Normalization of increased protein phosphatase 1 activity by using an high efficiency myocardial gene transfer technique in chronic heart failure

背景资料：据报道，1型蛋白磷酸酶（PP 1）在实验性和人类衰竭心脏中过度活化，导致Ca^2+循环和收缩性的抑制。我们以前报道过，在遗传性心肌病，UMX心肌病（CM）仓鼠模型中也观察到PP 1活性增加，并且通过过表达抑制剂-2（I-2）来体内抑制PP 1可改善短期心脏功能。方法和结果：我们在此研究了通过使用高效腺相关病毒（rAAV-）介导的心脏I-2基因递送慢性PP 1抑制对CM仓鼠心力衰竭进展和存活的影响。内源性抑制剂-2（I-2）仅在心肌细胞的微粒体部分中检测到，并且I-2的腺病毒过表达优先定位于肌膜，表明I-2是膜结合的（m-）内源性PP 1抑制剂。另外，腺病毒I-2转染心肌细胞后，PP 1活性显著降低，增加心肌细胞Ca^2+循环和细胞缩短。rAAV介导的体内心脏I-2基因递送恢复了CM仓鼠的心脏功能并延长了3个月的存活时间。结论：这些结果表明，心肌细胞中m-PP 1的增加是抑制Ca ~（2+）循环的重要因素，通过抑制剂-2抑制m-PP 1可能为心力衰竭的治疗提供新的分子靶点。

Background : The type 1 protein phosphatase (PP1) has been reported to be overactivated in experimental and human failing hearts, leading to a depression of Ca^<2+> cycling and contractility. We previously reported that increased PP1 activity was also observed in the models of genetic cardiomyopathy, UMX cardiomyopathic(CM) hamster, and in vivo inhibition of PPl by overexpressing inhibitor-2(I-2) improved short-term cardiac function. Method and Results : We here investigated the effect of chronic PP1 inhibition by using high efficiency adeno-associated virus (rAAV-) mediated cardiac I-2 gene delivery on heart failure progression and survival in CM hamster. Endogeonus inhibitor-2 (I-2) was only detected in the microsomal fraction of cardiomyocytes, and adenoviral overexpresion of I-2 preferentially localized in the sarcolemma, suggesting that I-2 is a membrane-bound (m-) endogenous PP1 inhibitor. In addition, PP1 activity following adenovirus I-2 transfection in cardiomyocytes dramatically decreased PP1 activity and augmented Ca^<2+> cycling and cell shortening in cardiomyocytes. rAAV-mediated in vivo cardiac I-2 gene delivery restored cardiac function and extended survival time for 3 months in CM hamsters. Conclusions: These findings suggest that increased m- PP1 in cardiomyocytes is an important contributor of depressed Ca2+ cycling, and inhibition of m- PP1 via inhibitor-2 may provide a new molecular target for the treatment of heart failure.