
2012-01-13
影响因子：
3.1
通讯作者：
Hosoya, Hiroshi
中科院分区：
文献类型：
--
作者：
Kondo, Tomo;Isoda, Rieko;Hosoya, Hiroshi
肌球蛋白II通过其调节轻链（MRLC）Ser 19（1 P-MRLC）的单磷酸化激活。其ATP酶活性通过MRLC在Thr 18/Ser 19处的二磷酸化（2 P-MRLC）进一步增强。由于这些磷酸化的MRLC在分裂细胞的收缩环上与其重链共定位，我们认为磷酸化的MRLC在胞质分裂过程中作为激活的肌球蛋白II的亚基。然而，1 P-和2 P-MRLC在胞质分裂期间的不同作用尚未阐明。本研究制备了2 P-MRLC的单克隆抗体（4F 12），并利用该抗体研究了2 P-MRLC在培养的哺乳动物细胞中的作用。我们使用4F 12的共聚焦显微镜观察显示，2 P-MRLC定位于收缩环，并且出乎意料地，也定位于中间区。有趣的是，2 P-MRLC并不与1 P-MRLC，肌球蛋白II重链，和F-肌动蛋白在中间区共定位。这些结果表明，2 P-MRLC的作用不同于1 P-MRLC的中间区，并不是肌球蛋白II的亚基。(C)2011 Elsevier Inc. All rights reserved.
Myosin II is activated by the monophosphorylation of its regulatory light chain (MRLC) at Ser19 (1P-MRLC). Its ATPase activity is further enhanced by MRLC diphosphorylation at Thr18/Ser19 (2P-MRLC). As these phosphorylated MRLCs are colocalized with their heavy chains at the contractile ring in dividing cells, we believe that the phosphorylated MRLC acts as a subunit of the activated myosin II during cytokinesis. However, the distinct role(s) of 1P- and 2P-MRLC during cytokinesis has not been elucidated. In this study, a monoclonal antibody (4F12) specific for 2P-MRLC was raised and used to examine the roles of 2P-MRLC in cultured mammalian cells. Our confocal microscopic observations using 4F12 revealed that 2P-MRLC localized to the contractile ring, and, unexpectedly, to the midzone also. Interestingly, 2P-MRLC did not colocalize with 1P-MRLC, myosin II heavy chain, and F-actin at the midzone. These results suggest that 2P-MRLC has a role different from that of 1P-MRLC at the midzone, and is not a subunit of myosin II. (C) 2011 Elsevier Inc. All rights reserved.