Analyses of the functions of MYPT family, novel anchoring proteins, in cardiovascular system by their knockout and transgenic mice

MYPT是肌球蛋白磷酸（myosin phosphate， MP）的靶亚基，其中MYPT与一个催化亚基（pp1cδ）和另一个调控亚基M20相互作用。MYPT还可以与其他分子相互作用，包括RhoA和cgmp依赖性蛋白激酶Iα，表明MYPT具有锚定蛋白的作用。MYPT1是平滑肌/非肌肉MP的靶亚基，MYPT2是心脏/骨骼肌MP的靶亚基。为了研究MYPTs在体内的功能，我们生成了MYPT1缺陷小鼠和MYPT2转基因小鼠，并对这些表型进行了分析。与野生型小鼠相比，MYPT1缺陷小鼠的杂合子没有显示出MYPT1表达水平的变化，也没有表型，但F2小鼠中没有MYPT1缺失的纯合子，这表明靶向破坏MYPT1基因会导致胚胎致死。胚胎致死点被认为是在7.5 dpc之前。这些发现表明，MYPT1对小鼠胚胎发育至关重要。更多的是，使用α-MHC启动子过表达MYPT2 （Tg）的转基因小鼠显示，MYPT2在心脏中的表达显著增加（> - 20倍），并伴随内源性PP1cδ的增加。Tg中调节性肌球蛋白轻链（RLC）磷酸化水平显著低于野生型小鼠（Wt）。这些结果表明MYPT2与PP1cδ在体内的特异性相互作用可以使心脏中的RLC去磷酸化。Tg组与Wt组生存率、体重、心率、血压无显著差异。Tg组心脏重量/体重比显著高于Wt组。超声心动图显示Tg组左室尺寸（LVDd和LVDs）扩张，左室功能中度损害。这些结果表明，MYPT2的过表达和伴随的MP活性升高降低了左室收缩力，导致轻微的左室扩张。综上所述，MP似乎在体内心脏功能中发挥作用较少

MYPT is a target subunit of myosin phosphates (MP), in which MYPT interacts with a catalytic subunit (PP 1 cδ) and the other regulatory subunit, M20. MYPT could also interact with other molecules including RhoA and cGMP-dependent protein kinase Iα, indicating that MYPT has a role as an anchoring protein. MYPT1 is a target subunit of smooth muscle/nonmuscle MP and MYPT2 is that of cardiac/skeletal muscle MP. To investigate the in vivo function of MYPTs, we generated MYPT1-deficient mice and MYPT2 transgenic mice, and analyzed these phenotypesThe heterozygous of MYPT1-deficient mice showed no changes in the expression levels of MYPT1 and no phenotypes as compared with those in the wild type mice, however, none of the F2 mice was homozygous for the MYPT1 deletion, indicating that the targeted disruption of the MYPT1 gene results in embryonic lethality. The point of embryonic lethality is considered to be before 7.5 dpc. These findings indicate that MYPT1 is essential for mouse embryogenes … More isThe transgenic mice overexpressing MYPT2 (Tg) using α-MHC promoter demonstrated a significantly increased expression of MYPT2 (>20 folds) specifically in hearts with a concomitant increase of the endogenous PP1cδ. The phosphorylation levels of regulatory myosin light chain (RLC) in Tg were significantly lower than those in the wild type mice (Wt). These results suggest the specific in vivo interaction of MYPT2 with PP1cδ, which could dephosphorylate RLC in heart. Survival rate, body weight, heart rate and blood pressure were not significantly different between Tg and Wt. Heart weight/body weight ratio of Tg was significantly higher than that of Wt. Echocardiography demonstrated the dilation of LU dimension (LVDd and LVDs) and the moderate impairment of LV function in Tg. These results suggest that the overexpression of MYPT2 and the concomitant increased MP activity decreased LV contractility, resulting in mild LV dilatation. Taken together, MP seems to play a role in cardiac function in vivo Less