Role of Rho-kinase signaling in heart and its involvement of cardiac diseases

研究了RhoA/Rho激酶/肌球蛋白磷酸酶（Myosin phosphatase，MP）信号通路在心脏中的作用及其在心脏疾病中的作用，发现MYPT 2可与1型磷酸酶δ催化亚基（PP 1c δ）和HS-M_2相互作用，<21>形成心肌肌球蛋白磷酸酶全酶。MYPT 2被鉴定为RhoA活性形式的靶标。Rho激酶磷酸化MYPT 2及其硫代磷酸化可诱导MP活性抑制。在培养的乳鼠心肌细胞中，过表达MYPT 2-PP 1c δ的心肌细胞表现出较低的肌球蛋白轻链2（myosin light chain 2，MLC 2）磷酸化水平，并且对血管紧张素II诱导的肌节组织化有抵抗作用，表明MYPT 2-PP 1c δ可以作为MP参与肌节组织化。包括左室内径增大、室壁变薄、左室收缩分数降低 ...更多信息 ortening。与野生型相比，Tg心脏的乳头肌收缩的Ca^&lt;2+&gt;敏感性降低，MLC 2的磷酸化水平显著降低。结果表明，MP对MLC 2磷酸化具有调节作用，MLC 2磷酸化水平对维持正常的心脏功能具有重要意义。然而，每个Tg和心脏特异性Cre小鼠的双转基因小鼠未能诱导足够量的每个片段，并且未观察到表型。因此，我们建立了过表达白血病相关Rho鸟嘌呤核苷酸交换因子活性片段（LARG-Tg）的条件转基因小鼠，以研究心脏Rho/Rho激酶信号转导。我们将继续构建LARG-Tg和Cre双转基因小鼠，研究其表型，以了解Rho/Rho激酶信号通路在心脏中的作用。少

The roles of RhoA/Rho-kinase/myosin phosphatase (MP) signaling in heart and its involvement in cardiac diseases had been investigated.Myosin phosphatase target subunit 2 (MYPT2) could interact with a catalytic subunit of type 1 phosphatase δ isoform (PP1cδ) and HS-M_<21> to form a cardiac myosin phosphatase holoenzyne. MYPT2 was identified to be a target of the active form of RhoA. Rho-kinase phosphorylated MYPT2 and its thiophosphorylation could induce the inhibition of MP activity. The cultured rat neonatal cardiomyocytes overexpressing MYPT2-PP1cδ showed the lower levels of myosin light chain 2 (MLC2) phosphorylation and were resistant to the sarcomere organization induced by angitensin II, indicating that MYPT2-PP1cδ could act as MP and was involved in sarcomere organization.The heart of the cardiac-specific MYPT2-PP1cδ transgenic mice (Tg) showed the dilated cardiomyopathy-like phenotypes, including the enlargement of LV dimension, thinning of LV wall and the reduced fractional sh … More ortening. The papillary muscle of Tg heart showed the reduced Ca^<2+> sensitivity of contraction and the phosphorylation levels of MLC2 were signfficantly lower as compared with wild type. These results suggested that MP play a role to regulate MLC2 phosphorylation and MLC2 phosphorylation level is important to maintain normal cardiac functions in vivo.To analyze the functions of Rho-kinase in heart, the conditional transgenic mice overexpressing the dominant negative or the constitutively active fragment of Rho-kinase were generated. However, the double transgenic mice of each Tg and heart-specific Cre mice failed to induce an enough amount of each fragment and no phenotypes were observed. Therefore, the conditional transgenic mice overexpressing the active fragment of leukemia-associated Rho guanine nucleotide exchange factors (LARG-Tg) were generated to investigate the Rho/Rho-kinase signaling in heart. We will continue to make the double transgenic mice of LARG-Tg and Cre mice to investigate its phenotypes to understand the role of Rho/Rho-kinase signaling in heart. Less