Cardiac SR-coupled PP1 activity and expression are increased and inhibitor 1 protein expression is decreased in failing hearts
Cardiac SR-coupled PP1 activity and expression are increased and inhibitor 1 protein expression is decreased in failing hearts
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DOI：
10.1152/ajpheart.00442.2003
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发表时间：
2003-12-01
影响因子：
4.8
通讯作者：
Sabbah, HN
中科院分区：
文献类型：
--
作者：
Gupta, RC;Mishra, S;Sabbah, HN
1型蛋白磷酸酶（PP 1）是心脏功能的负调节因子。然而，在衰竭的心脏肌浆网（SR）相关的PP 1活性的状态和调节的研究是有限的。我们研究了6只心力衰竭（HF; LV射血分数，23+/-2%）犬和6只正常犬左心室（LV）心肌中PP 1活性、PP 1催化亚基（PP 1C）的蛋白和mRNA表达以及PP 1特异性抑制剂[抑制剂1（Inh-1）和抑制剂2（Inh-2）]的蛋白水平。在衰竭的LV组织中，匀浆、粗膜、胞质溶胶和纯化SR中的PP 1活性值（以pmol P-32.min（-1）.mg非胶原蛋白（-1）表示）分别增加了52%、54%、55%和72%。用胰蛋白酶处理SR，可释放PP 1，但不能释放2A型蛋白磷酸酶。在用胰蛋白酶处理SR的上清液中，衰竭心脏的PP 1活性比正常对照心脏高24%。在非胰蛋白酶化SR中观察到PP 1C蛋白表达的类似增加。热变性磷酸化SR抑制PP 1活性的30%，这表明存在的Inh-1或-2或2在SR中。随着使用特异性抗体，Inh-1和-2蛋白被发现在SR中，前者下降了56%，在失败的SR，而后者没有改变。这些结果表明，与SR结合的蛋白磷酸酶活性增加，并且主要是1型。心力衰竭时SR相关PP 1活性增加似乎部分是由于PP 1C表达增加，部分是由于Inh-1蛋白水平降低，而不是Inh-2蛋白水平降低。因此，抑制SR中的PP 1活性似乎是改善衰竭心脏中LV功能的潜在治疗靶点，因为它可能导致SR Ca 2+摄取增加，这在衰竭心脏中受损。
Type 1 protein phosphatase (PP1) is a negative regulator of cardiac function. However, studies on the status and regulation of sarcoplasmic reticulum (SR)-associated PP1 activity in failing hearts are limited. We studied PP1 activity and protein and mRNA expression of the catalytic subunit of PP1 (PP1C) and protein levels of PP1-specific inhibitors [inhibitor 1 (Inh-1) and inhibitor 2 (Inh-2)] in the left ventricular (LV) myocardium of 6 dogs with heart failure (HF; LV ejection fraction, 23+/-2%) and 6 normal dogs. In failing LV tissue, PP1 activity values (expressed as pmol P-32.min(-1).mg of noncollagen protein(-1)) in the homogenate, crude membranes, cytosol, and purified SR were increased by 52, 54, 55, and 72%, respectively. Trypsin treatment released PP1 but not type 2A protein phosphatase from the SR. In the supernatant of trypsin-treated SR, PP1 activity was similar to24% higher in failing hearts than in normal control hearts. A similar increase in protein expression of PP1C was observed in the nontrypsinized SR. Heat-denatured phosphorylated SR inhibited PP1 activity by 30%, which suggests the presence of Inh-1 or -2 or both in the SR. With the use of a specific antibody, both Inh-1 and -2 proteins were found in the SR; the former was decreased by 56% in the failing SR, whereas the latter did not change. These results suggest that protein phosphatase activity bound to the SR is increased and is predominantly type 1. Increased SR-associated PP1 activity in failing hearts appears to be due partly to increased expression of PP1C and partly to reduced levels of Inh-1 but not Inh-2 protein. Thus inhibition of PP1 activity in the SR appears to be a potential therapeutic target for improving LV function in failing hearts, because it may lead to increased SR Ca2+ uptake, which is impaired in failing hearts.