Inhibition of MLC20 phosphorylation downstream of Ca2+ and RhoA: A novel mechanism involving phosphorylation of myosin phosphatase interacting protein (M-RIP) by PKG and stimulation of MLC phosphatase activity.
Inhibition of MLC20 phosphorylation downstream of Ca2+ and RhoA: A novel mechanism involving phosphorylation of myosin phosphatase interacting protein (M-RIP) by PKG and stimulation of MLC phosphatase activity.
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DOI：
10.1007/s12013-013-9677-6
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发表时间：
2014-01
影响因子：
2.6
通讯作者：
Murthy KS
中科院分区：
文献类型：
--
作者：
Mahavadi S;Nalli A;Al-Shboul O;Murthy KS
先前的研究表明，cGMP 依赖性蛋白激酶 (PKG) 作用于收缩通路中的多个靶标，以减少细胞内 Ca2+ 和/或增强 RhoA 调节的肌球蛋白轻链磷酸酶 (MLCP) 活性并导致肌肉松弛。最近的研究发现了一种与 MYPT1（MLCP 的调节亚基）相关的新型蛋白 M-RIP。在此，我们检查 PKG 是否通过胃平滑肌细胞中 M-RIP 的磷酸化增强 Ca2+ 和 RhoA 下游的 MLCP 活性。用 10 μM Ca2+ 处理透化的肌肉细胞会导致 MLC20 磷酸化和肌肉收缩增加，但对 Rho 激酶活性没有影响。 PKG 激活剂（GSNO 或 cGMP）降低了响应 10 μM Ca2+ 的 MLC20 磷酸化和收缩，这意味着存在独立于 Ca2+ 和 RhoA 的抑制机制。 M-RIP siRNA 减弱了 PKG 对 Ca2+ 诱导的 MLC20 磷酸化的影响。 GSNO 和 8-pCPT-cGMP 均诱导 M-RIP 磷酸化；磷酸化伴随着 M-RIP 与 MYPT1 和 MLCP 活性关联的增加。总而言之，这些结果提供了证据表明 PKG 诱导 M-RIP 磷酸化并增强其与 MYPT1 的关联，从而增强 MLCP 活性和 MLC20 去磷酸化并抑制 Ca2+ 或 RhoA 依赖性途径下游的肌肉收缩。
Previous studies have shown that cGMP-dependent protein kinase (PKG) act on several targets in the contractile pathway to reduce intracellular Ca2+ and/or augment RhoA-regulated myosin light chain phosphatase (MLCP) activity and cause muscle relaxation. Recent studies have identified a novel protein M-RIP that associates with MYPT1, the regulatory subunit of MLCP. Herein, we examine whether PKG enhance MLCP activity downstream of Ca2+ and RhoA via phosphorylation of M-RIP in gastric smooth muscle cells. Treatment of permeabilized muscle cells with 10 μM Ca2+ caused an increase in MLC20 phosphorylation and muscle contraction, but had no effect on Rho kinase activity. Activators of PKG (GSNO or cGMP) decreased MLC20 phosphorylation and contraction in response to 10 μM Ca2+, implying existence of inhibitory mechanism independent of Ca2+ and RhoA. The effect of PKG on Ca2+-induced MLC20 phosphorylation was attenuated by M-RIP siRNA. Both GSNO and 8-pCPT-cGMP induced phosphorylation of M-RIP; phosphorylation was accompanied by an increase in the association of M-RIP with MYPT1 and MLCP activity. Taken together, these results provide evidence that PKG induces phosphorylation of M-RIP and enhances its association with MYPT1 to augment MLCP activity and MLC20 dephosphorylation and inhibits muscle contraction, downstream of Ca2+- or RhoA-dependent pathways.
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影响因子：
7.8
作者：
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通讯作者：
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