Heart-specific Small Subunit of Myosin Light Chain Phosphatase Activates Rho-associated Kinase and Regulates Phosphorylation of Myosin Phosphatase Target Subunit 1
Heart-specific Small Subunit of Myosin Light Chain Phosphatase Activates Rho-associated Kinase and Regulates Phosphorylation of Myosin Phosphatase Target Subunit 1
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DOI：
10.1074/jbc.m110.122390
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发表时间：
2010-10-29
影响因子：
4.8
通讯作者：
Kimura, Akinori
中科院分区：
文献类型：
--
作者：
Shichi, Daisuke;Arimura, Takuro;Kimura, Akinori
肌球蛋白调节轻链（MLC）的磷酸化在肌肉收缩中发挥调节作用，MLC磷酸化水平通过MLC激酶和MLC磷酸酶（MLCP）来平衡。 MLCP 由一个催化亚基、一个大亚基（MYPT1 或 MYPT2）和一个小亚基组成。 MLCP 活性受 MYPT 磷酸化调节，而小亚基在调节中的作用仍不清楚。我们之前描述了人类心脏特异性小亚基 (hHS-M-21)，它增加了肌肉收缩时对 Ca2+ 的敏感性。在本研究中，我们研究了 hHS-M-21 在 MLCP 磷酸化调节中的作用。 hHS-M-21 的两种同工型 hHS-M(21)A 和 hHS-M21B 分别优先结合 MYPT1 和 MYPT2 的 C 端三分之一区域。 MYPT1 磷酸化位点 Ser-852 的氨基酸取代会损害 MYPT1 和 hHS-M-21 的结合。 hHS-M21 增加了 MYPT1 Thr-696 处的磷酸化水平，该磷酸化水平被 Rho 相关激酶 (ROCK) 抑制剂和 ROCK 的小干扰 RNA 减弱。此外，hHS-M-21结合ROCK并增强ROCK活性。这些发现表明 hHS-M-21 是 ROCK 的心脏特异性效应子，并在 ROCK 对 MYPT1 Thr-696 磷酸化中发挥调节作用。
Phosphorylation of myosin regulatory light chain (MLC) plays a regulatory role in muscle contraction, and the level of MLC phosphorylation is balanced by MLC kinase and MLC phosphatase (MLCP). MLCP consists of a catalytic subunit, a large subunit (MYPT1 or MYPT2), and a small subunit. MLCP activity is regulated by phosphorylation of MYPTs, whereas the role of small subunit in the regulation remains unknown. We previously characterized a human heart-specific small subunit (hHS-M-21) that increased the sensitivity to Ca2+ in muscle contraction. In this study, we investigated the role of hHS-M-21 in the regulation of MLCP phosphorylation. Two isoforms of hHS-M-21, hHS-M(21)A and hHS-M21B, preferentially bound the C-terminal one-third region of MYPT1 and MYPT2, respectively. Amino acid substitutions at a phosphorylation site of MYPT1, Ser-852, impaired the binding of MYPT1 and hHS-M-21. The hHS-M21 increased the phosphorylation level of MYPT1 at Thr-696, which was attenuated by Rho-associated kinase (ROCK) inhibitors and small interfering RNAs for ROCK. In addition, hHS-M-21 bound ROCK and enhanced the ROCK activity. These findings suggest that hHS-M-21 is a heart-specific effector of ROCK and plays a regulatory role in the MYPT1 phosphorylation at Thr-696 by ROCK.